Frequencies of Short-Period Rainfall Rates Along Lines

Abstract

Two-minute rainfall rates have been measured along lines of recording rain gages in Florida and Illinois. Knowledge of the frequencies of occurrence of short-duration rainfall rates is needed for estimating attenuation of radio communications and radars. Rainfall rate frequencies are also useful in estimating the erosion of high-speed devices by rain. Results are presented for one summer of data taken at each location. The Florida lines were 9.6 and 21.5 km in length and the Illinois lines 23.9 and 62.2 km. These line frequencies are compared with single gage frequencies at each location. The frequencies by which various rates are exceeded are shown for those that occur more than 0.001% of the time. Rain at rates greater than 0.1 mm h?1 occurred less than 6% of the time at either location and for the longest line lengths. For similar line lengths, most rainfall rates have higher frequencies of occurrence in Florida than in Illinois. The rainfall rate frequencies were not significantly different for differing line orientations.