Abstract:
Climate change is a dominant environmental factor that has been affecting Bangladesh by causing a significant shift in the rainfall trend of the country. Variation in quantities of precipitation is often assessed by detecting and characterizing trends in available meteorological data. A study period from 1965-2015 has been taken in which daily rainfall records of 8 stations, distributed all over the country has been examined. The objective of the study is to analyse historic annual rainfall data of different locations from all over the country and observe the trend. These studies aim to understand the trend of change in rainfall patterns by analysing long term historical rainfall data, which then forms the basis of forecasting future scenarios. Seasonal and annual rainfall variation has been assessed. Mann-Kendall test and Sen’s Slope model is used to detect the trend and estimate the magnitude of change, respectively. It has been observed that about 69% of rainfall occurs in the Monsoon season throughout the country. Monsoon and Post-Monsoon season shows a significant increasing trend whereas Pre-Monsoon and Dry season shows significant decrease. Mean annual rainfall is highest in Sylhet whereas Rajshahi has the least mean annual rainfall. It has been revealed that Khulna has a significant increase in mean annual rainfall trend. Annual mean rainfall in Bangladesh is found to be 2388 mm/year from this study. Moreover, a non-significant trend has been found in annual mean rainfall all over the country. Monthly mean and extreme event indices are also analyzed where the trend is decreasing for the extreme event. This study also aims to analyse some of the extreme rainfall indices using reliable, consistent and sufficient amount of rain gauge station data. Extreme rainfall analysis was also performed to study the changes in the intensity of extreme
weather events. In case of annual, seasonal and extreme rainfall, most of the stations have negative trend so it is seen that the rainfall is decreasing all over the country in the 51 years study period.
