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Abstract:
Vegetation fires emit large amounts of nitrogen compounds in the
atmosphere, including ammonia (NH3). These emissions are still subject
to large uncertainties. In this study, we analyze time series of monthly
NH3 total columns (molec cm(-2)) from the IASI sounder on board MetOp-A
satellite and their relation with MODIS fire radiative power (MW)
measurements. We derive monthly NH3 emissions estimates for four regions
accounting for a major part of the total area affected by fires (two in
Africa, one in central South America and one in Southeast Asia), using a
simplified box model, and we compare them to the emissions from both the
GFEDv3.1 and GFASv1.0 biomass burning emission inventories. In order to
strengthen the analysis, we perform a similar comparison for carbon
monoxide (CO), also measured by IASI and for which the emission factors
used in the inventories to convert biomass burned to trace gas emissions
are thought to be more reliable. In general, a good correspondence
between NH3 and CO columns and the FRP is found, especially for regions
in central South America with correlation coefficients of 0.82 and 0.66,
respectively. The comparison with the two biomass burning emission
inventories GFASv1.0 and GFEDv3.1 shows good agreements, particularly in
the time of the maximum of emissions for the central South America
region and in the magnitude for the region of Africa south of the
equator. We find evidence of significant non-pyrogenic emissions for the
regions of Africa north of the equator (for NH3) and Southeast Asia (for
NH3 and CO). On a yearly basis, total emissions calculated from IASI
measurements for the four regions reproduce fairly well the interannual
variability from the GFEDv3.1 and GFASv1.0 emissions inventories for NH3
but show values about 1.5-2 times higher than emissions given by the two
biomass burning emission inventories, even when assuming a fairly long
lifetime of 36 h for that species. (C) 2015 Elsevier Ltd. All rights
reserved.