Circulation and Dynamics of the Western North Atlantic. Part III: Forecasting the Meanders and Rings

Abstract

The multiscale feature models (MSFMs) developed for the circulation of the western North Atlantic (Part I) have been used for initialization in this study to forecast the Gulf Stream meanders and rings. The Harvard primitive equation model, which was calibrated and verified for the statistics of the synoptical dynamics in this region (Part II), provides the basis for these simulations. Three 2-week-long synoptical dynamical hindcasts are presented. These hindcasts are carried out in a forecast mode without assimilating any future information. In general, when compared against SST-derived frontal location and ring?stream interactions, 2-week-long forecasts are found to be statistically superior than persistence and dynamically consistent. These forecasts are also compared against similar forecasts based on the U.S. Navy?s Optimum Thermal Interpolation System (OTIS) initializations. It is found that the MSFM-initialized simulations provide a better predictive capability than OTIS-initialized simulations over 2 weeks. Quantitatively, in terms of a statistical measure called the average offset of the axis of the stream, the former did better than persistence in all three cases over the 2-week periods. However, OTIS has two inherent characteristics, namely, a longitudinal distribution of temperature?salinity from climatology, and a warm pool at the core of the stream, which should be incorporated in the MSFM scheme to further enhance its predictive capability. The usefulness of multiscale kinematic synthesis in the initialization of the calibrated primitive equation dynamical model for forecasting the region over a 2-week period brings a closure to this three-part study of circulation and dynamics of the western North Atlantic.