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Direct measurements of the effect of biomass burning over the Amazon on the atmospheric temperature profile
1Department of Environmental Sciences, Weizmann Institute, Rehovot, Israel
2NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Abstract. Aerosols suspended in the atmosphere interact with the solar radiation and thus change the radiation energy fluxes in the atmospheric column. In particular, absorbing aerosols can stabilize the lower atmosphere by warming the aerosol layer; while cooling both: the layers beneath and the surface. Changes in atmospheric stability can affect cloud formation and cloud properties. In this paper we measure changes in the atmospheric temperature profile as a function of the smoke loading and the cloudiness over the Amazon basin, during the dry seasons (August and September) of 2005–2007. We show that as the aerosol optical depth (AOD) increases from 0.02 to a value of ~0.6, there is a decrease of ~4.3°C at 1000 hPa, and an increase of ~1.6°C at 850 hPa. The warming of the aerosol layer at 850 hPa is likely due to aerosol absorption when the particles are exposed to direct illumination by the sun. The large values of cooling in the lower layers are explained by a combination of aerosol extinction of the solar flux in the layers aloft and by an aerosol-induced increase of cloud cover and further shading of the lower atmosphere. We estimate that the increase in cloud fraction due to aerosol contributes about half of the observed cooling in the lower layers.
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Citation: Davidi, A., Koren, I., and Remer, L.: Direct measurements of the effect of biomass burning over the Amazon on the atmospheric temperature profile, Atmos. Chem. Phys. Discuss., 9, 12007-12025, 2009. Bibtex EndNote Reference Manager
