Mesoscale Latent Heat Release and Its Influence on Mid-Tropospheric Warming

Abstract

A study of the effect of mesoscale latent heat release on synoptic-scale mid-tropospheric warming was made by employing a 10-level diagnostic model and the special data gathered by the National Severe Storms Laboratory. The elementary area consists of 200 ? 200 km2. A horizontal grid distance of 20 km and a vertical separation of 100 mb were used. The initial input comprises the geopotential height and relative humidity fields. The latent heat is calculated from the diagnostic fields the model produced under the assumption that it is released by saturated stable and conditionally unstable ascents, respectively, on grid and subgrid scales. The latter is computed utilizing Kuo's parameterization scheme. Results showed that the maximum latent heat was released along a line parallel to the rear of the surface position of the squall line. The percentage convective cloud cover was calculated to reach a maximum of 20 to the north and 10 to the south. In addition, the outline of the calculated horizontal area covered by convective clouds agreed well with radar observation. Furthermore, the computed latent heat adequately accounted for the observed mid-tropospheric warming.