Dynamic Trends of Intensity of Rainfall Extremes in Sri Lanka

Abstract

Changes in extreme weather and climate events are among the most serious challenges to society in coping with a changing climate. Occurrence of extreme rainfall events with higher intensity accomplishing flash floods is becoming a common phenomenon. It is timely important, identifying spatial and temporal characteristics of intensity of extreme rainfall events by countries. Maximum 5 day rainfall (Rx-5day) is an effective index which leads to identify intensity of rainfall extreme events, recommended by World Meteorological Organization. This considers the highest total rainfall within a consecutive 5 day period. This study focuses on spatial and temporal characteristics of Rx-5day in Sri Lanka from 1981 to 2010. Daily rainfall data collected from Meteorological Department, Sri Lanka is used in the study and extremes are calculated using RClimDex 1.0 package, designed by Expert Team on Climate Change Detection and Indices (ETCCDI). IDW interpolation technique in GIS, non-parametric Mann Kendall test is used to analyze the significance of trends. Average maximum 5-day rainfall values ranges between 100mm-400mm. Among the severest extremes, Colombo is accounted by the highest value in 2010. Spatially, Rathnapura, Rathmalana, Colombo are highly affected by these extremes. Temporally there is an emergent increase of this index after 2002. Annual maximum consecutive five day rainfall predicates significant increasing trends in Batticaloa, Colombo, Hambanthota, Rathmalana and Trincomalee. Variation of Monsoonal regimes seems rely on variations of this index. These detections of trends of spatial and temporal patterns of rainfall extremes thus facilitate in decision making and planning related to disaster management and development in Sri Lanka. Keywords – Extreme rainfall events, ETCCDI, GIS, Non- parametric Mann Kendall trend test, spatial pattern, temporal trends