Gravity wave generation by convection and momentum deposition in the mesosphere-lower thermosphere

Abstract

[1] The Tropical Warm Pool International Cloud Experiment campaign centered on Darwin (12°S, 131°E) in northern Australia in January–February 2006 provided an opportunity to study gravity wave generation by convection and the associated wave propagation and momentum transport. In this study, we discuss wave generation by a single mesoscale convective system (MCS) that occurred on 23 January. The project used a variety of radars to study the spatial and temporal variability of rainfall and the associated latent heat release during the storm. A high-resolution numerical model utilized the latent heat release derived from radar rainfall measurements to compute the spatial and geographic variation of gravity wave generation and propagation into the lower stratosphere. Gravity wave ray-tracing techniques were then used to estimate the wave energy flux penetrating to heights near 90 km, where the results were compared with direct measurements made with a meteor wind radar. This comparison is used to calibrate the momentum fluxes derived from the model and the ray-tracing results using an iterative technique. The momentum was deposited in a relatively compact region. Body forces computed from the flux divergences had their maximum values at heights near 98 km with a peak values of about 400 m s⁻¹h⁻¹. The effects of secondary gravity wave generation are discussed, as is the overall contribution of gravity waves generated by MCSs to the momentum budget of the tropical middle atmosphere.