@article{petters_pujiastuti_satheesh_kasparoglu_sutherland_meskhidze_2024, title={Wind-driven emissions of coarse-mode particles in an urban environment}, volume={24}, ISSN={["1680-7324"]}, DOI={10.5194/acp-24-745-2024}, abstractNote={Abstract. Quantifying surface–atmosphere exchange rates of particles is important for understanding the role of suspended particulate matter in radiative transfer, clouds, precipitation, and climate change. Emissions of coarse-mode particles with a diameter greater than 0.5 µm provide giant cloud condensation nuclei and ice nuclei. These emissions are critical for understanding the evolution of cloud microphysical properties yet remain poorly understood. Here we introduce a new method that uses lidar retrievals of the elastic backscatter and Doppler velocity to obtain surface number emissions of particles with a diameter greater than 0.53 µm. The technique is applied to study particle number fluxes over a 2-month period from 1 June to 10 August 2022 during the TRACER campaign at an urban site near Houston, TX, USA. We found that all the observed fluxes were positive (upwards), indicating particle emission from the surface. The fluxes followed a diurnal pattern and peaked near noon local time. Flux intensity varied through the 2 months with multi-day periods of strong fluxes and multi-day periods of weak fluxes. Emission particle number fluxes peaked near ∼ 100 cm−2 s−1. The daily averaged emission fluxes correlated with friction velocity and were anticorrelated with surface relative humidity. The emission flux can be parameterized as F= 3000 u*4, where u* is the friction velocity in m s−1 and the emission flux F is in cm−2 s−1. The u* dependence is consistent with emission from wind-driven erosion. Estimated values for the mass flux are in the lower range of literature values from non-urban sites. These results demonstrate that urban environments may play an important role in supplying coarse-mode particles to the boundary layer. We anticipate that quantification of these emissions will help constrain aerosol–cloud interaction models that use prognostic aerosol schemes.
                    }, number={1}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Petters, Markus D. and Pujiastuti, Tyas and Satheesh, Ajmal Rasheeda and Kasparoglu, Sabin and Sutherland, Bethany and Meskhidze, Nicholas}, year={2024}, month={Jan}, pages={745–762} }
 @article{mahant_yadav_gilbert_kjaergaard_jensen_kessler_bilde_petters_2023, title={An open-hardware community ice nucleation cold stage for research and teaching}, volume={16}, ISSN={["2468-0672"]}, DOI={10.1016/j.ohx.2023.e00491}, abstractNote={Aerosol particles with rare specific properties act as nuclei for ice formation. The presence of ice nucleating particles in the atmosphere leads to heterogeneous freezing at warm temperatures and thus these particles play an important role in modulating microphysical properties of clouds. This work presents an ice nucleation cold stage instrument for measuring the concentration of ice nucleating particles in liquids. The cost is ∼ $10 k including an external chiller. Using a lower cost heat sink reduces the cost to ∼ $6 k. The instrument is suitable for studying ambient ice nucleating particle concentrations and laboratory-based process-level studies of ice nucleation. The design plans allow individuals to self-manufacture the cold-stage using 3D printing, off-the-shelf parts, and a handful of standard tools. Software to operate the instrument and analyze the data is also provided. The design is intended to be simple enough that a graduate student can build it as part of a course or thesis project. Costs are kept to a minimum to facilitate use in classroom demonstrations and laboratory classes.}, journal={HARDWAREX}, author={Mahant, Sunandan and Yadav, Shweta and Gilbert, Cameron and Kjaergaard, Eva R. and Jensen, Mads M. and Kessler, Tommy and Bilde, Merete and Petters, Markus D.}, year={2023}, month={Dec} }
 @article{cornwell_mccluskey_hill_levin_rothfuss_tai_petters_demott_kreidenweis_prather_et al._2023, title={Bioaerosols are the dominant source of warm-temperature immersion-mode INPs and drive uncertainties in INP predictability}, volume={9}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.adg3715}, abstractNote={Ice-nucleating particles (INPs) are rare atmospheric aerosols that initiate primary ice formation, but accurately simulating their concentrations and variability in large-scale climate models remains a challenge. Doing so requires both simulating major particle sources and parameterizing their ice nucleation (IN) efficiency. Validating and improving model predictions of INP concentrations requires measuring their concentrations delineated by particle type. We present a method to speciate INP concentrations into contributions from dust, sea spray aerosol (SSA), and bioaerosol. Field campaign data from Bodega Bay, California, showed that bioaerosols were the primary source of INPs between −12° and −20°C, while dust was a minor source and SSA had little impact. We found that recent parameterizations for dust and SSA accurately predicted ambient INP concentrations. However, the model did not skillfully simulate bioaerosol INPs, suggesting a need for further research to identify major factors controlling their emissions and INP efficiency for improved representation in models.}, number={37}, journal={SCIENCE ADVANCES}, author={Cornwell, Gavin C. and McCluskey, Christina S. and Hill, Thomas C. J. and Levin, Ezra T. and Rothfuss, Nicholas E. and Tai, Sheng-Lun and Petters, Markus D. and DeMott, Paul J. and Kreidenweis, Sonia and Prather, Kimberly A. and et al.}, year={2023}, month={Sep} }
 @article{mahant_iversen_kasparoglu_bilde_petters_2023, title={Direct measurement of the viscosity of ternary aerosol mixtures}, volume={2}, ISSN={["2634-3606"]}, url={https://doi.org/10.1039/D2EA00160H}, DOI={10.1039/d2ea00160h}, abstractNote={The optical properties of particles change with change in their phase state. The optical change was exploited in this study to measure the transition temperature of sucrose, citric acid, and tartaric acid mixtures.}, journal={ENVIRONMENTAL SCIENCE-ATMOSPHERES}, author={Mahant, Sunandan and Iversen, Emil Mark and Kasparoglu, Sabin and Bilde, Merete and Petters, Markus D.}, year={2023}, month={Feb} }
 @article{kasparoglu_islam_meskhidze_petters_2022, title={Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements}, volume={15}, ISSN={["1867-8548"]}, DOI={10.5194/amt-15-5007-2022}, abstractNote={Abstract. The printed optical particle spectrometer (POPS) is a lightweight, low-cost
instrument for measurements of aerosol number concentrations and size
distributions. This work reports on modifications of the Handix Scientific
commercial version of the POPS to facilitate its use in multi-instrument
aerosol sampling systems. The flow system is modified by replacing the
internal pump with a needle valve and a vacuum pump. The instrument is
integrated into closed-flow systems by routing the sheath flow from filtered
inlet air. A high-precision multichannel analyzer (MCA) card is added to
sample the analog pulse signal. The MCA card is polled at 10 Hz frequency
using an external data acquisition system and improves upon the count-rate
limitation associated with the POPS internal data acquisition system. The
times required to change the concentration between 90 % and 10 % and vice versa
for a step change in concentration were measured to be 0.17 and 0.41 s at
a flow rate of 5 cm3 s−1. This yields a sampling frequency of
∼ 1–2 Hz, below which the amplitude of measured fluctuations is
captured with > 70 % efficiency. The modified POPS was
integrated into the dual tandem differential mobility analyzer system to
explore the coalescence of dimer particles. Results show that the
pulse-height response increases upon dimer coalescence. The magnitude of the
increase is broadly consistent with the change in light-scattering amplitude
predicted by the T-matrix method. It is anticipated that this modified
version of the POPS will extend the utilization of the technique for a range
of field and laboratory applications.
                    }, number={17}, journal={ATMOSPHERIC MEASUREMENT TECHNIQUES}, author={Kasparoglu, Sabin and Islam, Mohammad Maksimul and Meskhidze, Nicholas and Petters, Markus D.}, year={2022}, month={Sep}, pages={5007–5018} }
 @article{cornwell_sultana_petters_al-mashat_rothfuss_mohler_demott_martin_prather_2022, title={Discrimination between individual dust and bioparticles using aerosol time-of-flight mass spectrometry}, ISSN={["1521-7388"]}, DOI={10.1080/02786826.2022.2055994}, abstractNote={Abstract Ice nucleating particles (INPs) impact cloud properties and precipitation processes through their ability to trigger cloud glaciation. Dust and bioparticles are two important sources of INPs that have markedly different atmospheric loadings and ice nucleating efficiencies. In-situ identification of the sources of INPs in clouds has been accomplished using single particle mass spectrometry (SPMS). However, external mixtures of dust and bioparticles present a unique challenge as they have overlapping mass spectral ion signatures, complicating their unambiguous identification. This study presents a detailed discussion of dust and bioparticle SPMS signatures, uniting data from a broad array of studies. As emphasized, the ion signals from both dust and bioparticles are highly sensitive to ionization conditions. To understand the observed variations, we characterize the mass spectral dependence of distinct dust and bioparticle samples using total positive ion intensity (TPII) as an indicator of the laser pulse energy each particle encountered. Through this analysis, a broad range of characteristic biogenic low intensity ion peaks that may be useful to distinguish bioparticles from dust became apparent and are highlighted. Insights informed by this analysis were utilized to identify bioparticles in ambient SPMS data. Ambient particles exhibiting both dust and characteristic biogenic spectral fingerprints were excluded from the bioparticle classification. Although bioparticles only made up 0.2% of all sampled particles, their abundance was moderately correlated with INP concentrations measured at −15 °C. Copyright © 2022 American Association for Aerosol Research}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Cornwell, G. C. and Sultana, C. M. and Petters, M. D. and Al-Mashat, H. and Rothfuss, N. E. and Mohler, O. and DeMott, P. J. and Martin, A. C. and Prather, K. A.}, year={2022}, month={Mar} }
 @article{kasparoglu_perkins_ziemann_demott_kreidenweis_finewax_deming_devault_petters_2022, title={Experimental Determination of the Relationship Between Organic Aerosol Viscosity and Ice Nucleation at Upper Free Tropospheric Conditions}, volume={127}, ISSN={["2169-8996"]}, DOI={10.1029/2021JD036296}, abstractNote={Abstract}, number={16}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Kasparoglu, Sabin and Perkins, Russell and Ziemann, Paul J. and DeMott, Paul J. and Kreidenweis, Sonia M. and Finewax, Zachary and Deming, Benjamin L. and DeVault, Marla P. and Petters, Markus D.}, year={2022}, month={Aug} }
 @article{kasparoglu_wright_petters_2022, title={Open-hardware design and characterization of an electrostatic aerosol precipitator}, volume={11}, ISSN={["2468-0672"]}, DOI={10.1016/j.ohx.2022.e00266}, abstractNote={Electrostatic precipitators are devices that remove charged particles from an air stream. We present the design and characterization of an electrostatic precipitator that is intended to be incorporated into aerosol sampling equipment. Hardware and software components of the design are open, all components can be directly purchased from vendors, and the device can be assembled with standard tools. Generic components are used to allow the repurposing of parts for other uses. The computer-controlled high-voltage power supply box associated with the project can be used for other common high-voltage applications in Aerosol Science and Technology, such as data acquisition and control systems for scanning mobility particle sizers. Computational fluid dynamics simulations are used to quantify the 3D flow field. The transfer function associated with the partial transmission is characterized through modeling and experiments. The observed transfer function is unique but deviates from the ideal transfer function due to the distortion of the flow near the inlet and the outlet of the device. Singly charged particles up to 624 nm and 253 nm can be completely removed for 0.5 L min−1 and 1 L min−1, respectively. We anticipate that our device will increase the accessibility of the technique to a broader audience.}, journal={HARDWAREX}, author={Kasparoglu, Sabin and Wright, Timothy P. and Petters, Markus D.}, year={2022}, month={Apr} }
 @article{islam_meskhidze_satheesh_petters_2022, title={Turbulent Flux Measurements of the Near-Surface and Residual-Layer Small Particle Events}, volume={127}, ISSN={["2169-8996"]}, DOI={10.1029/2021JD036289}, abstractNote={Abstract}, number={17}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Islam, M. M. and Meskhidze, N. and Satheesh, A. Rasheeda and Petters, M. D.}, year={2022}, month={Sep} }
 @article{petters_2021, title={Interactive Worksheets for Teaching Atmospheric Aerosols and Cloud Physics}, volume={102}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-D-20-0072.1}, abstractNote={Abstract}, number={3}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Petters, Markus}, year={2021}, month={Mar}, pages={E672–E680} }
 @article{petters_2021, title={Revisiting matrix-based inversion of scanning mobility particle sizer (SMPS) and humidified tandem differential mobility analyzer (HTDMA) data}, volume={14}, ISSN={["1867-8548"]}, DOI={10.5194/amt-14-7909-2021}, abstractNote={Abstract. Tikhonov regularization is a tool for reducing noise amplification
during data inversion. This work introduces RegularizationTools.jl,
a general-purpose software package for applying Tikhonov regularization
to data. The package implements well-established numerical algorithms
and is suitable for systems of up to ∼ 1000 equations.
Included is an abstraction to systematically categorize specific inversion
configurations and their associated hyperparameters. A generic interface
translates arbitrary linear forward models defined by a computer function
into the corresponding design matrix. This obviates the need to explicitly
write out and discretize the Fredholm integral equation, thus facilitating
fast prototyping of new regularization schemes associated with measurement
techniques. Example applications include the inversion involving data
from scanning mobility particle sizers (SMPSs) and humidified tandem
differential mobility analyzers (HTDMAs). Inversion of SMPS size distributions
reported in this work builds upon the freely available software
DifferentialMobilityAnalyzers.jl. The speed of inversion is
improved by a factor of ∼ 200, now requiring between
2 and 5 ms per SMPS scan when using 120 size bins. Previously reported
occasional failure to converge to a valid solution is reduced by switching
from the L-curve method to generalized cross-validation as the metric
to search for the optimal regularization parameter. Higher-order inversions
resulting in smooth, denoised reconstructions of size distributions
are now included in DifferentialMobilityAnalyzers.jl. This
work also demonstrates that an SMPS-style matrix-based inversion can
be applied to find the growth factor frequency distribution from raw
HTDMA data while also accounting for multiply charged particles.
The outcome of the aerosol-related inversion methods is showcased
by inverting multi-week SMPS and HTDMA datasets from ground-based
observations, including SMPS data obtained at Bodega Marine Laboratory
during the CalWater 2/ACAPEX campaign and co-located SMPS and HTDMA
data collected at the US Department of Energy observatory located
at the Southern Great Plains site in Oklahoma, USA. Results show
that the proposed approaches are suitable for unsupervised, nonparametric
inversion of large-scale datasets as well as inversion in real time
during data acquisition on low-cost reduced-instruction-set architectures
used in single-board computers. The included software implementation
of Tikhonov regularization is freely available, general, and domain-independent
and thus can be applied to many other inverse problems arising in
atmospheric measurement techniques and beyond.
