Evaluation of Aquarius Sea Surface Salinity With Argo Sea Surface Salinity in the Tropical Indian Ocean

The performance of sea surface salinity (SSS) obtained from the Aquarius satellite is evaluated. Daily, weekly, and monthly Aquarius SSS data between September 2011 and August 2013 from the tropical Indian Ocean (TIO) are compared with the surface most salinity observations (< 5 m) from Argo floats. Statistics between a daily reporting Argo float (WMO 2901329) and daily Aquarius SSS resulted in a root-mean-square error (RMSE), a bias, and a correlation of 0.32 psu, 0.02 psu, and 0.81, respectively. Weekly 1 degrees x 1 degrees spatial resolution SSS was produced from the Argo data using variational analysis and was compared with Aquarius SSS data. RMSE was observed to be between 0 and 0.25 psu over most of the region. Bias was observed to be within 0.3 psu everywhere, except in the southeastern Arabian Sea and the southeastern TIO. Good correlation (> 0.6) was observed everywhere, except the coast of Oman, western equatorial Indian Ocean, and south of 20 degrees S. A seasonal comparison has also revealed that both Aquarius and Argo are in agreement; in addition, the Aquarius SSS clearly shows the seasonal salinity cycle of the TIO.