@article{ghasemi_guo_darabi_wang_wang_huang_lefler_taussig_chauhan_baucom_et al._2023, title={A multiscale ion diffusion framework sheds light on the diffusion-stability-hysteresis nexus in metal halide perovskites}, ISSN={["1476-4660"]}, DOI={10.1038/s41563-023-01488-2}, abstractNote={Stability and current-voltage hysteresis stand as major obstacles to the commercialization of metal halide perovskites. Both phenomena have been associated with ion migration, with anecdotal evidence that stable devices yield low hysteresis. However, the underlying mechanisms of the complex stability-hysteresis link remain elusive. Here we present a multiscale diffusion framework that describes vacancy-mediated halide diffusion in polycrystalline metal halide perovskites, differentiating fast grain boundary diffusivity from volume diffusivity that is two to four orders of magnitude slower. Our results reveal an inverse relationship between the activation energies of grain boundary and volume diffusions, such that stable metal halide perovskites exhibiting smaller volume diffusivities are associated with larger grain boundary diffusivities and reduced hysteresis. The elucidation of multiscale halide diffusion in metal halide perovskites reveals complex inner couplings between ion migration in the volume of grains versus grain boundaries, which in turn can predict the stability and hysteresis of metal halide perovskites, providing a clearer path to addressing the outstanding challenges of the field.}, journal={NATURE MATERIALS}, author={Ghasemi, Masoud and Guo, Boyu and Darabi, Kasra and Wang, Tonghui and Wang, Kai and Huang, Chiung-Wei and Lefler, Benjamin M. and Taussig, Laine and Chauhan, Mihirsinh and Baucom, Garrett and et al.}, year={2023}, month={Feb} }
 @article{jena_zhang_wang_campbell_2023, title={Decadal Application of WRF/Chem under Future Climate and Emission Scenarios: Impacts of Technology-Driven Climate and Emission Changes on Regional Meteorology and Air Quality}, volume={14}, ISSN={["2073-4433"]}, DOI={10.3390/atmos14020225}, abstractNote={This work presents new climate and emissions scenarios to investigate changes on future meteorology and air quality in the U.S. Here, we employ a dynamically downscaled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) simulations that use two Intergovernmental Panel on Climate Change scenarios (i.e., A1B and B2) integrated with explicitly projected emissions from a novel Technology Driver Model (TDM). The projected 2046–2055 emissions show widespread reductions in most gas and aerosol species under both TDM/A1B and TDM/B2 scenarios over the U.S. The WRF/Chem simulations show that under the combined effects of the TDM/A1B climate and emission changes, the maximum daily average 8-h ozone (MDA8 h O3) increases by ~3 ppb across the U.S. mainly due to widespread increases in near-surface temperature and background methane concentrations, with some contributions from localized TDM emission changes near urban centers. For the TDM/B2 climate and emission changes, however, the MDA8 h O3 is widely decreased, except near urban centers where the relative TDM emission changes and O3 formation regimes leads to increased O3. The number of O3 exceedance days (i.e., MDA8 h O3 > 70 ppb) for the entire domain is significantly reduced by a grid cell maximum of up to 43 days (domain average ~0.5 days) and 62 days (domain average ~2 days) for the TDM/A1B and TDM/B2 scenarios, respectively, while in the western U.S., larger O3 increases lead to increases in nonattainment areas, especially for the TDM/A1B scenario. The combined effects of climate and emissions (for both A1B and B2 scenarios) will lead to widespread decreases in the daily 24-h average (DA24 h) PM2.5 concentrations, especially in the eastern U.S. (max decrease up to 93 µg m−3). The PM2.5 changes are dominated by decreases in anthropogenic emissions for both the TDM/A1B and TDM/B2 scenarios, with secondary effects on decreasing PM2.5 from climate change. The number of PM2.5 exceedance days (i.e., DA24 h PM2.5 > 35 µg m−3) is significantly reduced over the eastern U.S. under both TDM/A1B and B2 scenarios, which suggests that both climate and emission changes may synergistically lead to decreases in PM2.5 nonattainment areas in the future.}, number={2}, journal={ATMOSPHERE}, author={Jena, Chinmay and Zhang, Yang and Wang, Kai and Campbell, Patrick C.}, year={2023}, month={Feb} }
 @article{yang_zhang_wang_doraiswamy_cho_2019, title={Health impacts and cost-benefit analyses of surface O-3 and PM2.5 over the US under future climate and emission scenarios}, volume={178}, ISSN={["1096-0953"]}, DOI={10.1016/j.envres.2019.108687}, abstractNote={Health impacts of surface ozone (O3) and fine particulate matter (PM2.5) are of major concern worldwide. In this work, the Environmental Benefits Mapping and Analysis Program tool is applied to estimate the health and economic impacts of projected changes in O3 and PM2.5 in the U.S. in future (2046–2055) decade relative to current (2001–2010) decade under the Representative Concentration Pathway (RCP) 4.5 and 8.5 climate scenarios. Future annual-mean O3 reductions under RCP 4.5 prevent ~1,800 all-cause mortality, 761 respiratory hospital admissions (HA), and ~1.2 million school loss days annually, and result in economic benefits of ~16 billion, 29 million, and 132 million U.S. dollars (USD), respectively. By contrast, the projected future annual-mean O3 increases under RCP8.5 cause ~2,400 mortality, 941 respiratory HA, and ~1.6 million school loss days annually and result in economic disbenefits of ~21 billion, 36 million, and 175 million USD, respectively. Health benefits of reduced O3 double under RCP4.5 and health dis-benefits of increased O3 increase by 1.5 times under RCP8.5 in future with 2050 population and baseline incidence rate. Because of the reduction in projected future PM2.5 over CONUS under both scenarios, the annual avoided all-cause deaths, cardiovascular HA, respiratory HA, and work loss days are ~63,000 and ~83,000, ~5,300 and ~7,000, ~12,000 and ~15,000, and ~7.8 million and ~10 million, respectively, leading to economic benefits of ~560 and ~740 billion, ~240 and ~320 million, ~450 and ~590 million, and ~1,400 and ~1,900 million USD for RCP4.5 and 8.5, respectively. Health benefits of reduced PM2.5 for future almost double under both scenarios with the largest benefits in urban areas. RCP8.5 projects larger health and economic benefits due to a greater reduction in PM2.5 but with a warmer atmosphere and higher O3 pollution than RCP4.5. RCP4.5 leads to multiple-benefit goals including reduced O3 and PM2.5, reduced mortality and morbidity, and saved costs. Greater reduction in future PM2.5 under RCP4.5 should be considered to achieve larger multi-benefits.}, journal={ENVIRONMENTAL RESEARCH}, author={Yang, Peilin and Zhang, Yang and Wang, Kai and Doraiswamy, Prakash and Cho, Seung-Hyun}, year={2019}, month={Nov} }
 @article{zhang_jena_wang_paton-walsh_guerette_utembe_silver_keywood_2019, title={Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models during Recent Field Campaigns in Australia, Part I: Model Description and WRF/Chem-ROMS Evaluation Using Surface and Satellite Data and Sensitivity to Spatial Grid Resolutions}, volume={10}, ISSN={["2073-4433"]}, DOI={10.3390/atmos10040189}, abstractNote={Air pollution and associated human exposure are important research areas in Greater Sydney, Australia. Several field campaigns were conducted to characterize the pollution sources and their impacts on ambient air quality including the Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2), and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). In this work, the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are applied during these field campaigns to assess the models’ capability in reproducing atmospheric observations. The model simulations are performed over quadruple-nested domains at grid resolutions of 81-, 27-, 9-, and 3-km over Australia, an area in southeastern Australia, an area in New South Wales, and the Greater Sydney area, respectively. A comprehensive model evaluation is conducted using surface observations from these field campaigns, satellite retrievals, and other data. This paper evaluates the performance of WRF/Chem-ROMS and its sensitivity to spatial grid resolutions. The model generally performs well at 3-, 9-, and 27-km resolutions for sea-surface temperature and boundary layer meteorology in terms of performance statistics, seasonality, and daily variation. Moderate biases occur for temperature at 2-m and wind speed at 10-m in the mornings and evenings due to the inaccurate representation of the nocturnal boundary layer and surface heat fluxes. Larger underpredictions occur for total precipitation due to the limitations of the cloud microphysics scheme or cumulus parameterization. The model performs well at 3-, 9-, and 27-km resolutions for surface O3 in terms of statistics, spatial distributions, and diurnal and daily variations. The model underpredicts PM2.5 and PM10 during SPS1 and MUMBA but overpredicts PM2.5 and underpredicts PM10 during SPS2. These biases are attributed to inaccurate meteorology, precursor emissions, insufficient SO2 conversion to sulfate, inadequate dispersion at finer grid resolutions, and underprediction in secondary organic aerosol. The model gives moderate biases for net shortwave radiation and cloud condensation nuclei but large biases for other radiative and cloud variables. The performance of aerosol optical depth and latent/sensible heat flux varies for different simulation periods. Among all variables evaluated, wind speed at 10-m, precipitation, surface concentrations of CO, NO, NO2, SO2, O3, PM2.5, and PM10, aerosol optical depth, cloud optical thickness, cloud condensation nuclei, and column NO2 show moderate-to-strong sensitivity to spatial grid resolutions. The use of finer grid resolutions (3- or 9-km) can generally improve the performance for those variables. While the performance for most of these variables is consistent with that over the U.S. and East Asia, several differences along with future work are identified to pinpoint reasons for such differences.}, number={4}, journal={ATMOSPHERE}, author={Zhang, Yang and Jena, Chinmay and Wang, Kai and Paton-Walsh, Clare and Guerette, Elise-Andree and Utembe, Steven and Silver, Jeremy David and Keywood, Melita}, year={2019}, month={Apr} }
