Assessment of Satellite-Derived Sea Surface Salinity in the Indian Ocean

Abstract

The study has been motivated by the desire to assess the performance of sea surface salinity (SSS) from the Soil Moisture and Ocean Salinity (SMOS) satellite launched by the European Space Agency. Daily Level 3 product on a 0.25 • × 0.25 • grid for the year 2010 has been used for this assessment in the Indian Ocean. Various data sets, like the in situ data sets available from the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) buoys and Argo floats and also the data sets from modular ocean model version 3 simulations, have been utilized for this purpose. Comparison made at two buoy locations suggests good quality of SMOS SSS with root-mean-square error of the order of 0.36 and 0.34 psu. The triple collocation method, which explicitly takes into account the error characteristics of the SMOS, Argo, and model data sets, has been used for further validation of the SMOS data. Since the Indian Ocean exhibits characteristically different patterns of SSS in its different subregions, the study area has been divided into different such subregions. The SMOS-derived SSS appears to be of very good quality in the equatorial Indian Ocean and southern Indian Ocean, while the data are of poorer quality in the Arabian Sea and the Bay of Bengal possibly because of the errors in SSS retrieval due to the land contamination and strong winds. Index Terms-Argo floats, functional relationship (FR), modular ocean model (MOM) version 3 (MOM3) ocean model, Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) buoys, Soil Moisture and Ocean Salinity (SMOS) salinity, triple collocation.

Salinity Measurements Collected by Fishermen Reveal a “River in the Sea” Flowing Along the Eastern Coast of India

“…SMOS and Aquarius surface salinity products are still very new and have not yet been thoroughly evaluated in many regions of the world. Preliminary studies, however, point out that, while remotely sensed salinity is rather accurate in the equatorial Indian Ocean (Durand et al 2013;Shinoda et al 2013), it is of poorer quality in the BoB (Ratheesh et al 2013), partly due to strong radio interference with radars close to the coast (Reul et al 2012). …”

Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current

“…It is now possible to measure salinity from space, but the variation in salinity in the NEAS is of the order of 0.5 psu, currently beyond the measurement accuracy (∼2 psu) of the Aquarius salinity sensor (Tsontos 2014) and of the same order as that of the SMOS (Soil Moisture and Ocean Salinity) sensor (∼0.36 psu; Ratheesh et al 2012;Subrahmanyam et al Fig. 13 Contribution of components of the sub-surface processes to the ML heat budget during October-March.…”

Large-Scale Air-Sea Coupling Processes in the Bay of Bengal Using Space-Borne Observations

“…The SMOS mission, launched by the European Space Agency, was a revolution in ocean remote sensing because it carried the first ocean salinity sensor onboard a space platform (Kerr et al, 2010). The salinity measured from this sensor is consistent with observations of the equatorial Indian Ocean (Ratheesh et al, 2013), but due to the larger satellite footprint and land contamination, the errors in SSS are found to be large in the BoB.…”