All India Summer Monsoon Rainfall Variability: Large-Scale Circulations and Climate Change Impacts and Processes

India much depends on monsoon rainfall for agricultural planning, industry, human and other life. A good monsoon resulting in improved agricultural brings down prices of essential food commodities and reduces their imports overall reducing the food and inflation. Further improved rains result in increased hydroelectric production. All these factors initiate positive ripple effects throughout the economy of India. Studies have been reported about the Indian summer monsoon onset and rainfall variability (Parthasarathy et.al., 1993). Recent studies have been reported that the variability of monsoon rainfall during the northern summer is well associated with the great deserts, equatorial lower stratospheric winds (QBO) and 11-year solar cycle (Reddy, et.al., 1988).  In the present study we further examine the seasonal, inter-annual and long-term variability of monsoon rainfall using all India rainfall data during June-September, for the period 1881-2010. We looked the impacts and processes including large-scale events such as QBO, ENSO and Climate Change including SST’s over the Arabian Sea, on monsoon variability. The study has pointed out that the cooling SST’s effect the monsoon onset and seasonal rainfall. The large-scale floods/droughts were associated with the westerly/easterly phases of the QBO. The large-scale droughts were associated with the ENSO and easterly phase of the QBO.  Decadal analysis revealed a long-term variability (~ 50 year) in all India rainfall. Some of the processes associated with the monsoon variability will be discussed.