VALIDATION OF TEMPERATURE-MEASUREMENTS FROM THE IMPROVED STRATOSPHERIC AND MESOSPHERIC SOUNDER

Atmospheric temperature measurements from the improved stratospheric a nd mesospheric sounder (ISAMS) are evaluated. Flown on the Upper Atmos phere Research Satellite (UARS), ISAMS obtained 180 days of science da ta between September 26, 1991 and July 29, 1992. Typically, over 2600 temperature profiles/day were retrieved, spaced every 200 km along the limb-viewing track and nominally extending from 100 to 0.01 mbar (15- 80 km). The latitude coverage ranged from 80 degrees S to 80 degrees N , depending on the particular ISAMS/UARS viewing geometry on any day. UARS is in a near-Sun-synchronous orbit, so that while the 15 orbits/d are spaced approximately every 24 degrees longitude around the equato r, the sampled local solar time actually changes by 20 min/d. The ISAM S temperature retrieval process is outlined and the various products a re described. A detailed error budget for the retrieval is presented a nd comparisons are made with temperature measurements from other sourc es. Finally, a table is provided summarizing the best estimates of ISA MS temperature bias and precision. The results suggest a general cold bias of around 1 K in the stratospheric temperatures, with a superimpo sed 2-3 K warm bias associated with the densest part of the Pinatubo a erosol cloud. The precision of individual profiles is +/-2 K throughou t the stratosphere but falls off in the mesosphere to about +/-10 K at 80 km. The error bars produced by the retrieval appear to be reasonab le (although slightly pessimistic) estimates of the precision.