Spatial and temporal variability of seasonal rainfall and mean
temperature over different region of Bangladesh
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.