89th American Meteorological Society Annual Meeting

Monday, 12 January 2009: 4:00 PM
The moist static energy budget and wave dynamics around the ITCZ in idealized WRF simulations
Room 126A (Phoenix Convention Center)
Scott W. Powell, University of Miami, Miami, FL; and D. S. Nolan
Prior studies have suggested the existence of a shallow return flow out of the intertropical convergence zone (ITCZ). The strength of this shallow meridional circulation (SMC) suggests that moisture and energy budgets of the ITCZ and Hadley circulation should be significantly affected by the export of moist air in the shallow meridional circulation between 2km and 4km and inflow of relatively dry air between 6km and 7km.

The Weather Research and Forecast Model (WRF) version 2.1.2 is used to model the circulation using various idealized sea surface temperature profiles to create several simulations of ITCZ regions over open ocean. Near the ITCZ, several vertically layered regions of meridional water and energy transport correspond with the boundary layer inflow, upper tropospheric outflow, and the SMC. This work examines the budget of moist static energy (MSE), consisting of meridional wind transport, incoming and outgoing radiation, and sensible and latent heat fluxes resulting from the ocean. In a strong SMC regime, wind-transported MSE in the shallow return flow and dry mid-level flow significantly contributes to the overall energy budget. Components of the MSE budget are quantified in each of the several simulations.

Recent simulations feature a deep-layered westward propagating equatorial wave as well as a shallow mixed Rossby gravity wave. The phase of the waves at a particular longitude in the model domain affects the magnitude and/or direction of the meridional wind at that location, therefore affecting the strength of the SMC. The study examines which wave features may actually exist in the atmosphere and which are likely artifacts of the model.

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