 @article{zhang_wang_jena_paton-walsh_guerette_utembe_silver_keywood_2019, title={Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models during Recent Field Campaigns in Australia, Part II: Comparison of WRF/Chem and WRF/Chem-ROMS and Impacts of Air-Sea Interactions and Boundary Conditions}, volume={10}, ISSN={["2073-4433"]}, DOI={10.3390/atmos10040210}, abstractNote={Air-sea interactions play an important role in atmospheric circulation and boundary layer conditions through changing convection processes and surface heat fluxes, particularly in coastal areas. These changes can affect the concentrations, distributions, and lifetimes of atmospheric pollutants. In this Part II paper, the performance of the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are intercompared for their applications over quadruple-nested domains in Australia during the three following field campaigns: The Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2) and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). The results are used to evaluate the impact of air-sea interaction representation in WRF/Chem-ROMS on model predictions. At 3, 9, and 27 km resolutions, compared to WRF/Chem, the explicit air-sea interactions in WRF/Chem-ROMS lead to substantial improvements in simulated sea-surface temperature (SST), latent heat fluxes (LHF), and sensible heat fluxes (SHF) over the ocean, in terms of statistics and spatial distributions, during all three field campaigns. The use of finer grid resolutions (3 or 9 km) effectively reduces the biases in these variables during SPS1 and SPS2 by WRF/Chem-ROMS, whereas it further increases these biases for WRF/Chem during all field campaigns. The large differences in SST, LHF, and SHF between the two models lead to different radiative, cloud, meteorological, and chemical predictions. WRF/Chem-ROMS generally performs better in terms of statistics and temporal variations for temperature and relative humidity at 2 m, wind speed and direction at 10 m, and precipitation. The percentage differences in simulated surface concentrations between the two models are mostly in the range of ±10% for CO, OH, and O3, ±25% for HCHO, ±30% for NO2, ±35% for H2O2, ±50% for SO2, ±60% for isoprene and terpenes, ±15% for PM2.5, and ±12% for PM10. WRF/Chem-ROMS at 3 km resolution slightly improves the statistical performance of many surface and column concentrations. WRF/Chem simulations with satellite-constrained boundary conditions (BCONs) improve the spatial distributions and magnitudes of column CO for all field campaigns and slightly improve those of the column NO2 for SPS1 and SPS2, column HCHO for SPS1 and MUMBA, and column O3 for SPS2 at 3 km over the Greater Sydney area. The satellite-constrained chemical BCONs reduce the model biases of surface CO, NO, and O3 predictions at 3 km for all field campaigns, surface PM2.5 predictions at 3 km for SPS1 and MUMBA, and surface PM10 predictions at all grid resolutions for all field campaigns. A more important role of chemical BCONs in the Southern Hemisphere, compared to that in the Northern Hemisphere reported in this work, indicates a crucial need in developing more realistic chemical BCONs for O3 in the relatively clean SH.}, number={4}, journal={ATMOSPHERE}, author={Zhang, Yang and Wang, Kai and Jena, Chinmay and Paton-Walsh, Clare and Guerette, Elise-Andree and Utembe, Steven and Silver, Jeremy David and Keywood, Melita}, year={2019}, month={Apr} }
 @article{goldberg_gupta_wang_jena_zhang_lu_streets_2019, title={Using gap-filled MAIAC AOD and WRF-Chem to estimate daily PM2.5 concentrations at 1 km resolution in the Eastern United States}, volume={199}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2018.11.049}, abstractNote={To link short-term exposures of air pollutants to health outcomes, scientists must use high temporal and spatial resolution estimates of PM2.5 concentrations. In this work, we develop a daily PM2.5 product at 1 × 1 km2 spatial resolution across the eastern United States (east of 90° W) with the aid of 1 × 1 km2 MAIAC aerosol optical depth (AOD) data, 36 × 36 km2 WRF-Chem output, 1 × 1 km2 land-use type from the National Land Cover Database, and 0.125° × 0.125° ERA-Interim re-analysis meteorology. A gap-filling technique is applied to MAIAC AOD data to construct robust daily estimates of AOD when the satellite data are missing (e.g., areas obstructed by clouds or snow cover). The input data are incorporated into a multiple-linear regression model trained to surface observations of PM2.5 from the EPA Air Quality System (AQS) monitoring network. The model generates a high-fidelity estimate (r2 = 0.75 using a 10-fold random cross-validation) of daily PM2.5 throughout the eastern United States. Of the inputs to the statistical model, WRF-Chem output (r2 = 0.66) is the most important contributor to the skill of the model. MAIAC AOD is also a strong contributor (r2 = 0.52). Daily PM2.5 output from our statistical model can be easily integrated into county-level epidemiological studies. The novelty of this project is that we are able to simulate PM2.5 in a computationally efficient manner that is constrained to ground monitors, satellite data, and chemical transport model output at high spatial resolution (1 × 1 km2) without sacrificing the temporal resolution (daily) or spatial coverage (>2,000,000 km2).}, journal={ATMOSPHERIC ENVIRONMENT}, author={Goldberg, Daniel L. and Gupta, Pawan and Wang, Kai and Jena, Chinmay and Zhang, Yang and Lu, Zifeng and Streets, David G.}, year={2019}, month={Feb}, pages={443–452} }
 @article{wang_zhang_zhang_fan_leung_zheng_zhang_he_2018, title={Fine-scale application of WRF-CAM5 during a dust storm episode over East Asia: Sensitivity to grid resolutions and aerosol activation parameterizations}, volume={176}, ISSN={1352-2310}, url={http://dx.doi.org/10.1016/J.ATMOSENV.2017.12.014}, DOI={10.1016/J.ATMOSENV.2017.12.014}, abstractNote={An advanced online-coupled meteorology and chemistry model WRF-CAM5 has been applied to East Asia using triple-nested domains at different grid resolutions (i.e., 36-, 12-, and 4-km) to simulate a severe dust storm period in spring 2010. Analyses are performed to evaluate the model performance and investigate model sensitivity to different horizontal grid sizes and aerosol activation parameterizations and to examine aerosol-cloud interactions and their impacts on the air quality. A comprehensive model evaluation of the baseline simulations using the default Abdul-Razzak and Ghan (AG) aerosol activation scheme shows that the model can well predict major meteorological variables such as 2-m temperature (T2), water vapor mixing ratio (Q2), 10-m wind speed (WS10) and wind direction (WD10), and shortwave and longwave radiation across different resolutions with domain-average normalized mean biases typically within ±15%. The baseline simulations also show moderate biases for precipitation and moderate-to-large underpredictions for other major variables associated with aerosol-cloud interactions such as cloud droplet number concentration (CDNC), cloud optical thickness (COT), and cloud liquid water path (LWP) due to uncertainties or limitations in the aerosol-cloud treatments. The model performance is sensitive to grid resolutions, especially for surface meteorological variables such as T2, Q2, WS10, and WD10, with the performance generally improving at finer grid resolutions for those variables. Comparison of the sensitivity simulations with an alternative (i.e., the Fountoukis and Nenes (FN) series scheme) and the default (i.e., AG scheme) aerosol activation scheme shows that the former predicts larger values for cloud variables such as CDNC and COT across all grid resolutions and improves the overall domain-average model performance for many cloud/radiation variables and precipitation. Sensitivity simulations using the FN series scheme also have large impacts on radiations, T2, precipitation, and air quality (e.g., decreasing O3) through complex aerosol-radiation-cloud-chemistry feedbacks. The inclusion of adsorptive activation of dust particles in the FN series scheme has similar impacts on the meteorology and air quality but to lesser extent as compared to differences between the FN series and AG schemes. Compared to the overall differences between the FN series and AG schemes, impacts of adsorptive activation of dust particles can contribute significantly to the increase of total CDNC (∼45%) during dust storm events and indicate their importance in modulating regional climate over East Asia.}, journal={Atmospheric Environment}, publisher={Elsevier BV}, author={Wang, Kai and Zhang, Yang and Zhang, Xin and Fan, Jiwen and Leung, L. Ruby and Zheng, Bo and Zhang, Qiang and He, Kebin}, year={2018}, month={Mar}, pages={1–20} }
 @article{yahya_wang_campbell_chen_glotfelty_he_pirhalla_zhang_2017, title={Decadal application of WRF/Chem for regional air quality and climate modeling over the US under the representative concentration pathways scenarios. Part 1: Model evaluation and impact of downscaling}, volume={152}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2016.12.029}, abstractNote={An advanced online-coupled meteorology-chemistry model, i.e., the Weather Research and Forecasting Model with Chemistry (WRF/Chem), is applied for current (2001–2010) and future (2046–2055) decades under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios to examine changes in future climate, air quality, and their interactions. In this Part I paper, a comprehensive model evaluation is carried out for current decade to assess the performance of WRF/Chem and WRF under both scenarios and the benefits of downscaling the North Carolina State University's (NCSU) version of the Community Earth System Model (CESM_NCSU) using WRF/Chem. The evaluation of WRF/Chem shows an overall good performance for most meteorological and chemical variables on a decadal scale. Temperature at 2-m is overpredicted by WRF (by ∼0.2–0.3 °C) but underpredicted by WRF/Chem (by ∼0.3–0.4 °C), due to higher radiation from WRF. Both WRF and WRF/Chem show large overpredictions for precipitation, indicating limitations in their microphysics or convective parameterizations. WRF/Chem with prognostic chemical concentrations, however, performs much better than WRF with prescribed chemical concentrations for radiation variables, illustrating the benefit of predicting gases and aerosols and representing their feedbacks into meteorology in WRF/Chem. WRF/Chem performs much better than CESM_NCSU for most surface meteorological variables and O3 hourly mixing ratios. In addition, WRF/Chem better captures observed temporal and spatial variations than CESM_NCSU. CESM_NCSU performance for radiation variables is comparable to or better than WRF/Chem performance because of the model tuning in CESM_NCSU that is routinely made in global models.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Yahya, Khairunnisa and Wang, Kai and Campbell, Patrick and Chen, Ying and Glotfelty, Timothy and He, Jian and Pirhalla, Michael and Zhang, Yang}, year={2017}, month={Mar}, pages={562–583} }
 @article{campbell_zhang_wang_leung_fan_zheng_zhang_he_2017, title={Evaluation of a multi-scale WRF-CAM5 simulation during the 2010 East Asian Summer Monsoon}, volume={169}, ISSN={1352-2310}, url={http://dx.doi.org/10.1016/J.ATMOSENV.2017.09.008}, DOI={10.1016/J.ATMOSENV.2017.09.008}, abstractNote={The Weather Research and Forecasting model with Chemistry (WRF-Chem) with the physics package of the Community Atmosphere Model Version 5 (CAM5) has been applied at multiple scales over Eastern China (EC) and the Yangtze River Delta (YRD) to evaluate how increased horizontal resolution with physics designed for a coarser resolution climate model impacts aerosols and clouds, and the resulting precipitation characteristics and performance during the 2010 East Asian Summer Monsoon (EASM). Despite large underpredictions in surface aerosol concentrations and aerosol optical depth, there is good spatial agreement with surface observations of chemical predictions, and increasing spatial resolution tends to improve performance. Model bias and normalized root mean square values for precipitation predictions are relatively small, but there are significant differences when comparing modeled and observed probability density functions for precipitation in EC and YRD. Increasing model horizontal resolution tends to reduce model bias and error for precipitation predictions. The surface and column aerosol loading is maximized between about 32°N and 42°N in early to mid-May during the 2010 EASM, and then shifts north while decreasing in magnitude during July and August. Changing model resolution moderately changes the spatiotemporal relationships between aerosols, cloud properties, and precipitation during the EASM, thus demonstrating the importance of model grid resolution in simulating EASM circulation and rainfall patterns over EC and the YRD. Results from this work demonstrate the capability and limitations in the aerosol, cloud, and precipitation representation of WRF-CAM5 for regional-scale applications down to relatively fine horizontal resolutions. Further WRF-CAM5 model development and application in this area is needed.}, journal={Atmospheric Environment}, publisher={Elsevier BV}, author={Campbell, Patrick and Zhang, Yang and Wang, Kai and Leung, Ruby and Fan, Jiwen and Zheng, Bo and Zhang, Qiang and He, Kebin}, year={2017}, month={Nov}, pages={204–217} }
