COMPARATIVE STUDY OF THE CHANGES IN CLIMATIC CONDITION AND SEASONAL DROUGHT IN THE NORTH-WESTERN PART OF BANGLADESH

The study attempted to examine the long term and seasonal climatic variations in north-western part of Bangladesh (NWPB). Long term variation of hydrometeorological parameters reveal that significant increases in temperature are associated with decreasing evaporation rates. This might be due to wind speed variation and seasonal variation of temperature. Irregularity of rainfall and increase of monsoon rainfall along with scarcity of rainwater during dry periods increase the region’s vulnerability to monsoon flood and seasonal drought during rest of the months. Changing trend of rainfall pattern with bimodal peak of rainfall at the second half (1986-2007) during July and September rather than a single peak in July during the first half (1964-1985) indicates the changes of climatic condition in the studied area. Annual variability of rainfall along with unpredictable shifting of rainfall periods might be a possible reason for the seasonal drought. The aridity index value indicates that overall the dryness has increased during winter. Humidity increased at all stations throughout the year. Long term seasonal variation of both surface and groundwater level was also prominent. Gradual decrease of surface water level was observed in Teesta River which might be due to the improper management of dam in the upstream country. Further investigations of climatic conditions in the study area are needed to better understand the future trend of local climate change.