Abstract
The semi-permanent systems such as Seasonal Heat Low (HL), Monsoon Trough (MT), Tibetan Anticyclone (TA), Tropical Easterly Jet (TEJ) and Low Level Jet (LLJ) or Somali jet are observed over Indian region during Indian summer monsoon season (June through September). These systems play a vital role in defining the strength of the Indian summer monsoon rainfall as a whole. Here we evaluate the ability of Consortium for Small-Scale Modeling (COSMO) regional Climate Model (COSMO-CLM), a high resolution regional climate model within the Coordinated Regional Climate Downscaling Experiment for South Asia (CORDEX-SA) framework, to simulate these systems of Indian summer monsoon. The historical runs of the COSMO-CLM for the period 1951-2000 are analysed. Overall the COSMO-CLM is able to simulate these components reasonably well. Possible changes in the position and the strength of these systems and their role in changing rainfall pattern over India are examined to assess the impact of global warming, under the RCP 4.5 simulations towards the end of the century (2051-2100). The analysis shows that the semi permanent systems may not strengthen in the future as compared to the present climate. The summer monsoon rainfall does not show uniform changes over the region. It is likely to enhance over the southern parts of the country, south of 20?S while it is projected to decrease in the northern parts under the global warming scenario.
Highlights
Southwest monsoon dominates the climate over the Indian sub-continent
There are various modeling groups participating in the CORDEX-SA domain, at present all the parameters required for the present study are available for only one Regional Climate Model (RCM) viz. Consortium for Small-Scale Modeling (COSMO)-CLM
To examine the ability of COSMO-CLM model to simulate summer monsoon rainfall and semi permanent systems during the monsoon season, the historical model simulations are evaluated over fifty years period 19512000
Summary
Southwest monsoon dominates the climate over the Indian sub-continent. Even more than 60% of the pop-. Performance of the monsoon and the spatio-temporal variation in the quantum of seasonal rainfall depends on the so called semi-permanent systems that are seen to be present over the Indian sub continent during summer monsoon season of June through September every year These systems include Seasonal Heat Low (HL), Monsoon Trough (MT), Tibetan Anticyclone (TA), Tropical Easterly Jet (TEJ) and Low Level Jet (LLJ) or Somali Jet. Krishnamurti and Bhalme (1976) [1] have shown that there exists a quasi-biweekly oscillation in these components of the summer monsoon system. The TEJ is found in the southern flank of the Tibetan high circulation stretching between South China Sea and Africa, south of 20 ̊N These abovementioned components of summer monsoon over India exist over Indian subcontinent during the four monsoon months of June through September. The results are presented for the period 2051-2100 to indicate the changes in semi-permanent systems in distant future due to global warming
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