California Current System: A Multiscale Overview and the Development of a Feature-Oriented Regional Modeling System (FORMS)

摘要

Every littoral or regional ocean has both coastal circulation components and influences from offshore regions. Over the past decade, the feature-oriented regional modeling approach has evolved to become operational in some of these regions (western North Atlantic, tropical North Atlantic). This methodology is model-independent and can be applied with or without satellite and/or in situ observations, especially in coastal regions. In applying this methodology for the subtropical North Pacific, we first present an overview of the synoptic nature of the different features that comprise the multiscale and complex circulation in the California Current system (CCS). This description is a prerequisite to feature modeling and is based on our present understanding of the features and their dominant space and time scales of variability. The region of interest is from 36 degrees N to 48 degrees N - essentially most of the eastern boundary current region of the subtropical North Pacific. We present a synergistic configuration of synoptic features interacting with one another on multiple and sometimes overlapping space and time scales as a meander-eddy-upwelling system. The second step is to define the feature-oriented regional modeling system (FORMS) for this system. The major multiscale synoptic circulation features include the mean flow and southeastward meandering jet(s) of the California Current, the poleward flowing California Undercurrent, and six upwelling regions along the western coast of the U.S. We first identify the typical synoptic width, location, vertical extent, and core characteristics of these features and their dominant spatial and temporal scales of variability from past observational theoretical and modeling studies. These synoptic features are then melded with available climatology of the region for initialization and assimilation. Finally, dynamical simulations are run as nowcasts and short-term (4-6 weeks) forecasts.