Statistical analysis of rainfall variability and its trends in the coastal zones of Bangladesh due to climate change

Abstract

"The coastal area of Bangladesh is highly vulnerable to climate change. Unpredictable rainfall or changes in rainfall patterns might have negative impacts on its socio-economic culture along with its ecosystem. Therefore, the aim of this study is to investigate the spatial distribution and trends of rainfall in the Coastal region of Bangladesh for the period 1980-2019. The Coefficient of Variation (CV) and Precipitation Concentration Index (PCI), Seasonality Index (SI), Standardized Anomaly Index (SAI) are calculated to observe the spatial variability and distribution of rainfall in the coastal region. For visualizing with a geographic information system, Inverse Distance Weighting method was used. To identify the trend of rainfall and its magnitude of changes Mann- Kendall and Sen's slope method are used respectively. The results show that the minimum annual rainfall of 1674 mm is observed in the coast of South-West which rises up to 4191 mm in the South-East coast. Above 70% of annual rainfall occurs during Monsoon with a uniform distribution and low variability. Maximum values of annual PCI are observed in the South-East coast and majority of the study area is characterized by irregular rainfall distribution. SI shows a significant increasing trend for the entire coastal area. SAI indicates a longer drier period for the South-West in recent years. The annual rainfall trend analysis shows mainly the zones exposed to the Bay of Bengal have an increasing trend at 95% level of confidence among which the South-East coast is experiencing a significant increasing trend. The seasonal rainfall trend analysis shows that the South-East region shows an increasing trend for Pre-Monsoon, Monsoon and Post-Monsoon whereas the South-West region has the increasing trend for Monsoon and Post-Monsoon. For the winter season, both regions show a negative trend."