Rainfall changes and possible linkages with the synoptic disturbances in eastern India

Abstract

In this study, the rainfall of Orissa, a tropical region in eastern India, and the cyclonic disturbances over the Bay of Bengal were analyzed to assess the trends and variations using parametric statistical procedures. This study revealed noticeable changes in the last century (1901–2000) in regard to the rainfall of Orissa and in the cyclonic disturbances over the Bay of Bengal. Test of structural changes and the locally weighted regression technique (LOWESS) indicated that the spatially averaged annual rainfall of Orissa experienced three significant regime shifts: 1,487mm with standard deviation 167mm during 1901–1940, 1,412mm with standard deviation 184mm during 1940–1969, and 1,354mm with standard deviation 241mm during 1970–2000, respectively. The study of structural breaks in rainfall during the period 1901–1940 and 1941–1969 indicated a significant change in both slope and the intercepts. However, structural break analysis during the period 1941–1969 and 1970–2000 indicated a nonsignificant change. The annual depression in the Bay of Bengal also exhibited a structural change with occurrence of an average of 10.7 depressions during 1901–1948 in comparison to 9.6 during 1949–2000.