Tuesday, 31 July 2001: 10:00 AM
The Effects of Nonhydrostatic Dynamics in High Resolution Numerical Forecasts
The NCEP nonhydrostatic Meso model is based on a new approach. Namely, a hydrostatic NWP model formulation using mass based vertical coordinate has been extended to include nonhydrostatic motions. In this way favorable features of the hydrostatic formulation have been preserved, and at the same time, no linearization or approximation were required. The nonhydrostatic dynamics has been introduced through an add–on module that can be turned on and off, so that easy comparison can be made of hydrostatic and nonhydrostatic solutions. The hybrid pressure-sigma vertical coordinate, time-differencing modifications and other recently introduced features of the model are reviewed. Examples of high resolution forecasts illustrating the differences due to the nonhydrostatic dynamics are presented. The examples are produced using the capability of the model to run with and without the nonhydrostatic extension.