Prediction of climate extreme indices over Bangladesh using regional climate model

Abstract

Extreme climate events are an important concern for a resource constraint country like Bangladesh due to its impacts on society in the form of loss of economic goods, life and property. Reliable estimates of future extreme climate events relating to extreme precipitation and extremes of temperature are a valuable guide for policy makers in determining infrastructure requirements for the 21st century. Using a standard set of annual and seasonal climate extreme indices derived from daily temperature and precipitation data, rate of change of extreme indices and 30- year average values of the indices are analyzed for the baseline period (1961-1990). Extreme indices from PRECIS (Providing REgional Climates for Impacts Studies) output data were validated against those calculated from the observed data of Bangladesh Meteorological Department (BMD), to predict the values of extreme indices in the coming decades. The results show that PRECIS is able to simulate daily temperature related extreme indices with lower percentage bias as compared to the precipitation extreme indices. From our knowledge of the climate patterns of Bangladesh we know that Sylhet region especially Srimangal receives heavy precipitation annually with respect to Rajshahi which is arid and known for infamous drought ridden lands. This is found true for the extreme indices calculated from PRECIS data during the period (1961-1990) which showed that the maximum value of the 30-year average of precipitation extreme indices is obtained at Sylhet or Srimangal. For the BMD data the precipitation extreme indices occur at Sitakunda and Patuakhali in addition to Sylhet and Srimangal. The temperature extremes are found to occur more at the coastal regions like Cox’s Bazar and Teknaf than at the inland stations for both the BMD and PRECIS data. PRECIS predicted that towards the end of coming decades like 2021, 2031 and 2051 Sylhet and Srimangal will remain as the wettest regions of the country with a stark change to come in 2071 and 2091 when Teknaf, Cox’s Bazar or Patuakhali will be receiving extreme precipitations. From the results obtained, extremes of maximum temperature will occur more often in Jessore. Furthermore the extremes for minimum temperature are predicted to occur at Rajshahi.