1. Multiple-scale Variability in the Southern California Bight Oceanic Current System Changming Charles Dong Institute of Geophysical and Planetary Physics, UCLA Collaborators: J. McWilliams, M.Hughes, Y. Uchiyama, Y. Chao, A. Hall, C. Zhang, E. Idica, K. Stolzenbach, M. Blaas

2. Outline 1.Introduction 2.Regional Oceanic Model System (ROMS) 3.Domain-scale oceanic current system 4.Mesoscale and submesoscale Variability: Island wake 5. Model delicacy and sensitivity: Upwelling Event 6. Summary

3. Pacific Ocean

4. (Strub and James, 2000, DSR) Seasonal SST (AVHRR) and SSH (TOPEX) SCB CCS:

5. (Digiacomo and Holt, 2001)

6. Regional Oceanic Model System (ROMS ) 1. It solves the primitive equations with the oceanic currents, potential temperature, salinity and the equation of state. It is a community model, and its source codes are open. More details, see the official website www.myroms.org 2. hydrostatic/non-hydrostatic versions 3.Application Packages: Sediment transport, Biological processes, Wave-current interaction, pollution discharge, sea ice, et al….

7. Regional Oceanic Model System (ROMS) One-way nested grids (~20km  ~6.7km  1km) Surface Forcing (MM5 18km, 6km, 2 km) Open Boundary Data (SODA, Carton et al, 2000a,b, JPO) Integration from 1996-2003 20km 6.7km 1km

8. Sverdrup Balance:

9. SCB Domain-scale Oceanic Current System

11. U = U geo + U ekman + U residue

17. Interannual Variability

18. (TOPEX TRACKS)

19. The domain-averaged depth (σ t = 25.5)

20. 290 th d310 th d330 th d 350 th d 5 th d 270 th d 75 th d95 th d115 th d 135 th d 35 th d55 th d 1997 1998

21. Anomalies of Dec., 1997 with respect to Eight-year Mean Dec.

22. Mesoscale and Submesoscale Variability

23. (Digiacomo and Holt, 2001) (Beckerbach and Washburn, 2004)

26. HF radar data by Libe Washburn Cyclonic eddy

27. Island Wakes in the SCB

28. LA

29. 1. Oceanic Response to Wind Wake 1a: Wind sheltering 1b: Wind Shear (curl) 2. Oceanic Island Wake (Tomczak, 1988) 2a: Deep water 2b: Shallow water 1. Oceanic Response to Wind Wake 1a: Wind sheltering 1b: Wind Shear (curl) 2. Oceanic Island Wake (Tomczak, 1988) 2a: Deep water 2b: Shallow water

30. SAR Image, June 8, 1999, UTC 02:00 (Caldeira et al, 2005)

31. (By courtesy of B. Perry, USC) (Caldeira and Marchesiello,2002,GRL) Oceanic Response to Wind Wake

32. (Dong and McWilliams, 2007, CSR) (Surface Vorticity) (Wind Stress and Curl) LA Vorticity Evolution Oceanic Response to Wind Wake

35. Model Sensitivity and Delicacy: An Upwelling Event, March 2002

36. AVHRR SST

38. Sensitivity Experiments 1.with tides, MM5 heat flux, freshwater flux 2.with no tides, MM5 heat flux, freshwater flux 3.with tides, COADS heat flux, freshwater flux 4.with tides, COADS heat flux, freshwater flux + analytical diurnal cycle

40. Summary ROMS is employed to study the domain-scale circulation in Southern California Bight forced by MM5 and SODA. The model is integrated over eight-year (1996-2003) The mean circulation and its interannual, seasonal variability are comparable with the observation. Island wakes play important role in the SCB current system especially in the mesoscale and submesoscale variation The model is sensitive to the external forcing and the tide is an important factor in the synoptic event.

41. THANK YOU! Upwelling Event, March 2002