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Abstract

The effects of vertically-propagating internal gravity waves in most weather and climate models still need to be parameterized. Estimates of gravity wave fluxes and sources from global analyses may have large uncertainties due to applied assumptions on the cutoff scale. While earlier studies proposed that the crossing scale between the Rossby and gravity wave energy spectra is considered in the filtering of the gravity waves in the models, this is less informative in the tropics where the Rossby and gravity wave regimes are complemented by the Kelvin and mixed Rossby-gravity waves. We shall present a new approach to the computation of the vertical momentum fluxes that quantifies momentum fluxes for the Rossby waves and non-Rossby waves, that is, inertia-gravity waves, Kelvin waves, and mixed Rossby-gravity waves. The approach is derived from the modal representation of atmospheric circulation in the pressure system and provides a unified approach to the computation of vertical motions associated with various wave species. The application to the ECMWF analyses will be presented focusing on the tropics.