This review is begun with a brief summary of the current status of our understanding of the physics of precipitation in warm clouds. The impact of warm-cloud precipitation processes on the evolution of the ice phase in supercooled clouds also is discussed.

This is followed by a review of experimental attempts to modify the microstructure of warm clouds. Modeling studies of warm cloud modification and observational studies of inadvertent warm cloud modification also are drawn upon to further elucidate the physics of warm cloud modification. The hypotheses, and evidence, for dynamic modification of warm clouds are then discussed. A few brief comments on modeling of warm cloud processes also are given. These comments are intended to serve as a warning to the non-modeler to be very cautious in taking the results of the modeling studies at face value. Finally, the review is concluded with specific recommendations regarding the current status of warm cloud modification, and future directions for the scientist and the weather modification practitioner.

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1 This review was prepared as a working paper for the World Meteorological Organization (WMO) Meeting of Experts on Warm Cloud Modification held at Kuala Lumpur, Malaysia, 18–24 March 1981. While the participants provided the author with numerous helpful comments and suggestions, many of which have been incorporated in this final manuscript, the conclusions and recommendations presented herein are solely those of the author and are not necessarily those of the participants of the meeting nor those of the representatives of WMO.