On the influence of entrainment and forced lifting on some products of a 1-D model of a Cb cloud

Abstract

A new parameterization of the entrainment process and forced lifting of air is incorporated into a 1-D model of a convective cloud. The entrainment is treated as an organized dynamical inflow/outflow caused by the horizontal gradient of pressure perturbation. Different sensitivity experiments are conducted. Orographically induced forced lifting of air is included in the model after consideration of the characteristics of the cold-air outflow from the cloud base and the warm-air motion toward the cloud base. This process is incorporated into a 1-D model of a convective cloud (although such a cloud is 3-D in nature). It is shown that the new entrainment parameterization causes the nonstationarity of vertical motion fields which is in agreement with numerous observations. The zone of downward motions below the cloud base is well correlated with the precipitation at ground level. The forced lifting of air nonlinearly intensifies upward and downward motions and the amount of precipitation. © 1987.