Variability of Gravity Wave Effects on the Zonal Mean Circulation and Migrating Terdiurnal Tide as Studied With the Middle and Upper Atmosphere Model (MUAM2019) Using a Nonlinear Gravity Wave Scheme
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Media type:
E-Article
Title:
Variability of Gravity Wave Effects on the Zonal Mean Circulation and Migrating Terdiurnal Tide as Studied With the Middle and Upper Atmosphere Model (MUAM2019) Using a Nonlinear Gravity Wave Scheme
Description:
Implementing a nonlinear gravity wave (GW) parameterization into a mechanistic middleand upper atmosphere model, which extends to the lower thermosphere (160 km), westudy the response of the atmosphere in terms of the circulation patterns, temperaturedistribution, and migrating terdiurnal solar tide activity to the upward propagating smallscaleinternal GWs originating in the lower atmosphere. We perform three test simulationsfor the Northern Hemisphere winter conditions in order to assess the effects of variations inthe initial GWspectrum on the climatology and tidal patterns of the mesosphere and lowerthermosphere. We find that the overall strength of the source level momentum flux has arelatively small impact on the zonal mean climatology. The tails of the GW source levelspectrum, however, are crucial for the lower thermosphere climatology. With respect to theterdiurnal tide, we find a strong dependence of tidal amplitude on the induced GW drag,generally being larger when GW drag is increased.