A MODELING STUDY OF THE EFFECTS OF THE CUMULUS ENSEMBLE ON THE ATMOSPHERIC STRATIFICATION

A two-dimensional compressible cumulus ensemble numerical model has been developed. In the model a given horizontally uniform and time-independent large-scale forcing velocity is imposed. The effect of the large-scale forcing updraft is included only in the equations for potential temperature and water vapor. Cumulus ensemble was initialized by the combine of a cool pool and random disturbances. Eleven numerical experiments are made under different conditions. Results show that under the condition of the given initial temperature and water vapor sounding and large-scale forcing,the cumulus ensemble causes the vertical profile of temperature and water vapor mixing ratio to adjust toward a common profile with different types of initial and random disturbances,whether having horizontal environmental wind shear or not,different model domains and different spectra of cloud sizes. These results show the atmosphere approaches the quasiequilibrium state that mainly depends on the initial sounding and the large-scale forcing. All these calculations agree with the idea of Betts' scheme of cumulus paramet erization.