Oct 3, 2017

A threefold rise in widespread extreme rain events over central India

M. K. Roxy, Subimal Ghosh, Amey Pathak, R. Athulya, Milind Mujumdar, Raghu Murtugudde, Pascal Terray & M. Rajeevan
Nature Communications
  • States that socioeconomic challenges continue to mount for half a billion residents of central India because of a decline in the total rainfall and a concurrent rise in the magnitude and frequency of extreme rainfall events
  • States that alongside a weakening monsoon circulation, the locally available moisture and the frequency of moisture-laden depressions from the Bay of Bengal have also declined
  • Shows that despite these negative trends, there is a threefold increase in widespread extreme rain events over central India during 1950–2015
  • Finds that the rise in these events is due to an increasing variability of the low-level monsoon westerlies over the Arabian Sea, driving surges of moisture supply, leading to extreme rainfall episodes across the entire central subcontinent
  • States that the homogeneity of these severe weather events and their association with the ocean temperatures underscores the potential predictability of these events by two-to-three weeks, which offers hope in mitigating their catastrophic impact on life, agriculture and property
  • States that the extreme rainfall events are preceded by warm SST anomalies over the northern Arabian Sea, at 2–3 weeks’ lead
  • States that the mean summer SSTs in the northern Arabian Sea are about 28°–29 °C which are highly conducive for active convection, and warm SST anomalies further enhance the humidity and convective activity in the tropospheric column
  • Finds that apart from the warm SST anomalies, the air temperature anomalies indicate a strengthening of the heat low over Pakistan and northwestern India, and that a combination of these warm land and ocean temperatures to the north of Arabian Sea (15° N) enhances the meridional thermal and pressure gradients over this location