Is summer monsoon rainfall decreasing over India in the global warming era?

Abstract

[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.

The Asian summer monsoon response to the La Niña event of 2010

“…Thus, the westward shift of large-scale circulation over the Indo-Pacific sector seems to modulate the convective activities over the India-Pakistan monsoon trough region. It may be also noted that various recent studies (Goswami et al, 2006;Guhathakurta and Rajeevan, 2008;Naidu et al, 2009) have investigated the trend in Indian summer monsoon rainfall over a longer period (more than a century) and concluded that the various regions of India (e.g. Central India, west coast, northeast sector) depict a gradual increasing/decreasing trend.…”

Do Himalayan treelines respond to recent climate change? An evaluation of sensitivity indicators

“…This trend mainly results from decreasing summer precipitation rates after the 1960s, and is associated with a weakening of the Southern Oscillation and a decrease in temperature gradients over southern Asia due to high warming rates over the Indian Ocean during recent decades (Basistha et al, 2009;Naidu et al, 2009). Long-term trends of winter precipitation rates are slightly negative but not statistically significant (Bhutiyani et al, 2010).…”

Analysis of rainfall and drought in Rajasthan state, India

“…Mainly natural processes and persistent anthropogenic influences are responsible for it, altering the composition of the global atmosphere and natural climatic system. According to Intergovernmental Panel on Climate Change Fourth Assessment Report the world indeed has become more drought prone with higher frequencies of extreme events (IPCC REPORT, 2007) some clear instances around the world can be noticed ,like changing trends of monsoonal rainfall over India due to climate change (Naidu et al, 2009) increase in drought events in UK (Arnell, 2007), in Korean peninsula (Kyoung et al, 2011), in Iran (Sayari et al, 2013), and over Indian subcontinent (Sivakumar and Stefanski, 2011) describing the impacts of climate change. In India, 80% of annual rainfall comes from southwest monsoon, and very important for the whole country, especially for the low rainfall belts like Rajasthan state.…”