 @article{zhang_wang_jena_2017, title={Impact of Projected Emission and Climate Changes on Air Quality in the US: from National to State Level}, volume={110}, ISSN={["1877-0509"]}, DOI={10.1016/j.procs.2017.06.074}, abstractNote={Future ambient air quality will respond to changes in anthropogenic and biogenic emissions as well as climate changes, which may vary at national and state levels in different regions of the world. In this work, we applied an advanced online-coupled meteorology and chemistry model, the Weather Research and Forecasting Model with Chemistry (WRF/Chem), to the continental U.S. for current (2001-2010) and future (2046-2055) decades under four climate scenarios including the Representative Concentration Pathways (RCP) 4.5 and 8.5 and the Technology Driver Model (TDM) A1B and B2. Our goal is to quantify the impact of projected changes in anthropogenic and biogenic emissions and climate on future air quality under various climate scenarios for policy analysis for emission control and mitigation of adverse climate change. The simulations are performed at 36-, 12-km, and 4-km over North America, Continental U.S., and selected states, respectively. A comprehensive evaluation has been performed for the current simulation period using available observations from surface networks and satellites and shows an overall good performance in reproducing climatic and chemical observations at all grid scales. Future air quality features greater reduction in PM2.5 by RCP 4.5/8.5 than TDM B2/A1B and decreased O3 over most areas in the U.S. by RCP4.5 and TDM B2, indicating the benefits of carbon policy and technology changes with greater emission reductions. Air quality responds differently to projected changes in anthropogenic emissions in different states and seasons, indicating a need to develop state-specific emission control strategies for different seasons.}, journal={14TH INTERNATIONAL CONFERENCE ON MOBILE SYSTEMS AND PERVASIVE COMPUTING (MOBISPC 2017) / 12TH INTERNATIONAL CONFERENCE ON FUTURE NETWORKS AND COMMUNICATIONS (FNC 2017) / AFFILIATED WORKSHOPS}, author={Zhang, Yang and Wang, Kai and Jena, Chinmay}, year={2017}, pages={167–173} }
 @article{duan_sun_zhang_yahya_wang_madden_caldwell_cohen_mcnulty_2017, title={Impact of air pollution induced climate change on water availability and ecosystem productivity in the conterminous United States}, volume={140}, ISSN={0165-0009 1573-1480}, url={http://dx.doi.org/10.1007/S10584-016-1850-7}, DOI={10.1007/S10584-016-1850-7}, number={2}, journal={Climatic Change}, publisher={Springer Science and Business Media LLC}, author={Duan, Kai and Sun, Ge and Zhang, Yang and Yahya, Khairunnisa and Wang, Kai and Madden, James M. and Caldwell, Peter V. and Cohen, Erika C. and McNulty, Steven G.}, year={2017}, pages={259–272} }
 @article{yahya_glotfelty_wang_zhang_nenes_2017, title={Modeling regional air quality and climate: Improving organic aerosol and aerosol activation processes in WRF/Chem version 3.7.1}, volume={10}, number={6}, journal={Geoscientific Model Development}, author={Yahya, K. and Glotfelty, T. and Wang, K. and Zhang, Y. and Nenes, A.}, year={2017}, pages={2333–2363} }
 @article{he_zhang_wang_chen_leung_fan_li_zheng_zhang_duan_et al._2017, title={Multi-year application of WRF-CAM5 over East Asia-Part I: Comprehensive evaluation and formation regimes of O-3 and PM2.5}, volume={165}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2017.06.015}, abstractNote={Accurate simulations of air quality and climate require robust model parameterizations on regional and global scales. The Weather Research and Forecasting model with Chemistry version 3.4.1 has been coupled with physics packages from the Community Atmosphere Model version 5 (CAM5) (WRF-CAM5) to assess the robustness of the CAM5 physics package for regional modeling at higher grid resolutions than typical grid resolutions used in global modeling. In this two-part study, Part I describes the application and evaluation of WRF-CAM5 over East Asia at a horizontal resolution of 36-km for six years: 2001, 2005, 2006, 2008, 2010, and 2011. The simulations are evaluated comprehensively with a variety of datasets from surface networks, satellites, and aircraft. The results show that meteorology is relatively well simulated by WRF-CAM5. However, cloud variables are largely or moderately underpredicted, indicating uncertainties in the model treatments of dynamics, thermodynamics, and microphysics of clouds/ices as well as aerosol-cloud interactions. For chemical predictions, the tropospheric column abundances of CO, NO2, and O3 are well simulated, but those of SO2 and HCHO are moderately overpredicted, and the column HCHO/NO2 indicator is underpredicted. Large biases exist in the surface concentrations of CO, NOx, and PM10 due to uncertainties in the emissions as well as vertical mixing. The underpredictions of NO lead to insufficient O3 titration, thus O3 overpredictions. The model can generally reproduce the observed O3 and PM indicators. These indicators suggest to control NOx emissions throughout the year, and VOCs emissions in summer in big cities and in winter over North China Plain, North/South Korea, and Japan to reduce surface O3, and to control SO2, NH3, and NOx throughout the year to reduce inorganic surface PM.}, journal={ATMOSPHERIC ENVIRONMENT}, author={He, Jian and Zhang, Yang and Wang, Kai and Chen, Ying and Leung, L. Ruby and Fan, Jiwen and Li, Meng and Zheng, Bo and Zhang, Qiang and Duan, Fengkui and et al.}, year={2017}, month={Sep}, pages={122–142} }
 @article{zhang_wang_he_2017, title={Multi-year application of WRF-CAM5 over East Asia-Part II: Interannual variability, trend analysis, and aerosol indirect effects}, volume={165}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2017.06.029}, abstractNote={Following a comprehensive evaluation of WRF-CAM5 in Part I, Part II describes analyses of interannual variability, multi-year variation trends, and the direct, indirect, and total effects of anthropogenic aerosols. The interannual variations of chemical column and surface concentrations, and ozone (O3)/particulate matter (PM) indicators are strongly correlated to anthropogenic emission changes. Despite model biases, the model captures well the observed interannual variations of temperature at 2-m, cloud fraction, shortwave cloud forcing, downwelling shortwave radiation, cloud droplet number concentration, column O3, and column formaldehyde (HCHO) for the whole domain. While the model reproduces the volatile organic compound (VOC)-limited regimes of O3 chemistry at sites in Hong Kong, Taiwan, Japan, South Korea, and from the Acid Deposition Monitoring Network in East Asia (EANET) and the degree of sulfate neutralization at the EANET sites, it has limited capability in capturing the interannual variations of the ratio of O3 and nitrogen dioxide (O3/NO2) and PM chemical regime indicators, due to uncertainties in the emissions of precursors for O3 and secondary PM, the model assumption for ammonium bisulfate (NH4HSO4) as well as lack of gas/particle partitioning of total ammonia and total nitrate. While the variation trends in multi-year periods in aerosol optical depth and column concentrations of carbon monoxide, sulfur dioxide, and NO2 are mainly caused by anthropogenic emissions, those of major meteorological and cloud variables partly reflect feedbacks of chemistry to meteorological variables. The impacts of anthropogenic aerosol indirect effects either dominate or play an important role in the aerosol total effects for most cloud and chemical predictions, whereas anthropogenic aerosol direct effects influence most meteorological and radiation variables. The direct, indirect, and total effects of anthropogenic aerosols exhibit a strong interannual variability in 2001, 2006, and 2011.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Zhang, Yang and Wang, Kai and He, Jian}, year={2017}, month={Sep}, pages={222–239} }
 @article{song_wang_zhang_hong_zhou_2017, title={Simulation and evaluation of dust emissions with WRF-Chem (v3.7.1) and its relationship to the changing climate over East Asia from 1980 to 2015}, volume={167}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2017.08.051}, abstractNote={Dust particles have been long recognized to affect the atmospheric radiative balance and are influenced by climate change. Impacts of climate change on dust emissions in East Asia, however, are not well understood. In this work, we conduct an evaluation of meteorological variables and dust emissions using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and examine the relationships between dust emissions and meteorological variables (wind speed, precipitation, and temperature) over East Asia during the period of 1980–2015. Model simulated surface meteorological variables compared well overall with surface-based observations, consistent with other WRF studies. Compared to observations, the coarse particulate matter (PM10-2.5) concentrations were underpredicted for most dust source regions of East Asia with a domain-wide mean bias and correlation of −40.2 μg m−3 and 0.5 against observations, respectively. Dust particulate concentrations simulated by WRF-Chem were found to reproduce the observed spatial variability in surface dust particulates over East Asia. The average annual dust emission (0 < r < 20 μm) is around 67.4 Tg yr−1 and the dust emission increased with the trend of 0.173 Tg yr−1 (R2 = 0.03, P = 0.32) in China and Mongolia over the past four decades. The spatial and temporal variations of dust emissions in China and Mongolia indicate that the annual dust flux has increased in desert areas of China and Mongolia, but decreased in most Gobi regions of China. Dust emission is significantly positively and negatively correlated with wind velocity and precipitation at the regional scale. Spatial patterns of seasonal correlations between dust flux and climate varies greatly during the period of 1980–2015.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Song, Hongquan and Wang, Kai and Zhang, Yang and Hong, Chaopeng and Zhou, Shenghui}, year={2017}, month={Oct}, pages={511–522} }
