Deciphering the desiccation trend of the South Asian monsoon hydroclimate in a warming world
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Rising propensity of precipitation extremes and concomitant decline of summer-monsoon rains are amongst the most distinctive hydroclimatic signals that have emerged over South Asia since 1950s. A clear understanding of the underlying causes driving these monsoon hydroclimatic signals has remained elusive. Using a state-of-the-art global climate model with high-resolution zooming over South Asia, we demonstrate that a juxtaposition of regional land-use changes, anthropogenic-aerosol forcing and the rapid warming signal of the equatorial Indian Ocean is crucial to produce the observed monsoon weakening in recent decades. Our findings also show that this monsoonal weakening significantly enhances occurrence of localized intense precipitation events, as compared to the global-warming response. A 21st century climate projection using the same high-resolution model indicates persistent decrease of monsoonal rains and prolongation of soil drying. Critical value-additions from this study include (1) realistic simulation of the mean and long-term historical trends in the Indian monsoon rainfall (2) robust attributions of changes in moderate and heavy precipitation events over Central India (3) a 21st century projection of drying trend of the South Asian monsoon. The present findings have profound bearing on the regional water-security, which is already under severe hydrological-stress.
KeywordsRecent trends in the South Asian Monsoon High-resolution model simulations Regional hydroclimatic response to climate change
The LMDZ4 simulations were performed on the IITM HPC. We thank Director, IITM for extending full support for this research. IITM receives full support from the Ministry of Earth Sciences, Government of India. We acknowledge Josefine Ghattas and Sebastien Denvil from LMD/IPSL for computational support and M. V. S. Ramarao, CCCR for analysis and technical support. We thank the Editor Prof. Jean-Claude Duplessy and the anonymous reviewers for providing constructive comments. This work is partly supported by the NORINDIA Project 216576/e10.
- Pai DS, Sridhar L, Badwaik, MR, Rajeevan M (2014) Analysis of the daily rainfall events over India using a new long period (1901–2010) high resolution (0.25° × 0.25°) gridded rainfall dataset. Clim Dyn. doi: 10.1007/s00382-014-2307-1
- Chaturvedi RK, Joshi J, Jayaraman M, Bala G, Ravindranath NH (2012) Multi-model climate change projections for India under representative concentration pathways. Curr Sci 103:791–802Google Scholar
- Douville H, Royer J-F, Polcher J, Cox P, Gedney N, Stephenson DB, Valdes PJ (2000) Impact of doubling CO2 on the Asian summer monsoon: robust versus model-dependent responses. J Meteorol Soc Jpn 78:421–439Google Scholar
- Emanuel KA (1993) A cumulus representation based on the episodic mixing model: the importance of mixing and microphysics in predicting humidity. AMS Meteorol Monographs 24(46):185–192Google Scholar
- Joseph PV, Simon A (2005) Weakening trend of the southwest monsoon current through peninsular India from 1950 to the present. Curr Sci 89:687–694Google Scholar
- Kale V (2010) The Western Ghat: the great escarpment of India. In: Migon P (eds) Geomorphological landscapes of the world. Springer, Netherlands, pp 257–264Google Scholar
- Kitoh A, Yukimoto S, Noda A, Motoi T (1997) Simulated changes in the Asian summer monsoon at times of increased atmospheric CO2. J Met Soc Jpn 75:1019–1031Google Scholar
- Rajeevan M, De US, Prasad RK (2000) Decadal variability of sea surface temperature, cloudiness and monsoon depressions in the north Indian Ocean. Curr Sci 79:283–285Google Scholar
- Sadourny R, Laval K (1984) January and July performance of the LMD general circulation model. New Perspectives in Climate Modelling. Eds. Berger A, Nicolis C Elsevier Science Publishers, Amsterdam, 173-197Google Scholar
- Salzmann M, Weser H, Cherian R (2014) Robust response of Asian summer monsoon to anthropogenic aerosols in CMIP5 models. J Geophys Res 119:11321–11337Google Scholar