Implementation and Validation of a Condensation Scheme in a Nonhydrostatic Mesoscale Model

Abstract

In this paper a condensation scheme is implemented in a nonhydrostatic mesoscale model (MEMO). An overview of the model and the modified Sundqvist condensation scheme are given. The model, including condensation (MEMOIC), is tested on two well-known phenomena that are likely to produce clouds in humid atmospheres: sea breeze and flow over a mesoscale mountain. First the sea-breeze simulations are used to show the effect increased horizontal resolution has on the results (wind velocities, cloud water, and precipitation pattern). It is concluded that the circulation generally increases due to increased resolution and that the Sundqvist condensation scheme performs well with horizontal model resolution as high as 2.5 km. Second, a number of simulations of flow over mountain are discussed. Upstream flow parameters and the shape of the mountain are changed to test the usability of MEMOIC. Also, for this flow pattern, MEMOIC performs well. It is shown that it is able to handle released instabilities and that it gives reasonable results for horizontal grid resolution as high as 500 m. For the discussed flow patterns it is hard to give a lower horizontal-resolution limit for MEMOIC.