Biomass burning emissions estimated with a global fire assimilation system based on observed fire radiative power

[摘要] The Global Fire Assimilation System (GFASv1.0) calculates biomassburning emissions by assimilating Fire Radiative Power (FRP)observations from the MODIS instruments onboard the Terra and Aquasatellites. It corrects for gaps in the observations, which aremostly due to cloud cover, and filters spurious FRP observations ofvolcanoes, gas flares and other industrial activity. The combustionrate is subsequently calculated with land cover-specific conversionfactors. Emission factors for 40 gas-phase and aerosol trace specieshave been compiled from a literature survey. The corresponding dailyemissions have been calculated on a global0.5^° × 0.5^° grid from 2003 to the present.General consistency with the Global Fire Emission Database version3.1 (GFED3.1) within its accuracy is achieved while maintaining theadvantages of an FRP-based approach: GFASv1.0 makes use of thequantitative information on the combustion rate that is contained inthe FRP observations, and it detects fires in real time at highspatial and temporal resolution. GFASv1.0 indicates omission errorsin GFED3.1 due to undetected small fires. It also exhibits slightlylonger fire seasons in South America and North Africa and a slightlyshorter fire season in Southeast Asia. GFASv1.0 has already beenused for atmospheric reactive gas simulations in an independentstudy, which found good agreement with atmospheric observations.Wehave performed simulations of the atmospheric aerosol distributionwith and without the assimilation of MODIS aerosol optical depth (AOD).They indicate that the emissions of particulate matter needto be boosted by a factor of 2–4 to reproduce the globaldistribution of organic matter and black carbon. This discrepancy isalso evident in the comparison of previously published top-down andbottom-up estimates. For the time being, a global enhancement of theparticulate matter emissions by 3.4 is recommended. Validation withindependent AOD and PM₁₀ observations recorded during theRussian fires in summer 2010 show that the global MonitoringAtmospheric Composition and Change (MACC) aerosol model withGFASv1.0 aerosol emissions captures the smoke plume evolution wellwhen organic matter and black carbon are enhanced by the recommendedfactor.In conjunction with the assimilation of MODIS AOD, the useof GFASv1.0 with enhanced emission factors quantitatively improvesthe forecast of the aerosol load near the surface sufficiently toallow air quality warnings with a lead time of up to four days.

[学科分类] 地球化学与岩石