Sub-Surface Ocean Structure from Satellite Surface Observations in the North Indian Ocean

Abstract

In this study interior plus Surface Quasi-Geostrophic (isQG) methodology is used to reconstruct subsurface density anomaly using sea surface temperature (SST), sea surface salinity (SSS) and sea surface height (SSH). The study is carried out in the Arabian Sea and Bay of Bengal of the Northern Indian ocean region. isQG is first tested for identical twin experiments, where the surface data and the stability profile (N²) were taken from a numerical ocean model. The root mean square error (RMSE) between isQG and model density anomalies lie within the error bars of model density anomaly in most of the levels. The impact of expected errors in synthetic observations of SST and SSS on isQG retrieved density anomalies was studied and it is found that error in SSS results in greater RMSE in isQG density anomaly profile in the Arabian sea than in the Bay of Bengal. isQG method is then applied to the satellite observations of SST, SSS and SSH and retrieved density profiles are then compared with model outputs and in-situ observations from RAMA buoy for the year 2019. The comparison indicates seasonal dependency and effect of N² on the performance of isQG method.

KEYWORDS:

• Density anomaly profile
• isQG
• ocean-interior

Acknowledgements

We would like to sincerely thank the Director, Space Applications Centre (SAC) for motivation and support. This work is carried out under “SAMUDRA” program. We acknowledge the GTMBA Project Office of NOAA/PMEL for providing buoy observations used in this study. All other data sources are thankfully acknowledged. Map contour data was taken from NOAA National Geophysical Data Center, 2009; 1 Arc-Minute Global Relief Model (ETOPO1). We thank NOAA National Centers for Environmental Information for the map data used in this study (https://www.ngdc.noaa.gov/mgg/global/global.html).

Disclosure statement

No potential conflict of interest was reported by the authors.