1. Progress on the Modification of Offshore Boundary Conditions for Full-Bay ROMS Simulations Have shown previously that ROMS simulations capture tides well, but that subtidal variability is not well simulated. Hypothesis in CHRP-II proposal: Poor subtidal model skill results from the fact that the shelf dynamics in the model is poorly simulated. Proposed to extend “large-domain” model farther out on the continental shelf and to force this model with output of regional models. Before building a new model, have examined the model and observations with an eye towards a better understanding of the dynamics.

2. Providence: sea level Newport: sea level East Passage Channel: currents Blue: “large-domain” model Red: “fullbay” model Large-domain model open boundary forcing: Tides from ADCIRC. T, S from seasonal climatology.

3. North/South Velocity (EP Channel) North South North

4. Model skill (Wilmott) = 0.75 Depth-Averaged North/South Velocity (EP Channel)

5. Approximate depth-averaged momentum balance (north/south direction) ABCDE A. Local acceleration (time change of velocity): estimate from ADCP obs. (E. Passage channel). B. Barotropic pressure gradient (due to surface slope): estimate from sea level obs. (Prov. and Newport). C. Baroclinic pressure gradient (due to density gradient): estimate by difference. D. Wind stress ( ): estimate from wind obs. (Quonset). E. Bottom stress ( ): estimate from ADCP obs. (near-bottom bin).

6. Depth-Averaged Momentum Balance (EP channel) Up-estuary Down-estuary

7. Depth-Averaged Momentum Balance (EP channel) Up-estuary Down-estuary

8. Momentum Balance Obs. vs Model

9. Forcing from FVCOM model Model results for 2006 obtained from C. Chen, UMASS Dartmouth (for OSAMP project). Model output sampled along large-domain model open boundary and used as forcing.

10. Force Large-Domain Model: Low-pass filtered sea level and velocity from FVCOM simulation applied along open boundaries of large-domain model (in addition to tides and T/S climatology as in standard run). Open boundaries

11. Momentum Balance Obs. vs Models

12. Sea Level, Obs. vs Models

13. Remaining Questions/Next Steps Big unanswered question: Why are model pressure gradient fluctuations in Bay so severely underestimated? 1.Open boundary forcing still not right? 2.Bottom drag coefficient in model needs adjustment? 3.Wind stress too weak? Next Steps: 1.Obtain updated version of Chen model. Check its fidelity with Newport sea level compared to present version. If improved, then extract forcing from it and re-run large-domain and fullbay models. 2.Run existing models with changes to drag coefficient and/or increased wind stress. Should provide useful insight. 3.Create new large-domain model to simulate shelf circulation and sea level setup in vicinity of Bay mouth. Use this to force fullbay model.

14. Sea Level and Wind

15. Sea level/wind correlations