Monsoon Rainstorm Characteristics for Varying Inter-event Intervals at a Site on West Coast of India

Abstract

Continuous hourly rainfall records from a site on the western coast of India were examined to ascertain the effects of the inter-event interval (IET) considered for the segregation of the individual rainstorms from the continuous datasets. The maximum 24-h rainfall displayed high variability though the number of rainy days, the total rainfall volume and the maximum hourly intensity all were within one standard deviation from the mean in most of the years. The reduction in number of independent rainstorms was very steep up to IET of 7 h, moderate from 7 to 20 h, and very gradual beyond the value of IET greater than 20 h. Wetter years required higher separation between rainstorms for statistical independence and consequently recorded fewer number of rainstorms for a particular separation period. The duration of segregated rainstorms as well as their total volume of rainfall in rainstorm displayed high variability, whereas the average rainfall intensity of the rainstorms varied in a somewhat haphazard fashion, possibly due to non-correlated variation of the duration and total rainfall. Like these characteristics, the temporal distribution of rainfall in a rainstorm was also observed to be severely affected by the choice of the IET.