Figure 8.  Time series of global weighted averaged SSS calculated from (a) SMAP V5.0 L3 monthly maps and (b) Argo floats. (c) is the global weighted average of salinity differences.

SMAP global weighted and averaged sea surface salinity ranges from 34.73 to 34.98 psu with a slight seasonal cycle. Global weighted averages of Argo SSS range from 34.74 to 34.92 psu. The differences between SMAP and Argo range from -0.02 to 0.05 psu except the first 5 months when the differences are as large as 0.14 psu. Note that when running the SMAP salinity retrieval algorithms, HYCOM is used for the ocean target calibration to ensure that the global average of SMAP matches the global average of the reference salinity field. Therefore, it is not surprising to see very small differences observed in SMAP and Argo global average salinity as HYCOM ingests Argo.