Gaussian quasi-optic approximation applied to orographic gravity waves in non-uniform large-scale flows

RODAS C. ; M. PULIDO

Foz Iguazu (Brazil)

Conferencia; The Meeting of the Americas, American Geophysical Union; 2010

American Geophysical Union

The gravity wave parameterizations used in climate models assume vertical propagation in a vertically sheared background flow. However, recent works show that horizontal propagation and therefore horizontal refraction of gravity waves introduce important modifications to the divergence of the wave momentum flux so that the vertical propagation hypothesis is not a good approximation. In this work we attempt to go further in the development of a high order ray tracing technique, named Gaussian quasi optics, and present a theoretical frame where the effects of horizontal nonuniform background flows on the gravity wave field are considered. The main hypothesis of the method is WKB approximation, so that the large-scale flows are assumed to be slowly varying. The numerical implementation of the technique is presented and the results for a bell mountain in an analytical background flow are shown and are compared with numerical simulations using the WRF model with analytical initial and boundary conditions.