25 juin 2009
Ammonia comes essentially from the use of fertilizers in agriculture and from intensive livestock production.
IASI** wasn’t designed to measure ammonia, which has an extremely weak absorption signal: once emitted, it only persists in the atmosphere for a few hours but it sets in train a cascade of knock-on environmental effects which, at high concentrations, impact wildlife, plants and local air quality.
“These ammonia measurements show just how good the IASI instrument is,” says Cathy Clerbaux, director of research at the French scientific research centre CNRS.
Ammonia is the most poorly understood of all pollutants regulated by EU air quality directives. Emission maps are not very accurate, and systematic, global surveillance of ammonia is difficult to achieve. “These 1st global maps of ammonia will help to establish more realistic emission inventories,” affirms Cathy Clerbaux.
1 million measurements per day
“IASI is enhancing weather forecasts while also telling us more about the gases involved in pollution peaks,” explains Cathy Clerbaux.
Flying on the MetOp meteorology satellite, IASI is a key instrument for monitoring the environment and climate.
IASI’s spectrometer has already measured several atmospheric elements: ozone, carbon monoxide, methane, carbon dioxide and now ammoniac.
“The wealth of measurements gathered over a period of 1 year made it possible to isolate the signature of ammonia from the background instrument noise and thus increase measurement accuracy,” explains Cathy Clerbaux.
Researchers used these observations to show that sources of ammonia have been underestimated in the northern hemisphere, particularly in the United States (California and Idaho), Europe (in the Po and Ebro valleys) and Central Asia.
Sources unaccounted for in current inventories have thus been detected. In all, 30 major sources of ammonia were identified for 2008.
* European Organisation for the Exploitation of Meteorological Satellites
** Infrared Atmospheric Sounding Interferometer