                    }, number={12}, journal={ATMOSPHERIC MEASUREMENT TECHNIQUES}, author={Petters, Markus D.}, year={2021}, month={Dec}, pages={7909–7928} }
 @article{kasparoglu_li_shiraiwa_petters_2021, title={Toward closure between predicted and observed particle viscosity over a wide range of temperatures and relative humidity}, volume={21}, ISSN={["1680-7324"]}, DOI={10.5194/acp-21-1127-2021}, abstractNote={Abstract. Atmospheric aerosols can exist in amorphous semi-solid or glassy phase
states whose viscosity varies with atmospheric temperature and relative
humidity. The temperature and humidity dependence of viscosity has
been hypothesized to be predictable from the combination of a water–organic
binary mixing rule of the glass transition temperature, a glass-transition-temperature-scaled viscosity fragility parameterization, and a water
uptake parameterization. This work presents a closure study between
predicted and observed viscosity for sucrose and citric acid. Viscosity
and glass transition temperature as a function of water content are
compiled from literature data and used to constrain the fragility
parameterization. New measurements characterizing viscosity of sub-100 nm particles using the dimer relaxation method are presented. These
measurements extend the available data of temperature- and humidity-dependent viscosity to −28 ∘C. Predicted relationships agree well
with observations at room temperature and with measured isopleths
of constant viscosity at ∼107 Pa s at temperatures warmer
than −28 ∘C. Discrepancies at colder temperatures
are observed for sucrose particles. Simulations with the kinetic multi-layer
model of gas–particle interactions suggest that the observed deviations
at colder temperature for sucrose can be attributed to kinetic limitations
associated with water uptake at the timescales of the dimer relaxation
experiments. Using the available information, updated equilibrium
phase-state diagrams (-80∘C<T<40∘C, temperature, and 0%<RH<100%, relative humidity) for sucrose
and citric acid are constructed and associated equilibration timescales
are identified.
                    }, number={2}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Kasparoglu, Sabin and Li, Ying and Shiraiwa, Manabu and Petters, Markus D.}, year={2021}, month={Jan}, pages={1127–1141} }
 @article{zimmerman_petters_meskhidze_2020, title={Observations of new particle formation, modal growth rates, and direct emissions of sub-10 nm particles in an urban environment}, volume={242}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2020.117835}, abstractNote={Ultrafine particles with diameters less than 100 nm suspended in the air are a topic of interest in air quality and climate sciences. Sub-10 nm particles are of additional interest due to their health effects and contribution to particle growth processes. Ambient measurements were carried out at North Carolina State University in Raleigh, NC between April to June 2019 and November 2019 to May 2020 to investigate the temporal variability of size distribution and number concentration of ultrafine particles. A mobile lab was deployed between March and May 2020 to characterize the spatial distribution of sub-10 nm particle number concentration. New particle formation and growth events were observed regularly. Also observed were direct emissions of sub-10 nm particles. Analysis against meteorological variables, gas-phase species, and particle concentrations show that the sub-10nm particles dominated number concentration during periods of low planetary boundary layer height, low solar radiation, and northeast winds. The spatial patterns observed during mobile deployments suggest that multiple temporally stable and spatially confined point sources of sub-10 nm particles are present within the city. These sources likely include the campus utility plants and the Raleigh-Durham International Airport. Additionally, the timing of data collection allowed for investigation of variations in the urban aerosol number size distribution due to reduced economic activity during the COVID-19 pandemic.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Zimmerman, Alyssa and Petters, Markus D. and Meskhidze, Nicholas}, year={2020}, month={Dec} }
 @article{petters_kasparoglu_2020, title={Predicting the influence of particle size on the glass transition temperature and viscosity of secondary organic material}, volume={10}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-020-71490-0}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Petters, Markus and Kasparoglu, Sabin}, year={2020}, month={Sep} }
 @article{hiranuma_adachi_bell_belosi_beydoun_bhaduri_bingemer_budke_clemen_conen_et al._2019, title={A comprehensive characterization of ice nucleation by three different types of cellulose particles immersed in water}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-4823-2019}, abstractNote={Abstract. We present the laboratory results of immersion freezing efficiencies of
cellulose particles at supercooled temperature (T) conditions. Three types of
chemically homogeneous cellulose samples are used as surrogates that
represent supermicron and submicron ice-nucleating plant structural
polymers. These samples include microcrystalline cellulose (MCC), fibrous
cellulose (FC) and nanocrystalline cellulose (NCC). Our immersion freezing
dataset includes data from various ice nucleation measurement techniques
available at 17 different institutions, including nine dry dispersion
and 11 aqueous suspension techniques. With a total of 20 methods, we
performed systematic accuracy and precision analysis of measurements from
all 20 measurement techniques by evaluating T-binned (1 ∘C)
data over a wide T range (−36 ∘C <T<-4 ∘C). Specifically, we intercompared the geometric surface
area-based ice nucleation active surface site (INAS) density data derived from
our measurements as a function of T, ns,geo(T). Additionally, we also
compared the ns,geo(T) values and the freezing spectral slope parameter
(Δlog(ns,geo)/ΔT) from our measurements to previous
literature results. Results show all three cellulose materials are
reasonably ice active. The freezing efficiencies of NCC samples agree
reasonably well, whereas the diversity for the other two samples spans
≈ 10 ∘C. Despite given uncertainties within each
instrument technique, the overall trend of the ns,geo(T) spectrum traced
by the T-binned average of measurements suggests that predominantly
supermicron-sized cellulose particles (MCC and FC) generally act as more
efficient ice-nucleating particles (INPs) than NCC with about 1 order of
magnitude higher ns,geo(T).
                    }, number={7}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Hiranuma, Naruki and Adachi, Kouji and Bell, David M. and Belosi, Franco and Beydoun, Hassan and Bhaduri, Bhaskar and Bingemer, Heinz and Budke, Carsten and Clemen, Hans-Christian and Conen, Franz and et al.}, year={2019}, month={Apr}, pages={4823–4849} }
 @article{yadav_venezia_paerl_petters_2019, title={Characterization of Ice‐Nucleating Particles Over Northern India}, volume={124}, ISSN={2169-897X 2169-8996}, url={http://dx.doi.org/10.1029/2019jd030702}, DOI={10.1029/2019JD030702}, abstractNote={Abstract}, number={19}, journal={Journal of Geophysical Research: Atmospheres}, publisher={American Geophysical Union (AGU)}, author={Yadav, S. and Venezia, R. E. and Paerl, R. W. and Petters, M. D.}, year={2019}, month={Oct}, pages={10467–10482} }
 @article{rothfuss_petters_champion_grieshop_petters_2019, title={Characterization of a dimer preparation method for nanoscale organic aerosol}, volume={53}, ISSN={["1521-7388"]}, url={https://doi.org/10.1080/02786826.2019.1623379}, DOI={10.1080/02786826.2019.1623379}, abstractNote={Abstract Nanoscale dimers have application in studies of aerosol physicochemical properties such as aerosol viscosity. These particle dimers can be synthesized using the dual tandem differential mobility analyzer (DTDMA) technique, wherein oppositely charged particle streams coagulate to form dimers that can be isolated using electrostatic filtration. Although some characterization of the technique has been published, a detailed thesis on the modes and theory of operation has remained outside the scope of prior work. Here, we present new experimental data characterizing the output DTDMA size distribution and the physical processes underlying its apparent modes. Key experimental limitations for both general applications and for viscosity measurements are identified and quantified in six distinct types of DTDMA experiments. The primary consideration is the production of an adequate number of dimers, which typically requires high mobility-selected number concentration in the range 25,000–100,000 cm−3. The requisite concentration threshold depends upon the rate of spontaneous monomer decharging, which arises predominately from interactions of the aerosol with ionizing radiation within the coagulation chamber and is instrument location dependent. Lead shielding of the coagulation chamber reduced the first-order decharging constant from ∼2.0 × 10−5 s−1 to ∼0.8 × 10−5 s−1 in our laboratory. Dimer production at monomer diameters less than 40 nm is hindered by low bipolar charging efficiency. Results from the characterization experiments shed light on design considerations for general applications and for characterization of viscous aerosol phase transitions. Copyright © 2019 American Association for Aerosol Research}, number={9}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, publisher={Informa UK Limited}, author={Rothfuss, Nicholas E. and Petters, Sarah S. and Champion, Wyatt M. and Grieshop, Andrew P. and Petters, Markus D.}, year={2019}, month={Sep}, pages={998–1011} }
 @article{atwood_kreidenweis_demott_petters_cornwell_martin_moore_2019, title={Classification of aerosol population type and cloud condensation nuclei properties in a coastal California littoral environment using an unsupervised cluster model}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-6931-2019}, abstractNote={Abstract. Aerosol particle and cloud condensation nuclei (CCN) measurements from a
littoral location on the northern coast of California at Bodega Bay Marine
Laboratory (BML) are presented for approximately six weeks of observations
during the boreal winter–spring as part of the CalWater-2015 field campaign.
The nature and variability of surface (marine boundary layer, MBL) aerosol
populations were evaluated by classifying observations into periods of
similar aerosol and meteorological characteristics using an unsupervised
cluster model to derive distinct littoral aerosol population types and link
them to source regions. Such classifications support efforts to understand
the impact of changing aerosol properties on precipitation and cloud
development in the region, including during important atmospheric river (AR)
tropical moisture advection events. Eight aerosol population types were
identified that were associated with a range of impacts from both marine and
terrestrial sources. Average measured total particle number concentrations,
size distributions, hygroscopicities, and activated fraction spectra between
0.08 % and 1.1 % supersaturation are given for each of the identified
aerosol population types, along with meteorological observations and
transport pathways during time periods associated with each type. Five
terrestrially influenced aerosol population types represented different
degrees of aging of the continental outflow from the coast and interior of
California, and their appearance at the BML site was often linked to changes
in wind direction and transport pathways. In particular, distinct aerosol
populations, associated with diurnal variations in source regions induced by
land- and sea-breeze shifts, were classified by the clustering technique. A
terrestrial type representing fresh emissions, and/or a recent new particle
formation event, occurred in approximately 10 % of the observations. Over
the entire study period, three marine-influenced population types were
identified that typically occurred when the regular diurnal land and sea-breeze
cycle collapsed and BML was continuously ventilated by air masses from marine
regions for multiple days. These marine types differed from each other
primarily in the degree of cloud processing evident in the size
distributions, and in the presence of an additional large-particle mode for
the type associated with the highest wind speeds. One of the marine types was
associated with a multi-day period during which an atmospheric river made
landfall at BML. Differences between many of the terrestrial and marine
population types in total CCN number concentrations active at a specific
supersaturation were often not as pronounced as the associated differences in
the corresponding activated fraction spectra, particularly for
supersaturations below about 0.4 %. This finding was due to the generally
higher number concentrations in terrestrial air masses offsetting the lower
fraction of particles activating at low supersaturations. At higher
supersaturations, CCN concentrations for aged terrestrial types were
typically above those of the marine types due to their higher number
concentrations.
                    }, number={10}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Atwood, Samuel A. and Kreidenweis, Sonia M. and DeMott, Paul J. and Petters, Markus D. and Cornwell, Gavin C. and Martin, Andrew C. and Moore, Kathryn A.}, year={2019}, month={May}, pages={6931–6947} }
 @article{wang_shilling_liu_zelenyuk_bell_petters_thalman_mei_zaveri_zheng_2019, title={Cloud droplet activation of secondary organic aerosol is mainly controlled by molecular weight, not water solubility}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-941-2019}, abstractNote={Abstract. Aerosol particles strongly influence global climate by modifying the
properties of clouds. An accurate assessment of the aerosol impact on
climate requires knowledge of the concentration of cloud condensation nuclei
(CCN), a subset of aerosol particles that can activate and form cloud
droplets in the atmosphere. Atmospheric particles typically consist of a
myriad of organic species, which frequently dominate the particle
composition. As a result, CCN concentration is often a strong function of
the hygroscopicity of organics in the particles. Earlier studies showed
organic hygroscopicity increases nearly linearly with oxidation level. Such
an increase in hygroscopicity is conventionally attributed to higher water
solubility for more oxidized organics. By systematically varying the water
content of activating droplets, we show that for the majority of secondary
organic aerosols (SOAs), essentially all organics are dissolved at the point
of droplet activation. Therefore, for droplet activation, the organic
hygroscopicity is not limited by solubility but is dictated mainly by the
molecular weight of organic species. Instead of increased water solubility
as previously thought, the increase in the organic hygroscopicity with
oxidation level is largely because (1) SOAs formed from smaller precursor
molecules tend to be more oxidized and have lower average molecular weight
and (2) during oxidation, fragmentation reactions reduce average organic
molecule weight, leading to increased hygroscopicity. A simple model of
organic hygroscopicity based on molecular weight, oxidation level, and
volatility is developed, and it successfully reproduces the variation in SOA
hygroscopicity with oxidation level observed in the laboratory and field
studies.
                    }, number={2}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Wang, Jian and Shilling, John E. and Liu, Jiumeng and Zelenyuk, Alla and Bell, David M. and Petters, Markus D. and Thalman, Ryan and Mei, Fan and Zaveri, Rahul A. and Zheng, Guangjie}, year={2019}, month={Jan}, pages={941–954} }
 @article{petters_kreidenweis_grieshop_ziemann_petters_2019, title={Temperature- and Humidity-Dependent Phase States of Secondary Organic Aerosols}, volume={46}, ISSN={["1944-8007"]}, url={https://doi.org/10.1029/2018GL080563}, DOI={10.1029/2018GL080563}, abstractNote={Abstract}, number={2}, journal={GEOPHYSICAL RESEARCH LETTERS}, publisher={American Geophysical Union (AGU)}, author={Petters, Sarah S. and Kreidenweis, Sonia M. and Grieshop, Andrew P. and Ziemann, Paul J. and Petters, Markus D.}, year={2019}, month={Jan}, pages={1005–1013} }
 @article{tandon_rothfuss_petters_2019, title={The effect of hydrophobic glassy organic material on the cloud condensation nuclei activity of particles with different morphologies}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-3325-2019}, abstractNote={Abstract. Particles composed of organic and inorganic components can assume
core-shell morphologies. The kinetic limitation of water uptake due to the
presence of a hydrophobic viscous outer shell may increase the critical
supersaturation required to activate such particles into cloud droplets. Here
we test this hypothesis through laboratory experiments. Results show that the
viscosity of polyethylene particles is 5×106 Pa s at
60 ∘C. Extrapolation of temperature dependent viscosity measurements
suggests that the particles are glassy at room temperature. Cloud
condensation nuclei (CCN) activity measurements demonstrate that pure
polyethylene particles are CCN inactive at diameters less than 741 nm and
2.5 % water supersaturation. Thus, polyethylene is used as proxy for
hydrophobic glassy organic material. Ammonium sulfate is used as proxy for
hygroscopic CCN active inorganic material. Mixed particles were generated
using coagulation of oppositely charged particles; charge-neutral
polyethylene–ammonium sulfate dimer particles were then isolated for online
observation. Morphology of these dimer particles was varied by heating, such
that liquefied polyethylene partially or completely engulfed the ammonium
sulfate. Critical supersaturation was measured as a function of dry particle
volume, particle morphology, and organic volume fraction. The data show that
kinetic limitations do not change the critical supersaturation of 50 nm
ammonium sulfate cores coated with polyethylene and polyethylene volume
fractions up to 97 %. Based on these results, and a synthesis of
literature data, it is suggested that mass transfer limitations by glassy
organic shells are unlikely to affect cloud droplet activation near
laboratory temperatures.
