Climatological Assessment of Natural Precipitation Characteristics for Use in Weather Modification

Abstract

A study has been made of the climatological characteristics of storm precipitation on a point and areal basis through the use of two sets of data. One is from a 12-year operation of a dense raingage network on 400 mi2 in central Illinois, and the other is the long-term point rainfall records of daily precipitation from U. S. Weather Bureau climatic stations throughout the state. The detailed network data were used to investigate effects of storm intensity and duration, precipitation type, synoptic weather type, wet and dry periods, and other factors upon storm distribution characteristics. Frequency distributions of both rainfall depth and number of storms were determined for various classifications, and these distributions were evaluated with respect to implications in weather modification during the critical growing season (May-September) and the water-supply replenishment period (October-April). Nomograms were developed from the climatological distributions to facilitate the evaluations. By relating areal to point distributions, a method was devised for deriving similar information for less dense network areas.