Abstract

Bangladesh is a small country of South Asia which is considered as one of the most vulnerable countries in the world to climate change and it is affected by severe weather and climate events. In this paper, the climatic change and variability over Bangladesh has been studied.  The time series analysis was applied to investigate the variability and trend over three zone [(Northern (North West & North East), Middle and Southern (Coastal, Island, Hilly)] of Bangladesh. The study was based upon the regional differences of climatic trends for the country and tested it for each region against other regions via a t-test. Result suggest that as a topical country, there is small temperature variation in Bangladesh. But there is regional variation between northwest and south zone. In winter there exists a north-south temperature gradient which reverses during summer (pre-monsoon and monsoon). There is an extreme large seasonal variation from winter- to summer- monsoon in Bangladesh. In all seasons the difference of maximum and minimum temperature is higher in the north zone than in the south zone. A remarkable correlation was discovered between this temperature range and the rainfall occurrence. All seasons the mean maximum temperature is increasing except in winter for the northwest and middle zone (-0.004 °C/year and –0.0069 °C/year). Hilly region is showing highest increasing rates of mean maximum Temperature in all season (+0.0754 °C/ year in winter, +0.0635 °C/year in Pre monsoon, +0.0554 °C/ year in monsoon, +0.0679 °C/year in Post monsoon); Where as in all season mean minimum temperature is decreasing only hilly region. Overall the temperature is increasing in whole of the country. We also find a positive trend in the rainfall, especially large during the summer monsoon and in the southern zone (in Hilly region, increasing rate of rainfall +17.784 mm/year). The northwest area on the contrary is characterized by decreasing rainfall values both in winter and summer. So we can conclude that the northwest is clearly becoming more arid. May be this is enhanced by the large scale deforestation processes going on.