Validation of winds from the high resolution Doppler imager on UARS

The High Resolution Doppler Imager (HRDI) on the Upper Atmospheric Research Satellite (UARS) is designed to measure horizontal winds in the mesosphere and lower thermosphere (50--115 km) and in the stratosphere (10--40 km), as part of a coordinated mission which is aimed at an improved understanding of global atmospheric change. Horizontal winds are obtained by observing the Doppler shifts of emission lines in the O2 Atmospheric band. The validity of the measurements depends on an accurate knowledge of the positions on the detector of the observed lines in the absence of a wind induced Doppler shift. These positions have been determined to an accuracy of better than 5 ms-1 from the comparison of winds measured by HRDI with 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 effect both on the amplitude of the HRDI derived diurnal tidal amplitude and the variance of the wind differences with correlative data