HR: 10:56h
AN: A22B-03    [Abstracts]
TI: Smoke Suppression of Clouds in Brazil
AU: * Jiang, H
EM: jiang@atmos.colostate.edu
AF: CIRA/NOAA, Foothills Campus, Fort Collins, CO 80523 United States
AU: Feingold, G
EM: graham.feingold@noaa.gov
AF: NOAA/ETL, 325 Broadway, Boulder, CO 80523 United States
AU: Harrington, J
EM: harring@admin.meteo.psu.edu
AF: Penn State University, Department of Meteorology, University Park, PA 16802 United States
AB: We present a study of smoke aerosol effects on cloud formation in the biomass burning regions of Brazil and investigate the reasons for the progressive reduction in cloud fraction with increasing smoke optical depth that has been observed by remote sensors. Numerical simulations of cumulus clouds are performed with a large eddy simulation (LES) coupled to an aerosol/cloud microphysical model and a radiation model. A sounding from the Smoke, Aerosols, Clouds, Rainfall and Climate (SMOCC) experiment is used as a framework for the numerical experiments. The model shows that the vertical distribution of smoke is important in determining the effect on clouds. Elevated smoke layers result in a strong reduction in cloud fraction whereas smoke confined mostly to the boundary layer has little effect on cloud fraction. Heating associated with smoke embedded in droplets has a negligible effect on the clouds for the conditions studied. On the other hand, the observed and modeled reduction in surface latent and sensible heat fluxes asssociated with smoke, is by itself sufficient to reduce cloud fraction significantly. This has important implications for land/ocean differences in the cloud response to smoke.
DE: 1600 GLOBAL CHANGE (New category)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting