VALIDATION OF UARS MICROWAVE LIMB SOUNDER TEMPERATURE AND PRESSURE MEASUREMENTS

The accuracy and precision of the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) atmospheric temperature and tangen t-point pressure measurements are described, Temperatures and tangent- point pressure (atmospheric pressure at the tangent height of the held of view boresight) are retrieved from a 15-channel 63-GHz radiometer measuring O-2 microwave emissions from the stratosphere and mesosphere , The Version 3 data (first public release) contains scientifically us eful temperatures from 22 to 0.46 hPa, Accuracy estimates are based on instrument performance, spectroscopic uncertainty and retrieval numer ics, and range from 2.1 K at 22 hPa to 4.8 K at 0.46 hPa for temperatu re and from 200 m (equivalent log pressure) at 10 hPa to 300 m at 0.1 hPa. Temperature accuracy is limited mainly by uncertainty in instrume nt characterization, and tangent-point pressure accuracy is limited ma inly by the accuracy of spectroscopic parameters. Precisions are aroun d 1 K and 100 m, Comparisons are presented among temperatures from MLS , the National Meteorological Center (NMC) stratospheric analysis and lidar stations at Table Mountain, California, Observatory of Haute Pro vence (OHP), France, and Goddard Spaceflight Center, Maryland. MLS tem peratures tend to be 1-2 K lower than NMC and lidar, but MLS is often 5 - 10 K lower than NMC in the winter at high latitudes, especially wi thin the northern hemisphere vortex. Winter MLS and OHP (44 degrees N) lidar temperatures generally agree and tend to be lower than NMC. Pro blems with Version 3 MLS temperatures and tangent-point pressures are identified, but the high precision of MLS radiances will allow improve ments with better algorithms planned for the future.