Validation of stratospheric ClO measurements from the Millimeter-wave Atmospheric Sounder (MAS)

During three missions in 1992, 1993, and 1994, the Millimeter-wave Atmosphe ric Sounder (MAS) measured volume mixing ratio profiles of stratospheric ch lorine monoxide (ClO) at 204 GHz from the space shuttle. Owing to the space shuttle orbit, measurements were restricted to tropical and midlatitudes. We compared zonal mean profiles to correlative ClO measurements by an airbo rne 649 GHz radiometer, a groundbased 278 GHz instrument on Mauna Kea, Hawa ii, and Version 4 ClO profiles by the Microwave Limb Sounder (MLS) on the U pper Atmosphere Research Satellite (UARS). The agreement between MAS and al l the other instruments was well within the combined error bars over a pres sure range of 0.4-40 hPa. Further comparisons of MAS and MLS day-night diff erence profiles produced an agreement of typically better than 0.1 ppbv. A detailed analysis proved that this agreement was independent of the a prior i information that was used for the retrieval of the different data sets.