| The latest report of the Intergovernmental Panel on Climate Change suggests a decrease in rainfall in the subtropics and tropics and an increase in precipitation in the middle and high latitudes. Furthermore, there are many studies showing that increases have occurred in extreme precipitation events; the pattern is thought to be consistent with model predictions for elevated concentrations of greenhouse gases.; The climate projections by the numerical models at the global level indicate an overall neutral to a slight increasing trend in the occurrence of precipitation on the Indian subcontinent. However, due to the significant role played by varied physiographic features over the Indian subcontinent, the climate models are not able to capture the local level variations in the climate.; The Indian summer monsoon rainfall has been widely researched since the beginning of the 20th century. However, many questions remain regarding how India's precipitation regimes have changed, and will change, given the buildup of greenhouse gases. The main results of the study include: (1) The overall association of El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and the Sea Surface Temperatures (SSTs) to the rainfall patterns in different parts of the country shows broadly similar patterns. Both ENSO and PDO have a significant negative forcing on the rainfall in the peninsular region centered on the southeast coast and the northeastern region. (2) In general, evidence exists for an increase in the frequency of extreme precipitation events over the period 1910 to 2000. (3) Overall the trends in the precipitation occurring in the two main rainy seasons and annually show a decreasing tendency. The declining trend is more pronounced during winter season compared to the summer monsoon season. (4) The trends in Diurnal Temperature Range (DTR) were not statistically significant for most of the country in either season. We found a significant decline in DTR in northwestern Kashmir. (5) The effect of cloud cover on the DTR was expectedly negative for most of the country for both seasons. Land surface processes associated with widespread deforestation and overgrazing may compound the relationship between the two.; The present study covers major issues which have been of concern for the global climate community, such as the trends in the extreme precipitation events and interrelationships among different climate variables. The results of this study should help to enhance the forecasting of the Indian monsoons by revealing detailed spatial variations in precipitation over the Indian subcontinent. |
