J5.5 Improvement in the representation of warm season convective precipitation in complex terrain using a Modified Kain-Fritsch convective parameterization scheme

Thursday, 10 January 2013: 9:30 AM
Room 10B (Austin Convention Center)
Thang Luong, University of Arizona, Tucson, AZ; and C. L. Castro, T. M. Nguyen, W. Cassell, and H. I. Chang

A modified Kain-Fritsch (KF) convective parameterization scheme (CPS) has been written that includes a new diagnostic equation to compute updraft velocity, closure assumption, and trigger function. These modifications take the vertical gradient of the pressure perturbation into account, making the scheme more appropriate for use in complex terrain. In the test case for a flash flood event in Vietnam, the regional model produced larger and deeper strati-form clouds that lead to a higher amount of resolvable precipitation. Overall model results with the modified scheme give almost double in the total precipitation for two days and are closer to observations. We have recently implementated this modified KF scheme into the Weather Research and Forecasting Model (WRF) to simulate organized convection during the North American monsoon. High-resolution experiments of Intensive Observing Periods (IOP) of the North American Monsoon Experiment (NAME), using a multiple grid nesting strategy, show that the modified scheme produces a stronger initial updrafts and enhances mesoscale convective system development and propagation. Therefore the modified CPS not only improves the regional model representation of precipitation in the coarse domain (10 km grid spacing) on which it is activated, but also on the finest domain (2.5 km grid spacing) where the convection is explicitly represented. We also get similar behavior for long term simulations considering WRF used as a regional climate model to simulate the North American Monsoon.
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