Moisture rainout fraction over the Indian Ocean during austral summer based on ^18O/^16O ratios of surface seawater, rainwater at latitude range of 10°N–60°S

Oxygen isotope ratios ( ^18O/^16O ) of surface seawater and rainwater samples from the Indian Ocean region (10°N–60°S) during austral summer collected onboard ORV Sagar Nidhi during 2011–2013 have been measured along with salinity, sea surface temperature and relative humidity. The rainwater is isotopically lighter (by 4.6± 2.7 ) compared to the equilibrium condensation of the vapour arising from the seawater at the ambient condition. The isotopic composition of the vapour at high altitude responsible for the rain formation at the sampling location is estimated from a global atmospheric water isotope model (IsoGSM2). The apparent deficit of ∼ 5 can be explained by invoking a high degree of rainout (on average, about 70