The role of ocean salinity in the water cycle associated with Indian monsoon

Indian monsoon is one of the most important of all tropical climate systems. Its onset and spatial/temporal variability have strong economic impact and may cause severe human suffering. Using sea surface salinity (SSS) data from Aquarius/SAC-D satellite mission, we study the seasonal and interannual variability of SSS, to identify the potential sources for the monsoon moisture supply. Preliminary analysis shows the rainfall integrated over India subcontinent, which often used as an indicator for the monsoon onset and intensity, is correlated higher with Aquarius SSS in Indian Ocean than the state-of-art estimate of evaporation (OAflux) minus precipitation (GPCP), indicating the important role of the oceanic processes. We also examine the relative importance of salinity tendency (dSSS/dt) and salinity advection at various stages of the monsoon. Ocean current data from OSCAR project is used to estimate the salinity advection. The role of ocean processes relative to other components of the water cycle is investigated in conjunction with data from multiple satellite missions. The atmospheric integrated moisture transport (IMT) is derived from ocean vector wind (OceanSAT2) and atmospheric precipitable water (SSMIS F17). Moisture in and out of the continent can be estimated by integrating IMT along the coasts, providing a quantitative description of moisture supply in the water budget. We analyze how IMT is influenced by oceanic processes and further related with large-scale circulation. This study underscores the importance of continuous good-quality and high-resolution spacebased observations towards the characterization, understanding, and prediction of the global water cycle.