Measurements of Cloud-Droplet-Size Distributions in Polluted and Unpolluted Stratiform Clouds

Alkezweeny, A.J.; Burrows, D. A.; Grainger, C. A.

doi:10.1175/1520-0450(1993)032<0106:mocdsd>2.0.co;2

Cited by 19 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[4] Several studies have looked at relationships between clouds and aerosols near large or very dirty cities [e.g., Alkezweeny et al, 1993;Lu et al, 2008;Sorooshian et al, 2007], but few studies have investigated cloud-aerosol interactions near moderate size cities that are common in North America. In addition, previous studies have focused on studying aerosol cloud relationships within stratiform or deep convective clouds [e.g., Russell et al, 2000;Yang et al, 2011], but conditions within short-lived shallow cumuli may differ due to different updraft velocities, supersaturations, and spatial dimensions.…”

Section: Introductionmentioning

confidence: 99%

Modeling aerosols and their interactions with shallow cumuli during the 2007 CHAPS field study

et al. 2013

View full text Add to dashboard Cite

[1] The Weather Research and Forecasting model coupled with chemistry, using 2 km horizontal grid spacing, is used to simulate two important relationships between aerosols and clouds in the vicinity of Oklahoma City during the June 2007 Cumulus Humilis Aerosol Processing Study (CHAPS). First, the model reproduces the trends of higher nitrate volume fractions in cloud droplet residuals compared to interstitial nonactivated aerosols, as measured using an aerosol mass spectrometer. Comparing simulations with cloud chemistry turned on and off, we show that nitric acid vapor uptake by cloud droplets explains the higher nitrate content of cloud droplet residuals. Second, the model reasonably represents the observations of the first aerosol indirect effect where pollutants in the vicinity of Oklahoma City increase cloud droplet number concentrations and decrease the droplet effective radius. In addition, as documented using an offline optical code, simulated aerosol optical properties depend on several compensating effects including aerosol water content, size-resolved chemical composition, and refractory index of various particle chemical species. All of our four sensitivity test cases clearly show an increase in simulated absorption and a decrease in single scattering albedo within the Oklahoma City plume relative to conditions outside the plume. While previous studies have often focused on cloud-aerosol interactions in stratiform and deep convective clouds, this study highlights the ability of regional-scale models to represent some of the important aspects of cloud-aerosol interactions associated with fields of short-lived shallow cumuli.

show abstract

Section: Introductionmentioning

confidence: 99%

Modeling aerosols and their interactions with shallow cumuli during the 2007 CHAPS field study

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Changes in the microphysical properties of warm stratocumulus over the oceans or land have been documented in a number of studies [e.g., Radke et al, 1989;Durkee et al, 2000;McFarquhar and Heymsfield, 2001;Feingold et al, 2003;Twohy et al, 2005]. Changes in the microphysical structure of cumuli downwind of St. Louis, Missouri were documented by Fitzgerald and Spyers-Duran [1973], while Alkezweeny et al [1993] presented evidence of changes in stratocumuli downwind of Denver Colorado. More recently, attention has been focused on details of aerosol-cloud interactions in shallow cumuli in the vicinity of Houston, Texas [Lu et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

Observations of the first aerosol indirect effect in shallow cumuli

Berg

Berkowitz

Barnard

et al. 2011

Geophys. Res. Lett.

View full text Add to dashboard Cite

Data from the Cumulus Humilis Aerosol Processing Study (CHAPS) are used to estimate the impact of both aerosol indirect effects and cloud dynamics on the microphysical and optical properties of shallow cumuli observed in the vicinity of Oklahoma City, Oklahoma. Not surprisingly, we find that the amount of light scattered by clouds is dominated by their liquid water content (LWC), which in turn is driven by buoyancy and cloud dynamics. However, removing the effect of cloud dynamics by examining the scattering normalized by LWC shows a statistically significant sensitivity of scattering to pollutant loading (increasing at a rate of 0.002 m2 g−1 ppbv−1). These results suggest that even moderately sized cities, like Oklahoma City, can have a measureable impact on the optical properties of shallow cumuli.

show abstract

“…Other studies conducted near cities have examined changes in both aerosols and clouds downwind of urban areas. For example, Alkezweeny et al (1993) found that wintertime stratiform clouds associated with the urban plumes of Denver, Colorado, and Kansas City, Missouri, have a larger number concentration and smaller median volume diameter of droplets than clouds that had not been affected by the urban plume. Likewise, Jirak and Cotton (2006) found a decrease in precipitation in polluted regions along the Front Range of the Rocky Mountains.…”

mentioning

confidence: 99%