The recent review of entrainment in cumulus clouds by Blyth [1993] provides a thorough review of this topic, and therefore only a few highlights from 1993 papers will be mentioned here. During the four-year period covered by this review, relatively few new papers have appeared on this subject compared to the number of studies conducted during the previous four years (Cooper [1991]).
A new graphical method to diagnose cloud mixing and entrainment structure was introduced by Telford and Chai [1993] in which the temperature and wet bulb temperature reduced to 1000 mb are used as coordinates of a general thermodynamic diagram. The use of this diagram allows direct readout of total water mixing ratio and condensation pressure. Grabowski and Clark [1993] and Grabowski [1993] showed that cloud top entrainment is mainly caused by dynamical instability near cloud top. In particular, they showed that penetrative downdrafts due to evaporative cooling are not the cause for cloud top entrainment, but rather a result of entrainment. The in-cloud downdrafts in their numerical model simulations were associated with interfacial instabilities and entraining eddies. The main effect of buoyancy reversal, as suggested from their numerical experiments, was to increase the intermittancy associated with cloud evolution.