Aerosol-climate interactions: The role of convective plumes and vortices on the global mineral dust budget and convective -radiative interactions.

Abstract

The MATADOR field experiment in Arizona was designed to quantify the effect of plumes and vortices on the lifting and vertical transport of mineral dust aerosols. The MATADOR data show that coherent (organized over their vertical extension) convective plumes and vortices produce dust fluxes in excess of 1 g m<super>-2</super> s<super>-1</super>. Thus a large dust devil of &sim;100 m in diameter can pump &sim;15,000 kg of dust into the atmosphere during its 30 min lifetime. From these observations and several other studies we hypothesize that coherent convective plumes and vortices play an important role in the global mineral dust aerosol budget. During the MATADOR experiment we also observed strong oscillations in ground temperature, solar radiation, and surface heat flux. We hypothesize that they are due to interactions between atmospheric convection, airborne dust and solar radiation. This thesis addresses the two hypotheses described above. I quantify the global contribution of plumes and vortices to the mineral dust budget. Using a combination of observation and theory I show that they contribute &sim;35% to the global mineral dust aerosol budget. Therefore this improves our understanding of climate by showing that small-scale processes play an important role in the global aerosol budget. We conclude that these small-scale processes must be included in global climate models. I also study the various physical processes that may lead to observed oscillations in the solar radiation flux, ground temperature, and surface heat flux. I find that the oscillations are coupled by interactions between convection, airborne dust and solar radiation and that their amplitude is a function of the frequency and intensity of local convective plumes and vortices. To the best of my knowledge, this is the first report of these coupled oscillations.