May 11, 2015

Robust signals of future projections of Indian summer monsoon rainfall by IPCC AR5 climate models: Role of seasonal cycle and interannual variability

C. B. Jayasankar, Sajani Surendran, Kavirajan Rajendran
Geophysical Research Letters
  • Analyzes CMIP5 RCP 8.5 simulations to derive robust signals of projected changes in Indian summer monsoon rainfall (ISMR) and its variability
  • Models project clear future temperature increase but diverse changes in ISMR with substantial intermodel spread
  • Finds projections fall into distinct groups—(based primarily on the physical association between mean changes in ISMR and its IAV, and validated through k-means clustering algorithm with Dunn's validity index, seasonal cycle of all-India rainfall, and REA method)
  • Finds that the two consistent groups of simulations with highest reliability (comprising 19 models) project a future enhancement in June–November rainfall and reduction in rainfall during other months
  • Finds the mean model ensemble of these models also project increase in IAV (change in CV) by 0.91%, in response to global warming
  • Also finds the models project future reduction in the frequency of light rainfall but increase in high to extreme rainfall and thereby future increase in ISMR by 0.74 ± 0.36 mm d−1, along with increased future IAV
  • States these robust estimates of future changes are important for useful impact assessments