Winds in the Mesosphere and Lower Thermosphere

A review is given of present knowledge of air motions and physical factors affecting the general circulation in the mesosphere and lower thermosphere. Mean latitudinal cross sections of zonal wind at the equinoxes and solstices are given from pole to pole for the height range 30 to 120 km and used to derive corresponding mean temperatures by means of the thermal wind equation. It is now possible, using rocket data, to construct limited synoptic charts up to about 60 km over North America. The general sequence of synoptic changes in the 30 to 60 km layer throughout the year is described. Above about 80 km measured air movements reveal large tidal motions and gravity waves of greater magnitude than the winds and the manner in which these vary with altitude and the factors controlling them are discussed.