                    }, number={5}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Tandon, Ankit and Rothfuss, Nicholas E. and Petters, Markus D.}, year={2019}, month={Mar}, pages={3325–3339} }
 @article{duan_petters_barros_2019, title={Understanding aerosol-cloud interactions through modeling the development of orographic cumulus congestus during IPHEx}, volume={19}, ISSN={["1680-7324"]}, DOI={10.5194/acp-19-1413-2019}, abstractNote={Abstract. A new cloud parcel model (CPM) including activation,
condensation, collision–coalescence, and lateral entrainment processes is
used to investigate aerosol–cloud interactions (ACIs) in cumulus development
prior to rainfall onset. The CPM was applied with surface aerosol
measurements to predict the vertical structure of cloud development at early
stages, and the model results were evaluated against airborne observations of
cloud microphysics and thermodynamic conditions collected during the
Integrated Precipitation and Hydrology Experiment (IPHEx) in the inner region
of the southern Appalachian Mountains (SAM). Sensitivity analysis was
conducted to examine the model response to variations in key ACI
physiochemical parameters and initial conditions. The CPM sensitivities
mirror those found in parcel models without entrainment and
collision–coalescence, except for the evolution of the droplet spectrum and
liquid water content with height. Simulated cloud droplet number
concentrations (CDNCs) exhibit high sensitivity to variations in the initial
aerosol concentration at cloud base, but weak sensitivity to bulk aerosol
hygroscopicity. The condensation coefficient ac plays a governing
role in determining the evolution of CDNC, liquid water content (LWC), and
cloud droplet spectra (CDS) in time and with height. Lower values of
ac lead to higher CDNCs and broader CDS above cloud base, and
higher maximum supersaturation near cloud base. Analysis of model simulations
reveals that competitive interference among turbulent dispersion, activation,
and droplet growth processes modulates spectral width and explains the
emergence of bimodal CDS and CDNC heterogeneity in aircraft measurements from
different cloud regions and at different heights. Parameterization of
nonlinear interactions among entrainment, condensational growth, and
collision–coalescence processes is therefore necessary to simulate the
vertical structures of CDNCs and CDSs in convective clouds. Comparisons of
model predictions with data suggest that the representation of lateral
entrainment remains challenging due to the spatial heterogeneity of the
convective boundary layer and the intricate 3-D circulations in mountainous
regions.
                    }, number={3}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Duan, Yajuan and Petters, Markus D. and Barros, Ana P.}, year={2019}, month={Feb}, pages={1413–1437} }
 @article{champion_rothfuss_petters_grieshop_2019, title={Volatility and Viscosity Are Correlated in Terpene Secondary Organic Aerosol Formed in a Flow Reactor}, volume={6}, ISSN={["2328-8930"]}, url={https://doi.org/10.1021/acs.estlett.9b00412}, DOI={10.1021/acs.estlett.9b00412}, abstractNote={Secondary organic aerosol (SOA) is a complex mixture of largely unspeciated compounds. The volatility and viscosity of the bulk organic aerosol influence new particle formation, processing, and lifetime in the atmosphere. Relationships between these properties are well-defined for pure compounds but currently unavailable for bulk organic aerosol. In this survey study, we characterized SOA formed from a range of biogenic precursors and conditions in an oxidation flow reactor for volatility (thermodenuder), viscosity (dimer coagulation, isolation, and coalescence), and oxidation state (aerosol chemical speciation monitor). We find linear trends in log–linear and log–log plots of single-parameter representations of volatility and viscosity, with higher condensed-phase fractions of extremely low and low volatility material associated with an increased viscosity (R = 0.69). Per this relationship, an increase in the contribution of these fractions (i.e., lower volatility) by 0.1 results in an increase in viscos...}, number={9}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS}, publisher={American Chemical Society (ACS)}, author={Champion, Wyatt M. and Rothfuss, Nicholas E. and Petters, Markus D. and Grieshop, Andrew P.}, year={2019}, month={Sep}, pages={513–519} }
 @article{petters_2018, title={A language to simplify computation of differential mobility analyzer response functions}, volume={52}, ISSN={["1521-7388"]}, DOI={10.1080/02786826.2018.1530724}, abstractNote={Abstract A language for computation of differential mobility analyzer (DMA) response functions is introduced. The language consists of short programming language expressions that evaluate to the size distribution of particles exiting a DMA. The language permits application of the same framework to single and tandem DMA setups. Expressions are derived for calculation of the convolution matrix used in inversion of size distribution data, calculation of the convolution matrix for transit through tandem DMA systems, and calculation of the size and mobility distribution through DMA systems that involve one or multiple DMAs. The contribution of multiply charged particles to the total response distributions can be explicitly resolved. The derived convolution matrix is suitable for inverting scanning mobility particle sizer response functions using standard regularization techniques. Users can modify and substitute any of the convolution terms—comprising the DMA transfer function, detector efficiency, loss rate, and charging efficiencies—to express response functions of nonstandard DMA configurations. Example applications are presented, including classification of particle size, measurement of size-resolved cloud condensation nuclei activity, characterization of hygroscopicity and volatility tandem DMA response functions, and characterization of the dual tandem DMA system for dimer preparation. The source code and examples are shared as free software and are hosted on an online collaborative software development platform that allows for version tracking and crediting contributors. Adoption of the language may facilitate the design and optimization of custom-built systems that involve unique arrangements of DMAs and detectors. Copyright © 2018 The Author(s). Published with license by Taylor & Francis Group, LLC.}, number={12}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Petters, Markus D.}, year={2018}, month={Dec}, pages={1437–1451} }
 @article{marsh_petters_rothfuss_rovelli_song_reid_petters_2018, title={Amorphous phase state diagrams and viscosity of ternary aqueous organic/organic and inorganic/organic mixtures}, volume={20}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/C8CP00760H}, DOI={10.1039/C8CP00760H}, abstractNote={A Dimer Coagulation, Isolation and Coalescence (DCIC) technique is used to probe the phase behaviour and glass transition temperatures of ternary aerosol mixtures.}, number={22}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Marsh, Aleksandra and Petters, Sarah Suda and Rothfuss, Nicholas Ernest and Rovelli, Grazia and Song, Young Chul and Reid, Jonathan Philip and Petters, Markus Dirk}, year={2018}, pages={15086–15097} }
 @article{rothfuss_marsh_rovelli_petters_reid_2018, title={Condensation Kinetics of Water on Amorphous Aerosol Particles}, volume={9}, ISSN={["1948-7185"]}, DOI={10.1021/acs.jpclett.8b01365}, abstractNote={Responding to changes in the surrounding environment, aerosol particles can grow by water condensation changing rapidly in composition and changing dramatically in viscosity. The timescale for growth is important to establish for particles undergoing hydration processes in the atmosphere or during inhalation. Using an electrodynamic balance, we report direct measurements at -7.5, 0, and 20 °C of timescales for hygroscopic condensational growth on a range of model hygroscopic aerosol systems. These extend from viscous aerosol particles containing a single saccharide solute (sucrose, glucose, raffinose, or trehalose) and a starting viscosity equivalent to a glass of ∼1012 Pa·s, to nonviscous (∼10-2 Pa·s) tetraethylene glycol particles. The condensation timescales observed in this work indicate that water condensation occurs rapidly at all temperatures examined (<10 s) and for particles of all initial viscosities spanning 10-2 to 1012 Pa·s. Only a marginal delay (<1 order of magnitude) is observed for particles starting as a glass.}, number={13}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Rothfuss, Nicholas E. and Marsh, Aleksandra and Rovelli, Grazia and Petters, Markus D. and Reid, Jonathan P.}, year={2018}, month={Jul}, pages={3708–3713} }
 @article{meskhidze_royalty_phillips_dawson_petters_reed_weinstein_hook_wiener_2018, title={Continuous flow hygroscopicity-resolved relaxed eddy accumulation (Hy-Res REA) method of measuring size-resolved sodium chloride particle fluxes}, volume={52}, ISSN={["1521-7388"]}, DOI={10.1080/02786826.2017.1423174}, abstractNote={ABSTRACT The accurate representation of aerosols in climate models requires direct ambient measurement of the size- and composition-dependent particle production fluxes. Here, we present the design, testing, and analysis of data collected through the first instrument capable of measuring hygroscopicity-based, size-resolved particle fluxes using a continuous-flow Hygroscopicity-Resolved Relaxed Eddy Accumulation (Hy-Res REA) technique. The Hy-Res REA system used in this study includes a 3D sonic anemometer, two fast-response solenoid valves, two condensation particle counters, a scanning mobility particle sizer, and a hygroscopicity tandem differential mobility analyzer. The different components of the instrument were tested inside the US Environmental Protection Agency's Aerosol Test Facility for sodium chloride and ammonium sulfate particle fluxes. The new REA system design does not require particle accumulation, and therefore avoids the diffusional wall losses associated with long residence times of particles inside the air collectors of traditional REA devices. A linear relationship was found between the sodium chloride particle fluxes measured by eddy covariance and REA techniques. The particle detection limit of the Hy-Res REA flux system is estimated to be ∼3 × 105 m−2 s−1. The estimated sodium chloride particle classification limit, for the mixture of sodium chloride and ammonium sulfate particles of comparable concentrations, is ∼6 × 106 m−2 s−1. Copyright © 2018 American Association for Aerosol Research}, number={4}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Meskhidze, N. and Royalty, T. M. and Phillips, B. N. and Dawson, K. W. and Petters, M. D. and Reed, R. and Weinstein, J. P. and Hook, D. A. and Wiener, R. W.}, year={2018}, pages={433–450} }
 @article{phillips_royalty_dawson_reed_petters_meskhidze_2018, title={Hygroscopicity‐ and Size‐Resolved Measurements of Submicron Aerosol on the East Coast of the United States}, volume={123}, ISSN={2169-897X 2169-8996}, url={http://dx.doi.org/10.1002/2017JD027702}, DOI={10.1002/2017JD027702}, abstractNote={Abstract}, number={3}, journal={Journal of Geophysical Research: Atmospheres}, publisher={American Geophysical Union (AGU)}, author={Phillips, B. N. and Royalty, T. M. and Dawson, K. W. and Reed, R. and Petters, M. D. and Meskhidze, N.}, year={2018}, month={Feb}, pages={1826–1839} }
 @article{demott_moehler_cziczo_hiranuma_petters_petters_belosi_bingemer_brooks_budke_et al._2018, title={The Fifth International Workshop on Ice Nucleation phase 2 (FIN-02): laboratory intercomparison of ice nucleation measurements}, volume={11}, ISSN={["1867-8548"]}, DOI={10.5194/amt-11-6231-2018}, abstractNote={Abstract. The second phase of the Fifth International Ice Nucleation Workshop (FIN-02)
involved the gathering of a large number of researchers at the Karlsruhe
Institute of Technology's Aerosol Interactions and Dynamics of the Atmosphere
(AIDA) facility to promote characterization and understanding of ice
nucleation measurements made by a variety of methods used worldwide.
Compared to the previous workshop in 2007, participation was doubled,
reflecting a vibrant research area. Experimental methods involved sampling of
aerosol particles by direct processing ice nucleation measuring systems from
the same volume of air in separate experiments using different ice nucleating
particle (INP) types, and collections of aerosol particle samples onto
filters or into liquid for sharing amongst measurement techniques that
post-process these samples. In this manner, any errors introduced by
differences in generation methods when samples are shared across laboratories
were mitigated. Furthermore, as much as possible, aerosol particle size
distribution was controlled so that the size limitations of different methods
were minimized. The results presented here use data from the workshop to
assess the comparability of immersion freezing measurement methods activating
INPs in bulk suspensions, methods that activate INPs in condensation and/or
immersion freezing modes as single particles on a substrate, continuous flow
diffusion chambers (CFDCs) directly sampling and processing particles well
above water saturation to maximize immersion and subsequent freezing of
aerosol particles, and expansion cloud chamber simulations in which liquid
cloud droplets were first activated on aerosol particles prior to freezing.
The AIDA expansion chamber measurements are expected to be the closest
representation to INP activation in atmospheric cloud parcels in these
comparisons, due to exposing particles freely to adiabatic cooling. The different particle types used as INPs included the minerals illite NX and
potassium feldspar (K-feldspar), two natural soil dusts representative of arable sandy loam
(Argentina) and highly erodible sandy dryland (Tunisia) soils, respectively,
and a bacterial INP (Snomax®). Considered
together, the agreement among post-processed immersion freezing measurements
of the numbers and fractions of particles active at different temperatures
following bulk collection of particles into liquid was excellent, with
possible temperature uncertainties inferred to be a key factor in determining
INP uncertainties. Collection onto filters for rinsing versus directly into
liquid in impingers made little difference. For methods that activated
collected single particles on a substrate at a controlled humidity at or
above water saturation, agreement with immersion freezing methods was good in
most cases, but was biased low in a few others for reasons that have not been
resolved, but could relate to water vapor competition effects. Amongst
CFDC-style instruments, various factors requiring (variable) higher
supersaturations to achieve equivalent immersion freezing activation dominate
the uncertainty between these measurements, and for comparison with bulk
immersion freezing methods. When operated above water saturation to include
assessment of immersion freezing, CFDC measurements often measured at or
above the upper bound of immersion freezing device measurements, but often
underestimated INP concentration in comparison to an immersion freezing
method that first activates all particles into liquid droplets prior to
cooling (the PIMCA-PINC device, or Portable Immersion Mode Cooling chAmber–Portable Ice Nucleation Chamber), and typically slightly underestimated INP
number concentrations in comparison to cloud parcel expansions in the AIDA
chamber; this can be largely mitigated when it is possible to raise the
relative humidity to sufficiently high values in the CFDCs, although this is
not always possible operationally. Correspondence of measurements of INPs among direct sampling and
post-processing systems varied depending on the INP type. Agreement was best
for Snomax® particles in the temperature regime
colder than −10 ∘C, where their ice nucleation activity is nearly
maximized and changes very little with temperature. At temperatures warmer than
−10 ∘C, Snomax® INP measurements (all
via freezing of suspensions) demonstrated discrepancies consistent with
previous reports of the instability of its protein aggregates that appear to
make it less suitable as a calibration INP at these temperatures. For
Argentinian soil dust particles, there was excellent agreement across all
measurement methods; measures ranged within 1 order of magnitude for INP
number concentrations, active fractions and calculated active site densities
over a 25 to 30 ∘C range and 5 to 8 orders of corresponding
magnitude change in number concentrations. This was also the case for all
temperatures warmer than −25 ∘C in Tunisian dust experiments. In
contrast, discrepancies in measurements of INP concentrations or active site
densities that exceeded 2 orders of magnitude across a broad range of temperature
measurements found at temperatures warmer than −25 ∘C in a previous study were
replicated for illite NX. Discrepancies also exceeded 2 orders of magnitude at
temperatures of −20 to −25 ∘C for potassium feldspar (K-feldspar), but these coincided
with the range of temperatures at which INP concentrations increase rapidly at
approximately an order of magnitude per 2 ∘C cooling for
K-feldspar. These few discrepancies did not outweigh the overall positive outcomes of the
workshop activity, nor the future utility of this data set or future similar
efforts for resolving remaining measurement issues. Measurements of the same
materials were repeatable over the time of the workshop and demonstrated
strong consistency with prior studies, as reflected by agreement of data
broadly with parameterizations of different specific or general (e.g., soil
dust) aerosol types. The divergent measurements of the INP activity of illite
NX by direct versus post-processing methods were not repeated for other
particle types, and the Snomax® data
demonstrated that, at least for a biological INP type, there is no expected
measurement bias between bulk collection and direct immediately processed
freezing methods to as warm as −10 ∘C. Since particle size ranges
were limited for this workshop, it can be expected that for atmospheric
populations of INPs, measurement discrepancies will appear due to the
different capabilities of methods for sampling the full aerosol size
distribution, or due to limitations on achieving sufficient water
supersaturations to fully capture immersion freezing in direct processing
instruments. Overall, this workshop presents an improved picture of present
capabilities for measuring INPs than in past workshops, and provides
direction toward addressing remaining measurement issues.
