Gravity waves captured in high-resolution global atmospheric analyses, forecasts and climate simulations using the Goddard Earth Observing System (GEOS-5) AGCM/DAS

The GEOS-5 global atmospheric model (AGCM) and data assimilation system (DAS) have been run at high-resolution - 0.5x0.666 degree in global DAS mode and up to 0.25x0.333 degree in global forecasts. Analyzed dynamical fields are in excellent agreement with those from other analysis products, e.g. ERA 40. Analyzed precipitation fields are in excellent agreement with observational estimates, both in terms of spatial distribution and intensity. High resolution global forecasts have performed comparably with other operational forecasts in predicting track and intensity of individual hurricanes. In this presentation we will survey resolved gravity wave motions in both data-assimilation and free-running experiments using the GEOS-5 system. Orographic and convective generation will be examined. We will evaluate the realism of resolved wave propagation and breakdown in the model. The connection of gravity wave generation to model physics parameterizations, in particular the deep convection scheme, will also be explored. It is known, for example, that the parameterized convective relaxation time scale plays an important role in determining the realism of DAS precipitation intensity and in forecast hurricane intensity in GEOS-5. We will examine the response of high-frequency convection and heating to this time-scale, and assess the subsequent effect on gravity wave generation.