CLOUD PERTURBATIONS OF TEMPERATURE AND HUMIDITY - A LES STUDY

A series of Large-Eddy Simulations (LES) has been run for typical case s of marine cloud-topped boundary layers under suppressed conditions, ranging from cumulus-topped to stratocumulus boundary layers, in order to assess the temperature and humidity perturbations of boundary-laye r clouds with respect to the environmental air. The results show that the mean incloud values of temperature and virtual potential temperatu re are close to the respective environmental values, but slightly cool er (approximate to 0.1 K). Clouds form in regions that are essentially more moist than the environment. In contrast, the conservative variab les liquid potential temperature and total water specific humidity hav e very different incloud and environmental values for which an analyti cal solution is given. Furthermore, the practical consequences of thes e findings for large-scale meteorological parameterizations are discus sed.