Further Studies with a Quasi-Geostrophic Numerical Model Incorporating Effects of Released Latent Heat

Abstract

Numerical integrations with a 5-level quasi-geostrophic model incorporating effects of released latent heat were carried out for three cases of winter cyclogenesis. For purposes of comparison, calculations were also performed for each case with an initially dry atmosphere. The following typical features were noted: In areas of predicted precipitation, the ?moist? prognoses yielded heights at 1000 mb up to 150 m lower than those of the ?dry? forecasts. Furthermore, the heights of the cyclone centers were more accurately predicted by the ?moist? scheme than by the ?dry.? At 300 mb the differences were similar in magnitude to those at 100 mb but opposite in sign. Precipitation associated with the frontal waves was predicted with some success but convective rainfall along and ahead of the cold fronts was inadequately forecast. The above characteristics were also observed in a fourth case study described in an earlier paper by the author.