Articles | Volume 16, issue 22
Research article
18 Nov 2016
Research article |  | 18 Nov 2016

First detection of ammonia (NH3) in the Asian summer monsoon upper troposphere

Michael Höpfner, Rainer Volkamer, Udo Grabowski, Michel Grutter, Johannes Orphal, Gabriele Stiller, Thomas von Clarmann, and Gerald Wetzel

Abstract. Ammonia (NH3) has been detected in the upper troposphere by the analysis of averaged MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) infrared limb-emission spectra. We have found enhanced amounts of NH3 within the region of the Asian summer monsoon at 12–15 km altitude. Three-monthly, 10° longitude  ×  10° latitude average profiles reaching maximum mixing ratios of around 30 pptv in this altitude range have been retrieved, with a vertical resolution of 3–8 km and estimated errors of about 5 pptv. These observations show that loss processes during transport from the boundary layer to the upper troposphere within the Asian monsoon do not deplete the air entirely of NH3. Thus, ammonia might contribute to the so-called Asian tropopause aerosol layer by the formation of ammonium aerosol particles. On a global scale, outside the monsoon area and during different seasons, we could not detect enhanced values of NH3 above the actual detection limit of about 3–5 pptv. This upper bound helps to constrain global model simulations.

Short summary
Ammonia (NH3) in the atmosphere is important because of its influence on aerosol and cloud formation and its increasing anthropogenic emissions. We report the first detection of NH3 in the upper troposphere by the analysis of infrared limb emission spectra measured by the MIPAS instrument on Envisat. We have found enhanced values of NH3 within the Asian summer monsoon upper troposphere, where it might contribute to the composition of the Asian tropopause aerosol layer.
Final-revised paper