 @article{zhang_zhang_wang_zhang_duan_he_2016, title={Application of WRF/Chem over East Asia: Part II. Model improvement and sensitivity simulations}, volume={124}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2015.07.023}, abstractNote={To address the problems and limitations identified through a comprehensive evaluation in Part I paper, several modifications are made in model inputs, treatments, and configurations and sensitivity simulations with improved model inputs and treatments are performed in this Part II paper. The use of reinitialization of meteorological variables reduces the biases and increases the spatial correlations in simulated temperature at 2-m (T2), specific humidity at 2-m (Q2), wind speed at 10-m (WS10), and precipitation (Precip). The use of a revised surface drag parameterization further reduces the biases in simulated WS10. The adjustment of only the magnitudes of anthropogenic emissions in the surface layer does not help improve overall model performance, whereas the adjustment of both the magnitudes and vertical distributions of anthropogenic emissions shows moderate to large improvement in simulated surface concentrations and column mass abundances of species in terms of domain mean performance statistics, hourly and monthly mean concentrations, and vertical profiles of concentrations at individual sites. The revised and more advanced dust emission schemes can help improve PM predictions. Using revised upper boundary conditions for O3 significantly improves the column O3 abundances. Using a simple SOA formation module further improves the predictions of organic carbon and PM2.5. The sensitivity simulation that combines all above model improvements greatly improves the overall model performance. For example, the sensitivity simulation gives the normalized mean biases (NMBs) of −6.1% to 23.8% for T2, 2.7–13.8% for Q2, 22.5–47.6% for WS10, and −9.1% to 15.6% for Precip, comparing to −9.8% to 75.6% for T2, 0.4–23.4% for Q2, 66.5–101.0% for WS10, and 11.4%–92.7% for Precip from the original simulation without those improvements. It also gives the NMBs for surface predictions of −68.2% to −3.7% for SO2, −73.8% to −20.6% for NO2, −8.8%–128.7% for O3, −61.4% to −26.5% for PM2.5, and −64.0% to 7.2% for PM10, comparing to −84.2% to −44.5% for SO2, −88.1% to −44.0% for NO2, −11.0%–160.3% for O3, −63.9% to −25.2% for PM2.5, and −68.9%–33.3% for PM10 from the original simulation. The improved WRF/Chem is applied to estimate the impact of anthropogenic aerosols on regional climate and air quality in East Asia. Anthropogenic aerosols can increase cloud condensation nuclei, aerosol optical depth, cloud droplet number concentrations, and cloud optical depth. They can decrease surface net radiation, temperature at 2-m, wind speed at 10-m, planetary boundary layer height, and precipitation through various direct and indirect effects. These changes in turn lead to changes in chemical predictions in a variety of ways.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Zhang, Yang and Zhang, Xin and Wang, Kai and Zhang, Qiang and Duan, Fengkui and He, Kebin}, year={2016}, month={Jan}, pages={301–320} }
 @article{wang_zhang_wang_zheng_zhang_wei_2016, title={Application of Weather Research and Forecasting Model with Chemistry (WRF/Chem) over northern China: Sensitivity study, comparative evaluation, and policy implications}, volume={124}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.12.052}, abstractNote={An extremely severe and persistent haze event occurred over the middle and eastern China in January 2013, with the record-breaking high concentrations of fine particulate matter (PM2.5). In this study, an online-coupled meteorology-air quality model, the Weather Research and Forecasting Model with Chemistry (WRF/Chem), is applied to simulate this pollution episode over East Asia and northern China at 36- and 12-km grid resolutions. A number of simulations are conducted to examine the sensitivities of the model predictions to various physical schemes. The results show that all simulations give similar predictions for temperature, wind speed, wind direction, and humidity, but large variations exist in the prediction for precipitation. The concentrations of PM2.5, particulate matter with aerodynamic diameter of 10 μm or less (PM10), sulfur dioxide (SO2), and nitrogen dioxide (NO2) are overpredicted partially due to the lack of wet scavenging by the chemistry-aerosol option with the 1999 version of the Statewide Air Pollution Research Center (SAPRC-99) mechanism with the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) and the Volatility Basis Set (VBS) for secondary organic aerosol formation. The optimal set of configurations with the best performance is the simulation with the Gorddard shortwave and RRTM longwave radiation schemes, the Purdue Lin microphysics scheme, the Kain-Fritsch cumulus scheme, and a nudging coefficient of 1 × 10−5 for water vapor mixing ratio. The emission sensitivity simulations show that the PM2.5 concentrations are most sensitive to nitrogen oxide (NOx) and SO2 emissions in northern China, but to NOx and ammonia (NH3) emissions in southern China. 30% NOx emission reductions may result in an increase in PM2.5 concentrations in northern China because of the NH3-rich and volatile organic compound (VOC) limited conditions over this area. VOC emission reductions will lead to a decrease in PM2.5 concentrations in eastern China. However, 30% reductions in the emissions of SO2, NOx, NH3, and VOC, individually or collectively, are insufficient to effectively mitigate the severe pollution over northern China. More aggressive emission controls, which needs to be identified in further studies, are needed in this area to reach the objective of 25% PM2.5 concentration reduction in 2017 proposed in the Action Plan for Air Pollution Prevention and Control by the State Council in 2013.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Wang, Litao and Zhang, Yang and Wang, Kai and Zheng, Bo and Zhang, Qiang and Wei, Wei}, year={2016}, month={Jan}, pages={337–350} }
 @article{yahya_wang_campbell_glotfelty_he_zhang_2016, title={Decadal evaluation of regional climate, air quality, and their interactions over the continental US and their interactions using WRF/Chem version 3.6.1}, volume={9}, number={2}, journal={Geoscientific Model Development}, author={Yahya, K. and Wang, K. and Campbell, P. and Glotfelty, T. and He, J. and Zhang, Y.}, year={2016}, pages={671–695} }
 @article{cai_zhang_wang_zhang_wang_zhang_duan_he_yu_2016, title={Incorporation of new particle formation and early growth treatments into WRF/Chem: Model improvement, evaluation, and impacts of anthropogenic aerosols over East Asia}, volume={124}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2015.05.046}, abstractNote={New particle formation (NPF) provides an important source of aerosol particles and cloud condensation nuclei, which may result in enhanced cloud droplet number concentration (CDNC) and cloud shortwave albedo. In this work, several nucleation parameterizations and one particle early growth parameterization are implemented into the online-coupled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) to improve the model's capability in simulating NPF and early growth of ultrafine particles over East Asia. The default 8-bin over the size range of 39 nm–10 μm used in the Model for Simulating Aerosol Interactions and Chemistry aerosol module is expanded to the 12-bin over 1 nm–10 μm to explicitly track the formation and evolution of new particles. Although model biases remain in simulating H2SO4, condensation sink, growth rate, and formation rate, the evaluation of July 2008 simulation identifies a combination of three nucleation parameterizations (i.e., COMB) that can best represent the atmospheric nucleation processes in terms of both surface nucleation events and the resulting vertical distribution of ultrafine particle concentrations. COMB consists of a power law of Wang et al. (2011) based on activation theory for urban areas in planetary boundary layer (PBL), a power law of Boy et al. (2008) based on activation theory for non-urban areas in PBL, and the ion-mediated nucleation parameterization of YU10 for above PBL. The application and evaluation of the improved model with 12-bin and the COMB nucleation parameterization in East Asia during January, April, July, and October in 2001 show that the model has an overall reasonably good skill in reproducing most observed meteorological variables and surface and column chemical concentrations. Relatively large biases in simulated precipitation and wind speeds are due to inaccurate surface roughness and limitations in model treatments of cloud formation and aerosol-cloud-precipitation interactions. Large biases in the simulated surface concentrations of PM10, NOx, CO, SO2, and VOCs at some sites are due in part to possible underestimations of emissions and in part to inaccurate meteorological predictions. The simulations of 2001 show that anthropogenic aerosols can increase aerosol optical depth by 64.0–228.3%, CDNC by 40.2–76.4%, and cloud optical thickness by 14.3–25.3%; they can reduce surface net shortwave radiation by up to 42.5–52.8 W m−2, 2-m temperature by up to 0.34–0.83 °C, and PBL height by up to 76.8–125.9 m. Such effects are more significant than those previously reported for the U.S. and Europe.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Cai, Changjie and Zhang, Xin and Wang, Kai and Zhang, Yang and Wang, Litao and Zhang, Qiang and Duan, Fengkui and He, Kebin and Yu, Shao-Cai}, year={2016}, month={Jan}, pages={262–284} }
 @article{wang_yahya_zhang_hogrefe_pouliot_knote_hodzic_san jose_perez_jiménez-guerrero_et al._2015, title={A multi-model assessment for the 2006 and 2010 simulations under the Air Quality Model Evaluation International Initiative (AQMEII) Phase 2 over North America: Part II. Evaluation of column variable predictions using satellite data}, volume={115}, ISSN={1352-2310}, url={http://dx.doi.org/10.1016/J.ATMOSENV.2014.07.044}, DOI={10.1016/J.ATMOSENV.2014.07.044}, abstractNote={Within the context of the Air Quality Model Evaluation International Initiative Phase 2 (AQMEII2) project, this part II paper performs a multi-model assessment of major column abundances of gases, radiation, aerosol, and cloud variables for 2006 and 2010 simulations with three online-coupled air quality models over the North America using available satellite data. It also provides the first comparative assessment of the capabilities of the current generation of online-coupled models in simulating column variables. Despite the use of different model configurations and meteorological initial and boundary conditions, most simulations show comparable model performance for many variables. The evaluation results show an excellent agreement between all simulations and satellite-derived radiation variables including downward surface solar radiation, longwave radiation, and top-of-atmospheric outgoing longwave radiation, as well as precipitable water vapor with domain-average normalized mean biases (NMBs) of typically less than 5% and correlation coefficient (R) typically more than 0.9. Most simulations perform well for column-integrated abundance of CO with domain-average NMBs of −9.4% to −2.2% in 2006 and −12.1% to 4.6% in 2010 and from reasonably well to fair for column NO2, HCHO, and SO2, with domain-average NMBs of −37.7% to 2.1%, −27.3% to 59.2%, and 16.1% to 114.2% in 2006, respectively, and, 12.9% to 102.1%, −25.0% to 87.6%, −65.2% to 7.4% in 2010, respectively. R values are high for CO and NO2 typically between 0.85 and 0.9 (i.e., R2 of 0.7–0.8). Tropospheric ozone residuals are overpredicted by all simulations due to overestimates of ozone profiles from boundary conditions. Model performance for cloud-related variables is mixed and generally worse compared to gases and radiation variables. Cloud fraction (CF) is well reproduced by most simulations. Other aerosol/cloud related variables such as aerosol optical depth (AOD), cloud optical thickness, cloud liquid water path, cloud condensation nuclei, and cloud droplet number concentration (CDNC) are moderately to largely underpredicted by most simulations, due to underpredictions of aerosol loadings and also indicating high uncertainties associated with the current model treatments of aerosol–cloud interactions and the need for further model development. Negative correlations are found for AOD for most simulations due to large negative biases over the western part of the domain. Inter-model discrepancies also exist for a few variables such as column abundances of HCHO and SO2 and CDNC due likely to different chemical mechanisms, biogenic emissions, and treatments of aerosol indirect effects. Most simulations can also capture the inter-annual trend observed by satellites between 2006 and 2010 for several variables such as column abundance of NO2, AOD, CF, and CDNC. Results shown in this work provide the important benchmark for future online-couple air quality model development.}, journal={Atmospheric Environment}, publisher={Elsevier BV}, author={Wang, Kai and Yahya, Khairunnisa and Zhang, Yang and Hogrefe, Christian and Pouliot, George and Knote, Christoph and Hodzic, Alma and San Jose, Roberto and Perez, Juan L. and Jiménez-Guerrero, Pedro and et al.}, year={2015}, month={Aug}, pages={587–603} }
 @article{campbell_zhang_yahya_wang_hogrefe_pouliot_knote_hodzic_san jose_perez_et al._2015, title={A multi-model assessment for the 2006 and 2010 simulations under the Air Quality Model Evaluation International Initiative (AQMEII) phase 2 over North America: Part I. Indicators of the sensitivity of O-3 and PM2.5 formation regimes}, volume={115}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.12.026}, abstractNote={Under the Air Quality Model Evaluation International Initiative, Phase 2 (AQMEII-2), three online-coupled air quality model simulations, with six different configurations, are analyzed for their performance, inter-model agreement, and responses to emission and meteorological changes between 2006 and 2010. In this Part I paper, we focus on evaluating O3 and PM2.5 indicator-based analyses, which are important in the development of applicable control strategies of O3 and PM2.5 pollution in different regions worldwide. The O3 indicators agree on widespread NOx-limited and localized VOC-limited conditions in the U.S. The NOy and O3/NOy indicators overpredict the extent of the VOC-limited chemistry in southeast U.S., but are more robust than the H2O2/HNO3, HCHO/NOy, and HCHO/NO2 indicators at the surface, which exhibit relatively more inter-model variability. The column HCHO/NO2 indicator is underpredicted in the O3 and non-O3 seasons, but there is regional variability. For surface PM2.5 indicators, there is good inter-model agreement for the degree of sulfate neutralization; however there are systematic underpredictions in the southeast U.S. There is relatively poor inter-model agreement for the less robust adjusted gas ratio indicator, which is largely overpredicted in the summer and both under- and overpredicted in winter in the southeast U.S. There is good inter-model agreement for the O3 indicator sensitivities, indicating a predominant shift to more NOx-limited conditions in 2010 relative to 2006. There is less agreement for PM2.5 indicator sensitivities, which are less robust, while indicating shifts to either regime due to different responses of aerosol treatments to changes in emissions and meteorology.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Campbell, Patrick and Zhang, Yang and Yahya, Khairunnisa and Wang, Kai and Hogrefe, Christian and Pouliot, George and Knote, Christoph and Hodzic, Alma and San Jose, Roberto and Perez, Juan L. and et al.}, year={2015}, month={Aug}, pages={569–586} }
 @article{yahya_wang_gudoshava_glotfelty_zhang_2015, title={Application of WRF/Chem over North America under the AQMEII Phase 2: Part I. Comprehensive evaluation of 2006 simulation}, volume={115}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.08.063}, abstractNote={The Weather Research and Forecasting model with Chemistry (WRF/Chem) version 3.4.1 has been modified to include the Carbon Bond 2005 (CB05) gas-phase mechanism, the Modal for Aerosol Dynamics for Europe (MADE) and the Volatility Basis Set (VBS) approach for secondary organic aerosol (hereafter WRF/Chem-CB05-MADE/VBS), and aerosol-cloud-radiation feedbacks to improve predictions of secondary organic aerosols (SOA) and to study meteorology-chemistry feedbacks. In this Part I paper, a comprehensive evaluation is performed for WRF/Chem-CB05-MADE/VBS to simulate air quality over a large area in North America for the full year of 2006. Operational, diagnostic, and mechanistic evaluations have been carried out for major meteorological variables, gas and aerosol species, as well as aerosol-cloud-radiation variables against surface measurements, sounding data, and satellite data on a seasonal and annual basis. The model performs well for most meteorological variables with moderate to relatively high correlation and low mean biases (MBs), but with a cold bias of 0.8–0.9 °C in temperature, a moderate overprediction with normalized mean biases (NMBs) of 17–22% in wind speed, and large underpredictions with NMBs of −65% to −62% in cloud optical depths and cloud condensation nuclei over the ocean. Those biases are attributed to uncertainty in physical parameterizations, incomplete treatments of hydrometeors, and inaccurate aerosol predictions. The model shows moderate underpredictions in the mixing ratios of O3 with an annual NMB of −12.8% over rural and national park sites, which may be caused by biases in temperature and wind speed, underestimate in wildfire emissions, and underestimate in biogenic organic emissions (reflected by an NMB of −79.1% in simulated isoprene mixing ratio). The model performs well for PM2.5 concentrations with annual NMBs within ±10%; but with possible bias compensation for PM2.5 species concentrations. The model simulates well the domainwide organic carbon and SOA concentrations at two sites in the southeastern U.S. but it overpredicts SOA concentrations at two sites and underpredicts OC at one site in the same area. Those biases in site-specific SOA and OC predictions are attributed to underestimates in observed SOA, uncertainties in VOC emissions, inaccurate meteorology, and the inadequacies in the VBS treatment. Larger biases exist in predictions of dry and wet deposition fluxes of gas and PM species due mainly to overpredictions in their concentrations and precipitation, uncertainties in model treatments of deposition processes, and uncertainties in the CASTNET dry deposition data. Comparison of WRF and WRF/Chem simulations shows that the inclusion of chemical feedbacks to meteorology, clouds, and radiation results in improved predictions in most meteorological variables. Aerosol optical depth correlates strongly with aerosol concentration and cloud optical depth. The relationships between the aerosol and cloud variables are complex as the cloud variables are not only influenced by aerosol concentrations but by larger-scale dynamical processes.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Yahya, Khairunnisa and Wang, Kai and Gudoshava, Masi Lin and Glotfelty, Timothy and Zhang, Yang}, year={2015}, month={Aug}, pages={733–755} }
 @article{im_bianconi_solazzo_kioutsioukis_badia_balzarini_baró_bellasio_brunner_chemel_et al._2015, title={Evaluation of operational online-coupled regional air quality models over Europe and North America in the context of AQMEII phase 2. Part II: Particulate matter}, volume={115}, ISSN={1352-2310}, url={http://dx.doi.org/10.1016/J.ATMOSENV.2014.08.072}, DOI={10.1016/J.ATMOSENV.2014.08.072}, abstractNote={The second phase of the Air Quality Model Evaluation International Initiative (AQMEII) brought together seventeen modeling groups from Europe and North America, running eight operational online-coupled air quality models over Europe and North America using common emissions and boundary conditions. The simulated annual, seasonal, continental and sub-regional particulate matter (PM) surface concentrations for the year 2010 have been evaluated against a large observational database from different measurement networks operating in Europe and North America. The results show a systematic underestimation for all models in almost all seasons and sub-regions, with the largest underestimations for the Mediterranean region. The rural PM10 concentrations over Europe are underestimated by all models by up to 66% while the underestimations are much larger for the urban PM10 concentrations (up to 75%). On the other hand, there are overestimations in PM2.5 levels suggesting that the large underestimations in the PM10 levels can be attributed to the natural dust emissions. Over North America, there is a general underestimation in PM10 in all seasons and sub-regions by up to ∼90% due mainly to the underpredictions in soil dust. SO42− levels over EU are underestimated by majority of the models while NO3− levels are largely overestimated, particularly in east and south Europe. NH4+ levels are also underestimated largely in south Europe. SO4 levels over North America are particularly overestimated over the western US that is characterized by large anthropogenic emissions while the eastern USA is characterized by underestimated SO4 levels by the majority of the models. Daytime AOD levels at 555 nm is simulated within the 50% error range over both continents with differences attributed to differences in concentrations of the relevant species as well as in approaches in estimating the AOD. Results show that the simulated dry deposition can lead to substantial differences among the models. Overall, the results show that representation of dust and sea-salt emissions can largely impact the simulated PM concentrations and that there are still major challenges and uncertainties in simulating the PM levels.}, journal={Atmospheric Environment}, publisher={Elsevier BV}, author={Im, Ulas and Bianconi, Roberto and Solazzo, Efisio and Kioutsioukis, Ioannis and Badia, Alba and Balzarini, Alessandra and Baró, Rocío and Bellasio, Roberto and Brunner, Dominik and Chemel, Charles and et al.}, year={2015}, month={Aug}, pages={421–441} }
 @article{im_bianconi_solazzo_kioutsioukis_badia_balzarini_baro_bellasio_brunner_chemel_et al._2015, title={Evaluation of operational online-coupled regional air quality models over Europe and North America in the context of AQMEII phase 2. Part II: Particulate matter}, volume={115}, journal={Atmospheric Environment}, author={Im, U. and Bianconi, R. and Solazzo, E. and Kioutsioukis, I. and Badia, A. and Balzarini, A. and Baro, R. and Bellasio, R. and Brunner, D. and Chemel, C. and et al.}, year={2015}, pages={421–441} }
 @article{zheng_zhang_zhang_he_wang_zheng_duan_ma_kimoto_2015, title={Heterogeneous chemistry: a mechanism missing in current models to explain secondary inorganic aerosol formation during the January 2013 haze episode in North China}, volume={15}, number={4}, journal={Atmospheric Chemistry and Physics}, author={Zheng, B. and Zhang, Q. and Zhang, Y. and He, K. B. and Wang, K. and Zheng, G. J. and Duan, F. K. and Ma, Y. L. and Kimoto, T.}, year={2015}, pages={2031–2049} }
 @article{wang_zhang_yahya_wu_grell_2015, title={Implementation and initial application of new chemistry-aerosol options in WRF/Chem for simulating secondary organic aerosols and aerosol indirect effects for regional air quality}, volume={115}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.12.007}, abstractNote={Atmospheric aerosols play important roles in affecting regional meteorology and air quality through aerosol direct and indirect effects. Two new chemistry-aerosol options have been developed in WRF/Chem v3.4.1 by incorporating the 2005 Carbon Bond (CB05) mechanism and coupling it with the existing aerosol module MADE with SORGAM and VBS modules for simulating secondary organic aerosol (SOA), aqueous-phase chemistry in both large scale and convective clouds, and aerosol feedback processes (hereafter CB05-MADE/SORGAM and CB05-MADE/VBS). As part of the Air Quality Model Evaluation International Initiative (AQMEII) Phase II model intercomparison that focuses on online-coupled meteorology and chemistry models, WRF/Chem with the two new options is applied to an area over North America for July 2006 episode. The simulations with both options can reproduce reasonably well most of the observed meteorological variables, chemical concentrations, and aerosol/cloud properties. Compared to CB05-MADE/SORGAM, CB05-MADE/VBS greatly improves the model performance for organic carbon (OC) and PM2.5, reducing NMBs from −81.2% to −13.1% and from −26.1% to −15.6%, respectively. Sensitivity simulations show that the aerosol indirect effects (including aqueous-phase chemistry) can reduce the net surface solar radiation by up to 53 W m−2 with a domainwide mean of 12 W m−2 through affecting cloud formation and radiation scattering and reflection by increasing cloud cover, which in turn reduce the surface temperature, NO2 photolytic rate, and planetary boundary layer height by up to 0.3 °C, 3.7 min−1, and 64 m, respectively. The changes of those meteorological variables further impact the air quality through the complex chemistry-aerosol-cloud-radiation interactions by reducing O3 mixing ratios by up to 5.0 ppb. The results of this work demonstrate the importance of aerosol indirect effects on the regional climate and air quality. For comparison, the impacts of aerosol direct effects on both regional meteorology and air quality are much lower with the reduction on net surface solar radiation only by up to 17 W m−2 and O3 only by up to 1.4 ppb, which indicates the importance and necessity to accurately represent the aerosol indirect effects in the online-couple regional models.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Wang, Kai and Zhang, Yang and Yahya, Khairunnisa and Wu, Shiang-Yuh and Grell, Georg}, year={2015}, month={Aug}, pages={716–732} }
 @article{zhang_zhang_wang_he_leung_fan_nenes_2015, title={Incorporating an advanced aerosol activation parameterization into WRF-CAM5: Model evaluation and parameterization intercomparison}, volume={120}, ISSN={["2169-8996"]}, DOI={10.1002/2014jd023051}, abstractNote={Abstract}, number={14}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Zhang, Yang and Zhang, Xin and Wang, Kai and He, Jian and Leung, L. Ruby and Fan, Jiwen and Nenes, Athanasios}, year={2015}, month={Jul}, pages={6952–6979} }
 @article{li_zhang_zhang_zheng_wang_chen_wallington_han_shen_zhang_et al._2015, title={Source contributions of urban PM2.5 in the Beijing-Tianjin-Hebei region: Changes between 2006 and 2013 and relative impacts of emissions and meteorology}, volume={123}, DOI={10.1016/j.atmosenv.2015.10.048}, abstractNote={Anthropogenic emissions in China have been controlled for years to improve ambient air quality. However, severe haze events caused by atmospheric aerosols with aerodynamic diameter less than or equal to 2.5 μm (PM2.5) have continued to occur, especially in the Beijing–Tianjin–Hebei (BTH) region. The Chinese government has set an ambitious goal to reduce urban PM2.5 concentrations by 25% in BTH by 2017 relative to the 2012 levels. Source apportionment (SA) is necessary to the development of the effective emission control strategies. In this work, the Comprehensive Air Quality Model with extensions (CAMx) with the Particulate Source Apportionment Technology (PSAT) is applied to the China domain for the years 2006 and 2013. Ambient surface concentrations of PM2.5 and its components are generally well reproduced. To quantify the contributions of each emission category or region to PM2.5 in BTH, the total emissions are divided into 7 emission categories and 11 source regions. The source contributions determined in this work are generally consistent with results from previous work. In 2013, the industrial (44%) and residential (27%) sectors are the dominant contributors to urban PM2.5 in BTH. The residential sector is the largest contributor in winter; the industry sector dominates in other seasons. A slight increasing trend (+3% for industry and +6% for residential) is found in 2013 relative to 2006, necessitating more attention to these two sectors. Local emissions make the largest contribution (40%–60%) for all receptors. Change of source contribution of PM2.5 in Beijing and northern Hebei are dominate by change of local emission. However, for Tianjin, and central and southern Hebei, change of meteorology condition are as important as change of emission, because regional inflow in these areas is more important than in Beijing and northern Hebei and can increase under unfavorable weather conditions, indicating a strong need for regional joint emission control efforts. The results in this study enhance the quantitative understanding of the source–receptor relationships and provide an important basis for policymaking to advance the control of PM2.5 pollution in China.}, journal={Atmospheric Environment}, author={Li, X. and Zhang, Q. and Zhang, Y. and Zheng, B. and Wang, K. and Chen, Y. and Wallington, T. J. and Han, W. J. and Shen, W. and Zhang, X. Y. and et al.}, year={2015}, pages={229–239} }
 @article{wang_zhang_2014, title={3-D agricultural air quality modeling: Impacts of NH3/H2S gas-phase reactions and bi-directional exchange of NH3}, volume={98}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.09.010}, abstractNote={Abstract Accurately simulating the transport and fate of reduced nitrogen (NHx = ammonia (NH3) + ammonium (NH4+))- and sulfur-containing compounds emitted from agricultural activities represents a major challenge in agricultural air quality modeling. In this study, the Community Multiscale Air Quality (CMAQ) modeling system is further developed and improved by implementing 22 ammonia (NH3)/hydrogen sulfide (H2S) related gas-phase reactions and adjusting a few key parameters (e.g., emission potential) for bi-directional exchange of NH3 fluxes. Several simulations are conducted over the eastern U.S. domain at a 12-km horizontal resolution for January and July 2002 to examine the impacts of those improved treatments on air quality. The 5th generation mesoscale model (MM5) and CMAQ predict an overall satisfactory and consistent performance with previous modeling studies, especially for 2-m temperature, 2-m relative humidity, ozone (O3), and fine particulate matter (PM2.5). High model biases exist for precipitation in July and also dry/wet depositions. The updated model treatments contribute to O3, NHx, and PM2.5 by up to 0.4 ppb, 1.0 μg m−3, and 1.0 μg m−3 in January, respectively, and reduce O3 by up to 0.8 ppb and contribute to NHx and PM2.5 by up to 1.2 and 1.1 μg m−3 in July, respectively. The spatial distributions of O3 in both months and sulfur dioxide (SO2) in January are mainly affected by inline dry deposition velocity calculation. The spatial distributions of SO2 and sulfate (SO42−) in July are affected by both inline dry deposition velocity and NH3/H2S reactions. The variation trends of NH3, NHx, ammonium nitrate (NH4NO3), PM2.5 and total nitrogen (TN) are predominated by bi-directional exchange of NH3 fluxes. Uncertainties of NH3 emission potentials and empirical constants used in the bi-directional exchange scheme may significantly affect the concentrations of NHx and PM2.5, indicating that a more accurate and explicit treatment for those parameters should be considered in the future work.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Wang, Kai and Zhang, Yang}, year={2014}, month={Dec}, pages={554–570} }
 @article{penrod_zhang_wang_wu_leung_2014, title={Impacts of future climate and emission changes on US air quality}, volume={89}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.01.001}, abstractNote={Changes in climate and emissions will affect future air quality. In this work, simulations of regional air quality during current (2001–2005) and future (2026–2030) winter and summer are conducted with the newly released CMAQ version 5.0 to examine the impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current meteorological and chemical predictions are evaluated against observations to assess the model's capability in reproducing the seasonal differences. WRF and CMAQ capture the overall observational spatial patterns and seasonal differences. Biases in model predictions are attributed to uncertainties in emissions, boundary conditions, and limitations in model physical and chemical treatments as well as the use of a coarse grid resolution. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) are found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NOx emissions drive the decrease in O3 over most of the U.S. in summer. Future PM2.5 concentrations in winter and summer and many of its components decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants as well as increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with decreasing surface resistance and precipitation, respectively. They decrease with a decrease in ambient particulate concentrations. Anthropogenic emissions play a more important role in summer than in winter for future O3 and PM2.5 levels, with a dominance of the effects of significant emission reductions over those of climate change on future PM2.5 levels.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Penrod, Ashley and Zhang, Yang and Wang, Kai and Wu, Shiang-Yuh and Leung, L. Ruby}, year={2014}, month={Jun}, pages={533–547} }
 @article{zhang_wang_wu_wang_minoura_wang_2014, title={Impacts of updated emission inventories on source apportionment of fine particle and ozone over the southeastern US}, volume={88}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2014.01.035}, abstractNote={As the U.S. Environmental Protection Agency updates the National Emission Inventory (NEI), the source contributions (SC) of major source sectors to major pollutants based on source apportionment techniques should be periodically reassessed to reflect changes in SCs due to changes in emissions. This work assesses emission updates from the 1999 NEI version 2 (NEI99v2) and the 2005 NEI (NEI05) and the resulting differences in SCs using the two inventories. Large differences exist in the emissions of nitrogen oxide, formaldehyde, ammonia, terpene, and primary PM2.5 between NEI99v2 and NEI05. Differences in emissions lead to differences in model performance and source appointment. SCs of ten major source categories to fine particulate matter (PM2.5) are estimated using the Community Multiscale Air Quality modeling system with the Brute Force Method (CMAQ/BFM) andNEI05and compared with those obtained previously using CMAQ/BFM with NEI99v2. In January, compared to CMAQ/BFM (NEI99v2), CMAQ/BFM (NEI05) shows that miscellaneous areas, biomass burning, and coal combustion remain the top three contributors to PM2.5 but with different ranking and higher SCs (17.7%, 16.0%, and 14.1% for NEI05 vs. 11.8%, 13.7%, and 10.8% for NEI99v2, respectively). In July, coal combustion, miscellaneous areas, and industrial processes remain the top three with higher SCs (41.9%, 14.1%, and 8.8% for NEI05 vs.30.8%, 8.9%, and 6.9% for NEI99v2, respectively). Those changes in SCs are attributed to increased primary PM2.5 (PPM) emissions in NEI05 and increases in relative contributions of miscellaneous areas and coal combustion to the emissions of PPM, NH3, and SO2.SCs from diesel and gasoline vehicles decrease in both months, due to decreased contributions of gasoline vehicles to SO2 and NH3 emissions and those of diesel vehicles to NOx and PPM emissions. Compared with CMAQ/BFM (NEI99v2), SCs from other combustion and biomass burning are higher in Florida, due to substantial increases in formaldehyde and PPM emissions in NEI05, resulting from higher wildfire emissions and state emission updates. SCs from industrial processes increase and those from diesel and gasoline vehicles decrease in urban areas. SCs of O3 from most sources in both months increase due to a large increase in their contributions to NOx emissions, except for diesel vehicles in July, which decreases over domainwide due to a relative decrease in NOx emissions. These results provide valuable information for policy makers to formulate and adjust emission control strategies as the NEI is continuously updated.}, journal={ATMOSPHERIC ENVIRONMENT}, author={Zhang, Yang and Wang, Wei and Wu, Shiang-Yuh and Wang, Kai and Minoura, Hiroaki and Wang, Zifa}, year={2014}, month={May}, pages={133–154} }
