Impact of CCN on the Microphysical Properties of a Deep Convective Cloud

In this study, the microphysical properties of an ideal bubble case for representation of a deep convective cloud are investigated using the weather research and forecasting (WRF) model. A series of simulations with a CCN layer at different heights are studied. The initial position of the thermal bubble also varies in different simulations. The deep convective cloud shows distinctive response to the height of the CCN layer and the initial position of the thermal bubble.

The CCN effect on the microphysical properties of the deep convective cloud depends on the relative position of the CCN layer and the initial thermal bubble. CCN layers at or just below the initial height of the thermal bubble are much easier to enter the cloud because of the existence of strong convergence. As a result, more but smaller cloud particles invigorate the development of the convective cloud and reduce the precipitation. In contrast, CCN layers at higher or lower heights almost cannot enter the cloud and have little influence.

Besides, it is also found that increasing the initial height of thermal bubble within a certain range changes the dynamical properties of the cloud remarkably and enhances the precipitation and cloud mass generally.