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Published August 16, 2008 | Published + Supplemental Material
Journal Article Open

Aerosol-cloud relationships in continental shallow cumulus


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.

Additional Information

© 2008 American Geophysical Union. Received 4 September 2007; revised 29 February 2008; accepted 12 May 2008; published 5 August 2008. This work was supported by National Oceanic and Atmospheric Administration grant NA06OAR4310082.

Attached Files

Published - 269-Lu-2008.pdf

Supplemental Material - jgrd14384-sup-0001-t01.txt

Supplemental Material - jgrd14384-sup-0002-t02.txt

Supplemental Material - jgrd14384-sup-0003-t03.txt

Supplemental Material - jgrd14384-sup-0004-t04.txt


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