1. IDEALZED KERNEL SIMULATIONS REPORT #3 SATOSHI MITARAI UCSB F3 MEETING, 12/3/04

2. GOAL OF THIS WORK ■ To investigate larval transport in “idealized” simulations ● To describe long term & short term dispersal kernels ● Four scenarios considered ▷ Strong or weak upwelling ▷ Northern or southern California ■ To develop modeling to establish short time kernels from available data sets

3. IDEALIZED SIMULATIONS ■ Idealized is state that shows 1) statistical stationarity 2) statistical homogeneity in alongshore 3) characteristics of coastal current ■ Make particle tracking easier ■ No such simulation in literature ● Need to construct our own ● Focus on Summer, Northern California

4. ROADMAP ■ Numerical simulation setting 1) Numerical domain 2) Boundary conditions 3) Initial conditions 4) Forcings ■ Show obtained simulation fields & trajectories ■ “Larval dispersion” experiment ○ Issues: particle release, defintion of settlement, etc

5. 1) NUMERICAL DOMAIN ■ 64 x 32 x 20 grid points (8-km resolution) 512 km x 256 kmDepth: 20 m -- 500 m COAST O

6. 2) BOUNDARY CONDITIONS Periodic Free-slip wall Nudging layer (heats up domain) Wind stress Open B.C.'s

7. 4) FORCINGS ■ Wind stress ● Modeled with Gaussian random process ▷ Statistics determined from NDBC archive ■ Pressure gradient ● Imposed as external force ▷ Computed from dynamic height difference between Pt. Arena & Pt. Conception

8. 3) INITIAL CONDITIONS ■ Determined using CALCOFI data ● Velocity: geostrophic velocity ▷ No motion at 500db (500m) ● Temperature ▷ Consistent with given density field ● Sea level ▷ Dynamic height with zero mean

9. COMPUTATION ■ 1080-day simulation with 30-minute time stepping ● Reaches equilibrium within 900 days ■ Release Lagrangian particle ● Every day between 900 and 990 days ▷ Particles travel 90 – 180 days ● Every 8 km in alongshore direction ● 200 km from coast

10. TEMPERATURE FIELD (SIDE VIEW)

11. TEMPERATURE FIELD (TOP VIEW)

12. MEAN TEMPERATURE FIELD Simulation field Calcofi data #70

13. LAGRANGIAN PARTICLE DISPERSION

14. LAGRANGIAN STATISTICS ■ Time scale (days) ● Zonal/meridional: 5.5 ± 2.4 / 5.5 ± 2.3 ● Poulain & Niiler (1989): 4.6 ± 1.3 / 6.1 ± 3.4 ■ Length scale (km) ● Zonal/meridional: 34. ± 20. / 33. ± 19. ● Poulain & Niiler (1989): 39. ± 13. / 54. ± 28. ■ Diffusivity (10 7 cm 2 s -1 ) ● Zonal/meridional: 3.1 ± 3.0 / 2.9 ± 2.8 ● Poulain & Niiler (1989): 4.1 ± 1.8 / 5.9 ± 3.7

15. “LARVAL PARTICLE” DISPERSION ■ Release particles ● Every 8 km in alongshore direction ● Every 8 km in cross-shore within 36 km from coast ▷ Corresponding depth: 50 ~ 200 m ■ Define settlement ● As event that particles within 4 km from coast ▷ Corresponding depth: 50 m ▷ Once settle, particles stop there

16. “LARVAL PARTICLE” TRAJECTORIES

17. “LARVAL PARTICLE” DISPERSION ■ Two types of “larval particles” ● Short PLD ▷ Competency window = 5 ~ 15 days ● Long PLD ▷ Competency window = 30 ~ 90 days ■ Define successful settlement ● As settlement during competency

18. COUNTING SUCCESSFUL SETTLEMENT ■ Define stations ● Depending on alongshore location ▷ 8-km bin size ■ Sit on one station & observe successful settelers ● How long they were planktonic ▷ Short / long PLD larval particles ● Where they come from

19. SUCCESSFULL SETTLEMENT AT A STATION (SHORT PLD)

20. SUCCESSFULL SETTLEMENT AT A STATION (LONG PLD)

21. SOURCE-DESTINATION MATRIX (SHORT PLD)

22. SOURCE-DESTINATION MATRIX (LONG PLD)

23. SUMMARY ■ Stochastic settlement observed, but it depends on ● Particle release ▷ How often (or dense) in space & time? ● Definition of settlement ● Station size ■ We need help on determination of these