RAINFALL VARIABILITY OVER BANGLADESH AND NEPAL - COMPARISON AND CONNECTIONS WITH FEATURES OVER INDIA

In this study monthly rainfall data for 14 stations over Bangladesh fo r the period 1901-1977 are used to investigate and understand the inte rannual variability of the summer monsoon rainfall. Monthly, seasonal, and annual spatial rainfall patterns, and the spatial patterns of var iability, are presented. Dominant structures of seasonal rainfall are determined through the empirical orthogonal functions. A homogeneous s eries for All Bangladesh Monsoon Rainfall is prepared and its temporal characteristics are studied. It is observed that the standardized rai nfall for this series shows random fluctuations up to 1963, thereafter the standardized values are much above the normal values. Further the rainfall variations over Bangladesh are not related to large-scale va riables such as the Northern Hemisphere surface temperature, Danvin pr essure tendency, and the subtropical ridge over the Indian region. How ever, the rainfall variations over Bangladesh are related well with ra infall variations over north-east India. Similar analysis is done for the Nepal region by examining the monthly rainfall data over Kathmandu for a 105 year period (1851-1900, 1921-1975). Results reveal that Nep al rainfall is well related with rainfall variations over northern and central parts of India.