HR: 0800h
AN: A31A-0811    [Abstracts]
TI: Convective-Radiative Feedback Mechanisms By Dusty Convective Plumes And Vortices
AU: * Koch, J
EM: jkochz@engin.umich.edu
AF: University of Michigan Atmospheric, Oceanic and Space Sciences, 2455 Hayward Street, Ann Arbor, MI 48109-2143 United States
AU: Renno, N O
EM: nrenno@umich.edu
AF: University of Michigan Atmospheric, Oceanic and Space Sciences, 2455 Hayward Street, Ann Arbor, MI 48109-2143 United States
AB: We have been conducting field campaigns in Arizona to quantify the role of convective plumes and vortices on the content and vertical distribution of atmospheric dust aerosols. Data collected during our field campaigns show that coherent (organized over their vertical extension) convective vortices produce dust fluxes of nearly 1 g m^-2 s^-1 (Renno et al., 2004). Thus, very large dust devils of ~100 m in diameter can pump nearly 15,000 kg of dust in their lifetime of about 30 minutes. We used a combination of observational data and theory to determine the role of convective plumes and vortices on the global aerosol budget and show that they contribute to about 35% of the global budget of mineral dust (Koch and Renno, in press). This value was based on theoretical predictions of the fractional area covered by dusty plumes and vortices during the convectively active period of the diurnal cycle. We use measurements made during our field campaigns in Arizona to refine this calculation by detecting dust events based on heat flux and surface velocities intense enough to lift dust. We also use data from our field campaigns to better understand the radiative-convective feedback mechanisms due to convective plumes and vortices. We observed strong oscillations in surface temperature and solar flux. These oscillations, with a frequency of about 30 minutes, are of the order of the convective time scale. We speculate that intense boundary layer convection produces an increase in the concentration of atmospheric dust, which absorbs and scatters solar radiation, decreasing surface temperature and stabilizing the atmosphere, therefore causing a decrease in the intensity of atmospheric convection and surface dust flux. Therefore, we expect to see a correlation between the variability in the surface temperature and dust flux with the frequency of convective plumes and vortices on a regional scale.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 3314 Convective processes
DE: 3359 Radiative processes
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005