@article{wilbanks_yuter_szoeke_brewer_miller_hall_burleyson_2015, title={Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer*}, volume={143}, ISSN={["1520-0493"]}, DOI={10.1175/mwr-d-14-00359.1}, abstractNote={Abstract
               Density currents (i.e., cold pools or outflows) beneath marine stratocumulus clouds are characterized using 30 days of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An air density increase criterion applied to the Improved Meteorological (IMET) sensor data identified 71 density current front, core (peak density), and tail (dissipating) zones. The similarity in speeds of the mean density current propagation speed (1.8 m s−1) and the mean cloud-level advection relative to the surface layer wind (1.9 m s−1) allowed drizzle cells to deposit elongated density currents in their wakes. Scanning Doppler lidar captured prefrontal updrafts with a mean intensity of 0.91 m s−1 and an average vertical extent of 800 m. Updrafts were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. The observed density currents were 5–10 times thinner and weaker than typical continental thunderstorm cold pools. Nearly 90% of density currents were identified when C-band radar estimated areal average rain rates exceeded 1 mm day−1 over a 30-km diameter. Rather than peaking when rain rates were highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurred with shallow subcloud dry and stable layers. The dry layers may have contributed to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occurred in a large region of predominantly open cells but also occurred in regions of closed cells.}, number={9}, journal={MONTHLY WEATHER REVIEW}, publisher={American Meteorological Society}, author={Wilbanks, Matt C. and Yuter, Sandra E. and Szoeke, Simon P. and Brewer, W. Alan and Miller, Matthew A. and Hall, Andrew M. and Burleyson, Casey D.}, year={2015}, month={Sep}, pages={3532–3555} }
 @article{burleyson_yuter_2015, title={Patterns of Diurnal Marine Stratocumulus Cloud Fraction Variability}, volume={54}, ISSN={["1558-8432"]}, DOI={10.1175/jamc-d-14-0178.1}, abstractNote={AbstractThe spatial patterns of subtropical marine stratocumulus cloud fraction variability on diurnal time scales are examined using high-temporal-resolution cloud masks that are based on 30-min, 4 km × 4 km geosynchronous infrared data for 2003–10. This dataset permits comparison of the characteristics of variability in low cloud fraction among the three subtropical marine stratocumulus regions in the northeastern (NE) Pacific, southeastern (SE) Pacific, and SE Atlantic Oceans. In all three regions, the largest diurnal cycles and earliest time of cloud breakup occur on the edges of the cloud field where cloud fractions are generally lower. The rate at which the cloud breaks up during the day is tied to the starting cloud fraction at dawn, which determines the amount of longwave cooling that is initially available to offset shortwave radiative fluxes during the day. The maximum rate of cloud breakup occurs near 1200 LT. Cloud fraction begins to increase by 1600 LT (before the sun sets) and reaches its maximum value just before dawn. The diurnal-cycle characteristics of the SE Pacific and SE Atlantic marine stratocumulus cloud decks are more similar to each other than to those in the NE Pacific. The NE Pacific cloud deck has a smaller-amplitude diurnal cycle, slower rates of cloud breakup during the day for a given cloud fraction at dawn, and a higher probability of cloud breakup overnight.}, number={4}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Burleyson, Casey D. and Yuter, Sandra E.}, year={2015}, month={Apr}, pages={847–866} }
 @article{burleyson_yuter_2015, title={Subdiurnal Stratocumulus Cloud Fraction Variability and Sensitivity to Precipitation}, volume={28}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-14-00648.1}, abstractNote={Abstract