                    }, number={11}, journal={ATMOSPHERIC MEASUREMENT TECHNIQUES}, author={DeMott, Paul J. and Moehler, Ottmar and Cziczo, Daniel J. and Hiranuma, Naruki and Petters, Markus D. and Petters, Sarah S. and Belosi, Franco and Bingemer, Heinz G. and Brooks, Sarah D. and Budke, Carsten and et al.}, year={2018}, month={Nov}, pages={6231–6257} }
 @article{reid_bertram_topping_laskin_martin_petters_pope_rovelli_2018, title={The viscosity of atmospherically relevant organic particles}, volume={9}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/S41467-018-03027-Z}, DOI={10.1038/S41467-018-03027-Z}, abstractNote={Abstract}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Reid, Jonathan P. and Bertram, Allan K. and Topping, David O. and Laskin, Alexander and Martin, Scot T. and Petters, Markus D. and Pope, Francis D. and Rovelli, Grazia}, year={2018}, month={Mar} }
 @misc{reid_bertram_topping_laskin_martin_petters_pope_rovelli_2018, title={The viscosity of atmospherically relevant organic particles}, volume={9}, journal={Nature Communications}, author={Reid, J. P. and Bertram, A. K. and Topping, D. O. and Laskin, A. and Martin, S. T. and Petters, M. D. and Pope, F. D. and Rovelli, G.}, year={2018} }
 @article{royalty_phillips_dawson_reed_meskhidze_petters_2017, title={Aerosol Properties Observed in the Subtropical North Pacific Boundary Layer}, volume={122}, ISSN={["2169-8996"]}, DOI={10.1002/2017jd026897}, abstractNote={Abstract}, number={18}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Royalty, T. M. and Phillips, B. N. and Dawson, K. W. and Reed, R. and Meskhidze, N. and Petters, M. D.}, year={2017}, month={Sep}, pages={9990–10012} }
 @article{rothfuss_petters_2017, title={Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols}, volume={19}, ISSN={["1463-9084"]}, DOI={10.1039/c6cp08593h}, abstractNote={The amorphous phase state diagram for sucrose aerosol is obtained from a mix of measurements and model calculations.}, number={9}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Rothfuss, Nicholas E. and Petters, Markus D.}, year={2017}, month={Mar}, pages={6532–6545} }
 @article{demott_hill_petters_bertram_tobo_mason_suski_mccluskey_levin_schill_et al._2017, title={Comparative measurements of ambient atmospheric concentrations of ice nucleating particles using multiple immersion freezing methods and a continuous flow diffusion chamber}, volume={17}, number={18}, journal={Atmospheric Chemistry and Physics}, author={DeMott, P. J. and Hill, T. C. J. and Petters, M. D. and Bertram, A. K. and Tobo, Y. and Mason, R. H. and Suski, K. J. and McCluskey, C. S. and Levin, E. J. T. and Schill, G. P. and et al.}, year={2017}, pages={11227–11245} }
 @article{petters_pagonis_claflin_levin_petters_ziemann_kreidenweis_2017, title={Hygroscopicity of Organic Compounds as a Function of Carbon Chain Length and Carboxyl, Hydroperoxy, and Carbonyl Functional Groups}, volume={121}, ISSN={["1520-5215"]}, DOI={10.1021/acs.jpca.7b04114}, abstractNote={The albedo and microphysical properties of clouds are controlled in part by the hygroscopicity of particles serving as cloud condensation nuclei (CCN). Hygroscopicity of complex organic mixtures in the atmosphere varies widely and remains challenging to predict. Here we present new measurements characterizing the CCN activity of pure compounds in which carbon chain length and the numbers of hydroperoxy, carboxyl, and carbonyl functional groups were systematically varied to establish the contributions of these groups to organic aerosol apparent hygroscopicity. Apparent hygroscopicity decreased with carbon chain length and increased with polar functional groups in the order carboxyl > hydroperoxy > carbonyl. Activation diameters at different supersaturations deviated from the -3/2 slope in log-log space predicted by Köhler theory, suggesting that water solubility limits CCN activity of particles composed of weakly functionalized organic compounds. Results are compared to a functional group contribution model that predicts CCN activity of organic compounds. The model performed well for most compounds but underpredicted the CCN activity of hydroperoxy groups. New best-fit hydroperoxy group/water interaction parameters were derived from the available CCN data. These results may help improve estimates of the CCN activity of ambient organic aerosols from composition data.}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Petters, Sarah Suda and Pagonis, Demetrios and Claflin, Megan S. and Levin, Ezra J. T. and Petters, Markus D. and Ziemann, Paul J. and Kreidenweis, Sonia M.}, year={2017}, month={Jul}, pages={5164–5174} }
 @article{rothfuss_petters_2017, title={Influence of Functional Groups on the Viscosity of Organic Aerosol}, volume={51}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.6b04478}, abstractNote={Organic aerosols can exist in highly viscous or glassy phase states. A viscosity database for organic compounds with atmospherically relevant functional groups is compiled and analyzed to quantify the influence of number and location of functional groups on viscosity. For weakly functionalized compounds the trend in viscosity sensitivity to functional group addition is carboxylic acid (COOH) ≈ hydroxyl (OH) > nitrate (ONO2) > carbonyl (CO) ≈ ester (COO) > methylene (CH2). Sensitivities to group addition increase with greater levels of prior functionalization and decreasing temperature. For carboxylic acids a sharp increase in sensitivity is likely present already at the second addition at room temperature. Ring structures increase viscosity relative to linear structures. Sensitivities are correlated with analogously derived sensitivities of vapor pressure reduction. This may be exploited in the future to predict viscosity in numerical models by piggybacking on schemes that track the evolution of organic aerosol volatility with age.}, number={1}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Rothfuss, Nicholas E. and Petters, Markus D.}, year={2017}, month={Jan}, pages={271–279} }
 @article{martin_cornwell_atwood_moore_rothfuss_taylor_demott_kreidenweis_petters_prather_2017, title={Transport of pollution to a remote coastal site during gap flow from California's interior: impacts on aerosol composition, clouds, and radiative balance}, volume={17}, number={2}, journal={Atmospheric Chemistry and Physics}, author={Martin, A. C. and Cornwell, G. C. and Atwood, S. A. and Moore, K. A. and Rothfuss, N. E. and Taylor, H. and DeMott, P. J. and Kreidenweis, S. M. and Petters, M. D. and Prather, K. A.}, year={2017}, pages={1491–1509} }
 @article{rothfuss_petters_2016, title={Coalescence-based assessment of aerosol phase state using dimers prepared through a dual-differential mobility analyzer technique}, volume={50}, ISSN={0278-6826 1521-7388}, url={http://dx.doi.org/10.1080/02786826.2016.1221050}, DOI={10.1080/02786826.2016.1221050}, abstractNote={ABSTRACT Viscosity of atmospheric aerosol spans at least 15 orders of magnitude, from thin liquids to glassy solids, with possible concomitant impact on multiple processes of meteorological and/or climatological concern. Recently there has been interest in aerosol phase assessment techniques based upon dimer coalescence. Theoretical treatment suggests discernible reductions in dimer diameter begin when viscosity ∼108 Pa·s and the dimer is spherical at ∼105 Pa·s for submicron particles, or the middle range of the semisolid regime. A method using nanoparticle dimers synthesized by utilizing differential mobility analyzers of opposite polarity to produce monomers of opposite charge that subsequently undergo electrostatically mediated coagulation has been developed and is detailed in this work. This method was used to assess the aerosol phase state of several atmospherically relevant organic species and inorganic salts at relative humidity (RH) values ranging between 10% and 100%. Ammonium sulfate, monosodium α-ketoglutaric acid, sodium chloride, and sucrose all displayed RH-dependent phase state. These observed viscous transitions occurred at RH values less than existing deliquescence RH data, a result consistent with existing literature reports of RH-induced structural rearrangements. Fully coalesced and fully uncoalesced diameters could be fitted to single values, indicating that the presented technique is absolute. The method was also used to assess the phase state of dry sucrose aerosol at temperatures between 20°C and 70°C. A phase transition was noted at 63.7°C ± 4.4°C, near the glass transition temperature, suggesting the presented method may also be useful for probing phase responses to temperature perturbations. Copyright © 2016 American Association for Aerosol Research}, number={12}, journal={Aerosol Science and Technology}, publisher={Informa UK Limited}, author={Rothfuss, Nicholas E. and Petters, Markus D.}, year={2016}, month={Aug}, pages={1294–1305} }
 @article{dawson_petters_meskhidze_petters_kreidenweis_2016, title={Hygroscopic growth and cloud droplet activation of xanthan gum as a proxy for marine hydrogels}, volume={121}, ISSN={["2169-8996"]}, DOI={10.1002/2016jd025143}, abstractNote={Abstract}, number={19}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Dawson, K. W. and Petters, M. D. and Meskhidze, N. and Petters, S. Suda and Kreidenweis, S. M.}, year={2016}, month={Oct}, pages={11803–11818} }
 @article{piens_kelly_harder_petters_rachel e. o'brien_wang_teske_dowell_laskin_gilles_2016, title={Measuring Mass-Based Hygroscopicity of Atmospheric Particles through in Situ Imaging}, volume={50}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.6b00793}, abstractNote={Quantifying how atmospheric particles interact with water vapor is critical for understanding the effects of aerosols on climate. We present a novel method to measure the mass-based hygroscopicity of particles while characterizing their elemental and carbon functional group compositions. Since mass-based hygroscopicity is insensitive to particle geometry, it is advantageous for probing the hygroscopic behavior of atmospheric particles, which can have irregular morphologies. Combining scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), scanning transmission X-ray microscopy (STXM) analysis, and in situ STXM humidification experiments, this method was validated using laboratory-generated, atmospherically relevant particles. Then, the hygroscopicity and elemental composition of 15 complex atmospheric particles were analyzed by leveraging quantification of C, N, and O from STXM, and complementary elemental quantification from SEM/EDX. We found three types of hygroscopic responses, and correlated high hygroscopicity with Na and Cl content. The mixing state of 158 other particles from the sample broadly agreed with those of the humidified particles, indicating the potential to infer atmospheric hygroscopic behavior from a selected subset of particles. These methods offer unique quantitative capabilities to characterize and correlate the hygroscopicity and chemistry of individual submicrometer atmospheric particles.}, number={10}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Piens, Dominique S. and Kelly, Stephen T. and Harder, Tristan H. and Petters, Markus D. and Rachel E. O'Brien and Wang, Bingbing and Teske, Ken and Dowell, Pat and Laskin, Alexander and Gilles, Mary K.}, year={2016}, month={May}, pages={5172–5180} }
 @article{petters_kreidenweis_ziemann_2016, title={Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods}, volume={9}, number={1}, journal={Geoscientific Model Development}, author={Petters, M. D. and Kreidenweis, S. M. and Ziemann, P. J.}, year={2016}, pages={111–124} }
 @article{petters_petters_2016, title={Surfactant effect on cloud condensation nuclei for two-component internally mixed aerosols}, volume={121}, ISSN={["2169-8996"]}, DOI={10.1002/2015jd024090}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Petters, Sarah Suda and Petters, Markus Dirk}, year={2016}, month={Feb}, pages={1878–1895} }
 @article{wright_song_sears_petters_2016, title={Thermodynamic and kinetic behavior of glycerol aerosol}, volume={50}, ISSN={0278-6826 1521-7388}, url={http://dx.doi.org/10.1080/02786826.2016.1245405}, DOI={10.1080/02786826.2016.1245405}, abstractNote={ABSTRACT Glycerol and propylene glycol mixtures are common carrier solutions in electronic cigarettes. Aerosols produced from these mixtures will evaporate quickly in a dry environment due to their high volatility. In a humid environment, such as the lungs, the kinetics of evaporation and hygroscopic growth determine the evolution of aerosol plume glycerol. Here, we apply a temperature and relative humidity-controlled hygroscopicity/volatility tandem differential mobility analyzer system to study the growth and evaporation kinetics of glycerol aerosol over a wide range of temperature, relative humidity, and residence times. Results show that at dry conditions glycerol aerosols evaporate within seconds at temperatures warmer than 20°C and that the accommodation coefficient of glycerol vapor on dry glycerol particles is 0.8. Under humidified conditions, the mutual depression of vapor pressures of the aqueous glycerol/water solution slows the glycerol evaporation rate consistent with thermodynamic and kinetic model predictions. Model calculations show that water vapor aided condensation of glycerol can occur at high relative humidity for glycerol vapor concentrations that result in glycerol particle evaporation under dry conditions. The combined results will help with constraining computational modules that model the evolution of glycerol-containing aerosols along a prescribed thermodynamic trajectory. Copyright © 2016 American Association for Aerosol Research}, number={12}, journal={Aerosol Science and Technology}, publisher={Informa UK Limited}, author={Wright, Timothy P. and Song, Chen and Sears, Stephen and Petters, Markus D.}, year={2016}, month={Oct}, pages={1385–1396} }
 @article{hiranuma_augustin-bauditz_bingemer_budke_curtius_danielczok_diehl_dreischmeier_ebert_frank_et al._2015, title={A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: A comparison of 17 ice nucleation measurement techniques}, volume={15}, number={5}, journal={Atmospheric Chemistry and Physics}, author={Hiranuma, N. and Augustin-Bauditz, S. and Bingemer, H. and Budke, C. and Curtius, J. and Danielczok, A. and Diehl, K. and Dreischmeier, K. and Ebert, M. and Frank, F. and et al.}, year={2015}, pages={2489–2518} }
 @article{demott_prenni_mcmeeking_sullivan_petters_tobo_niemand_mohler_snider_wang_et al._2015, title={Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles}, volume={15}, number={1}, journal={Atmospheric Chemistry and Physics}, author={DeMott, P. J. and Prenni, A. J. and McMeeking, G. R. and Sullivan, R. C. and Petters, M. D. and Tobo, Y. and Niemand, M. and Mohler, O. and Snider, J. R. and Wang, Z. and et al.}, year={2015}, pages={393–409} }
 @article{petters_wright_2015, title={Revisiting ice nucleation from precipitation samples}, volume={42}, ISSN={["1944-8007"]}, DOI={10.1002/2015gl065733}, abstractNote={An emerging and unsolved question is the sensitivity of cloud processes, precipitation, and climate to the atmospheric ice nucleus spectrum. This work revisits estimation of atmospheric ice‐nucleating particle concentration derived from cloud water and precipitation samples representing a wide range of geographical locations, seasons, storm systems, precipitation types, instruments, concentrations, and temperatures. Concentrations of ice‐nucleating particles are shown to vary over 10 orders of magnitude. High variability is observed in the −5°C to −12°C range which is suggested to be biologically derived nuclei whose life cycle is associated with intermittent source and efficient sink processes. The highest ever observed nucleus concentrations at −8°C are 3 orders of magnitude lower than observed ice crystal concentrations in tropical cumuli at the same temperature. The observed upper and lower limits of the nucleus spectrum provide a possible constraint on minimum enhancement factors for secondary ice formation processes.}, number={20}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Petters, M. D. and Wright, T. P.}, year={2015}, month={Oct}, pages={8758–8766} }
