Assessing the Seasonal Variability of the Global Sea Surface Salinity from Aquarius
[13-Nov-2013] Song, Y.T., Yueh, S., Moon, J-H., and Qu, T.
Presented at the 2013 Aquarius/SAC-D Science Team Meeting
Using two different Aquarius sea-surface-salinity (SSS) datasets, Argo in-situ measurements, and two ocean models, we have assessed the ability of Aquarius to observe seasonal variability of the global SSS. The two Aquarius datasets are the project-released v2.0 SSS (aquSSS) using NCEP winds in the retrievals and the Combined Active-Passive (CAP) algorithm-retried SSS (capSSS) using wind vectors from Aquarius instruments. The two ocean models are the HYCOM and the non-Boussinesq ROMS (NB-ROMS). Although the overall spatial structure and temporal evolution observed by Aquarius are consistent with the Argo measurements and the two ocean models, there are significant differences among them: (1) Both Aquarius datasets have much stronger seasonal variability than the Argo measurements, but only slightly stronger than the model outputs (2) Over river discharge regions, Aquarius and the two ocean models capture the SSS seasonal variability well, while Argo ineffective because of insufficient resolution and (3) Aquarius shows the largest freshening of about 0.3 PSU from Argo over high E-P variability zones, suggesting some freshwater exchanges across the first centimeter surface sampled by Aquarius but does not necessarily reach the 5m depth measured by Argo. These differences between Aquarius and Argo observations are explained with the models that represent the surface layer salinity.