Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind

An updated empirical climatic zonally averaged prevailing wind model for th e upper mesosphere/lower thermosphere (70-110 km), extending from 80 degree s N to 80 degrees S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude cont our plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannu al harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and S outhern Hemispheres. Some results of comparison between the ground-based wi nd models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provid ed by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.