Modeling the impact of the gravity wave source strength on the thermal structure of the middle atmosphere

The role of gravity wave (GW) forcing in the zonal mean circulation of the middle atmosphere (16–120 km) is investigated on the base of a two-dimensional, time-dependent, mechanistic model. The globally averaged prescribed profiles of O3 and CO2 are used to calculate net diabatic heating basing on the detailed non-LTE algorithm for cooling due to CO2 15-μm bands [Fomichev, V.I., Kutepov, A.A., Akmaev, R.A., Shved, G.M., 1993. Parameterization of the 15 micron CO2 band cooling in the middle atmosphere (15–115 km). Journal of Atmospheric and Terrestrial Physics 55, 7–18] and O3 9.6-micron band [Fomichev, V.I., Shved, G.M., 1985. Parameterization of the radiative divergence in the 9.6 micron O3 band. Journal of Atmospheric and Terrestrial Physics 47, 1037–1049]. The GW parameterization scheme has been developed to account for momentum deposition, heating, and turbulent heat transfer associated to the GW breaking.Motivated by possible changes in atmospheric GW climatology, we have investigated the sensitivity of the middle atmosphere structure to tropospheric GW source strength by prescribing the appropriate value of the vertical wave action flux at the lower boundary of the model domain. The results show, that the associated temperature response varies greatly with height, latitude, and season, and attains its maximum in the mesosphere and lower thermosphere (MLT) region primary due to the adiabatic effect caused by the corresponding changes in the vertical velocity field. Thus, the long-term variability of tropospheric GW source strength can produce substantial effect on MLT temperatures, which should be accounted for in the analysis of the observed climatological changes in the thermal structure of the middle atmosphere.