Coastal effects in the Eastern Mediterranean as seen from experiments using a cloud ensemble model with detailed description of warm and ice microphysical processes

Coastal effects on cloud generation and convective type precipitation during the cold season in the Eastern Mediterranean are investigated by use of a 2D cloud ensemble model with a relatively high resolution (1.5 km) of the finite-difference grid. The model is based on the deep convection equation system. The description of microphysical processes is based on solving kinetic equations for size distribution functions for water droplets and ice particles. The rain event at the end of November 1991 in the Eastern Mediterranean was simulated using the model. It is shown that the model is able to reproduce wind velocity, spatial distribution and to some extent, the intensity of rainfall. It is shown that the precipitation amount and distribution depend on the synergetic contribution of two factors: the sea-ground temperature difference and background wind velocity. The contribution of each factor into precipitation over land is negligible compared to their combined effect. An additional experiment, in which latent heat release was switched off, showed that the latent heat release within clouds greatly increases the intensity of breeze circulation and to a great extent determines the amount of rain. The sensitivity experiments, in which the sea surface temperature and the background wind velocity were changed show that there are "optimum" values of these parameters, which provide the maximum precipitation intensity over the land. These optimum values correspond to the stationary position of the breeze front over the sea at the distance of 10-20 km from the shore and persistent cloud generation in this region.