A comparison of shelf observation platforms for assimilation in an eddy-resolving ocean model

An assessment of the likely benefits of assimilating in situ temperature (T) and salinity (S) observations from repeat glider transects and surface velocity observations from high-frequency radar arrays into an eddy-resolving ocean model is presented. The deployment of new shelf observation platforms around Australia is being undertaken through the Australian Integrated Marine Observing System program. In this study, various options for an observing system along the coast of New South Wales, Australia, are assessed for their benefits to an ocean forecast and reanalysis system. The forecast system considered here uses ensemble optimal interpolation (EnOI) for data assimilation. Using error estimates from the EnOI scheme, estimates of the theoretical analysis errors are calculated for different observing systems that include a range of remotely sensed and in situ observations. The results demonstrate that if HF radar observations are assimilated along with the standard components of the global ocean observing system, the analysis errors are likely to reduce by as much as 80% for velocity and 60% for T, S and sea-level in the vicinity of the observations. Owing to the relatively short along-shore decorrelation length-scales for T and S near the shelf, the glider observations are likely to provide the forecast system with a more modest gain.