Stratospheric CH₃CN from the UARS Microwave Limb Sounder

CH 3 CN in the stratosphere has been measured by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS), providing the first global CH 3 CN dataset. The MLS observations are in broad agreement with past high and midlatitude observations of CH 3 CN, although concentrations are a little larger than previously observed. In the tropics, where CH 3 CN has not up to now been measured, a persistent ‘peak’ in the profiles is seen around 22 hPa, which may be evidence of a tropical stratospheric CH 3 CN source. Comparisons are made with the NCAR SOCRATES model, including runs having an artificial tropical stratospheric CH 3 CN source.