Empirical model of vertical structure of the middle atmosphere: Seasonal variations and long-term changes of temperature and number density

An empirical model of the mid-latitude (40°N-55°N, altitudes 25-110 km) monthly averaged vertical structure of temperature and number density is presented. It is based on the Soviet and Russian rocket, emission and radioionospheric temperature data and also aerologic pressure data, obtained during 1955-1995. The model reveals a long-term trend and solar activity effect in seasonal variations of temperature profiles. Here we present some new results for number density model vertical profiles and season-altitude and season-pressure maps of temperature for different years. Some conclusions concerning seasonal, solar activity and long-term variations in the vertical structure of the middle atmosphere are elaborated. The monthly averaged one-humped structure of temperature (one maximum and two minima) near the mid-latitude mesopause is found to be typical for all the seasons, both for periods of low and high solar activity. This structure is maintained despite the process of long-term changes at the second half of 20th century. The model confirmed the well-known fact that atmospheric density in lower thermosphere is greater in years of solar maxima. During the second half of 20th century, pressure and density decreased gradually. For altitudes around 100 km, lines of constant number density descended at a mean rate of 1-4 km per 10 years.