Poster Session P6.2 An evaluation of "RKW Theory" using a model intercomparison

Wednesday, 6 October 2004
George H. Bryan, NCAR, Boulder, CO; and J. Knievel and M. D. Parker

Handout (724.3 kB)

We are using several numerical models to simulate idealized squall lines in varying environmental shear. The goals of the study are to determine whether conclusions drawn from the model output differ significantly depending on the model that is used, and whether there are notable biases in any of the models. So far, simulations have been conducted with the Klemp-Wilhelmson Model, the ARPS Model, the WRF Model, and the Bryan-Fritsch Model.

The simulations are based on a recent paper by Weisman and Rotunno, who argue that low-level shear has a "profound effect" on system organization. They also argue for an "optimal state," wherein some system properties such as surface wind speed are maximized. We evaluate whether our numerical model simulations support these conclusions.

This intercomparison also facilitates the discovery of biases that may exist in the numerical models. One notable result is that the Klemp-Wilhelmson model tends to produce deeper, colder surface-based cold pools. The reason for this difference, and its implications on the theory advanced by Weisman and Rotunno, are discussed.

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