Ammonia detected in upper troposphere for the first time

KARLSRUHE, Germany, Dec. 5 (UPI) -- For the first time, trace amounts of ammonia, a chemical compound of nitrogen and hydrogen, have been measured in the upper troposphere, the lowest of Earth's atmospheric layers.

The chemical compound was found at elevations ranging from 7.5 miles to 9.3 miles above sea level. The troposphere rises between 11 and 12 miles in height.

Measurements were made by the Michelson Interferometer for Passive Atmospheric Sounding, or MIPAS, an infrared spectrometer on the the European Space Agency's Earth-observing satellite Envisat.

Because ammonia traces were measured among Asian monsoons, scientists hypothesize the gas plays a role in aerosol formation. Aerosols, tiny colloid particles, part liquid and part solid, inhibit storm cloud formation. Ammonia gas can react with acids to form ammonia salts, the particles of which can become nuclei for clouds.

Ammonia emissions are greatest in Asia, with concentrations highest above China and India -- the result of growing populations and agricultural expansion. Ammonia is a main ingredient in most commercial fertilizers.

"Observations show that ammonia is not washed out completely when air ascends in monsoon circulation," Michael Höpfner, a researcher at the Karlsruhe Institute of Technology's Institute of Meteorology and Climate Research, said in a news release. "Hence, it enters the upper troposphere from the boundary layer close to the ground, where the gas occurs at relatively high concentrations. It is therefore assumed that part of the Asian tropopause aerosol layer consists of ammonium salts."

Researchers say their findings -- detailed in the journal Atmospheric Chemistry and Physics -- can be used to update climate models.

Though scientists believe it is likely global warming is encouraging the propagation of ammonia in the upper troposphere, its presence could have a slight cooling effect.