Abstract
Field observations from three different areas in the United States are used to determine the rates of appearance of ice particles in cumulus clouds. Those rates are compared to predictions obtained using the laboratory studies of the Hallett-Mossop process for secondary ice production. The rates of appearance of ice show the trends predicted by laboratory studies of secondary ice production, and average rates of production are within about a factor of three of the predictions. The roles of graupel, large and small droplets, and temperature are consistent with the laboratory findings.
