Seasonal behaviour of the long-term temperature trends in the middle atmosphere on the mid-latitudes

On the basis of rocket, nightglow and radiophysical measurements at heights of 30- 110 km in middle latitudes the seasonal variations of the long-term temperature trends at various altitude levels are determined. At heights of 25-87 km the trends are mainly negative within all year. Only in winter period in middle and upper stratosphere the trend within several months becomes positive. At heights of 92-93 km the trend is steadily close to zero during all year. In summer period the area of zero trend extends downwards to heights of 82-85 km, where the noctilucent clouds are usually observed. In a region of heights of 95-110 km the trends during all year are steadily positive. Mean annual distribution with height of the temperature trend shows steady long-term process of cooling of an atmosphere at heights of 30-90 km ensuring systematic subsidence of the upper layers of an atmosphere. Analytic equations for evaluatting the time of the subsidence of different layers of the upper atmosphere are presented.