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  • Kripalani, R.H., J.H. Oh, Ashwini Kulkarni, S.S.Sabade and H.S. Chaudhari, 2007: South Asian summer monsoon precipitation variability: Coupled Climate simulations and projections under IPCC AR4. Theoretical and Applied Climatology, 90, 133-159, DOI 10.1007/s00704-006-0282-0.

The South Asian summer monsoon precipitation and its variability are examined from the simulated outputs of the coupled climate models under the Intergovernmental Panel on Climate Change Fourth Assessment Report. Out of the 22 models examined, 19 models are able to capture the maximum rainfall during the summer monsoon period (June through September) with varying amplitude. While 2 models are unable to reproduce the annual cycle well, one model is unable to simulate the summer monsoon season. The simulated inter-annual variability for the 19 models is examined with respect the mean precipitation, coefficient of variation, long-term trends and the biennial tendency. The model simulated mean precipitation varies from 500 mm to 900 mm and coefficient of variation from 3 to 13 %. While 7 models exhibit long-term trends, 8 models are able to simulate the biennial nature of the monsoon rainfall. Six models that generate the most realistic 20th century monsoon climate over South Asia are selected to examine future projections under the doubling CO2 scenario.
Projections reveal a significant increase in mean monsoon precipitation of 8 % and possible extension of the monsoon period based on the multi-model ensemble technique. Extreme excess and deficient monsoons are projected to intensify. The projected increase in precipitation could be attributed to the projected intensification of the heat low over northwest India, trough of low pressure over the Indo-Gangetic plains and the land-ocean pressure gradient during the establishment phase of the monsoon. The intensification of these pressure systems could be attributed to the decline in winter / spring snowfall. Besides a decrease of winter snowfall over western Eurasia models also project an increase of winter snowfall over Siberia/eastern Eurasia. This projected dipole snow configuration during winter could imply changes in mid-latitude circulation conducive for subsequent summer monsoon precipitation activity. Increase in precipitable water of 12-16 % is projected over major parts of India. However maximum increase of about 20-24 % is projected over the Arabian Peninsula, adjoining regions of Pakistan, northwest India and Nepal. Though the projected summer monsoon circulation appears to weaken, the projected flow over the Bay of Bengal (Arabian Sea) will support oceanic moisture convergence towards the southern parts of India and Sri Lanka (northwest India and adjoining regions). ENSO-Monsoon relationship is projected to weaken.

Last Updated: 2007-10-11

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