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
Received: 06 April 2009 – Published in Atmos. Chem. Phys. Discuss.: 15 May 2009 Abstract. Aerosols suspended in the atmosphere interact with solar radiation and
clouds, thus change the radiation energy fluxes in the atmospheric column.
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 2005–2008. 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°C at 1000 hPa, and an increase of
~1.5°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
could be explained by a combination of aerosol extinction of the solar flux
in the layers aloft together with an aerosol-induced increase of cloud cover
which shade 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.
Revised: 16 October 2009 – Accepted: 19 October 2009 – Published: 03 November 2009
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., 9, 8211-8221, doi:10.5194/acp-9-8211-2009, 2009.