Gravity wave transports and their effects on the large-scale circulation of the upper mesosphere and lower thermosphere

Gravity wave transports of momentum, heat, energy, and minor constituents have a strong effect on background variations of the upper mesosphere and lower thermosphere (MLT), including the seasonal-latitudinal variations of the general circulation. Wave control of the general circulation is accomplished by wave flux divergences and the wave-induced residual circulation. The most dramatic manifestation of the wave control of the general circulation in the MLT is the deceleration of the zonal winds and the reversal of the latitudinal temperature gradients above the mesospheric jets, with the coldest temperatures in the atmosphere being at the mesopause over the summer pole, contrary to radiative equilibrium. Observations show momentum fluxes that agree with the forcing required to maintain the observed meridional temperature gradient. Observations and modeling suggest that heat transports are an important contributor to the heat budget and help explain the persistent mid-winter mesospheric inversion. Constituent transports may play a large role in maintaining the mean-state constituent profiles and may help explain the rapid brightening of airglow layers observed on occasion. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.