VALIDATION OF MESOSPHERE AND LOWER THERMOSPHERE WINDS FROM THE HIGH-RESOLUTION DOPPLER IMAGER ON UARS

Horizontal wind fields in the mesosphere and lower thermosphere are ob tained with the high resolution Doppler imager (HRDI) on the Upper Atm osphere]Research Satellite (UARS) by observing the Doppler shifts of e mission lines in the O-2 atmospheric band, The validity of the derived winds depends on an accurate knowledge of the positions on the detect or of the observed lines in the absence of a wind-induced Doppler shif t, Relative changes in these positions are readily identified in the r outine measurements of onboard calibration lines. The determination of the absolute values relies on the comparison of HRDI observations wit h those obtained by MF radars and rockets. In addition, the degrees of horizontal and vertical smoothing of the recovered wind profiles have been optimized by examining the effects of these parameters both on t he amplitude of the HRDI-derived diurnal tidal amplitude and on the va riance of the wind differences with correlative measurements. This pap er describes these validation procedures and presents comparisons with correlative data. The main discrepancy appears to be in the relative magnitudes measured by HRDI and by the MF radar technique. Specificall y, HRDI generally observes larger winds than the MF radars, but the si ze of the discrepancy varies significantly between different stations, HRDI wind magnitudes are found to be somewhat more consistent with me asurements obtained by the rocket launched falling sphere technique an d are in very good agreement with the wind imaging interferometer (WIN DII), also flown on UARS.