Aerosol-cloud relationships in continental shallow cumulus
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Authors
Lu, Miao-Ling
Feingold, Graham
Jonsson, Haflidi
Chuang, Patrick Y.
Gates, Harmony
Flagan, Richard C.
Seinfeld, John H.
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Date of Issue
2008
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Abstract
Aerosol-cloud relationships are derived from 14 warm continental cumuli cases
sampled during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study
(GoMACCS) by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies
(CIRPAS) Twin Otter aircraft. Cloud droplet number concentration is clearly
proportional to the subcloud accumulation mode aerosol number concentration. An
inverse correlation between cloud top effective radius and subcloud aerosol number
concentration is observed when cloud depth variations are accounted for. There are no
discernable aerosol effects on cloud droplet spectral dispersion; the averaged spectral
relative dispersion is 0.30 ± 0.04. Aerosol-cloud relationships are also identified from
comparison of two isolated cloud cases that occurred under different degrees of
anthropogenic influence. Cloud liquid water content, cloud droplet number
concentration, and cloud top effective radius exhibit subadiabaticity resulting from
entrainment mixing processes. The degree of LWC subadiabaticity is found to increase
with cloud depth. Impacts of subadiabaticity on cloud optical properties are assessed.
It is estimated that owing to entrainment mixing, cloud LWP, effective radius, and
cloud albedo are decreased by 50–85%, 5–35%, and 2–26%, respectively, relative to
adiabatic values of a plane-parallel cloud. The impact of subadiabaticity on cloud
albedo is largest for shallow clouds. Results suggest that the effect of entrainment
mixing must be accounted for when evaluating the aerosol indirect effect.
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Article
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The article of record as published may be located at http://dx.doi.org/10.1029/2007JD009354
Series/Report No
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Meteorology
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This work was supported by National Oceanic and Atmospheric Administration grant NA06OAR4310082.
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Lu, M.-L., G. Feingold, H. H. Jonsson, P. Y. Chuang, H. Gates, R. C. Flagan, and J. H. Seinfeld (2008), Aerosol-cloud
relationships in continental shallow cumulus, J. Geophys. Res., 113, D15201, doi:10.1029/2007JD009354.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.