Clim. Dyn. http://doi.org/b6zb (2017)

Credit: ELEREIN/MOMENT/GETTY IMAGES

The Indian summer monsoon (ISM) is characterized by extensive rainfall across the sub-continent, driven, in part, by land–sea temperature contrasts and the resulting landward flow of moist oceanic air. The ISM is a lifeline for more than one billion people, necessitating increased understanding of projections under anthropogenic climate change.

C. Thelliyil Sabeerali and Ajaya Ravindran from New York University Abu Dhabi, United Arab Emirates, examine how the length of the rainy summer monsoon season may change in the future. They use a subset of 12 CMIP5 coupled general circulation models, forced with the RCP8.5 emission scenario, that reasonably simulate the dynamic and thermodynamic properties that drive the ISM.

The authors reveal a reduction in the length of the ISM season by ∼11 days, which, depending on changes in the rate of precipitation, will likely be accompanied by a concurrent decrease in the amount of rainfall. They attribute this change to rapid warming in the western Indian Ocean, which triggers deep convection, heat release in the upper atmosphere, and an associated weakening of the thermal gradient that drives the monsoonal circulation. However, continued development of model precipitation schemes is required to increase our confidence in monsoon projections.