A troposphere–stratosphere–mesosphere general circulation model with parameterization of gravity waves: climatology and sensitivity studies

Abstract

The climatology of the troposphere–stratosphere–mesosphere model of the Institute forNumerical Mathematics (INM) with the uppermost level at 0.003 hPa is presented. This modelis vertically extended from the upper level of 10 hPa for the earlier version, and a drag parameterizationdue to internal gravity waves (GW) is included. The model describes the mainfeatures of the mesospheric circulation: decreasing and reversion of westerly and easterly winds, equatorward shift of the westerly wind maximum with height and reversal of the meridionaltemperature gradient in the upper mesosphere. The model underestimates to some extent theamplitude of wave number 1 for stationary waves in the winter hemisphere. The same holdsfor the internal low-frequency variability in the winter stratosphere. The sensitivity of the modelclimate is studied with respect to the inclusion of orographic gravity wave drag and the variationof the source height of internal gravity waves.