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The long-term goal of this project is to develop and apply practical methods for data assimilation to improve the short-range prediction of mesoscale ocean variability. The primary objective of this work is to develop an ocean data assimilation system that exploits the strengths of both the ensemble-based (e.g., Evensen 2003; Houtekamer and Mitchell 1998; Tippett et al. 2003) and variational (e.g., Bennett 2002) approaches to data assimilation. The first step in this project is to perform a comprehensive inter-comparison of an ensemble-based data assimilation system with a 4d-var system for a suite of coastal model configurations. The second step is to identify the strengths and weaknesses of each system and to improve both systems by borrowing components from the other system. Ultimately, a single ensemble-var system will be developed. We will investigate the extent to which the ensemble-var system can outperform both the ensemble-based and variational approaches, both in terms of forecast skill (accuracy) and computational efficiency (throughput).

The long-term goals of this research project are to advance data assimilation (DA) methods for coastal ocean circulation models. After several years of research focused on various aspects of advanced, variational DA with nonlinear coastal ocean models, we have come close to development of an optimal, versatile, and relocatable DA system based on a primitive equation model with a turbulence submodel. The system can be used efficiently both for operational needs (forecasting, search and rescue, environmental response) and for fundamental studies of coastal ocean dynamics. The modeling system will have the capability to assimilate time-series measurements from moorings and coastal based high frequency (HF) standard and long-range radars, satellite information (SSH, SST), and hydrographic survey data (including observations from underwater gliders).

The long-term goals of this research project are to advance data assimilation (DA) methods for coastal ocean circulation models. After several years of research focused on various aspects of advanced, variational DA with nonlinear coastal ocean models, we are coming close to development of an optimal, versatile, and relocatable DA system based on a primitive equation model with a turbulence submodel. The system can be used efficiently both for operational needs (forecasting, search and rescue, environmental response) and for fundamental studies of coastal ocean dynamics. The modeling system will have the capability to assimilate time-series measurements from moorings and coastally-based high frequency (HF) standard- and long-range radars, satellite information (SSH, SST), and hydrographic survey data (including observations from underwater gliders).

Three-dimensional circulation in the coastal transition zone (CTZ) off Oregon is studied using a 3-km resolution model based on the Regional Ocean Modeling System (ROMS). The study period is spring-summer 2002, when extensive observations are available from the North Eastern Pacific Component of the Global Ocean Ecosystems Dynamics (GLOBEC-NEP) project. Our main focus is on near-surface transports, particularly in an area off Cape Blanco where an energetic coastal current is separated in the CTZ. Comparisons with available observations (velocities from mid-shelf moorings, surface velocities from high-frequency radars, satellite SST maps, along-track SSH altimetry, and SeaSoar hydrography) show that the model reproduces qualitatively correctly the flow structure and variability in the study area., Submitted to the Journal of Geophysical Research.

The Oregon Coastal Transition Zone (OCTZ) extends several hundred kilometers offshore where shelf flows interact with the northern California Current. A primitive-equation numerical ocean model is used to study the upwelling circulation in this region from May 1 to November 1, 2001. This OCTZ model obtains initial and boundary conditions from a larger-scale model of the California Current System and forcing from a regional atmospheric model product. The model results are compared with extensive in situ and remotely sensed data, and the model is found to provide a useful representation of flows both over the shelf and in the broader OCTZ. Simulation of coastal sea level and shelf currents over the complex topography of the central Oregon coast is improved quantitatively relative to previous regional models. A particularly significant qualitative improvement is realistic representation of coastal jet separation and eddy formation offshore of Cape Blanco. A three-dimensional Lagrangian analysis of water parcel displacement shows that the surface waters inshore of the separated jet are upwelled from near the bottom along the shelf as far north as 45.5 degrees N. A large eddy, which incorporates some of this upwelled water and carries it farther westward, forms offshore in the late summer. Ensemble simulations point toward a distinction between the strongly deterministic response to wind forcing over the shelf, and more unstable, less predictable jet separation and offshore eddy formation processes in the region near Cape Blanco., Prepared in collaboration with the Oceanography Division, Naval Research Laboratory, Stennis Space Center, MS. Submitted to Journal of Geophysical Research; final version published in v114 nC2 article C02010.. Supported through the National Ocean Partnership Program. The original document contains color images.

The goal of this research project is to develop data assimilation (DA) methods for coastal circulation models and to apply these methods to measurements from the Oregon shelf. We envision the development of an optimal, versatile, and relocatable DA system based on a primitive equation model with a turbulence submodel. The planned system could be used efficiently both for operational needs (forecasting, search and rescue, environmental response) and for fundamental studies of coastal ocean dynamics., The original document contains color images.

The immediate scientific objectives of this research project are to develop practical, but still nearly optimal methods for the assimilation of data into coastal circulation models, and to apply these methods to time-series measurements from moorings and coastally-based high frequency (HF) standard and long range radars, satellite data (SSH, SST), and hydrographic survey data (e.g., from autonomous underwater vehicles, AUVs). An important additional scientific objective is to utilize data assimilation to study the physics of coastal ocean circulation processes.