 @inbook{zhang_zhang_cai_wang_wang_2014, place={Cham, Switzerland}, series={Springer Proceedings in Complexity}, title={Studying Aerosol-Cloud-Climate Interactions over East Asia Using WRF/Chem}, ISBN={9783319043784 9783319043791}, ISSN={2213-8684 2213-8692}, url={http://dx.doi.org/10.1007/978-3-319-04379-1_10}, DOI={10.1007/978-3-319-04379-1_10}, abstractNote={East Asia provides an ideal testbed to study aerosol feedbacks into climate via direct and indirect effects because of high anthropogenic emissions and unique climatology. In this work, an online coupled meteorology-chemistry model, WRF/Chem, is applied to simulate air quality and climate interactions for multiple months in 2001, 2005, and 2008 to characterize long-term seasonal variations of pollutant concentrations and quantify the contributions of anthropogenic aerosols to aerosol direct and indirect effects. The results show a reasonably good performance for most meteorological variables and chemical species concentrations. Large biases in some variables may be caused by large uncertainties in emissions. Anthropogenic aerosols in East Asia can reduce the surface net solar radiation by up to 6 % and enhance cloud condensation nuclei and cloud droplet number concentrations by a factor of up to 3 on domain-average, with much greater impacts over urban areas. These results suggest that aerosol feedbacks are potentially important over polluted areas and should be taken into account in the development of emission control and climate mitigation policies for areas where the aerosol feedback signals are strong.}, booktitle={Air Pollution Modeling and its Application XXIII}, publisher={Springer International Publishing}, author={Zhang, Yang and Zhang, Xin and Cai, Changjie and Wang, Kai and Wang, Litao}, editor={Steyn, D. and Mathur, R.Editors}, year={2014}, pages={61–66}, collection={Springer Proceedings in Complexity} }
 @article{zhang_sartelet_zhu_wang_wu_zhang_wang_tran_seigneur_wang_2013, title={Application of WRF/Chem-MADRID and WRF/Polyphemus in Europe - Part 2: Evaluation of chemical concentrations and sensitivity simulations}, volume={13}, ISSN={["1680-7324"]}, DOI={10.5194/acp-13-6845-2013}, abstractNote={Abstract. An offline-coupled model (WRF/Polyphemus) and an online-coupled model (WRF/Chem-MADRID) are applied to simulate air quality in July 2001 at horizontal grid resolutions of 0.5° and 0.125° over Western Europe. The model performance is evaluated against available surface and satellite observations. The two models simulate different concentrations in terms of domainwide performance statistics, spatial distribution, temporal variations, and column abundance. WRF/Chem-MADRID at 0.5° gives higher values than WRF/Polyphemus for the domainwide mean and over polluted regions in Central and southern Europe for all surface concentrations and column variables except for the tropospheric ozone residual (TOR). Compared with observations, WRF/Polyphemus gives better statistical performance for daily HNO3, SO2, and NO2 at the European Monitoring and Evaluation Programme (EMEP) sites, maximum 1 h O3 at the AirBase sites, PM2.5 at the AirBase sites, maximum 8 h O3 and PM10 composition at all sites, column abundance of CO, NO2, TOR, and aerosol optical depth (AOD), whereas WRF/Chem-MADRID gives better statistical performance for NH3, hourly SO2, NO2, and O3 at the AirBase and BDQA (Base de données de la qualité de l'air) sites, maximum 1 h O3 at the BDQA and EMEP sites, and PM10 at all sites. WRF/Chem-MADRID generally reproduces well the observed high hourly concentrations of SO2 and NO2 at most sites except for extremely high episodes at a few sites, and WRF/Polyphemus performs well for hourly SO2 concentrations at most rural or background sites where pollutant levels are relatively low, but it underpredicts the observed hourly NO2 concentrations at most sites. Both models generally capture well the daytime maximum 8 h O3 concentrations and diurnal variations of O3 with more accurate peak daytime and minimal nighttime values by WRF/Chem-MADRID, but neither model reproduces extremely low nighttime O3 concentrations at several urban and suburban sites due to underpredictions of NOx and thus insufficient titration of O3 at night. WRF/Polyphemus gives more accurate concentrations of PM2.5, and WRF/Chem-MADRID reproduces better the observations of PM10 concentrations at all sites. The differences between model predictions and observations are mostly caused by inaccurate representations of emissions of gaseous precursors and primary PM species, as well as biases in the meteorological predictions. The differences in model predictions are caused by differences in the heights of the first model layers and thickness of each layer that affect vertical distributions of emissions, model treatments such as dry/wet deposition, heterogeneous chemistry, and aerosol and cloud, as well as model inputs such as emissions of soil dust and sea salt and chemical boundary conditions of CO and O3 used in both models.  WRF/Chem-MADRID shows a higher sensitivity to grid resolution than WRF/Polyphemus at all sites. For both models, the use of a finer grid resolution generally leads to an overall better statistical performance for most variables, with greater spatial details and an overall better agreement in temporal variations and magnitudes at most sites. The use of online biogenic volatile organic compound (BVOC) emissions gives better statistical performance for hourly and maximum 8 h O3 and PM2.5 and generally better agreement with their observed temporal variations at most sites. Because it is an online model, WRF/Chem-MADRID offers the advantage of accounting for various feedbacks between meteorology and chemical species. However, this model comparison suggests that atmospheric pollutant concentrations are most sensitive in state-of-the-science air quality models to vertical structure, inputs, and parameterizations for dry/wet removal of gases and particles in the model.
                    }, number={14}, journal={ATMOSPHERIC CHEMISTRY AND PHYSICS}, author={Zhang, Y. and Sartelet, K. and Zhu, S. and Wang, W. and Wu, S. -Y. and Zhang, X. and Wang, K. and Tran, P. and Seigneur, C. and Wang, Z. -F.}, year={2013}, pages={6845–6875} }
 @article{zhang_olsen_wang_2013, title={Fine scale modeling of agricultural air quality over the southeastern United States using two air quality models. Part I. Application and evaluation}, volume={13}, number={4}, journal={Aerosol and Air Quality Research}, author={Zhang, Y. and Olsen, K. M. and Wang, K.}, year={2013}, pages={1231–1252} }
 @article{wang_zhang_nenes_fountoukis_2012, title={Implementation of dust emission and chemistry into the community multiscale air quality modeling system and initial application to an asian dust storm episode}, volume={12}, number={21}, journal={Atmospheric Chemistry and Physics}, author={Wang, K. and Zhang, Y. and Nenes, A. and Fountoukis, C.}, year={2012}, pages={10209–10237} }
 @article{wang_jang_zhang_wang_zhang_streets_fu_lei_schreifels_he_et al._2010, title={Assessment of air quality benefits from national air pollution control policies in China. Part I: Background, emission scenarios and evaluation of meteorological predictions}, volume={44}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2010.05.051}, abstractNote={Under the 11th Five Year Plan (FYP, 2006–2010) for national environmental protection by the Chinese government, the overarching goal for sulfur dioxide (SO2) controls is to achieve a total national emissions level of SO2 in 2010 10% lower than the level in 2005. A similar nitrogen oxides (NOx) emissions control plan is currently under development and could be enforced during the 12th FYP (2011–2015). In this study, the U.S. Environmental Protection Agency (U.S.EPA)’s Community Multi-Scale Air Quality (Models-3/CMAQ) modeling system was applied to assess the air quality improvement that would result from the targeted SO2 and NOx emission controls in China. Four emission scenarios — the base year 2005, the 2010 Business-As-Usual (BAU) scenario, the 2010 SO2 control scenario, and the 2010 NOx control scenario—were constructed and simulated to assess the air quality change from the national control plan. The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) was applied to generate the meteorological fields for the CMAQ simulations. In this Part I paper, the model performance for the simulated meteorology was evaluated against observations for the base case in terms of temperature, wind speed, wind direction, and precipitation. It is shown that MM5 model gives an overall good performance for these meteorological variables. The generated meteorological fields are acceptable for using in the CMAQ modeling.}, number={28}, journal={ATMOSPHERIC ENVIRONMENT}, author={Wang, Litao and Jang, Carey and Zhang, Yang and Wang, Kai and Zhang, Qiang and Streets, David and Fu, Joshua and Lei, Yu and Schreifels, Jeremy and He, Kebin and et al.}, year={2010}, month={Sep}, pages={3442–3448} }
 @article{wang_jang_zhang_wang_zhang_streets_fu_lei_schreifels_he_et al._2010, title={Assessment of air quality benefits from national air pollution control policies in China. Part II: Evaluation of air quality predictions and air quality benefits assessment}, volume={44}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2010.05.058}, abstractNote={Following the meteorological evaluation in Part I, this Part II paper presents the statistical evaluation of air quality predictions by the U.S. Environmental Protection Agency (U.S. EPA)’s Community Multi-Scale Air Quality (Models-3/CMAQ) model for the four simulated months in the base year 2005. The surface predictions were evaluated using the Air Pollution Index (API) data published by the China Ministry of Environmental Protection (MEP) for 31 capital cities and daily fine particulate matter (PM2.5, particles with aerodiameter less than or equal to 2.5 μm) observations of an individual site in Tsinghua University (THU). To overcome the shortage in surface observations, satellite data are used to assess the column predictions including tropospheric nitrogen dioxide (NO2) column abundance and aerosol optical depth (AOD). The result shows that CMAQ gives reasonably good predictions for the air quality. The air quality improvement that would result from the targeted sulfur dioxide (SO2) and nitrogen oxides (NOx) emission controls in China were assessed for the objective year 2010. The results show that the emission controls can lead to significant air quality benefits. SO2 concentrations in highly polluted areas of East China in 2010 are estimated to be decreased by 30–60% compared to the levels in the 2010 Business-As-Usual (BAU) case. The annual PM2.5 can also decline by 3–15 μg m−3 (4–25%) due to the lower SO2 and sulfate concentrations. If similar controls are implemented for NOx emissions, NOx concentrations are estimated to decrease by 30–60% as compared with the 2010 BAU scenario. The annual mean PM2.5 concentrations will also decline by 2–14 μg m−3 (3–12%). In addition, the number of ozone (O3) non-attainment areas in the northern China is projected to be much lower, with the maximum 1-h average O3 concentrations in the summer reduced by 8–30 ppb.}, number={28}, journal={ATMOSPHERIC ENVIRONMENT}, author={Wang, Litao and Jang, Carey and Zhang, Yang and Wang, Kai and Zhang, Qiang and Streets, David and Fu, Joshua and Lei, Yu and Schreifels, Jeremy and He, Kebin and et al.}, year={2010}, month={Sep}, pages={3449–3457} }
