Temperature and wind variation in the tropical upper stratosphere and lower mesosphere during a sunspot cycle

The year-to-year variations of temperature and vertical shear of the zonal wind in the height interval 40–55 km have been examined for the equinoctial months at the rocketsonde stations of Ascension Island and Fort Sherman, Panama. Both the wind shear and the temperature were a maximum in about 1964 and 1970 and a minimum during 1967–1968. The period between the maxima is too short to be coincident with the sunspot cycle but may possibly be related to half the sunspot cycle. The results show that large-scale persistent temperature and wind shear changes occur near the tropical stratopause, the amplitude being largest near the equator. These variations are probably of dynamic origin. If any of the variations are related to variable solar ultraviolet emissions, the relationship is not represented by a simple direct solar heating during a sunspot cycle.