               This paper presents an analysis of subtropical marine stratocumulus cloud fraction variability using a 30-min and 3° × 3° cloud fraction dataset from 2003 to 2010. Each of the three subtropical marine stratocumulus regions has distinct diurnal characteristics, but the southeast (SE) Pacific and SE Atlantic are more similar to each other than to the northeast (NE) Pacific. The amplitude and season-to-season diurnal cycle variations are larger in the Southern Hemisphere regions than in the NE Pacific. Net overnight changes in cloud fraction on 3° × 3° scales are either positive or neutral >77% of the time in the NE Pacific and >88% of the time in the SE Pacific and SE Atlantic. Cloud fraction often increases to 100% by dawn when cloud fraction at dusk is >30%. In the SE Pacific and SE Atlantic, a typical decrease in cloud area (median ≤ −5.7 × 105 km2) during the day is equivalent to 25% or more of the annual-mean cloud deck area. Time series for 3° × 3° areas where cloud fraction was ≥90% sometime overnight and <60% at dawn, such as would result from nocturnal formation of pockets of open cells (POCs), only occur 1.5%, 1.6%, and 3.3% of the time in the SE Pacific, SE Atlantic, and NE Pacific, respectively. Comparison of cloud fraction changes to ship-based radar and satellite-derived precipitation intensity and area measurements shows a lack of sensitivity of cloud fraction to drizzle on time scales of 1–3 h and spatial scales of 100–300 km.}, number={8}, journal={JOURNAL OF CLIMATE}, author={Burleyson, Casey D. and Yuter, Sandra E.}, year={2015}, month={Apr}, pages={2968–2985} }
 @article{sobel_burleyson_yuter_biasutti_2013, title={Rain on small tropical islands (vol 118, pg 2301, 2013)}, volume={118}, ISSN={["2169-897X"]}, DOI={10.1002/jgrd.50205}, abstractNote={Key Points

Observations of pitch‐angle distributions with repeated probe configurations
Electron flux variations depend on probe relative to the flow
type of electron PAD depends on position relative to the neutral sheet}, number={5}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Sobel, A. H. and Burleyson, C. D. and Yuter, S. E. and Biasutti, M.}, year={2013}, month={Mar}, pages={2301–2302} }
 @article{burleyson_szoeke_yuter_wilbanks_brewer_2013, title={Ship-Based Observations of the Diurnal Cycle of Southeast Pacific Marine Stratocumulus Clouds and Precipitation}, volume={70}, ISSN={["1520-0469"]}, DOI={10.1175/jas-d-13-01.1}, abstractNote={Abstract
               The diurnal cycle of marine stratocumulus in cloud-topped boundary layers is examined using ship-based meteorological data obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx). The high temporal and spatial continuity of the ship data, as well as the 31-day sample size, allows the diurnal transition in degree of coupling of the stratocumulus-topped boundary layer to be resolved. The amplitude of diurnal variation was comparable to the magnitude of longitudinal differences between regions east and west of 80°W for most of the cloud, surface, and precipitation variables examined. The diurnal cycle of precipitation is examined in terms of areal coverage, number of drizzle cells, and estimated rain rate. East of 80°W, the drizzle cell frequency and drizzle area peaks just prior to sunrise. West of 80°W, total drizzle area peaks at 0300 local solar time (LST), 2–3 h before sunrise. Peak drizzle cell frequency is 3 times higher west of 80°W compared to east of 80°W. The waning of drizzle several hours prior to the ramp up of shortwave fluxes may be related to the higher peak drizzle frequencies in the west. The ensemble effect of localized subcloud evaporation of precipitation may make drizzle a self-limiting process where the areal density of drizzle cells is sufficiently high. The daytime reduction in vertical velocity variance in a less coupled boundary layer is accompanied by enhanced stratification of potential temperature and a buildup of moisture near the surface.}, number={12}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Burleyson, Casey D. and Szoeke, Simon P. and Yuter, Sandra E. and Wilbanks, Matt and Brewer, W. Alan}, year={2013}, month={Dec}, pages={3876–3894} }