 @article{eidhammer_barth_petters_wiedinmyer_prenni_2014, title={Aerosol microphysical impact on summertime convective precipitation in the Rocky Mountain region}, volume={119}, ISSN={["2169-8996"]}, DOI={10.1002/2014jd021883}, abstractNote={We present an aerosol‐cloud‐precipitation modeling study of convective clouds using the Weather Research and Forecasting model fully coupled with Chemistry (WRF‐Chem) version 3.1.1. Comparison of the model output with measurements from a research site in the Rocky Mountains in Colorado revealed that the fraction of organics in the model is underpredicted. This is most likely due to missing processes in the aerosol module in the model version used, such as new particle formation and growth of secondary organic aerosols. When boundary conditions and domain‐wide initial conditions of aerosol loading are changed in the model (factors of 0.1, 0.2, and 10 of initial aerosol mass of SO4−2, NH4+, and NO3−), the domain‐wide precipitation changes by about 5%. Analysis of the model results reveals that the Rocky Mountain region and Front Range environment is not conducive for convective invigoration to play a major role, in increasing precipitation, as seen in some other studies. When localized organic aerosol emission are increased to mimic new particle formation, the resulting increased aerosol loading leads to increases in domain‐wide precipitation, opposite to what is seen in the model simulations with changed boundary and initial conditions.}, number={20}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Eidhammer, Trude and Barth, Mary C. and Petters, Markus D. and Wiedinmyer, Christine and Prenni, Anthony J.}, year={2014}, month={Oct}, pages={11709–11728} }
 @article{hader_wright_petters_2014, title={Contribution of pollen to atmospheric ice nuclei concentrations}, volume={14}, number={11}, journal={Atmospheric Chemistry and Physics}, author={Hader, J. D. and Wright, T. P. and Petters, M. D.}, year={2014}, pages={5433–5449} }
 @article{nakao_suda_camp_petters_kreidenweis_2014, title={Droplet activation of wet particles: development of the Wet CCN approach}, volume={7}, number={7}, journal={Atmospheric Measurement Techniques}, author={Nakao, S. and Suda, S. R. and Camp, M. and Petters, M. D. and Kreidenweis, S. M.}, year={2014}, pages={2227–2241} }
 @article{wright_hader_mcmeeking_petters_2014, title={High Relative Humidity as a Trigger for Widespread Release of Ice Nuclei}, volume={48}, ISSN={0278-6826 1521-7388}, url={http://dx.doi.org/10.1080/02786826.2014.968244}, DOI={10.1080/02786826.2014.968244}, abstractNote={Copyright 2014 American Association for Aerosol Research}, number={11}, journal={Aerosol Science and Technology}, publisher={Informa UK Limited}, author={Wright, Timothy P. and Hader, John D. and McMeeking, Gavin R. and Petters, Markus D.}, year={2014}, month={Oct}, pages={i-v} }
 @misc{wright_hader_mcmeeking_petters_2014, title={High relative humidity as a trigger for widespread release of ice nuclei}, volume={48}, number={11}, journal={Aerosol Science and Technology}, author={Wright, T. P. and Hader, J. D. and McMeeking, G. R. and Petters, M. D.}, year={2014} }
 @article{suda_petters_yeh_strollo_matsunaga_faulhaber_ziemann_prenni_carrico_sullivan_et al._2014, title={Influence of Functional Groups on Organic Aerosol Cloud Condensation Nucleus Activity}, volume={48}, ISSN={["1520-5851"]}, DOI={10.1021/es502147y}, abstractNote={Organic aerosols in the atmosphere are composed of a wide variety of species, reflecting the multitude of sources and growth processes of these particles. Especially challenging is predicting how these particles act as cloud condensation nuclei (CCN). Previous studies have characterized the CCN efficiency for organic compounds in terms of a hygroscopicity parameter, κ. Here we extend these studies by systematically testing the influence of the number and location of molecular functional groups on the hygroscopicity of organic aerosols. Organic compounds synthesized via gas-phase and liquid-phase reactions were characterized by high-performance liquid chromatography coupled with scanning flow CCN analysis and thermal desorption particle beam mass spectrometry. These experiments quantified changes in κ with the addition of one or more functional groups to otherwise similar molecules. The increase in κ per group decreased in the following order: hydroxyl ≫ carboxyl > hydroperoxide > nitrate ≫ methylene (where nitrate and methylene produced negative effects, and hydroperoxide and nitrate groups produced the smallest absolute effects). Our results contribute to a mechanistic understanding of chemical aging and will help guide input and parametrization choices in models relying on simplified treatments such as the atomic oxygen:carbon ratio to predict the evolution of organic aerosol hygroscopicity.}, number={17}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Suda, Sarah R. and Petters, Markus D. and Yeh, Geoffrey K. and Strollo, Christen and Matsunaga, Aiko and Faulhaber, Annelise and Ziemann, Paul J. and Prenni, Anthony J. and Carrico, Christian M. and Sullivan, Ryan C. and et al.}, year={2014}, month={Sep}, pages={10182–10190} }
 @article{nguyen_petters_suda_guo_weber_carlton_2014, title={Trends in particle-phase liquid water during the Southern Oxidant and Aerosol Study}, volume={14}, number={20}, journal={Atmospheric Chemistry and Physics}, author={Nguyen, T. K. V. and Petters, M. D. and Suda, S. R. and Guo, H. and Weber, R. J. and Carlton, A. G.}, year={2014}, pages={10911–10930} }
 @article{petters_kreidenweis_2013, title={A single parameter representation of hygroscopic growth and cloud condensation nucleus activity - Part 3: Including surfactant partitioning}, volume={13}, number={2}, journal={Atmospheric Chemistry and Physics}, author={Petters, M. D. and Kreidenweis, S. M.}, year={2013}, pages={1081–1091} }
 @article{suda_petters_2013, title={Accurate Determination of Aerosol Activity Coefficients at Relative Humidities up to 99% Using the Hygroscopicity Tandem Differential Mobility Analyzer Technique}, volume={47}, ISSN={["1521-7388"]}, DOI={10.1080/02786826.2013.807906}, abstractNote={Aerosol water content plays an important role in aqueous phase reactions, in controlling visibility, and in cloud formation processes. One way to quantify aerosol water content is to measure hygroscopic growth using the hygroscopicity tandem differential mobility analyzer (HTDMA) technique. However, the HTDMA technique becomes less reliable at relative humidity (RH) >90% due to the difficulty of controlling temperature and RH inside the second DMA. For this study, we have designed and implemented a new HTDMA system with improved temperature and RH control. Temperature stability in the second DMA was achieved to ±0.02°C tolerance by implementing active control using thermoelectric heat exchangers and PID control loops. The DMA size resolution was increased by operating high-flow DMA columns at a sheath:sample flow ratio of 15:0.5. This improved size resolution allowed for improving the accuracy of the RH sensors by interspersing ammonium sulfate reference scans at high frequency. We present growth factor data for pure compounds at RH up to 99% and compare the data to theoretical values and to available bulk water activity data. With this HTDMA instrument and method, the osmotic coefficients of spherical, nonvolatile aerosols of known composition between 30 and 200 nm in diameter can be determined within ±20%. We expect that data from this instrument will lead to an improvement of aerosol water content models by contributing to the understanding of aerosol water uptake at high RH. Copyright 2013 American Association for Aerosol Research}, number={9}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Suda, Sarah R. and Petters, Markus D.}, year={2013}, month={Sep}, pages={991–1000} }
 @article{wright_petters_hader_morton_holder_2013, title={Minimal cooling rate dependence of ice nuclei activity in the immersion mode}, volume={118}, ISSN={["2169-8996"]}, DOI={10.1002/jgrd.50810}, abstractNote={Abstract}, number={18}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Wright, Timothy P. and Petters, Markus D. and Hader, John D. and Morton, Travis and Holder, Amara L.}, year={2013}, month={Sep}, pages={10535–10543} }
 @article{meskhidze_petters_tsigaridis_bates_o'dowd_reid_lewis_gantt_anguelova_bhave_et al._2013, title={Production mechanisms, number concentration, size distribution, chemical composition, and optical properties of sea spray aerosols}, volume={14}, ISSN={1530-261X}, url={http://dx.doi.org/10.1002/ASL2.441}, DOI={10.1002/ASL2.441}, abstractNote={Production mechanisms, number concentration, size distribution, chemical composition, and optical properties of sea spray aerosols}, number={4}, journal={Atmospheric Science Letters}, publisher={Wiley}, author={Meskhidze, Nicholas and Petters, Markus D. and Tsigaridis, Kostas and Bates, Tim and O'Dowd, Colin and Reid, Jeff and Lewis, Ernie R. and Gantt, Brett and Anguelova, Magdalena D. and Bhave, Prakash V. and et al.}, year={2013}, month={Jun}, pages={207–213} }
 @article{meskhidze_petters_tsigaridis_bates_o'dowd_reid_lewis_gantt_anguelova_bhave_et al._2013, title={Production mechanisms, number concentration, size distribution, chemical composition, and optical properties of sea spray aerosols}, volume={14}, number={4}, journal={Atmospheric Science Letters}, author={Meskhidze, N. and Petters, M. D. and Tsigaridis, K. and Bates, T. and O'Dowd, C. and Reid, J. and Lewis, E. R. and Gantt, B. and Anguelova, M. D. and Bhave, P. V. and et al.}, year={2013}, pages={207–213} }
 @inproceedings{levin_prenni_palm_day_campuzano-jost_petters_kreidenweis_demott_jimenez_smith_2013, title={The importance of organic aerosol to CCN concentrations and characteristics at a forested site in Colorado}, url={http://dx.doi.org/10.1063/1.4803401}, DOI={10.1063/1.4803401}, abstractNote={We measured size-resolved CCN concentrations over an annual cycle and during a summer intensive study at a remote, forested location in Colorado. From these data we derived aerosol hygroscopicity and size-resolved two-component composition. During the summer intensive, aerosol composition was also measured with an aerosol mass spectrometer, and we use these data to confirm hygroscopicity-derived composition. Throughout the study and at all measured sizes, aerosol composition was predominately organic with resulting low hygroscopicity, κave = 0.16 ± 0.08. New particle formation appeared to be an important source of aerosol number and the newly nucleated particles were inferred to be predominately organic.}, publisher={AIP}, author={Levin, E. J. T. and Prenni, A. J. and Palm, B. and Day, D. and Campuzano-Jost, P. and Petters, M. D. and Kreidenweis, S. M. and DeMott, P. J. and Jimenez, J. and Smith, J. N.}, year={2013} }
 @inproceedings{petters_suda_christensen_2013, title={The role of dynamic surface tension in cloud droplet activation}, volume={1527}, url={http://dx.doi.org/10.1063/1.4803393}, DOI={10.1063/1.4803393}, abstractNote={We present new data on the cloud droplet forming abilities of two-component particles that contain the surfactant sodium dodecyl sulfate and sodium chloride or ammonium sulfate. The experiments were designed to test specific predictions made by Kohler theory that accounts for the reduction of surface tension and the partitioning of the surfactant between the interior and the surface of the droplet. We also introduced a pre-humidification step followed by a six minute time delay to test whether dynamic surface tension may lead to kinetic limitations on the partitioning process. Our results confirm previous studies that show that surfactants do not enhance cloud droplet activation relative to what would be predicted from water activity alone. The data obtained with and without time delay were indistinguishable within measurement uncertainty, suggesting that dynamic surface tension does not need to be considered in Kohler theory.}, publisher={AIP}, author={Petters, Markus D. and Suda, Sarah R. and Christensen, Sara I.}, year={2013}, pages={801–807} }
 @article{wright_petters_2013, title={The role of time in heterogeneous freezing nucleation}, volume={118}, ISSN={["2169-8996"]}, DOI={10.1002/jgrd.50365}, abstractNote={A small fraction of particles in the atmosphere can catalyze ice formation in cloud water drops through heterogeneous freezing nucleation at temperatures warmer than the homogeneous freezing temperature of approximately −38°C. The rate for heterogeneous freezing nucleation is dependent on several factors, including the type and surface area of dust that is immersed inside the drop. Although nucleation is an inherently stochastic process resulting from size fluctuations of the incipient ice germ, there is a growing body of literature that suggests that quasi‐deterministic models of ice nucleation can describe laboratory experiments. Here we present new experiments and simulations that aim to better constrain theoretical models fitted to laboratory data. We collected ice nucleation data for Arizona Test Dust aerosol immersed in water using a droplet freezing assay setup that allows for the cooling rates to be changed between 10 and 0.01 K min−1. Discrete event simulations based on a variant of the multiple‐component stochastic model of heterogeneous freezing nucleation were used to simulate different experimental procedures. The nucleation properties of the dust are specified by four material‐dependent parameters that accurately describe the time dependence of the freezing process. We anticipate that the combination of discrete event simulations and a spectrum of experimental procedures described here can be used to design more meaningful laboratory experiments probing ice nucleation and will aid the development of better parameterizations for use in models.}, number={9}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Wright, Timothy P. and Petters, Markus D.}, year={2013}, month={May}, pages={3731–3743} }
 @article{levin_prenni_petters_kreidenweis_sullivan_atwood_ortega_demott_smith_2012, title={An annual cycle of size-resolved aerosol hygroscopicity at a forested site in Colorado}, volume={117}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2011JD016854}, DOI={10.1029/2011JD016854}, abstractNote={The ability of particles composed wholly or partially of biogenic secondary organic compounds to serve as cloud condensation nuclei (CCN) is a key characteristic that helps to define their roles in linking biogeochemical and water cycles. In this paper, we describe size‐resolved (14–350 nm) CCN measurements from the Manitou Experimental Forest in Colorado, where particle compositions were expected to have a large biogenic component. These measurements were conducted for 1 year as part of the Bio‐hydro‐atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics, and Nitrogen program and determined the aerosol hygroscopicity parameter, κ, at five water supersaturations between ∼0.14% and ∼0.97%. The average κ value over the entire study and all supersaturations was κavg = 0.16 ± 0.08. Kappa values decreased slightly with increasing supersaturation, suggesting a change in aerosol composition with dry diameter. Furthermore, some seasonal variability was observed with increased CCN concentrations and activated particle number fraction, but slightly decreased hygroscopicity, during the summer. Small particle events, which may indicate new particle formation, were observed throughout the study period, especially in the summer, leading to increases in CCN concentration, followed by a gradual increase in the aerosol mode size. The condensing material appeared to be predominantly composed of organic compounds and led to a small decrease in κ at the larger activation diameters during and immediately after those events.}, number={D6}, journal={Journal of Geophysical Research: Atmospheres}, publisher={American Geophysical Union (AGU)}, author={Levin, E. J. T. and Prenni, A. J. and Petters, M. D. and Kreidenweis, S. M. and Sullivan, R. C. and Atwood, S. A. and Ortega, J. and DeMott, P. J. and Smith, J. N.}, year={2012}, month={Mar}, pages={n/a-n/a} }