 @article{liu_zhang_xing_zhang_wang_streets_jang_wang_hao_2010, title={Understanding of regional air pollution over China using CMAQ, part II. Process analysis and sensitivity of ozone and particulate matter to precursor emissions}, volume={44}, ISSN={["1873-2844"]}, DOI={10.1016/j.atmosenv.2010.03.036}, abstractNote={Following model evaluation in part I, this part II paper focuses on the process analysis and chemical regime analysis for the formation of ozone (O3) and particulate matter with aerodynamic diameter less than or equal to 10 μm (PM10) in China. The process analysis results show that horizontal transport is the main contributor to the accumulation of O3 in Jan., Apr., and Oct., and gas-phase chemistry and vertical transport contribute to the production and accumulation of O3 in Jul. Removal pathways of O3 include vertical and horizontal transport, gas-phase chemistry, and cloud processes, depending on locations and seasons. PM10 is mainly produced by primary emissions and aerosol processes and removed by horizontal transport. Cloud processes could either decrease or increase PM10 concentrations, depending on locations and seasons. Among all indicators examined, the ratio of PHNO3/PH2O2 provides the most robust indicator for O3 chemistry, indicating a VOC-limited O3 chemistry over most of the eastern China in Jan., NOx-limited in Jul., and either VOC- or NOx-limited in Apr. and Oct. O3 chemistry is NOx-limited in most central and western China and VOC-limited in major cities throughout the year. The adjusted gas ratio, AdjGR, indicates that PM formation in the eastern China is most sensitive to the emissions of SO2 and may be more sensitive to emission reductions in NOx than in NH3. These results are fairly consistent with the responses of O3 and PM2.5 to the reductions of their precursor emissions predicted from sensitivity simulations. A 50% reduction of NOx or AVOC emissions leads to a reduction of O3 over the eastern China. Unlike the reduction of emissions of SO2, NOx, and NH3 that leads to a decrease in PM10, a 50% reduction of AVOC emissions increases PM10 levels. Such results indicate the complexity of O3 and PM chemistry and a need for an integrated, region-specific emission control strategy with seasonal variations to effectively control both O3 and PM2.5 pollution in China.}, number={30}, journal={ATMOSPHERIC ENVIRONMENT}, author={Liu, Xiao-Huan and Zhang, Yang and Xing, Jia and Zhang, Qiang and Wang, Kai and Streets, David G. and Jang, Carey and Wang, Wen-Xing and Hao, Ji-Ming}, year={2010}, month={Sep}, pages={3719–3727} }
 @article{zhang_pan_wang_fast_grell_2010, title={WRF/Chem-MADRID: Incorporation of an aerosol module into WRF/Chem and its initial application to the TexAQS2000 episode}, volume={115}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2009JD013443}, DOI={10.1029/2009JD013443}, abstractNote={The Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (MADRID) with three improved gas/particle mass transfer approaches (i.e., bulk equilibrium (EQUI), hybrid (HYBR), and kinetic (KINE)) has been incorporated into the Weather Research and Forecast/Chemistry Model (WRF/Chem) (referred to as WRF/Chem‐MADRID) and evaluated with a 5‐day episode from the 2000 Texas Air Quality Study (TexAQS2000). WRF/Chem‐MADRID demonstrates an overall good skill in simulating surface/aloft meteorological parameters and chemical concentrations of O3 and PM2.5, tropospheric O3 residuals, and aerosol optical depths. The discrepancies can be attributed to inaccuracies in meteorological predictions (e.g., overprediction in mid‐day boundary layer height), sensitivity to meteorological schemes used (e.g., boundary layer and land‐surface schemes), inaccurate total emissions or their hourly variations (e.g., HCHO, olefins, other inorganic aerosols) or uncounted wildfire emissions, uncertainties in initial and boundary conditions for some species (e.g., other inorganic aerosols, CO, and O3) at surface and aloft, and some missing/inactivated model treatments for this application (e.g., chlorine chemistry and secondary organic aerosol formation). Major differences in the results among the three gas/particle mass transfer approaches occur over coastal areas, where EQUI predicts higher PM2.5 than HYBR and KINE due to improperly redistributing condensed nitrate from chloride depletion process to fine PM mode. The net direct, semi‐direct, and indirect effects of PM2.5 decrease domainwide shortwave radiation by 11.2–14.4 W m−2 (or 4.1–5.6%) and near‐surface temperature by 0.06–0.14°C (or 0.2–0.4%), lead to 125 to 796 cm−3 cloud condensation nuclei at a supersaturation of 0.1%, produce cloud droplet numbers as high as 2064 cm−3, and reduce domainwide mean precipitation by 0.22–0.59 mm day−1.}, number={D18}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Zhang, Yang and Pan, Ying and Wang, Kai and Fast, Jerome D. and Grell, Georg A.}, year={2010}, month={Sep} }
 @article{wang_zhang_jang_phillips_wang_2009, title={Modeling intercontinental air pollution transport over the trans-Pacific region in 2001 using the Community Multiscale Air Quality modeling system}, volume={114}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2008JD010807}, DOI={10.1029/2008JD010807}, abstractNote={The Community Multiscale Air Quality modeling system is used to study the intercontinental transport of air pollution across the Pacific region. Baseline simulations are conducted for January, April, July, and October 2001 at a 108 km horizontal grid resolution. A sensitivity simulation is conducted for April 2001 to study the impact of Asian anthropogenic emissions on the United States's air quality. Process analysis is conducted to study pollutant formation and transport and to quantify the relative contributions of atmospheric processes to ozone (O3) and fine particulate matter (PM2.5). Model simulations are evaluated with available surface, aircraft, and satellite observations. Simulated meteorology basically captures the synoptic pattern, but precipitation amounts are significantly underpredicted. Most of the PM2.5 components are overestimated over the United States and most gases are underestimated over east Asia. Simulated NO2 and CO columns agree well with satellite observations. Aerosol optical depths and tropospheric O3 residuals are underpredicted, especially in July. The simulated horizontal fluxes and process analyses show that the transport in the lower free troposphere followed by a large‐scale subsidence over the United States provides a major Asian pollution export pathway for most pollutants, while the transport in the planetary boundary layer also plays an important role, especially for CO, O3, PM2.5, and SO42−. The background concentrations of O3 and SO42− in the western United States can increase by ∼1 ppb (∼2.5%) and 0.4 μg m−3 (∼20%) in monthly average, up to 2.5 ppb and 1.0 μg m−3 in daily average, respectively, due to the Asian emissions in April.}, number={D4}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Wang, Kai and Zhang, Yang and Jang, Carey and Phillips, Sharon and Wang, Binyu}, year={2009}, month={Feb} }
 @article{zhang_wen_wang_vijayaraghavan_jacobson_2009, title={Probing into regional O3 and particulate matter pollution in the United States: 2. An examination of formation mechanisms through a process analysis technique and sensitivity study}, volume={114}, ISSN={0148-0227}, url={http://dx.doi.org/10.1029/2009JD011900}, DOI={10.1029/2009JD011900}, abstractNote={Following a comprehensive model evaluation in part 1, this part 2 paper describes results from 1 year process analysis and a number of sensitivity simulations using the Community Multiscale Air Quality (CMAQ) modeling system aimed to understand the formation mechanisms of O3 and PM2.5, their impacts on global environment, and implications for pollution control policies. Process analyses show that the most influential processes for O3 in the planetary boundary layer (PBL) are vertical and horizontal transport, gas‐phase chemistry, and dry deposition and those for PM2.5 are primary PM emissions, horizontal transport, PM processes, and cloud processes. Exports of O3 and Ox from the U.S. PBL to free troposphere occur primarily in summer and at a rate of 0.16 and 0.65 Gmoles day−1, respectively. In contrast, export of PM2.5 is found to occur during all seasons and at rates of 25.68–34.18 Ggrams day−1, indicating a need to monitor and control PM2.5 throughout the year. Among nine photochemical indicators examined, the most robust include PH2O2/PHNO3, HCHO/NOy, and HCHO/NOz in winter and summer, H2O2/(O3 + NO2) in winter, and NOy in summer. They indicate a VOC‐limited O3 chemistry in most areas in winter, but a NOx‐limited O3 chemistry in most areas except for major cities in April–November, providing a rationale for nationwide NOx emission control and integrated control of NOx and VOCs emissions for large cities during high O3 seasons (May–September). For sensitivity of PM2.5 to its precursors, the adjusted gas ratio provides a more robust indicator than that without adjustment, especially for areas with insufficient sulfate neutralization in winter. NH4NO3 can be formed in most of the domain. Integrated control of emissions of PM precursors such as SO2, NOx, and NH3 are necessary for PM2.5 attainment. Among four types of VOCs examined, O3 formation is primarily affected by isoprene and low molecular weight anthropogenic VOCs, and PM2.5 formation is affected largely by terpenes and isoprene. Under future emission scenarios, surface O3 may increase in summer; surface PM2.5 may increase or decrease. With 0.71°C increase in future surface temperatures in summer, surface O3 may increase in most of the domain and surface PM2.5 may decrease in the eastern U.S. but increase in the western U.S.}, number={D22}, journal={Journal of Geophysical Research}, publisher={American Geophysical Union (AGU)}, author={Zhang, Yang and Wen, Xin-Yu and Wang, Kai and Vijayaraghavan, Krish and Jacobson, Mark Z.}, year={2009}, month={Nov} }
 @article{zhang_wu_krishnan_wang_queen_aneja_arya_2008, title={Modeling agricultural air quality: Current status, major challenges, and outlook}, volume={42}, ISSN={["1873-2844"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41549095063&partnerID=MN8TOARS}, DOI={10.1016/j.atmosenv.2007.01.063}, abstractNote={Agricultural air quality is an important emerging area of atmospheric sciences that represents significant challenges in many aspects of research including measurements, modeling, regulations, emission control, and operation managements. This work presents a review of current status, major challenges, and future research needs and opportunities of several important aspects of agricultural air quality modeling including chemical species, concentration and deposition measurements for model verification, emission inventories, major physical and chemical processes, model application and evaluation, and policy implications.}, number={14}, journal={ATMOSPHERIC ENVIRONMENT}, author={Zhang, Yang and Wu, Shiang-Yuh and Krishnan, Srinath and Wang, Kai and Queen, Ashley and Aneja, Viney P. and Arya, S. Pal}, year={2008}, month={Apr}, pages={3218–3237} }