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MEASUREMENTS OF AEROSOL PROPERTIES IN THE AMAZON BASIN 
Brent Holben 
Alberto Setzer, T.F. Eck 
I. Slutsker, Alfredo Pereira 
NASA/GSFC 
Code 923 
Greenbelt, MD 20771, USA 
ISPRS Commission VII / Working Group 1 
ABSTRACT 
Typical remote sensing investigations of aerosol optical properties from biomass burning reveal that most 
ground aircraft and satellite studies are of short duration. An automatic ground based network of sun and 
sky viewing radiometers measured the aerosol optical properties prior during and after the burning season 
at seven cerrado and forest sites in the Amazon basin of Brazil during the dry season o 1993. The data 
base includes aerosol optical thickness and precipitable water observations at 15 minutes intervals and 
aerosol size distributions and phase function retrievals from aureole and sky radiances at one hour 
intervals weather permitting. The data for 1993 show the background optical thickness is at or below the 
global average of 0.1 in the forest and cerrado regions approximately 30% of which is due to 
stratospheric Pinatubo aerosol. Most sites reported elevated values during August through September due 
to local and regional biomass burning. The optical thickness varied spatially and temporally during this 
period from near background levels to optical thicknesses greater than 2. Because of the enormous 
variability in local aerosol optical thickness, no obvious spatial relationship is apparent between regional 
stations. The size distributions showed a weak accumulation mode, a pronounced Pinatubo ode, and a 
very weak coarse particle mode for background conditions at all sites. Depending on the optical 
thickness, the accumulation mode typically increased one to two orders of magnitude masking the 
influence of the Pinatubo aerosol. The coarse particle mode typically showed a proportionally smaller 
increase for fresh smoke than aged smoke. Measurements from the network will continue through 1995 
providing validation of satellite retrievals of aerosols as well as significant information on atmospheric 
quality. 
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