Abstract:
In this study, efforts have been made to study the effect of urbanization on selected climatic
parameters such as rainfall, surface temperature 'and atmospheric pressure for Dhaka
metropolitan area. The development of Dhaka metropolis was very rapid between the 70's and
90' s of this century. Dhaka city is often criticized as the city of unplanned growth, which if
continued would have adverse effects on the environment and economy. An understanding of
the changes in the magnitude of rainfall, surface temperature and atmospheric pressure due to
increased urbanization is essential for proper land use planning and checking unplanned
growth of metropolitan area. Mymensingh and Tangail have been chosen together with Dhaka
city to compare the changes of climatic parameters between less urban area and a highly urban
area. The annual and seasonal data were studied for the period from 1953 to 1995 for Dhaka,
1951 to 1995 for Mymensingh and 1962 to 1995 for Tangail. The data required for this study
are daily values of rainfall, maximum temperature, minimum temperature and atmospheric
pressure.
Changing trends of summer, monsoon and annual data senes of rainfall for Dhaka show
different patterns from that of less urban area i.e. Mymensingh and Tangail. Annual rainfall
and monsoon rainfall of Dhaka does not show any significantly increasing or decreasing trend;
only the pre-monsoon rainfall shows a linearly increasing trend. One day annual maximum
rainfall and the number of monsoon rainy days for Dhaka exhibit a significantly decreasing
trend. Whereas, these data series of rainfall for Mymensingh and Tangail show a significantly
increasing trend. Coefficient of variation of mean monthly rainfall is less in Dhaka than the
other two less urban stations. Significantly decreasing trend of coefficient of variation of
annual rainfall for Dhaka and Tangail provides the evidence that the increase in the rainfall
variability is occurring at a slower rate, and this rate of decreasing tendency is more in Dhaka
than Tangail. The decreasing trend of coefficient of variation of annual rainfall for
Mymensingh is not significant
Surface temperature in Dhaka, a rapidly growing urban area, exhibits an increasing trend
during the last two to three decades compared to less urban area. Significant urban heating
effects have apparently taken place in Dhaka, as urban-affected temperature increase of O.75°C
to 1.15°C over 43-year period have been found in this study. In contrast, temperature for less
