Time series of monthly, global averaged salinity difference variations for SMAP V4.0 and V5.0 and SMOS are shown in Figure 5. SMAP V5.0 are close to SMAP V4.0 for most of the record. An exception is that after July 2020, negative biases appeared in SMAP V4.0 but not in SMAP V5.0. In contrast to SMAP, salinity differences between SMOS and Argo salinity show a strong annual cycle up to 0.08 psu. Biases are positive in northern hemisphere spring and become negative in autumn.