Figure 1. Global maps of sea surface salinity observed by (a) Argo floats, (b) SMAP V4.0, (c) SMAP V5.0 and (d) SMOS V700 in psu.

Figure 1 shows SMAP retrieved salinity at the in situ matchup points for V4.0 and V5.0 observations from April 2015 to June 2022. In Figure 1 we also include SMOS V700 and Argo salinity data at the same matchup points. The correspondence is visibly quite clear with SMAP L2 data resolving the salient large-scale ocean features. Global salinity maps from SMAP V4.0 and V5.0 are very similar. SMAP V5.0 includes more data in high latitudes due to the improved sea-ice masking. SMOS V700 also captures the major patterns of salinity. However, SMOS salinity values in the polar regions and Southern Ocean are much lower compared to Argo and SMAP salinity.