Observations on the Formation and Spread of Precipitation in Convective Clouds

Data gathered by the Thunderstorm Project in Ohio during 1947, by use of a radar set AN/TPS–10, were analyzed to study the process of precipitation initiation in natural convective clouds. It is shown that about 60 per cent of all echoes first appeared at temperatures warmer than 0C. By use of RHI-data taken at intervals of time averaging about two minutes, the time history of precipitation in clouds was studied. Composite height vs. time curves show the rate of spread of the echoes. From these data it is concluded that, in middle latitudes, precipitation is frequently formed through a process involving only the liquid phase of water.