 @article{suda_petters_matsunaga_sullivan_ziemann_kreidenweis_2012, title={Hygroscopicity frequency distributions of secondary organic aerosols}, volume={117}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2011JD016823}, DOI={10.1029/2011JD016823}, abstractNote={Secondary organic compounds are an important component of ambient aerosol and potentially lower the supersaturation that is required for individual particles to serve as cloud condensation nuclei (CCN). Secondary organic aerosol (SOA) formed from the oxidation of a single precursor can be composed of many different compounds and their overall CCN efficiency has been reported for many different SOA systems. An aerosol's CCN efficiency can be described by a single hygroscopicity parameter, κ. However, this κ comprises an unknown distribution of underlying κ‐values resulting from each individual compound in the SOA mixture. Here we report on a new technique for characterizing this distribution ofκ. Precursor hydrocarbons were oxidized in an environmental chamber to form SOA, which was collected on filters and extracted using ethyl acetate. Extracts were then fractionated by reversed‐phase high‐performance liquid chromatography using gradient elution with acetonitrile and water. The eluate was atomized, the solvent was removed by evaporation, and the residual aerosol particles were analyzed as a function of retention time using scanning flow CCN analysis. Kappa‐values generally decreased with component retention time, consistent with expected decreasing polarity. Averaged SOAκ‐values reconstructed by integrating over the chromatogram agreed well with values measured for SOA sampled directly from the environmental chamber, suggesting thatκfor SOA represents the volume‐weighted average of the constituent compounds'κ‐values. We anticipate that our measured hygroscopicity distributions will serve as validation points for mechanistic models that seek to predict the generation and evolution of organic aerosol composition and properties in the atmosphere.}, number={D4}, journal={Journal of Geophysical Research: Atmospheres}, publisher={American Geophysical Union (AGU)}, author={Suda, S. R. and Petters, M. D. and Matsunaga, A. and Sullivan, R. C. and Ziemann, P. J. and Kreidenweis, S. M.}, year={2012}, month={Feb}, pages={n/a-n/a} }
 @article{christensen_petters_2012, title={The Role of Temperature in Cloud Droplet Activation}, volume={116}, ISSN={["1520-5215"]}, DOI={10.1021/jp3064454}, abstractNote={Aerosols are prevalent in the atmosphere where they can serve as cloud condensation nuclei (CCN). Here we report on new CCN measurements to characterize the temperature dependence of CCN activity for single component organic aerosol and secondary organic aerosol from the reaction of α-pinene and O(3) generated in the laboratory. For compounds with a weak dependence of water activity on temperature, the critical supersaturation of the particles can be well-modeled using temperature-dependent surface tension and Köhler theory. We also demonstrate that Köhler theory is valid for sparingly soluble compounds and can quantitatively explain the temperature-dependent activation properties of adipic acid aerosol over a broad range of temperatures. Accounting for temperature-dependent surface tension strongly affects CCN activity, and we anticipate that including this effect in global and regional model simulations may significantly change the estimated aerosol indirect forcing.}, number={39}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Christensen, S. I. and Petters, M. D.}, year={2012}, month={Oct}, pages={9706–9717} }
 @misc{hoyle_boy_donahue_fry_glasius_guenther_hallar_hartz_petters_petaja_et al._2011, title={A review of the anthropogenic influence on biogenic secondary organic aerosol}, volume={11}, number={1}, journal={Atmospheric Chemistry and Physics}, author={Hoyle, C. R. and Boy, M. and Donahue, N. M. and Fry, J. L. and Glasius, M. and Guenther, A. and Hallar, A. G. and Hartz, K. H. and Petters, M. D. and Petaja, T. and et al.}, year={2011}, pages={321–343} }
 @article{niedermeier_hartmann_clauss_wex_kiselev_sullivan_demott_petters_reitz_schneider_et al._2011, title={Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles}, volume={11}, number={21}, journal={Atmospheric Chemistry and Physics}, author={Niedermeier, D. and Hartmann, S. and Clauss, T. and Wex, H. and Kiselev, A. and Sullivan, R. C. and DeMott, P. J. and Petters, M. D. and Reitz, P. and Schneider, J. and et al.}, year={2011}, pages={11131–11144} }
 @article{niedermeier_hartmann_clauss_wex_kiselev_sullivan_demott_petters_reitz_schneider_et al._2011, title={Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles (vol 11, pg 11131, 2011)}, volume={11}, number={22}, journal={Atmospheric Chemistry and Physics}, author={Niedermeier, D. and Hartmann, S. and Clauss, T. and Wex, H. and Kiselev, A. and Sullivan, R. C. and DeMott, P. J. and Petters, M. D. and Reitz, P. and Schneider, J. and et al.}, year={2011}, pages={11919–11919} }
 @article{mcmeeking_good_petters_mcfiggans_coe_2011, title={Influences on the fraction of hydrophobic and hydrophilic black carbon in the atmosphere}, volume={11}, number={10}, journal={Atmospheric Chemistry and Physics}, author={McMeeking, G. R. and Good, N. and Petters, M. D. and McFiggans, G. and Coe, H.}, year={2011}, pages={5099–5112} }
 @article{demott_mohler_stetzer_vali_levin_petters_murakami_leisner_bundke_klein_et al._2011, title={Resurgence in ice nuclei measurement research}, volume={92}, number={12}, journal={Bulletin of the American Meteorological Society}, author={DeMott, P. J. and Mohler, O. and Stetzer, O. and Vali, G. and Levin, Z. and Petters, M. D. and Murakami, M. and Leisner, T. and Bundke, U. and Klein, H. and et al.}, year={2011}, pages={1623-} }
 @article{reitz_spindler_mentel_poulain_wex_mildenberger_niedermeier_hartmann_clauss_stratmann_et al._2011, title={Surface modification of mineral dust particles by sulphuric acid processing: implications for ice nucleation abilities}, volume={11}, number={15}, journal={Atmospheric Chemistry and Physics}, author={Reitz, P. and Spindler, C. and Mentel, T. F. and Poulain, L. and Wex, H. and Mildenberger, K. and Niedermeier, D. and Hartmann, S. and Clauss, T. and Stratmann, F. and et al.}, year={2011}, pages={7839–7858} }
 @article{martin_andreae_althausen_artaxo_baars_borrmann_chen_farmer_guenther_gunthe_et al._2010, title={An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08)}, volume={10}, number={23}, journal={Atmospheric Chemistry and Physics}, author={Martin, S. T. and Andreae, M. O. and Althausen, D. and Artaxo, P. and Baars, H. and Borrmann, S. and Chen, Q. and Farmer, D. K. and Guenther, A. and Gunthe, S. S. and et al.}, year={2010}, pages={11415–11438} }
 @article{martin_andreae_althausen_artaxo_baars_borrmann_chen_farmer_guenther_gunthe_et al._2010, title={An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08) (vol 10, pg 11415, 2010)}, volume={10}, number={23}, journal={Atmospheric Chemistry and Physics}, author={Martin, S. T. and Andreae, M. O. and Althausen, D. and Artaxo, P. and Baars, H. and Borrmann, S. and Chen, Q. and Farmer, D. K. and Guenther, A. and Gunthe, S. S. and et al.}, year={2010}, pages={11565–11565} }
 @article{sullivan_moore_petters_kreidenweis_qafoku_laskin_roberts_prather_2010, title={Impact of Particle Generation Method on the Apparent Hygroscopicity of Insoluble Mineral Particles}, volume={44}, ISSN={["1521-7388"]}, DOI={10.1080/02786826.2010.497514}, abstractNote={Calcite (CaCO 3 ) mineral particles are commonly generated by atomization techniques to study their heterogeneous chemistry, hygroscopicity, and cloud nucleation properties. Here we investigate the significant artifact introduced in generating calcium mineral particles through the atomization of a saturated suspension of the powder in water, by measuring particle hygroscopicity via CCN activation curves. Particles produced from atomization displayed hygroscopicities as large as κapp > 0.1, 100 times more hygroscopic than that obtained for dry-generated calcite, κapp = 0.0011. The hygroscopicity of the wet-generated particles increased as a function of time the calcite powder spent in water, and with decreasing particle size. Wet-generated calcium oxalate was more hygroscopic through wet- (κapp = 0.34) versus dry-generation (κapp = 0.048). Atomized calcium sulfate particles, however, were only slightly more hygroscopic (κapp = 0.0045) than those generated dry (κapp = 0.0016). Single-particle analysis by ATOFMS and SEM/EDX, and bulk analysis of the calcite powders by ICP-MS and IC revealed no significant soluble contaminants. The atomized particles were likely composed of components that dissolved from the powder and then re-precipitated, and appeared to contain little of the original mineral powder. The increased hygroscopicity of atomized calcite may have been caused by aqueous carbonate chemistry producing Ca(OH) 2 , Ca(HCO 3 ) 2 , and metastable hydrates with increased solubility. Surface water adsorption may have also played a role, in addition to uncharacterized soluble components produced by wet-generation, and the precipitation of amorphous phases including glassy states. This study suggests that using wet-generation methods to suspend mineral dust samples will not produce particles with the correct physicochemical properties in laboratory studies, a finding which has important implications for past and future laboratory studies focusing on understanding relationships between the hygroscopicity and chemistry of mineral dust particles.}, number={10}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Sullivan, Ryan C. and Moore, Meagan J. K. and Petters, Markus D. and Kreidenweis, Sonia M. and Qafoku, Odeta and Laskin, Alexander and Roberts, Greg C. and Prather, Kimberly A.}, year={2010}, pages={830–846} }
 @article{snider_wex_rose_kristensson_stratmann_hennig_henning_kiselev_bilde_burkhart_et al._2010, title={Intercomparison of cloud condensation nuclei and hygroscopic fraction measurements: Coated soot particles investigated during the LACIS Experiment in November (LExNo)}, volume={115}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2009JD012618}, DOI={10.1029/2009JD012618}, abstractNote={Four cloud condensation nuclei (CCN) instruments were used to sample size‐selected particles prepared at the Leipzig Aerosol Cloud Interaction Simulator facility. Included were two Wyoming static diffusion CCN instruments, the continuous flow instrument built by Droplet Measurement Technologies, and the continuous flow Leipzig instrument. The aerosols were composed of ammonium sulfate, levoglucosan, levoglucosan and soot, and ammonium hydrogen sulfate and soot. Comparisons are made among critical supersaturation values from the CCN instruments and derived from measurements made with a humidified tandem differential mobility system. The comparison is quite encouraging: with few exceptions the reported critical supersaturations agree within known experimental uncertainty limits. Also reported are CCN‐ and hygroscopicity‐based estimates of the soot particles' solute fraction. Relative differences between these are as large as 40%, but an error analysis demonstrates that agreement within experimental uncertainty is achieved. We also analyze data from the Droplet Measurement Technologies and the two Wyoming static diffusion instruments for evidence of size distribution broadening and investigate levoglucosan particle growth kinetics in the Wyoming CCN instrument.}, number={D11}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Snider, J. R. and Wex, H. and Rose, D. and Kristensson, A. and Stratmann, F. and Hennig, T. and Henning, S. and Kiselev, A. and Bilde, M. and Burkhart, M. and et al.}, year={2010}, month={Jun} }
 @article{sullivan_petters_demott_kreidenweis_wex_niedermeier_hartmann_clauss_stratmann_reitz_et al._2010, title={Irreversible loss of ice nucleation active sites in mineral dust particles caused by sulphuric acid condensation}, volume={10}, number={23}, journal={Atmospheric Chemistry and Physics}, author={Sullivan, R. C. and Petters, M. D. and DeMott, P. J. and Kreidenweis, S. M. and Wex, H. and Niedermeier, D. and Hartmann, S. and Clauss, T. and Stratmann, F. and Reitz, P. and et al.}, year={2010}, pages={11471–11487} }
 @article{richardson_demott_kreidenweis_petters_carrico_2010, title={Observations of ice nucleation by ambient aerosol in the homogeneous freezing regime}, volume={37}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2009GL041912}, DOI={10.1029/2009GL041912}, abstractNote={We measured the freezing activation curves for ambient particles as a function of relative humidity with respect to water over the temperature range of −40° to −50°C using a continuous flow diffusion chamber, and compared the observations with those for ammonium sulfate particles and predictions from a parametric representation of homogeneous freezing of solution particles as a function of water activity and temperature. Since it has been proposed that the rate of homogeneous freezing depends on solution water activity, we made separate measurements of the hygroscopicity (κ) of the ambient aerosol. Observed κ ranged from 0.1 to 0.2, lower than that of ammonium sulfate (0.6) and representative of a continental aerosol. As predicted for this difference in κ, there was no significant difference between the homogeneous freezing conditions of size‐selected ammonium sulfate and the apparent homogeneous freezing conditions of same‐sized ambient aerosol. Further, the parameterization predicted freezing fraction‐relative humidity relationships for non size‐selected ambient aerosol that differed by only 0.5 to 1.5% relative humidity from observed relations at the tested temperatures, well within experimental uncertainty. Our findings confirm that the tested ambient aerosols, with hygroscopicities typical of continental regions, freeze homogeneously as expected based on present understanding for single component solution drops in the laboratory. Results also confirm that freezing is more sensitive to particle size than to composition, for particles containing at least a few percent by volume of hygroscopic species.}, number={4}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Richardson, Mathews S. and DeMott, Paul J. and Kreidenweis, Sonia M. and Petters, Markus D. and Carrico, Christian M.}, year={2010}, month={Feb} }
 @article{demott_prenni_liu_kreidenweis_petters_twohy_richardson_eidhammer_rogers_2010, title={Predicting global atmospheric ice nuclei distributions and their impacts on climate}, volume={107}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0910818107}, abstractNote={
            Knowledge of cloud and precipitation formation processes remains incomplete, yet global precipitation is predominantly produced by clouds containing the ice phase. Ice first forms in clouds warmer than -36 °C on particles termed ice nuclei. We combine observations from field studies over a 14-year period, from a variety of locations around the globe, to show that the concentrations of ice nuclei active in mixed-phase cloud conditions can be related to temperature and the number concentrations of particles larger than 0.5 μm in diameter. This new relationship reduces unexplained variability in ice nuclei concentrations at a given temperature from ∼10
            3
            to less than a factor of 10, with the remaining variability apparently due to variations in aerosol chemical composition or other factors. When implemented in a global climate model, the new parameterization strongly alters cloud liquid and ice water distributions compared to the simple, temperature-only parameterizations currently widely used. The revised treatment indicates a global net cloud radiative forcing increase of ∼1 W m
            -2
            for each order of magnitude increase in ice nuclei concentrations, demonstrating the strong sensitivity of climate simulations to assumptions regarding the initiation of cloud glaciation.
