Pre-monsoon rainfall and surface air temperature trends over India and its global linkages

An evidence of a changing climate is already sensed in India where there is a large diversity from region to region and from season to season. The rainfall pattern in the pre-monsoon (March-April-May) season is important as it helps in determining many crop-related activities in many parts of the country. In the present study, an attempt is made to analyze the current trends in pre-monsoon season rainfall and temperatures over 34 meteorological subdivisions in India using the India Meteorological Department observed analysis datasets of rainfall (1951-2013) and temperatures (1981-2013). The results suggest that a significant decreasing trend in the pre-monsoon rainfall at all-India level and the maximum reduction is found in the month of March. From the regional scale analysis, the south peninsular India is found to have an increasing trend, whereas a decreasing trend is observed over Jammu and Kashmir, Himachal Pradesh and northeast parts of the country. The analyses reveal an association of pre-monsoon rainfall over India with precipitation over China and temperature over the South China Sea, which may act as a precursor for the pre-monsoon rainfall that ultimately could affect the Indian summer monsoon rainfall. The increase of rainfall activity over south peninsular India is attributed to increases in the meridional temperature gradient with an increase of specific humidity. The results of the study will be useful for a long-term risk management in various sectors and would aid in adapting new technologies for a sustainable development in the changing climate scenario.