[hal-00439408] First global ammonia distributions from infrared satellite observations

Infrared sounding of our atmosphere is at present confined to a number of species with lifetimes of several weeks to years. Short lived species are mainly confined to the boundary layer, close to their emission sources and for a long time it has been assumed that infrared instruments are not well suited for monitoring them. Yet, satellite monitoring of such species is highly desirable, as ground based measurements are sparse and are unable to map the regional and seasonal variability. Ammonia is one of the most important short lived species in our atmosphere, being the principal alkaline component and a large contributor to reactive nitrogen. In the last century global ammonia emissions have doubled and are expected to increase further in the coming decades, with huge implications on the Earth's biogeochemistry, environment and climate. The ammonia budget is poorly understood and accounts for the largest uncertainty in the global nitrogen cycle. Ammonia has been observed in the last years with infrared sounders locally and for the first time with IASI in biomass burning plumes. In this talk we present the first global ammonia concentrations from space based observations. Concentrations are retrieved using the infrared spectra of the space-borne sounder IASI onboard the MetOp-A platform. We present the 2008 global yearly average and identify a multitude of hotspots, notably over biomass burning regions and agricultural areas. Next we compare the measured concentrations with the concentrations from a global chemistry model, and draw robust conclusions on underestimates in the model in large parts of North-America, Europe and Asia. IASI provides daily global coverage with a high spatial resolution and is therefore ideal in monitoring the spatio-temporal variability of ammonia. As a test case, we analyse in detail the seasonal and geographical variations of ammonia in the San Joaquin Valley, California, for which we also present measurements from the AIRS sounder.



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