Retrieval of upper stratospheric and mesospheric temperature profiles fromMillimeter-Wave Atmospheric Sounder data

The Millimeter-Wave Atmospheric Sounder (MAS) is a shuttle-based instrument , observing the atmosphere in limb sounding geometry. Temperature informati on is derived from three oxygen lines near 60 GHz. Temperature profiles in the altitude range from 30 to 90 km can be measured, The data evaluation is tone with the aid of an atmospheric radiative transfer model. Usually, the radiation is assumed to be unpolarized, so that spectral power is a scalar quantity, This assumption is not valid for oxygen lines that show Zeeman s plitting in the Earth's magnetic field. A more general form of the radiativ e transfer in which spectral power is represented by a vector has to be use d in this case. The obtained information depends on the magnetic field. Usi ng the MAS instrument characteristics, we investigate the possible temperat ure information that can be obtained from observation of polarized O-2 emis sion lines with a spaceborne instrument. Synthetic retrievals show that the obtained accuracy of the retrieved temperature profile is below 3 K from 3 0 to 55 km and below 6 K for altitudes up to 90 km. The resolution is 4 km for altitudes of 30 to 50 km and 10 km above. The magnetic parameters influ ence the accuracy of the obtained profile by as much as 2 K. The obtained M AS temperature profiles were validated by a comparison to data from the Tip per Atmosphere Research Satellite (UARS). Three UARS instruments were chose n: Microwave Limb Sounder, Improved Stratospheric and Mesospheric Sounder, and the Cryogenic Limb Array Etalon Spectrometer. All comparisons show simi lar features for the stratospheric and mesospheric temperatures.