Seasonal and diurnal variations of middle atmosphere winds

Abstract

Previously published meridional cross sections of monthly mean W —E and S -N wind components from 60 to 130 km are reviewed in the light of wind data obtained by ground-based radio methods over various timescales including that of the solar cycle. A mean meridional circulation in the winter hemisphere is implied in which a dominant mesospheric cell between low and high latitudes is confined to lower heights at higher latitudes: a second meridional circulation is tentatively located above the former in the lower thermosphere extending downwards to lower heights at higher latitudes and introducing the possibility of polar and equatorial air mixing at midlatitudes at heights close to 90 km. Meridional circulation is discussed in relation to the winter anomaly in D -region radio-w ave absorption.