Changes in total, direct and diffuse solar and PAR radiation at the surface due to Amazonian biomass burning: a modeled study
Aline
S.
Procopio, Instituto de Física e Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo, Brazil, aline@if.usp.br
(Presenting)
Paulo
Artaxo, Instituto de Física da Universidade de São Paulo, Brazil;, artaxo@if.usp.br
Lorraine
A.
Remer, NASA/GSFC, USA, remer@climate.gsfc.nasa.gov
Yoram
J.
Kaufman, NASA/GSFC, USA, kaufman@climate.gsfc.nasa.gov
Joel
S.
Schafer, NASA/GSFC, USA, joel.schafer@gsfc.nasa.gov
The Amazon region has been experiencing a large number of forest fires in the past years, mainly in the peak of the dry season, with a considerable increase in the atmospheric aerosol loading. Using the optical properties of these aerosols derived from measurements by the AERONET sun photometer network in Amazonia, the total, direct and diffuse solar and PAR fluxes at the surface were calculated as a function of aerosol optical thickness at 500 nm (AOT), with a temporal resolution of 5 minutes. A considerable reduction of the total downward solar and PAR fluxes at the surface and a significant increase at the diffuse component were found. Consider that for aerosol background conditions, when AOT =0.10, there are not any reductions of either solar or PAR fluxes at the surface. For AOT =1.0, the daily reductions of solar and PAR fluxes were found to be 21 % and 28 %, respectively. If AOT =3.0, for example, the reductions found are 48 % and 61 %, in the same order. The average ratios of diffuse to total radiation, for solar zenith angle between 40o and -40o, increased from 0.12, for AOT =0.10, to 0.66, for AOT =3.00; for PAR radiation, this ratio increased from 0.16, for AOT =0.10, to 0.91, for AOT =3.00. For AOT =1.0, these ratios were 0.43 and 0.60, for solar and PAR radiation, in that order. The increase in the diffuse component of the total downward radiation at the surface may cause an impact on the net ecosystem productivity, due to the likely enhancement of carbon assimilation. On the order hand, the reduction of total radiation at the surface might decrease the carbon assimilation, due to the less availability of PAR radiation. The value of AOT that corresponds to the saturation in the enhancement of carbon assimilation due to the reduction of total radiation, should be investigated in details in a future study.
Submetido por Aline Sarmento Procopio em 24-MAR-2004