HR: 0800h
AN: A11A-0038    [Abstracts]
TI: An LES model study of the indirect aerosol effects of marine stratocumulus clouds
AU: * Song, K Y
EM: doitsky@yonsei.ac.kr
AF: Yonsei university, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, Korea, Republic of
AU: Yum, S S
EM: ssyum@yonsei.ac.kr
AF: Yonsei university, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, Korea, Republic of
AU: Park, S K
EM: spark@ewha.ac.kr
AF: Ewha Womans University, 11-1 Daehyun-dong, Seodaemun-gu, Seoul, 120-850, Korea, Republic of
AB: Stratocumulus clouds that cover one-fourth of the entire global ocean exert significant impact on the global radiation balance and the earth's climate. Their high albedo (30-40%) compared with the ocean background (10%) gives rise to large deficits in the absorbed solar radiative flux at the top of the atmosphere, while their low altitude prevents significant compensation in thermal emission. Importantly, the radiative properties of clouds are crucially affected by the concentrations of the atmospheric particles onto which the cloud droplets form, i.e., cloud condensation nuclei (CCN). This study investigates the CCN impacts on stratocumulus cloud development using the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) Large Eddy Simulation (LES) model with size-resolving microphysics and attempts to understand how turbulence interacts with cloud microphysics. The CCN spectra are from observations over typical maritime, continental and extreme continental air masses; CCN concentrations at 1% supersaturation are 163, 1023 and 5292 cm^-3, respectively. The cloud droplet number concentration, cloud optical depth, and albedo increase but the cloud droplet effective radius decreases with the increase of CCN concentration. High CCN concentration enhances cloud reflectivity (albedo) by increasing the cloud droplet number concentration, leading to a cooling effect. There was no precipitation for the continental and extreme continental clouds while the maritime cloud precipitated after 130 minute integration. Although precipitation may depend on various environmental factors, stratocumulus clouds seem to be mainly affected by cloud microphysics, i.e., cloud droplet number concentration. The domain average shortwave cloud radiative forcing for maritime, continental, and extreme continental clouds are -204.13, -283.27, and -307.99 W m^-2, respectively. More details will be discussed at the conference.
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting