Abstract:
The modeling of the weekly rainfall percentile is
imperative for better understanding of rainfall patterns in any
region. This study focuses on selecting the most appropriate
probability distributions for weekly rainfall and use those to
make reliable rainfall percentile with the 95% confidence
intervals. Daily rainfall data of 56 years (1960-2015) during the
South West Monsoon in Colombo City were used for this
analysis. The three parameter Weibull distribution has been
found most probable distribution for most of weekly rainfall
totals. Weibull, two parameter Exponential, Exponential and
Lognormal distributions were well fitted distributions for
remaining totals. Based on the 95% confidence intervals of
percentiles, the weeks 18-23, and 38-39 during SWM showed not
only high rainfall, but also high rainfall variation results which
caused high possibility to form extreme rainfall events. Heavy
rainfall with great variation during the period of 30th April to
10th June and 17-30th of September was further confirmed by the
result of running total of weekly rainfall.
