Relationship between Monsoon Rainfall and Winter Minimum Temperature over Bangladesh

Abstract

In this thesis it has been tried to find the correlation between the rainfall of the monsoon months and the minimum temperature of the winter months and rainfall of the monsoon season and minimum temperature of the winter season all over Bangladesh. The thermal capacity of the soil changes with the available moisture present in the soil. So it is assumed/expected that winter minimum temperature has some relationship/dependency on the monsoon rainfall. Hence regression equation is developed to estimate winter minimum temperature on the basis of the monsoon rainfall. In this research work the data of 34 stations all over Bangladesh has been used. These raw data have been collected from Bangladesh Meteorological Department (BMD). The collected raw data have been processed by developing and using Fortran code to obtain the monthly and seasonal average. The data have been broken decade wise because of the data volume and data distribution is not suitable enough for a single calculation by taking the whole period. For the analysis purpose a package software has been used to get the regression equation and the coefficient of determination (r2) from which the coefficient of correlation(r) is determined. The primary investigation showed that the relationship is not systematic and guided not to accommodate all the results. So only 9 stations has been chosen region wise: two stations from southern, two from eastern, two from northern, two from western and one from central region. The following cases has been investigated i) Monsoon rainfall vs Winter minimum temperature ii) July rainfall vs January minimum temperature iii) August rainfall vs January minimum temperature It has been found that some correlation coefficients are positive and some are negative. On the basis of magnitude out of 108 possible cases only 39 have been found with values greater than or equal to 0.4. It is also observed that except the stations of the northern region all other stations experienced negative correlation between August rainfall and January minimum temperature during the decade 1994-2003. It is also found that the negative correlation coefficients less than or equal to 0.4 is not found in the southern and central regions.