The role of sea surface salinity over the Indian Ocean in the South Asian Summer Monsoon

Sea surface salinity (SSS) data from both the Aquarius satellite and Argo float in the Indian Ocean (IO) are utilized to investigate the SSS’ role in South Asian Summer Monsoon (SASM). SSS reflects the basic east-west contrast feature of the IO during the period of SASM linking with freshwater flux [evaporation minus precipitation (E-P)]. The SSS anomalies characterized as a negative to positive change near equator is proved to be related to the monsoon precipitation. A key area of SSS anomalies (4.5⁰S-0.5⁰S, 60⁰E-80⁰E) is identified crucial to study the relationship between SSS and the SASM. It is also found that when the value of SSS anomalies in the key area change from negative to positive, the South Asian high moves to the Indo-China peninsula, the northeastern winter wind in the lower layer over (EQ-20⁰N, 40⁰E-80⁰E) is replaced by the southwestern cross-equatorial current which brings more vapor flux to the continent for the monsoon precipitation, and it is also worthy to note that the Hadley circulation moves northward, which means the ascending branch instead of descending current over (EQ-10⁰N, 60⁰E-80⁰E). Thus, the SSS anomalies in the key area provide the basic signal to further investigate the SASM with SSS.

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