          }, number={25}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={DeMott, P. J. and Prenni, A. J. and Liu, X. and Kreidenweis, S. M. and Petters, M. D. and Twohy, C. H. and Richardson, M. S. and Eidhammer, T. and Rogers, D. C.}, year={2010}, month={Jun}, pages={11217–11222} }
 @article{poschl_martin_sinha_chen_gunthe_huffman_borrmann_farmer_garland_helas_et al._2010, title={Rainforest aerosols as biogenic nuclei of clouds and precipitation in the Amazon}, volume={329}, number={5998}, journal={Science}, author={Poschl, U. and Martin, S. T. and Sinha, B. and Chen, Q. and Gunthe, S. S. and Huffman, J. A. and Borrmann, S. and Farmer, D. K. and Garland, R. M. and Helas, G. and et al.}, year={2010}, pages={1513–1516} }
 @article{petters_carrico_kreidenweis_prenni_demott_collett_moosmüller_2009, title={Cloud condensation nucleation activity of biomass burning aerosol}, volume={114}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2009JD012353}, DOI={10.1029/2009JD012353}, abstractNote={We examine the hygroscopic properties of particles freshly emitted from laboratory biomass burning experiments conducted during the second Fire Lab At Missoula Experiment (FLAME‐II). Values of the hygroscopicity parameter, kappa, were derived from both hygroscopic growth measurements and size‐resolved (30–300 nm in diameter) cloud condensation nuclei (CCN) measurements for smokes emitted by the open combustion of 24 biomass fuels from the United States and Asia. To analyze the complex cloud condensation nuclei response curves we propose a new inversion scheme that corrects for multiple charge effects without the necessity of prior assumptions about the chemical composition and mixing state of the particles. Kappa varied between 0.02 (weakly hygroscopic) and 0.8 (highly hygroscopic). For individual smokes, kappa was a function of particle size, with 250 nm particles being generally weakly hygroscopic and sub‐100 nm particles being more hygroscopic. At any given size the emissions were often externally mixed, showing more and less hygroscopic growth modes and bimodal CCN activation spectra. Comparisons between growth factor‐derived and CCN‐derived hygroscopicities were consistent when taking this heterogeneity into account. A conceptual model of biomass burning emissions suggests that most particles are CCN active at the point of emission and do not require conversion in the atmosphere to more hygroscopic compositions before they can participate in cloud formation and undergo wet deposition.}, number={D22}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Petters, Markus D. and Carrico, Christian M. and Kreidenweis, Sonia M. and Prenni, Anthony J. and DeMott, Paul J. and Collett, Jeffrey L., Jr. and Moosmüller, Hans}, year={2009}, month={Nov} }
 @article{koehler_demott_kreidenweis_popovicheva_petters_carrico_kireeva_khokhlova_shonija_2009, title={Cloud condensation nuclei and ice nucleation activity of hydrophobic and hydrophilic soot particles}, volume={11}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/b905334b}, DOI={10.1039/b905334b}, abstractNote={Cloud condensation nuclei (CCN) activity and ice nucleation behavior (for temperatures<or=-40 degrees C) of soot aerosols relevant for atmospheric studies were investigated. Soots were chosen to represent a range of physico-chemical properties, from hydrophobic through a range of hydrophilicity, to hygroscopic. These characteristics were achieved through generation by three different combustion sources; three soots from natural gas pyrolysis (original: TS; graphitized: GTS; and oxidized: TOS), soot from a diffusion flame in an oil lamp burning aviation kerosene (TC1), and soot from a turbulent diffusion flame in an aircraft engine combustor (AEC). All of the samples exhibited some heterogeneity in our experiments, which showed evidence of two or more particle sub-types even within a narrow size cut. The heterogeneity could have resulted from both chemical and sizing differences, the latter attributable in part to particle non-sphericity. Neither GTS nor TS, hydrophobic particles distinguished only by the lower porosity and polarity of the GTS surface, showed CCN activity at or below water supersaturations required for wettable, insoluble particles (the Kelvin limit). TC1 soot particles, despite classification as hydrophilic, did not show CCN activity at or below the Kelvin limit. We attribute this result to the microporosity of this soot. In contrast, oxidized, non-porous, and hydrophilic TOS particles exhibited CCN activation at very near the Kelvin limit, with a small percentage of these particles CCN-active even at lower supersaturations. Due to containing a range of surface coverage of organic and inorganic hydrophilic and hygroscopic compounds, up to approximately 35% of hygroscopic AEC particles were active as CCN, with a small percentage of these particles CCN-active at lower supersaturations. In ice nucleation experiments below -40 degrees C, AEC particles nucleated ice near the expected condition for homogeneous freezing of water from aqueous solutions. In contrast, GTS, TS, and TC1 required relative humidity well in excess of water saturation at -40 degrees C for ice formation. GTS particles required water supersaturation conditions for ice activation even at -51 degrees C. At -51 to -57 degrees C, ice formation in particles with electrical mobility diameter of 200 nm occurred in up to 1 in 1000 TS and TC1 particles, and 1 in 100 TOS particles, at relative humidities below those required for homogeneous freezing in aqueous solutions. Our results suggest that heterogeneous ice nucleation is favored in cirrus conditions on oxidized hydrophilic soot of intermediate polarity. Simple considerations suggest that the impact of hydrophilic soot particles on cirrus cloud formation would be most likely in regions of elevated atmospheric soot number concentrations. The ice formation properties of AEC soot are reasonably consistent with present understanding of the conditions required for aircraft contrail formation and the proportion of soot expected to nucleate under such conditions.}, number={36}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Koehler, Kirsten A. and DeMott, Paul J. and Kreidenweis, Sonia M. and Popovicheva, Olga B. and Petters, Markus D. and Carrico, Christian M. and Kireeva, Elena D. and Khokhlova, Tatiana D. and Shonija, Natalia K.}, year={2009}, pages={7906} }
 @article{prenni_petters_faulhaber_carrico_ziemann_kreidenweis_demott_2009, title={Heterogeneous ice nucleation measurements of secondary organic aerosol generated from ozonolysis of alkenes}, volume={36}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2008GL036957}, DOI={10.1029/2008GL036957}, abstractNote={Ice nuclei (IN) are those particles which catalyze ice nucleation in the atmosphere. Ambient measurements suggest that the main particle types that function as IN are metal oxides and dust. However, carbonaceous particles often are the next most abundant IN particle type, although the source and exact chemical compositions of these particles are unknown. Here we explore the ice nucleating ability of one potential source of carbonaceous IN to the atmosphere, secondary organic aerosol (SOA). We generated SOA by ozonolysis of 25 different organic precursors in the presence of an OH scavenger. For all experiments, ice nucleation was not observed in detectable quantities. We conclude that SOA generated from ozonolysis of alkenes is an unlikely source of IN to the atmosphere.}, number={6}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Prenni, Anthony J. and Petters, Markus D. and Faulhaber, Annelise and Carrico, Christian M. and Ziemann, Paul J. and Kreidenweis, Sonia M. and DeMott, Paul J.}, year={2009}, month={Mar} }
 @article{koehler_kreidenweis_demott_petters_prenni_carrico_2009, title={Hygroscopicity and cloud droplet activation of mineral dust aerosol}, volume={36}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2009GL037348}, DOI={10.1029/2009GL037348}, abstractNote={Hygroscopicity and cloud condensation nucleus (CCN) activity were measured for three mineral dust samples: one from the Canary Islands, representing North African dust transported across the Atlantic; one from outside Cairo, representing North African dust transported to the eastern Mediterranean; and Arizona Test Dust, representing dust in the southwestern United States. To reaerosolize bulk samples, dust samples were either suspended in high purity water and particles generated by atomization, or samples were resuspended in dry air using a fluidized bed. Only the Canary Island sample generated from aqueous suspension showed appreciable hygroscopic growth at subsaturated conditions; all other samples exhibited diameter growth factors of less than 1.1 for relative humidities ≤90%. Despite their low hygroscopicities at subsaturated conditions, all samples activated as cloud droplets at supersaturations lower than required for insoluble particles. We suggest that the CCN activity of these mineral dusts are well‐represented using the hygroscopicity parameter 0.01 ≤ κ ≤ 0.08.}, number={8}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Koehler, K. A. and Kreidenweis, S. M. and DeMott, P. J. and Petters, M. D. and Prenni, A. J. and Carrico, C. M.}, year={2009}, month={Apr} }
 @article{demott_petters_prenni_carrico_kreidenweis_collett_moosmüller_2009, title={Ice nucleation behavior of biomass combustion particles at cirrus temperatures}, volume={114}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2009JD012036}, DOI={10.1029/2009JD012036}, abstractNote={Measurements of ice formation by biomass combustion particles generated in controlled laboratory burns were made using a continuous flow diffusion chamber operating in the temperature range between −45 and −60°C. These measurements are the first of their kind to investigate the role that such particles may play in ice formation in upper tropospheric clouds. Measurements of aerosol water uptake were used to examine the role of hygroscopicity in low‐temperature ice nucleation by biomass combustion particles. Ice formation by the smoke particles at below −45°C and below water saturation followed the temperature and relative humidity dependencies predicted for water activity‐based homogeneous freezing within measurement uncertainties. As predicted, relative humidity dependence of homogeneous freezing fractions on hygroscopicity was weak in comparison with the temperature dependence for biomass particles of typical atmospheric sizes. The action of heterogeneous ice nucleation in or on these small smoke particles in the haze particle regime could not be distinguished within measurement uncertainties. Impedance of homogeneous freezing below −50°C was inferred for freezing higher number fractions of predominantly organic smoke particles separately reported to contain an abundance of large organic molecules, consistent with the recently predicted onset conditions for and impact of viscous or glassy aerosol phase states. Finally, we note that precision and accuracy requirements of instrumentation for resolving modest impacts (a few degrees less supercooling or a few percent lower relative humidity) of heterogeneous freezing, as compared with homogeneous freezing in the upper tropospheric temperature regime present difficulties for validating aerosol impacts on cirrus.}, number={D16}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={DeMott, Paul J. and Petters, Markus D. and Prenni, Anthony J. and Carrico, Christian M. and Kreidenweis, Sonia M. and Collett, Jeffrey L., Jr. and Moosmüller, Hans}, year={2009}, month={Aug} }
 @article{petters_parsons_prenni_demott_kreidenweis_carrico_sullivan_mcmeeking_levin_wold_et al._2009, title={Ice nuclei emissions from biomass burning}, volume={114}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2008JD011532}, DOI={10.1029/2008JD011532}, abstractNote={Biomass burning is a significant source of carbonaceous aerosol in many regions of the world. When present, biomass burning particles may affect the microphysical properties of clouds through their ability to function as cloud condensation nuclei or ice nuclei. We report on measurements of the ice nucleation ability of biomass burning particles performed on laboratory‐generated aerosols at the second Fire Lab at Missoula Experiment. During the experiment we generated smoke through controlled burns of 21 biomass fuels from the United States and Asia. Using a Colorado State University continuous flow diffusion chamber, we measured the condensation/immersion freezing potential at temperatures relevant to cold cumulus clouds (−30°C). Smokes from 9 of the 21 fuels acted as ice nuclei at fractions of 1:10,000 to 1:100 particles in at least one burn of each fuel; emissions from the remaining fuels were below the ice nuclei detection limit for all burns of each fuel. Using a bottom‐up emission model, we estimate that smokes that emit ice nuclei fractions exceeding 1:10,000 particles can perturb ice nuclei concentrations on a regional scale.}, number={D7}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Petters, Markus D. and Parsons, Matthew T. and Prenni, Anthony J. and DeMott, Paul J. and Kreidenweis, Sonia M. and Carrico, Christian M. and Sullivan, Amy P. and McMeeking, Gavin R. and Levin, Ezra and Wold, Cyle E. and et al.}, year={2009}, month={Apr} }
 @article{prenni_petters_kreidenweis_heald_martin_artaxo_garland_wollny_pöschl_2009, title={Relative roles of biogenic emissions and Saharan dust as ice nuclei in the Amazon basin}, volume={2}, ISSN={1752-0894 1752-0908}, url={http://dx.doi.org/10.1038/ngeo517}, DOI={10.1038/ngeo517}, number={6}, journal={Nature Geoscience}, publisher={Springer Science and Business Media LLC}, author={Prenni, Anthony J. and Petters, Markus D. and Kreidenweis, Sonia M. and Heald, Colette L. and Martin, Scot T. and Artaxo, Paulo and Garland, Rebecca M. and Wollny, Adam G. and Pöschl, Ulrich}, year={2009}, month={May}, pages={402–405} }
 @article{petters_kreidenweis_prenni_sullivan_carrico_koehler_ziemann_2009, title={Role of molecular size in cloud droplet activation}, volume={36}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2009GL040131}, DOI={10.1029/2009GL040131}, abstractNote={We examine the observed relationships between molar volume (the ratio of molar mass and density) and cloud condensation nuclei (CCN) activity for sufficiently soluble organic compounds found in atmospheric particulate matter. Our data compilation includes new CCN data for certain carbohydrates and oligoethylene glycols, as well as published data for organic compounds. We compare predictions of CCN activity using water activities based on Raoult's law and Flory‐Huggins theory to observations. The Flory‐Huggins water activity expression, with an assumed surface tension of pure water, generally predicts CCN activity within a factor of two over the full range of molar volumes considered. CCN activity is only weakly dependent on molar volume for values exceeding 600 cm3 mol−1, and the diminishing sensitivity to molar volume, combined with the significant scatter in the data, limits the accuracy with which molar volume can be inferred from CCN measurements.}, number={22}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Petters, M. D. and Kreidenweis, S. M. and Prenni, A. J. and Sullivan, R. C. and Carrico, C. M. and Koehler, K. A. and Ziemann, P. J.}, year={2009}, month={Nov} }
 @article{sullivan_moore_petters_kreidenweis_roberts_prather_2009, title={Timescale for hygroscopic conversion of calcite mineral particles through heterogeneous reaction with nitric acid}, volume={11}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/b904217b}, DOI={10.1039/b904217b}, abstractNote={Atmospheric heterogeneous reactions can potentially change the hygroscopicity of atmospheric aerosols as they undergo chemical aging processes in the atmosphere. A particle's hygroscopicity influences its cloud condensation nuclei (CCN) properties with potential impacts on cloud formation and climate. In this study, size-selected calcite mineral particles were reacted with controlled amounts of nitric acid vapour over a wide range of relative humidities in an aerosol flow tube to study the conversion of insoluble and thus apparently non-hygroscopic calcium carbonate into soluble and hygroscopic calcium nitrate. The rate of hygroscopic change particles undergo during a heterogeneous reaction is derived from experimental measurements for the first time. The chemistry of the reacted particles was determined using an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) while the particles' hygroscopicity was determined through measuring CCN activation curves fit to a single parameter of hygroscopicity, kappa. The reaction is rapid, corresponding to atmospheric timescales of hours. At low to moderate HNO3 exposures, the increase in the hygroscopicity of the particles is a linear function of the HNO3(g) exposure. The experimentally observed conversion rate was used to constrain a simple but accurate kinetic model. This model predicts that calcite particles will be rapidly converted into hygroscopic particles (kappa>0.1) within 4 h for low HNO3 mixing ratios (10 pptv) and in less than 3 min for 1000 pptv HNO3. This suggests that the hygroscopic conversion of the calcite component of atmospheric mineral dust aerosol will be controlled by the availability of nitric acid and similar reactants, and not by the atmospheric residence time.}, number={36}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Sullivan, Ryan C. and Moore, Meagan J. K. and Petters, Markus D. and Kreidenweis, Sonia M. and Roberts, Greg C. and Prather, Kimberly A.}, year={2009}, pages={7826} }
