Statistical analysis of the raindrop size distribution using disdrometer data

Abstract

The present study utilizes nine years of measurements taken from a Joss-Waldvogel disdrometer (JWD). From this dataset, thirty six rainfall events, were selected and categorized, respectively, in convective and stratiform types, according to specific criteria. Six statistical distributions namely the one- and two-parameter exponential, the two- and three-parameter lognormal and finally the two- and three-parameter gamma were fitted on the observed drop size distributions (DSDs). The goodness-of-fit between each statistical and the observed distribution was determined based on the Kolmogorov-Smirnov test. The results show that 72% of the stratiform events are best described by the three-parameter lognormal distribution while 28% are best described by the three-parameter gamma distribution. In the case of convective events, the results are more diversified; the two- and three-parameter gamma distribution fits best in 39% and 17% of the events, respectively, while the two- and three-parameter lognormal distribution fits best in 6% and 39% of the events. The one- and two-parameter exponential distribution was not the best fit in any case. Moreover, initial steps have already been taken in order for these findings to be used for calibration purposes of a recently employed X-band rainscanner in the Attica region in Greece.