SIMULATION OF THE GREAT-PLAINS LOW-LEVEL JET AND ASSOCIATED CLOUDS BYGENERAL-CIRCULATION MODELS

The low-level jet frequently observed in the Great Plains of the Unite d States forms preferentially at night and apparently influences the t iming of thunderstorms in the region. The authors have found that both the European Centre for Medium-Range Weather Forecasts general circul ation model and the National Center for Atmospheric Research Community Climate Model simulate the low-level jet rather well, although the sp atial distribution of the jet frequency simulated by the two GCMs diff ers considerably. Sensitivity experiments have demonstrated that the s imulated low-level jet is surprisingly robust, with similar simulation s at much coarser horizontal and vertical resolutions. However, both G CMs fail to simulate the observed relationship between clouds and the low-level jet. The pronounced nocturnal maximum in thunderstorm freque ncy associated with the low-level jet is not simulated well by either GCM, with only weak evidence of a nocturnal maximum in the Great Plain s.