Decadal and interdecadal variation of summer monsoon

Abstract

Fifty years (1950-1999) daily rainfall data of 30 meteorological stations of Bangladesh Meteorological Department (BMD) have been used in the present study. Study period has been divided into five decades namely Decade1 (1950-1959), Decade2 (1960-1969), Decade3 (1970-1979), Decade4 (1980-1989) and Decade5 (1990-1999). Distribution of rainfall over the country has been studied during premonsoon, monsoon and post-monsoon seasons for each Decade. Rainfall anomaly has been studied during the above three seasons to investigate the decadal and interdecadal variations. Annual rainfall has been studied for 50 years to observe long . term rainfall variation over Bangladesh. Average rainfall have been found 4.48, 14.21 and 3.45 mm1day during pre-monsoon, monsoon and post-monsoon respectively. Rainfall has been found to increase from west to eastward direction in the western part of the country and in the northeast region it increased towards northeast direction. The maximum rainfall is obtained in the northeast region of Bangladesh. The southeast region of the country is found to be the place of second maximum rainfall.