Towards a numerical laboratory for investigations of gravity-wave 2 mean-ow interactions in the atmosphere

Abstract

Idealized integral studies of the dynamics of atmospheric inertia-gravity waves (IGWs) from their sources in the troposphere (e.g., by spontaneous emission from jets and fronts) to dissipation and mean- ow e�ects at higher altitudes could contribute to a better treatment of these processes in IGW parameterizations in numerical weather prediction and climate simulation. It seems important that numerical codes applied for this purpose are e�cient and focus on the essentials. Therefore a previously published staggered-grid solver for f-plane soundproof pseudo-incompressible dynamics is extended here by two main components. These are 1) a semi-implicit time stepping scheme for the integration of buoyancy and Coriolis e�ects, and 2) the incorporation of Newtonian heating consistent with pseudo-incompressible dynamics. This heating function is used to enforce a temperature pro�le that is baroclinically unstable in the troposphere and it allows the background state to vary in time. Numerical experiments for several benchmarks are compared against a buoyancy/Coriolis-explicit third-order Runge-Kutta scheme, verifying the accuracy and ef- �ciency of the scheme. Preliminary mesoscale simulations with baroclinic-wave activity in the troposphere show intensive small-scale wave activity at high altitudes, and they also indicate there the expected reversal of the zonal-mean-zonal winds.