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First Global Map of Ammonia Sources

According to Cathy Clerbaux, from LATMOS,1 the first global map of ammonia emissions2 came about nearly by accident. Her team, collaborating with researchers in Belgium, had been analyzing data from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite (IASI/MetOp) designed for operational meteorological soundings with a very high level of accuracy. Their goal was to learn as much as possible about the chemistry of the Earth's atmosphere. This entailed studying concentrations of atmospheric carbon monoxide, methane, ozone, and other persistent gases. Ammonia (NH3), however, had not been on the agenda.
first global


Global distribution of ammonia in 2008, as measured by the IASI instrument on the MetOp satellite. The yellow to red colors indicate high ammonia concentrations.

Ammonia is a pollutant that contributes to the formation of airborne particles harmful to human health, and to other environmental effects. It comes from many sources, some natural, but the bulk is a result of agricultural activities. Despite ammonia's far-reaching effects, there is very little data on global emission levels. The gas tends to stay in the atmosphere for a short period of time–a few hours at most –making satellite observations almost impossible. Global data was therefore limited to a patchwork of Earth-based measurements.
“When we were analyzing our data, there was a very weak signal that we could not identify. It turned out to be ammonia,” explains Clerbaux. Although the IASI/MetOp satellite, launched in 2006, was not designed to observe ammonia, its two passes over the Earth's entire surface every 24 hours generate millions of observations a day. By accumulating data over a one-year period, the team was able to compensate for the gas's weak signal by filtering out background “noise” in their images, and then create a global map of ammonia emissions worldwide.
Their map was a wake-up call. It revealed many sources of the gas that had been previously unknown, and it showed high ammonia-concentration regions in South Asia, Europe, and California.
“We will continue to monitor ammonia to determine how the sources evolve and change over the years,” says Clerbaux. Now that her team has shown it is possible to observe ammonia from the skies, the MetOp follow-on satellite currently in development could be designed to measure these emissions more accurately.

Mark Reynolds

Notes :

1. Laboratoire atmosphères, milieux, observations spatiales (CNRS / Universités Paris-VI and Versailles-Saint-Quentin).
2. C. Lieven et al., “Global ammonia distribution derived from infrared satellite observations,” Nature Geoscience, 2009. 2: 479-83.

Contacts :

Cathy Clerbaux,
LATMOS, Paris.


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