Increasing Trend of “Break-Monsoon” Conditions Over India—Role of Ocean–Atmosphere Processes in the Indian Ocean

Analysis of daily rainfall data over India during the period 1951-2007 reveal an increased propensity in the occurrence of ldquomonsoon-breaksrdquo over the subcontinent. The increasing trend is seen both in the duration and frequency of monsoon-breaks over the subcontinent, the causes for which are investigated using in situ , satellite, and reanalysis data products. While noting that the increasing trend of break-monsoon conditions is consistently related to changes in large-scale monsoon circulation and vertically integrated moisture transport; the findings also point to the role of sea surface temperature (SST) warming trend (0.015 deg C middotyear -1 ) in the tropical eastern Indian Ocean (IO) in inducing anomalous changes favorable for the increased propensity of monsoon-breaks. The results indicate that the SST warming in the tropical eastern IO has altered the ocean-atmosphere processes in a manner as to intensify the near-equatorial trough over the IO, but has led to a weakening of the southwest summer monsoon flow in recent decades into the Indian landmass.