The use of ATOVS - AMSU data in NCEP stratospheric analyses

Temperature data from Advanced TIROS Operational Vertical Soundings (ATOVS) are being incorporated into NCEP stratospheric analyses, replacing TOVS data, which have been used since 1979. ATOVS stratospheric temperatures are derived from radiometric measurements of the new Advanced Microwave Sounding Unit (AMSU) on the NOAA-15 polar satellite, whereas TOVS upper stratosphere temperatures were based principally on measurements of Stratospheric Sounding Units (SSU). Temperature data from radiosondes, rocketsondes lidars, and the NASA Upper Atmosphere Research Satellie provide a basis for evaluating upper stratosphere temperatures. Comparisons with data from the new and older satellite derivations will be shown. Synoptic patterns of temperature fields derived from the ATOVS and TOVS data are very similar, with average differences ranging from 1 to 3 C degrees. Differences from ground based measurements range from 3 to 7 C degrees, RMS. We conclude that the temperature derivations from the new ATOVS system are superior to the TOVS data in depicting vertical profiles of upper stratospheric temperature. Differences in retrieval methodology, nmore than differences in the radiometric measurements, cause the improvements. Data from the new ATOVS system, on successive NOAA polar satellites, will form the basis for monitoring stratospheric temperature for at least the next two decades.