A Nudging Technique to Improve Salinity Performance for the San Francisco Bay Operational Forecast System (SFBOFS)

The San Francisco Bay Operational Forecast System was recently developed and implemented into operations to support the Center for Operational Products and Services' (CO-OPS) safe and efficient navigation mission. This forecast system was based on the Finite Volume Coastal Ocean Model (FVCOM) and became operational in May 2014. Model skill assessments indicate that the performance of water level, currents, and water temperature forecasts pass the National Ocean Service's accepted skill assessment criteria. Salinity forecasts, however, require substantial improvement. Therefore, a nudging technique has been developed and tested to improve the salinity predictions. The nudging scheme uses the model-observation salinity discrepancy at stations within an appropriate distance to the mouths of major rivers as an indicator to adjust the river stage vertical reference level, which subsequently changes the fresh water input. This paper presents the experimental results that indicate substantial improvement in modeled salinity between Crockett and Antioch.