Ocean–atmosphere coupled processes in the tropical Indian Ocean region prior to Indian summer monsoon onset over Kerala

摘要: The present study examines atmosphere–ocean interaction before MOK using various observational data sets during the last 35 years (1982–2016). analyses suggest a new mechanism for evolution of involving coupling radiation, sea surface temperature (SST), wind, evaporation, SST gradient, wind stress, total precipitable water (TPW), and convection processes. During pre-monsoon period, Arabian Sea (ArS) starts warming reaches maximum just four pentads MOK. Hence, meridional gradient develops that pulls air from colder southern Indian Ocean, which leads to enhanced speed thus stress towards warmer region. This is followed by cooling over southwestern ArS due wind-induced evaporation upwelling along Somali coast in response curl. low-level anticyclonic circulation north also aids this upwelling, builds up zonal between East West ArS. In response, enhances further. north-eastward directed drives eastern increase moisture content carried accumulates column high TPW near Kerala adjoining south-east That moist fosters rainfall monsoon onset Kerala. short, ocean short-wave radiation background, then provides necessary energy atmosphere form latent heat flux driven developing gradient. Significant inter-annual correlations are found precipitation North Ocean supporting interpretation detailed above.