 @article{allen_vaughan_toniazzo_coe_connolly_yuter_burleyson_minnis_ayers_2013, title={Gravity-wave-induced perturbations in marine stratocumulus}, volume={139}, ISSN={["1477-870X"]}, DOI={10.1002/qj.1952}, abstractNote={AbstractWe discuss the role of atmospheric gravity waves in modulating cloud radiative and dynamical properties over the southeast Pacific. Satellite imagery and satellite‐retrieved cloud properties during October 2008 illustrate three distinct episodes of horizontal propagation of gravity wave trains across the large‐scale stratocumulus (Sc) cloud deck capping the local marine boundary layer. In one period, 7–9 October 2008, the waves modulated cloud‐top‐height by up to 400 m peak‐to‐trough, propagating perpendicular to the synoptic boundary layer flow with phase speed 15.3 m s−1, period ∼1 h and horizontal wavelength 55 km. The gravity waves were observed to be non‐dispersive. These waves were first evident in the cloud deck near 30°S, 85°W during a 24 h period beginning at midday on 7 October 2008, and propagated northeastward toward the Peruvian coast for the following 48 h. During this time they induced both reversible and non‐reversible changes in cloud‐radiative and cloud‐dynamic properties, such that areas of clear sky developed in the troughs of passing wave‐fronts. These pockets of open cells persisted long after the passage of the gravity waves, advecting northwestward with the background wind. Using the analysis fields of the European Centre for Medium‐Range Weather Forecasts in conjunction with infrared and microwave satellite imagery, we show that these gravity waves emerged from a disturbed subtropical jet stream. The radiant of the waves was coincident in all cases with centres of large negative residuals in nonlinear balance, suggesting that geostrophic readjustment of sharply divergent flows associated with the disturbed jet provided a source for the wave energy. Conversely, gravity waves were not observed in more quiescent jet conditions. This case study highlights the important and irreversible effects that gravity waves propagating in the troposphere can have on cloud radiative properties (and hence surface radiation budgets) over a very wide area. It also highlights the importance of synoptic influence on Sc‐covered marine boundary layers. Copyright © 2012 Royal Meteorological Society}, number={670}, journal={QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY}, author={Allen, G. and Vaughan, G. and Toniazzo, T. and Coe, H. and Connolly, P. and Yuter, S. E. and Burleyson, C. D. and Minnis, P. and Ayers, J. K.}, year={2013}, month={Jan}, pages={32–45} }
 @article{szoeke_yuter_mechem_fairall_burleyson_zuidema_2012, title={Observations of Stratocumulus Clouds and Their Effect on the Eastern Pacific Surface Heat Budget along 20 degrees S}, volume={25}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-11-00618.1}, abstractNote={Abstract
               Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°–85°W in October–November of 2001–08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitude–vertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation. Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ.
               Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CB–lifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CB–LCL is 0–200 m and increases 400 m from dawn to 1600 LT, before collapsing in the evening.
               Despite zonal gradients in boundary layer and cloud vertical structure, surface radiation and cloud radiative forcing are relatively uniform in longitude. When present, clouds reduce solar radiation by 160 W m−2 and radiate 70 W m−2 more downward longwave radiation than clear skies. Coupled Model Intercomparison Project phase 3 (CMIP3) simulations of the climate of the twentieth century show 40 ± 20 W m−2 too little net cloud radiative cooling at the surface. Simulated clouds have correct radiative forcing when present, but models have ~50% too few clouds.}, number={24}, journal={JOURNAL OF CLIMATE}, author={Szoeke, Simon P. and Yuter, Sandra and Mechem, David and Fairall, Chris W. and Burleyson, Casey D. and Zuidema, Paquita}, year={2012}, month={Dec}, pages={8542–8567} }
 @article{sobel_burleyson_yuter_2011, title={Rain on small tropical islands}, volume={116}, ISSN={["2169-8996"]}, DOI={10.1029/2010jd014695}, abstractNote={[1] A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997–2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow rather than elevated surface heating.}, journal={JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES}, author={Sobel, A. H. and Burleyson, C. D. and Yuter, S. E.}, year={2011}, month={Apr} }