Atmospheric Science

An Eye for Ammonia

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Science  24 Jul 2009:
Vol. 325, Issue 5939, pp. 369
DOI: 10.1126/science.325_369a
CREDIT: JUPITERIMAGES

Ammonia is a trace gas of considerable importance for atmospheric chemistry, aerosol particle formation, and fertilization of the biosphere. Its global emissions have grown to more than twice their preindustrial values, mainly as a consequence of expanded agriculture and associated use of fertilizers. Yet large uncertainties in emissions budgets, due to the lack of adequate observational data, have hindered a confident assessment of the strengths of ammonia sources geographically. Clarisse et al. present infrared spectra obtained by satellite to map global atmospheric ammonia concentrations in 2008. They find that there is good qualitative agreement between these data and modeled values, but that large quantitative discrepancies exist, especially in regions above 30°N latitude. Additionally, they find a number of emission hot spots, all in the Northern Hemisphere, leading them to suggest that Northern Hemispheric ammonia emissions have been underestimated. These data, and this technique, should enhance our broader understanding of the global nitrogen cycle.

Nat. Geosci. 2, 479 (2009).

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