Dynamic entrainment rate influence on products of a one-dimensional cumulonimbus model

Abstract

In order to improved the standard entrainment parametrization in 1-D time-dependent hydrostatic Cb cloud models, we have introduced the new entrainment rate consistent with continuity conditions. This describes in a relatively simple way turbulent and dynamic entrainment/detrainment processes in convective clouds. The new introduced entrainment rate is sensitive to both vertical velocity and its gradient and their signs. It is shown that the entrainment rate which includes a dynamic term can describe non-stationary fields in agreement with many real situations. In many cases, the entrainment rate causes the formation of a precipitation zone well correlated with downdrafts. When we use only the turbulent mixing term, the steady-state solution occurs, which is quite unrealistic for a great variety of situations. Also, the precipitation zone is not well correlated with the downdraft zone. © 1989.