Assessment and adjustment of sea surface salinity products from Aquarius in the southeast Indian Ocean based on in situ measurement and MyOcean modeled data

Abstract

The in situ sea surface salinity (SSS) measurements from a scientific cruise to the western zone of the southeast Indian Ocean covering 30°–60°S, 80°–120°E are used to assess the SSS retrieved from Aquarius (Aquarius SSS). Wind speed and sea surface temperature (SST) affect the SSS estimates based on passive microwave radiation within the mid- to low-latitude southeast Indian Ocean. The relationships among the in situ, Aquarius SSS and wind-SST corrections are used to adjust the Aquarius SSS. The adjusted Aquarius SSS are compared with the SSS data from MyOcean model. Results show that: (1) Before adjustment: compared with MyOcean SSS, the Aquarius SSS in most of the sea areas is higher; but lower in the low-temperature sea areas located at the south of 55°S and west of 98°E. The Aquarius SSS is generally higher by 0.42 on average for the southeast Indian Ocean. (2) After adjustment: the adjustment greatly counteracts the impact of high wind speeds and improves the overall accuracy of the retrieved salinity (the mean absolute error of the Zonal mean is improved by 0.06, and the mean error is - 0.05 compared with MyOcean SSS). Near the latitude 42°S, the adjusted SSS is well consistent with the MyOcean and the difference is approximately 0.004.