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In this study, the global ocean analysis and forecast system is evaluated against the observations in the Indian Ocean for the 2017–2018 period. A comparison of temperature and salinity analysis with seven moored buoy observations showed an excellent mutual agreement with systematically underestimating the upper ocean variability. A similar comparison of ocean analysis with the ARGO dataset average over the different oceanic regions also shows an underestimation of temperature and salinity up to 300 m depth. Further, the temperature RMSE gradually increases from surface to thermocline depth for all regions. The sea surface temperature (SST) forecast is reasonably good at all buoy locations with RMSE less than 0.5°C and a correlation of more than 0.7 up to the day-7 forecasts for the 2017–2018 period. Similarly, the sea surface salinity (SSS) forecast is also good except northern Bay of Bengal (BoB) region where the high variability leads to poor correlation and large RMSE in this shallow and freshwater region. This study helps to understand how observations fit into the model through data assimilation and also quantifies the model forecast error. Further, the study is also vital for the development/research activity related to the model and data assimilation in the Tropical Indian Ocean (TIO) region. [ABSTRACT FROM AUTHOR]

A sea surface temperature (SST) and sea ice reanalysis has been produced at the Met Office based on the Operational SST and Sea Ice Analysis (OSTIA) system. The OSTIA reanalysis produces daily, high-resolution, global foundation SST and sea ice concentration fields from 1 January 1985 to 31 December 2007. The SST reanalysis uses reprocessed satellite and in situ observations that are assimilated using a multiscale optimal-interpolation-type scheme similar to that used in the near-real-time OSTIA system. Validation of the SST analysis using assimilated in situ observation-minus-background statistics shows that the accuracy of the analysis increases throughout the reanalysis period; the global root-mean-square difference is approximately 0.50 K by 2007. This approach to validation is supported in the recent period by results from comparisons with independent near-surface Argo data against which a global standard deviation error of 0.55 K was calculated. Assessment of the OSTIA reanalysis at high latitudes demonstrates that the SST and sea ice fields are more consistent with one another in the Southern Hemisphere than in the Northern Hemisphere. Comparison of the sea ice extents to those in a similar reanalysis shows OSTIA to have larger extents in the Northern Hemisphere, and the Southern Hemisphere extents are similar. The OSTIA reanalysis SSTs are shown to be regionally comparable with similar reanalyses, with the largest differences occurring at high latitudes in the summer hemisphere. Differences are observed around the ice edge and in regions with high SST gradients. The OSTIA reanalysis provides a valuable high-resolution addition to the satellite period SST data record that makes use of the (Advanced) Along-Track Scanning Radiometer [(A)ATSR] multimission data. [ABSTRACT FROM AUTHOR]