Additional radiative cooling of the upper mesosphere and lower thermosphere caused by tidal perturbations in temperature

Abstract

The effect of tidal perturbations in temperature on the rate of cooling the upper mesosphere and lower thermosphere in the CO2 15-µm band is revised. It is shown that the effect of solar semidiurnal tide on radiative cooling can be neglected. However, the solar diurnal tide leads to a marked increase in the rate of radiative cooling (up to a relative increase by about 0.1 to 0.2) near the equator at altitudes below 100 km. It is possible that this additional cooling is responsible for the air descent observed in the near-equatorial thermosphere at altitudes above 105 km.