The formation of precipitation is of great scientific as well as practical significance. It is known that atmospheric ice plays a crucial role in the development of precipitation, but not all the mechanisms by which ice forms in clouds are well understood. One of the most fundamental problems facing cloud physicists is explaining the enhancement of the number of ice particles in clouds beyond what would be expected from the number of ice nucleating particles that are available in the atmosphere. Under previously sponsored NSF research, the Principal Investigators have been involved in research on ice formation in clouds. Major findings include that, in certain types of clouds, ice formation occurs and appears to be enhanced near cloud top. These observations imply a fundamentally different mechanism for ice enhancement than the currently accepted process. This proposed research will continue field studies of ice in clouds. Primary goals are to determine the origins and mechanisms of formation of ice particles with particular emphasis on ice at cloud tops. These goals will be pursued through the acquisition of data sets in cumulus and altocumulus clouds. The data sets will include information from new airborne instruments which will provided improved capabilities in detecting ice, determining fine scale structure of streamers of ice within clouds and in measuring humidity.
