HR: 0800h
AN: A11C-0069    [Abstracts]
TI: The Role of Convective Plumes and Vortices on the Global Aerosol Budget
AU: * Koch, J
EM: jkochz@umich.edu
AU: Renno, N
EM: nrenno@umich.edu
AB: The significance of dust aerosol is evident based on the large surface area of arid and semi-arid regions on most continents. Suspended desert dust is a significant contributor to atmospheric aerosol loading, with strong absorption bands in the atmospheric window. Ginoux et al. (2001) estimates the global contribution of suspended aerosols by desert dust at several thousand millions of tons per year, supporting previous estimates by Hidy and Brock (1971), Schtz (1980), and d'Almeida (1986a). In the US Southwest, convective plumes and vortices produce an efficient vertical transport of dust that supplies enough aerosols to the atmospheric boundary layer to significantly scatter and absorb incoming solar radiation (DeLuisi et al., 1976). Evidence of this is given by Gillette and Sinclair's (1990) aircraft measurements of particle concentration and vertical velocities in dust devils. They estimated that at approximately 150 meters above the surface, dust devils over the U.S. Southwest have a mean dust flux of about 0.1 kg m-2 per year. This value represents almost 75% of the total dust flux caused by wind action. In the spring of 2002 our group led an NSF-sponsored pilot field experiment to quantify the intensity and variability of the surface flux of heat and mineral dust under convectively unstable conditions. Data collected in this pilot field campaign show that coherent (organized over their vertical extension) convective plumes and vortices produce heat and dust fluxes in excess of 10 kW m-2 and 1 g m-2 s-1 (Renno et al., 2004). Thus, a single dust devil with a 10 meter radius can pump approximately one half of a ton of dust into the atmosphere in a typical 30 minute life span. Observational data for the US Southwest shows that nearly 2 percent of the observed area is covered by updrafts due to dust devils during their active times from 10:30 to 18:00 (Sinclair, 1966; Ryan and Carroll, 1970). Based on this data and our measurements, a 100 by 100 km area in Arizona can pump nearly 200 tons of dust per second into the atmosphere during convectively active periods (from 10 am to 5 pm). We conclude that dust sources due to convective plumes and vortices, such as that over the US Southwest, may have a large impact on the global aerosol budget. Our presentation will focus on the role of coherent convective plumes and vortices on the global aerosol budget.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting