A COMPARATIVE-STUDY OF MESOSPHERIC WATER-VAPOR MEASUREMENTS FROM THE GROUND-BASED WATER-VAPOR MILLIMETER-WAVE SPECTROMETER AND SPACE-BASED INSTRUMENTS

We compare water vapor measurements from the Naval Research Laboratory groundbased Water Vapor Millimeter-wave Spectrometer (WVMS) instrumen ts with measurements taken by five space-based instruments. For coinci dent measurements the retrievals from all of the instruments show qual itatively similar altitude profiles. The retrieved mixing ratios from most instruments generally differ from an average calculated using ret rievals from all of the instruments by <1 ppmv at most altitudes from 40 km to 80 km. Comparisons with the Microwave Limb Sounder (MLS) and the Halogen Occultation Experiment (HALOE) allow for the validation of observed temporal variations. The observed variations show similar an nual and semiannual cycles. A comparison of several years of data from HALOE and WVMS also shows that the instruments are detecting similar interannual variations. A regression analysis of the WVMS and HALOE da ta sets shows that the observed variability is consistent within the e stimated errors in the mesosphere and that in the upper stratosphere, where the natural variability is small, there is a positive correlatio n between the WVMS and the HALOE data.