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| Titel |
Contribution to the study of tropical biomass burnings: Observation of carbon monoxide emitted by fires in Africa with IASI |
| VerfasserIn |
Thibaud Thonat, Cyril Crevoisier, Noëlle A. Scott, Alain Chédin, Raymond Armante, Laurent Crépeau |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053670
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| Zusammenfassung |
| Biomass burning is an important source of trace gases and aerosols to the atmosphere. In
particular, CO emissions are a key component of the global carbon budget. This is especially
true in Africa where some of the strongest emissions occur. However, there are still large
discrepancies between CO emission inventories (Stroppiana et al., 2010), stressing
the need of diverse approaches to this issue. The Infrared Atmospheric Sounding
Interferometer (IASI) onboard the Metop-A satellite launched in October 2006 enables
to observe CO twice a day, at 09:30 LT (day) and 21:30 LT (night): using such
observations, monthly mean tropospheric CO mixing ratios are retrieved over the South
of Africa, in clear sky conditions. The retrieval of CO is based on the difference
between observed and simulated brightness temperatures (BT) using the 4A radiative
transfer model (Scott and Chédin, 1981). In the 4.6 μm band highly sensitive to CO,
three couples of channels have been selected. For each of them, the two channels
have the same sensitivities to atmospheric and surface parameters, except for CO.
Thus the difference between the BT of these channels is mainly due to CO, and
minimizes the sensitivities to other variables. Following Chédin et al. (2005) who
revealed the existence of a daily tropospheric excess of CO2 (DTE) quantitatively
related to fire emissions in the tropics, we focus our analysis on the day minus night
differences of CO, and show that diurnal variations of CO are in good agreement with the
presence of fires, which are characterized by a diurnal cycle of their activity. We
show comparisons of retrieved CO for each month with fire products such as Fire
Radiative Power (FRP), Burned Areas (BA) and burning emissions from inventories
(GFEDv2,3). For several areas classified by their types of vegetation, IASI CO
is in good agreement with these products in terms of seasonal variations, with a
maximum in September and a length of the fire season of 5 months (May to October).
Nonetheless, for some areas of South West Africa, the excess of CO is longer than
the fire season given by the other products, with, sometimes, a maximum delayed
by about 2-3 months, that we are investigating. We assess the impact of surface
characteristics and other atmospheric variables on the retrieved CO, and also highlight the
influence of aerosol fire plumes on IASI channels. Quantifying these effects on
our retrievals allows improving our understanding of the biomass burning issue. |
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