HR: 1340h
AN: A23C-0824    [Abstracts]
TI: Aerosol Versus Dynamic and Thermodynamic Control of Early Anvil Particle Size Over Subtropical and Tropical Regions
AU: * Fridlind, A M
EM: ann.fridlind@nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Kucera, P A
EM: pkucera@aero.und.edu
AF: University of North Dakota, 4149 Campus Road, Clifford Hall 400, Box 9006, Grand Forks, ND 58202 United States
AU: Theisen, C
EM: pkucera@aero.und.edu
AF: University of North Dakota, 4149 Campus Road, Clifford Hall 400, Box 9006, Grand Forks, ND 58202 United States
AU: Ackerman, A S
EM: andrew.ackerman@nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Jensen, E J
EM: eric.j.jensen@nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-4, Moffett Field, CA 94035 United States
AB: A major challenge of general circulation models is the correct prediction of cumulonimbus anvil crystal size, which may strongly influence the radiative impact of long-lived anvil shields. Here we divide the factors affecting early anvil development into aerosol versus dynamic and thermodynamic categories, and we first test a strategy for using observations to constrain conclusions regarding which exerts greater control over crystal size distributions. Global surveying satellite data from the MODIS instruments on the Aqua and Terra platforms now provide retrieved effective radius from anvil tops throughout the tropics and subtropics. While MODIS also provides some measures of column-integrated aerosol properties in cloud-free regions, there is no information on aerosol vertical distribution and no direct measurement of cloud dynamics (e.g., updraft strength). To fill in these missing pieces as robustly as possible, we begin our analysis using in situ aerosol data and ground-based radar data from the July 2002 CRYSTAL-FACE campaign, which is representative of regional subtropical convection (primarily continental). Considering the days for which CRYSTAL-FACE aerosol and radar data are available, Aqua data indicate marked differences in retrieved cloud-top effective radius. Radar data indicate large variability in fractional area exceeding a reflectivity threshold of 40 dBZ and the peak height of a 30 dBZ echo, which are indicators of the convective intensity of a system. In situ aerosol data also differ markedly in a manner not easily simplified owing to changes in both size and number within surface and elevated layers. To bridge this complex phase space (aerosol and thermodynamic and dynamic values all varying with elevation), we perform large-eddy simulations with size-resolved aerosol and cloud particles to test the expected sensitivity of anvil properties on each day to the variability of measured conditions, and then compare results with radar and MODIS observations. We finally consider possibilities for using MODIS data alone to extend this analysis to other regions, beginning with the tropical eastern Pacific, where the TCSP campaign will take place.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting