The application of wave-activity conservation laws to cloud resolving model simulations of multiscale tropical convection

Pseudomomentum and pseudoenergy wave-activity diagnostics are applied to cloud resolving model simulations of multiscale tropical convection. Wave-activity conservation laws are the relevant budgets to consider when examining the transfers of momentum and energy between a disturbance (the convection and waves) and a background (shear-stratified) flow. The vertical fluxes of pseudomomentum represent those parameterized in climate models and include pseudomomentum transfers due to convection (convective momentum transport) and gravity waves (gravity wave drag).

The wave-activity diagnostics reveal that both non-conservative (diabatic) and transient processes contribute to the generation of the vertical fluxes of pseudomomentum and pseudoenergy. A spectral decomposition reveals that each horizontal phase speed spectral element has a source region between the surface and the uppermost cloud level with peaks associated with shallow through deep clouds and a sink region above. The fluxes are subsequently separated into upward and nonupward propagating contributions to isolate the pseudomomentum transfer by convection from those due to upward propagating waves. The nonupward propagating contribution is confined below the cloud layer. The upward propagating contribution is large both above and below the cloud level and highlights the importance of accounting for the source region in gravity wave drag parameterizations. The evolving convective organization is clearly seen in the transience term both above and below the cloud layer. The results highlight important connections between pseudomomentum transfers due to convection and upward propagating waves.