REMOTE-SENSING OF CARBONACEOUS AEROSOL PRODUCTION BY AFRICAN SAVANNA BIOMASS BURNING

We present an estimate of the yearly flux of total and black carbon ae rosols emitted by savanna biomass burning in Africa from satellite dat a and ground-based measurements. Smoke plumes are identified using vis ible, near-infrared, and thermal infrared derived information. In the savanna region of our study, these structures could either decrease or increase the visible albedo of advanced very high resolution radiomet er (AVHRR). It is hypothesized that variations of chemical composition and particulate size distribution may create such differences. The 5S model [Tanre et al., 1990] is used to simulate radiative transfer thr ough smoke plumes and background atmosphere. The overall uncertainty o f the derived aerosol optical depth (tau(a)) is 75% and mainly due to the choice in particulate composition and size distribution aerosol. I mpact of the aerosol mixture (internal versus external mixture) has be en also tested. For smoke plumes a typical value of tau(a) (at 0.55 mu m) is 0.5, and 0.1 for the background atmosphere. Specific extinction cross sections are calculated using Mie theory applied to different r epresentative aerosol models, allowing the retrieval of aerosol column ar concentrations from aerosol optical depth values and integrated aer osol mass loadings in fire plumes. The overall uncertainty on the dete rmination of aerosol load is estimated to be lower than a factor of 5. The atmospheric carbonaceous aerosol flux from savanna burning in Afr ica was estimated to be 6.5 Tg C yr(-1), which compares with that obta ined from emission factor on-site measurements (13 +/- 5 Tg C yr(-1)).