Nat. Commun. http://doi.org/cd58 (2017)
In late August and early September, 30 million people were affected by widespread flooding in India due to extreme rainfall. Such events have become increasingly common in recent decades, but coincide somewhat counter-intuitively with a long-term reduction in mean precipitation and a corresponding decline in the frequency of rain-bearing depressions.
Mathew Roxy from the Indian Institute of Tropical Meteorology and colleagues quantify changes in extreme rainfall across the Indian sub-continent, and further diagnose the mechanisms responsible for such enhanced hydroclimatic variability in the region. They use a combination of observations, reanalysis products, and results from a dynamic recycling model.
It is found that extreme rain events have increased threefold over central India during 1950–2015. The authors attribute this change to enhanced variability in the low-level monsoon winds over the northern Arabian Sea, themselves linked to patterns of surface warming and impacts on land–sea thermal contrasts. As a consequence, these low-level westerlies bring surges of moisture over the sub-continent, promoting episodic extreme rainfall. Projected warming of the Arabian Sea indicates these extreme events may continue in the future, thus presenting a sustained threat to life and livelihood in central India. GS