IDEALZED KERNEL SIMULATIONS

REPORT #3

SATOSHI MITARAI

UCSB F3 MEETING, 12/3/04

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

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

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

1) NUMERICAL DOMAIN

■ 64 x 32 x 20 grid points (8-km resolution)

512 km x 256 km Depth: 20 m -- 500 m

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2) BOUNDARY CONDITIONS

Periodic

Periodic

Free-slip wall

Nudging layer

(heats up domain)

Wind stressOpen B.C.'s

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

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

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

TEMPERATURE FIELD (SIDE VIEW)

TEMPERATURE FIELD (TOP VIEW)

MEAN TEMPERATURE FIELD

Simulation field Calcofi data #70

LAGRANGIAN PARTICLE DISPERSION

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 (107 cm2s-1)● Zonal/meridional: 3.1±3.0 / 2.9±2.8● Poulain & Niiler (1989): 4.1±1.8 / 5.9±3.7

“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

“LARVAL PARTICLE” TRAJECTORIES

“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

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

SUCCESSFULL SETTLEMENT AT A STATION (SHORT PLD)

SUCCESSFULL SETTLEMENT AT A STATION (LONG PLD)

SOURCE-DESTINATION MATRIX (SHORT PLD)

SOURCE-DESTINATION MATRIX (LONG PLD)

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