Observing Propagating Ocean Features Using SMOS Surface Salinity data

The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite has provided sea surface salinity (SSS) data for over six years. It has been shown that the operational ESA Level 2 SSS data have significant spatially and temporally varying biases between measurements from ascending passes (SSSA; SMOS moving south to north) and descending passes (SSSD; SMOS moving southwards). Therefore, without calibrating SSS to some reference salinity it is difficult to use these data to study long-term, basin-wide processes. The data used for this study were from two SMOS SSS climatologies one based on SSSA and the other from SSSD. These climatologies have been used to calculate salinity anomalies, which are shown to have significantly reduced the spatio-temporal biases. This presentation will show how these SSS anomalies can be used for oceanographic studies, including the detection of planetary waves/large eddies in the South Indian Ocean. Planetary, or Rossby, waves (RW) are important in oceanography (e.g. in maintaining western boundary currents). Prior to the availability of satellite measurements of sea surface height (SSH), only an indirect confirmation of the existence of RW had been possible from sparse in situ data. Signals attributed to RW have now been fully observed and characterised in satellite-derived fields of SSH, sea surface temperature (SST) and chlorophyll-a. At mesoscale wavelengths (<300 km) these signals seem to be dominated by non-linear eddies and at large length scales eddies and RW have the similar propagation speeds. Our analysis shows geophysical signals in the South Indian Ocean that are consistent among SSS anomalies, SST and SSH, and with previously published results, in detecting large-scale non-linear eddies/RW in the region.