THERMAL TIDES AND STUDIES TO TUNE THE MECHANISTIC TIDAL MODEL USING UARS OBSERVATIONS

Monthly simulations of the thermal diurnal and semidiurnal tides are c ompared to High-Resolution Doppler Imager (HRDI) and Wind Imaging Inte rferometer (WINDII) wind and temperature measurements on the Upper-Atm osphere Research Satellite (UARS). There is encouraging agreement betw een the observations and the linear global mechanistic tidal model res ults both for the diurnal and semidiurnal components in the, equatoria l and mid-latitude regions. This gives us the confidence to outline th e first steps of an assimilative analysis/interpretation for tides, di ssipation, and mean flow using a combination of model results and the global measurements from HRDI and WINDII. The sensitivity of the propo sed technique to the initial guess employed to obtain a best fit to th e data by tuning model parameters is discussed for the January and Mar ch 1993 cases, when the WINDII day and night measurements of the merid ional winds between 90 and 110 km are used along with the daytime HRDI measurements. Several examples for the derivation of the tidal variab les and decomposition of the measured winds into tidal and mean flow c omponents using this approach are compared with previous tidal estimat es and modeling results for the migrating tides. The seasonal cycle of the derived diurnal tidal amplitudes are discussed and compared with radar observation between 80 and 100 km and 40 degrees S and 40 degree s N.