[1] Using long-term (1871-2005) summer monsoon rainfall data over 30 meteorological subdivisions of India, overall tendencies of the rainfall have been studied. Further, the subseasonal (monthly) trends have been evaluated. For this purpose, simple linear regression technique is applied. To examine the trends in different segments for summer monsoon rainfall, 11-year running averages are calculated. Most of the subdivisions reveal systematic increasing and decreasing trends in different segments of the time series. India experienced wet monsoon conditions during the late 1950s and dry monsoon conditions around the early 1900s. In the global warming era , 19 out of 30 meteorological subdivisions showed negative tendencies in summer monsoon rainfall. This decrease in summer monsoon rainfall is associated with a weakening of the Southern Oscillation and relaxation of the meridional temperature gradient over the Indian Ocean. The gamma distribution is used to study the distribution of the rainfall by calculating scale and shape parameters. In general, larger values of scale parameter are found over west coast during summer monsoon and individual months. The shape parameter is high over northeast India.

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The seasonal and interannual variation of upwelling along the east coast of India between 68N and 228N was studied for the period 1985Á2003 using NOAAÁAVHRR sea surface temperature data. The seasonal migration of pronounced upwelling, which follows the seasonal shift of the winds in transition period and northeast monsoon, was confined. The temporal mean sea surface temperature images clearly show the upwelling season, as does the seasonal sea surface temperature anomaly. These dominant features of the upwelling system are also the most variable, with most of the variance being explained by the seasonal cycle. Quasi-cyclic behaviour of sea surface temperature on interannual scales has also been observed.

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