Drop size distribution of rainfall of different intensities

Abstract

Drop size distribution was measured at Thiruvananthapuram, Kerala State, India, during April, June and July 2001 using a Joss-Waldvogel type disdrometer. The instrument gives the number of drops in 20 size classes ranging from 0.3 mm to > 5 mm. Each month's data were sorted, based on rainfall intensity, into periods of rainfall intensity < 1 mm/h r, 1-3 mm/ hr, 3-10 mm/hr, 10-30 mm/hr and > 30 mm/hr. The average number of drops in each size class was computed for each set of data. Exponential and Г distribution functions were then fitted to each data set. The results showed that, in June and July, the data approximated an exponential distribution for low rainfall intensities, but became closer to the Г distribution at higher intensities. However, in April all data fitted the Г distribution, irrespective of rainfall intensity.