Evaluation of Global Sea Surface Salinity from Four Ocean Reanalysis Products

This study extends recent Sea Surface Salinity (SSS) comparisons to explore improvements to several next-generation ocean reanalysis products, including the Simple Ocean Data Assimilation version 3.11.2 (SODA 3.11.2), the Hybrid Coordinate Ocean Model (HYCOM), the GLORYS12 Reanalysis version 1 (GLORYS12V1) and the Global Ocean Data Assimilation System (GODAS) during the satellite era of SSS (2010–2020). All the four reanalysis products share similar inputs of historical hydrographic measurements, but their forward model, surface forcing and bias correction algorithms are distinctly different. A comprehensive SSS validation is conducted, taking the signals of climatological SSS field, interannual biases series, seasonal biases distributions, and zonal/meridional averaged biases into account. The comparison is conducted using both satellite products gridded in situ databases. The spatial distributions of SSS from four reanalysis products generally agree with both the satellite data and the in situ measurement. Except for GODAS, the biases carried by the other three reanalysis products are smaller than 0.3 PSU in the open sea. The seasonal to interannual analysis of RMSDs show that all the four reanalysis products tend to overestimate the SSS in open seas from tropical to subpolar regions. Finally, the SSS reanalysis are compared with tropical buoys, which shows optimistic results and suggests the potential of ocean reanalysis data to serve as quality control of buoy data.