Comparison of mesospheric and lower thermospheric residual wind with High Resolution Doppler Imager, medium frequency, and meteor radar winds

The objective of this study is to compare observed mean meridional winds wi th those deduced from theory. The diabatic circulation is computed from Hig h Resolution Dopper Imager (HRDI) mesospheric and lower thermospheric tempe ratures during January and July conditions. The meridional wind component i s compared with HRDI Eulerian mean meridional winds near 95 km and with sea sonal averages of meridional winds at a number of radar medium-frequency (M F) and meteor wind (MW) sites, The diabatic wind is directed from the summe r toward the winter hemisphere, Peak values exceed 20 m s(-1) and are obser ved at 105 km near 20 degrees in the summer hemisphere, A secondary maximum of about 10 m s(-1) is observed in the wintertime lower mesosphere during the July case. The diabatic wind is qualitatively consistent with HRDI 95-k m mean meridional winds at latitudes equatorward of 50 degrees, Time-averag ed summertime radar winds are consistent with HRDI and diabatic winds betwe en 50 degreesS and 20 degreesN, At winter midlatitudes, MF radar winds are directed oppositely to the diabatic wind, while one available MW measuremen t is directed with the diabatic wind. The zonal acceleration implied by the diabatic wind is about 150-200 m s(-1) d(-1) in the midlatitude summer low er thermosphere.