 @article{carrico_petters_kreidenweis_collett_engling_malm_2008, title={Aerosol hygroscopicity and cloud droplet activation of extracts of filters from biomass burning experiments}, volume={113}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2007JD009274}, DOI={10.1029/2007JD009274}, abstractNote={In this laboratory closure study, we compare sub‐ and supersaturated water uptake properties for aerosol particles possessing a range of hygroscopicity. Measurements for water sub‐saturated conditions used a hygroscopic tandem differential mobility analyzer (HTDMA). Simultaneously, measurements of particle critical supersaturation were conducted on the same sample stream with a continuous flow cloud condensation nuclei (CCN) counter. For these experiments, we used filter‐collected samples of biomass smoke generated in the combustion of two common wildland fire fuels, western sagebrush and Alaskan duff core. Extractions of separate sections of the filter were performed using two solvents, ultrapure water and methanol. The extracts were subsequently atomized, producing aerosols having a range of hygroscopic responses. HTDMA and CCN measurements were fit to a single‐parameter model of water uptake, in which the fit parameter is denoted κ, the hygroscopicity parameter. Here, for the four extracts we observed mean values of the hygroscopicity parameter of 0.06 < κ < 0.30, similar to the range found previously for numerous pure organic compounds. Particles generated from the aqueous extracts of the filters had consistently larger κ than methanol extracts, while western sagebrush extract aerosols κ exceeded those from Alaskan duff core. HTDMA‐ and CCN‐derived values of κ for each experiment agreed within approximately 20%. Applicability of the κ‐parameterization to other multicomponent aerosols relevant to the atmosphere remains to be tested.}, number={D8}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Carrico, Christian M. and Petters, Markus D. and Kreidenweis, Sonia M. and Collett, Jeffrey L., Jr. and Engling, Guenter and Malm, William C.}, year={2008}, month={Apr} }
 @article{popovicheva_persiantseva_shonija_demott_koehler_petters_kreidenweis_tishkova_demirdjian_suzanne_2008, title={Water interaction with hydrophobic and hydrophilic soot particles}, volume={10}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/b718944n}, DOI={10.1039/b718944n}, abstractNote={The interaction of water with laboratory soots possessing a range of properties relevant for atmospheric studies is examined by two complementary methods: gravimetrical measurement of water uptake coupled with chemical composition and porosity analysis and HTDMA (humidified tandem differential mobility analyzer) inference of water uptake accompanied by separate TEM (transmission electron microscopy) analysis of single particles. The first method clarifies the mechanism of water uptake for bulk soot and allows the classification of soot with respect to its hygroscopicity. The second method highlights the dependence of the soot aerosol growth factor on relative humidity (RH) for quasi-monodisperse particles. Hydrophobic and hydrophilic soot are qualitatively defined by their water uptake and surface polarity: laboratory soot particles are thus classified from very hydrophobic to very hydrophilic. Thermal soot particles produced from natural gas combustion are classified as hydrophobic with a surface of low polarity since water is found to cover only half of the surface. Graphitized thermal soot particles are proposed for comparison as extremely hydrophobic and of very low surface polarity. Soot particles produced from laboratory flame of TC1 aviation kerosene are less hydrophobic, with their entire surface being available for statistical monolayer water coverage at RH approximately 10%. Porosity measurements suggest that, initially, much of this surface water resides within micropores. Consequently, the growth factor increase of these particles to 1.07 at RH > 80% is attributed to irreversible swelling that accompanies water uptake. Hysteresis of adsorption/desorption cycles strongly supports this conclusion. In contrast, aircraft engine soot, produced from burning TC1 kerosene in a gas turbine engine combustor, has an extremely hydrophilic surface of high polarity. Due to the presence of water soluble organic and inorganic material it can be covered by many water layers even below water saturation conditions. This soot demonstrates a gradual diameter growth factor (D(wet)/D(dry)) increase up to 1.22 at 93% relative humidity, most likely due to the presence of single particles with water soluble material heterogeneously distributed over their surface.}, number={17}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Popovicheva, Olga and Persiantseva, Natalia M. and Shonija, Natalia K. and DeMott, Paul and Koehler, Kirsten and Petters, Markus and Kreidenweis, Sonia and Tishkova, Victoria and Demirdjian, Benjamin and Suzanne, Jean}, year={2008}, pages={2332} }
 @article{prenni_petters_kreidenweis_demott_ziemann_2007, title={Cloud droplet activation of secondary organic aerosol}, volume={112}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2006JD007963}, DOI={10.1029/2006JD007963}, abstractNote={Measurements of hygroscopicity and cloud condensation nuclei (CCN) activity were conducted on secondary organic aerosol (SOA) formed in a smog chamber. SOA precursors included α‐pinene, β‐pinene, Δ3‐carene, and toluene, representative of both naturally and anthropogenically emitted organic species. Measured CCN activation was comparable for all of the species studied and occurred at humidity conditions which are readily attained in the atmosphere. Further, there was little variation in hygroscopic growth between compounds. However, measured droplet activation conditions were inconsistent with hygroscopicity measured below water saturation and Köhler theory expressions based on Raoult’s law for several parameterizations for water activity. In the atmosphere, SOA may compose a large fraction of atmospheric particulate matter and will often exist internally mixed with inorganic species. Using the current results, we compare SOA to insoluble organic species to calculate CCN activation from mixed organic‐sulfate particles for a range of atmospheric conditions. We find that droplet activation behavior of mixed particles containing SOA is the same as that of mixed particles for which the organic component is nonhygroscopic, except for cases in which there are low particle concentrations, low updraft velocities, and the aerosol composition is dominated by organics.}, number={D10}, journal={Journal of Geophysical Research: Atmospheres}, publisher={American Geophysical Union (AGU)}, author={Prenni, Anthony J. and Petters, Markus D. and Kreidenweis, Sonia M. and DeMott, Paul J. and Ziemann, Paul J.}, year={2007}, month={May} }
 @article{petters_prenni_kreidenweis_demott_2007, title={On Measuring the Critical Diameter of Cloud Condensation Nuclei Using Mobility Selected Aerosol}, volume={41}, ISSN={0278-6826 1521-7388}, url={http://dx.doi.org/10.1080/02786820701557214}, DOI={10.1080/02786820701557214}, abstractNote={Cloud condensation nuclei (CCN) instruments determine the so-called “critical diameter” for activation of particles into cloud droplets at a fixed water supersaturation. A differential mobility analyzer is often used to size-select particles for purposes of scanning for the critical diameter. Usually the diameter where 50% of the particles have activated to cloud droplets is assumed to be equal to the critical diameter. We introduce a model that describes the transfer of polydisperse charge-equilibrated particles through an ideal differential mobility analyzer followed by transit through an ideal CCN instrument. We show that if the mode diameter of the polydisperse size distribution exceeds the critical diameter of the particles, multiply-charged particles may lead to nonmonotonic CCN counter response curves (plots of CCN-active fraction vs. mobility diameter) that exhibit multiple peaks, rather than a simple sigmoidally-shaped curve. Hence, determination of the 50% activation diameter is ambiguous. Multiply-charged particles significantly skew the CCNc response curves when sampling particles with critical diameters exceeding 0.1 μ m from particle size distributions with mode diameters also larger than the critical diameter. We present a method for inversion of CCN counter data that takes multiple-charging effects into account, and demonstrate its application to laboratory data. Our calculated CCN counter response curves are in good agreement with observations, and can be used to infer the critical activation diameter for a specified supersaturation.}, number={10}, journal={Aerosol Science and Technology}, publisher={Informa UK Limited}, author={Petters, Markus D. and Prenni, Anthony J. and Kreidenweis, Sonia M. and DeMott, Paul J.}, year={2007}, month={Aug}, pages={907–913} }
 @article{koehler_kreidenweis_demott_prenni_petters_2007, title={Potential impact of Owens (dry) Lake dust on warm and cold cloud formation}, volume={112}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2007JD008413}, DOI={10.1029/2007JD008413}, abstractNote={Owens lake bed is one of the largest sources of particulate matter in the western hemisphere. Because of the fine‐grained nature of this dust, it is easily lofted above the atmospheric boundary layer, where it may affect cloud formation. Further, unlike many other soil types, it has a large fraction of soluble material (∼3–37% of the mass on an organic‐matter‐free basis), so it can impact both warm and cold clouds. In this study, we measure the hygroscopicity, cloud condensation nucleus (CCN) activity, and ice nucleating ability of Owens (dry) Lake dust. Our studies confirm that a fraction of the Owens (dry) Lake dust (35% by number for particle sizes ∼200 nm) is quite hygroscopic and has CCN activity comparable to that of sodium chloride (50 nm particles activate at 0.33% supersaturation). These hygroscopic dust particles can readily initiate droplet formation at modest supersaturations in the atmosphere and may significantly impact liquid clouds in the southwestern United States. The less hygroscopic fraction had only modest CCN activity. However, such particles may still activate as cloud droplets at atmospheric supersaturations and could potentially modify cloud properties if particles with diameters larger than ∼300 nm are present. The less hygroscopic fraction also was found to nucleate ice heterogeneously at relative humidities significantly lower than required for homogeneous freezing of aqueous particles at temperatures colder than −40°C. In convective systems, this dust may be lofted to the upper troposphere where it may impact convection strength and onset conditions for ice formation in cold clouds.}, number={D12}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Koehler, Kirsten A. and Kreidenweis, Sonia M. and DeMott, Paul J. and Prenni, Anthony J. and Petters, Markus D.}, year={2007}, month={Jun} }
 @article{petters_snider_stevens_vali_faloona_russell_2006, title={Accumulation mode aerosol, pockets of open cells, and particle nucleation in the remote subtropical Pacific marine boundary layer}, volume={111}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2004JD005694}, DOI={10.1029/2004JD005694}, abstractNote={We analyze a marine boundary layer cloud field encountered during the second research flight of the second Dynamics and Chemistry of Marine Stratocumulus Experiment. The cloud field is distinguished by the presence of pockets of open cells. Differences between the pockets and the surrounding stratocumulus clouds are studied utilizing in situ and satellite data. The pockets are characterized as regions where cloud radar echo tops are unusually variable, accumulation mode aerosol concentrations are low, and Aitken mode particles with a mode diameter at 0.02 μm dominate aerosol number concentration. The Aitken mode particles are thought to be generated by a nucleation event which occurred within the marine boundary layer. The low accumulation mode concentrations associated with the pockets are proposed to be necessary for their maintenance.}, number={D2}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Petters, Markus D. and Snider, Jefferson R. and Stevens, Bjorn and Vali, Gabor and Faloona, Ian and Russell, Lynn M.}, year={2006} }
 @article{petters_prenni_kreidenweis_demott_matsunaga_lim_ziemann_2006, title={Chemical aging and the hydrophobic-to-hydrophilic conversion of carbonaceous aerosol}, volume={33}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2006GL027249}, DOI={10.1029/2006GL027249}, abstractNote={Laboratory experiments simulating chemical aging of carbonaceous aerosol by atmospheric oxidants demonstrate that oxidative processing increases their ability to activate as cloud droplets. A microphysical model shows, however, that the measured increase in hygroscopicity is insufficient to lead to efficient wet scavenging for sub‐100 nm particles that are typically emitted from combustion sources. The absence of an efficient atmospheric oxidation pathway for hydrophobic‐to‐hydrophilic conversion suggests that the fate of carbonaceous aerosol is instead controlled by its interaction with more hydrophilic species such as sulfates, nitrates, and secondary organic aerosol, leading to longer lifetimes, higher burdens, and greater contributions to climate forcing in the free troposphere than are currently estimated.}, number={24}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Petters, Markus D. and Prenni, Anthony J. and Kreidenweis, Sonia M. and DeMott, Paul J. and Matsunaga, Aiko and Lim, Yong B. and Ziemann, Paul J.}, year={2006}, month={Dec} }
 @article{kreidenweis_petters_demott_2006, title={Deliquescence-controlled activation of organic aerosols}, volume={33}, ISSN={0094-8276}, url={http://dx.doi.org/10.1029/2005GL024863}, DOI={10.1029/2005GL024863}, abstractNote={We examine the cloud condensation nucleation behavior expected for dry submicron particles composed of organic species having limited solubility in water and thus exhibiting deliquescence only under water‐supersaturated conditions. If saturated solution water activities aw are approximately 0.97 < aw < 1, then deliquescence is likely to control the supersaturation required to activate submicron particles, leading to high sensitivity of critical supersaturation to dry diameter. Similar behavior may occur for species, including polymeric compounds, that exhibit limited miscibility in water until very dilute conditions. Treating the sparingly‐soluble or limited‐miscibility species as insoluble aerosol components in calculations of their hygroscopic growth does not reproduce the predicted strong dependence of critical supersaturation on dry particle size. Lack of information on the solubility characteristics of organic‐species‐dominated atmospheric particulate matter may thus lead to discrepancies between predicted and measured droplet activation, even when particle composition and size are well‐constrained by measurements.}, number={6}, journal={Geophysical Research Letters}, publisher={American Geophysical Union (AGU)}, author={Kreidenweis, Sonia M. and Petters, Markus D. and DeMott, Paul J.}, year={2006} }
 @article{twohy_2005, title={Evaluation of the aerosol indirect effect in marine stratocumulus clouds: Droplet number, size, liquid water path, and radiative impact}, volume={110}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2004JD005116}, DOI={10.1029/2004JD005116}, abstractNote={Data from nine stratocumulus clouds in the northeastern Pacific Ocean were analyzed to determine the effect of aerosol particles on cloud microphysical and radiative properties. Seven nighttime and two daytime cases were included. The number concentration of below‐cloud aerosol particles (>0.10 μm diameter) was highly correlated with cloud droplet number concentration. Droplet number concentrations were typically about 75% of particle number concentration in the range of particle concentrations studied (≤400 cm−3). Particle number was anticorrelated with droplet size and with liquid water content in drizzle‐sized drops. Radiative impact also depends upon cloud liquid water content and geometric thickness. Although most variability in these macroscopic properties of the clouds could be attributed to variability in the large‐scale environment, a weak anticorrelation between particle concentration and cloud geometric thickness was observed. Because of these variations, no correlation between calculated cloud optical thickness or albedo and particle concentration was detectable for the data set as a whole. For regions with comparable liquid water contents in an individual cloud, higher particle concentrations did correspond to increased cloud optical thickness. These results verify that higher particle concentrations do directly affect the microphysics of stratiform clouds. However, the constant liquid water path assumption usually invoked in the Twomey aerosol indirect effect may not be valid.}, number={D8}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Twohy, Cynthia H.}, year={2005} }