Cloud perturbations of temperature and humidity : A LES study

A series of Large-Eddy Simulations (LES) has been run for typical cases 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-layer clouds with respect to the environmental air. The results show that the mean incloud values of temperature and virtual potential temperature are close to the respective environmental values, but slightly cooler ( identical with 0.1 K). Clouds form in regions that are essentially more moist than the environment. In contrast, the conservative variables liquid potential temperature and total water specific humidity have very different incloud and environmental values for which an analytical solution is given. Furthermore, the practical consequences of these findings for large-scale meteorological parameterizations are discussed.