High-Resolution Baroclinic OceanSimulations for the East Florida Shelf:

Frontal Eddies to Reef Scale Processes

Jerome Fiechter and Christopher N.K. Mooers

Ocean Prediction Experimental Laboratory

Rosenstiel School of Marine and Atmospheric Science

University of Miami

2003 Terrain-Following Ocean Models Users Workshop

Seattle, 06-AUG-2003

• Geographical domain

– Straits of Florida

– East Florida Shelf

– Florida Keys reef tract

• Circulation features

– Florida Current

– Gulf Stream

– Loop Current

– Tortugas gyre

– Frontal eddies

Region of interest

Source: NASA (MODIS image)

• Princeton Ocean Model (POM)

• Curvilinear grid

• Vertical sigma levels

• SEA-COOS program– COMPS (USF)– EFSIS (UM) – SABSOON (UNC)

Regional of interest

East Florida Shelf coastal ocean model (EFS-POM)

(www.seacoos.org; www.efsis.rsmas.miami.edu)

Horizontal: 251x101 nodes (~2-20km)Vertical: 25 σ-levels (~0.1-100m) – clustering in surface and bottom layersMin. depth: 5m (extended to physical coastline location)

EFS-POM ocean model

Domain grid - Resolution

EFS-POM ocean model

Forcing Boundary condition

UA, VA (external)from U, V

(30Sv, constant)

in: inflow

out: Flather radiation

U, V (internal)thermal wind balance

(inflow only)

in: inflow

out: Orlanski radiation

T, SLevitus

(monthly, 1ºx1º)

in: Orlanski radiation

out: Orlanski radiation

Wind stressETA winds

(6-hourly, 2ºx2º)

quadratic drag law

(drag coef. = 10-3)

Heat fluxEsbensen & Kushnir

(monthly, 4ºx5º)long wave rad., latent, sensible,

(penetrating) short wave rad.

Open and surface boundary conditions - Summary

SST and SSH daily animation

1999 Hindcast simulation - Seasonal cycle

Temperature and normal velocity (STACS: 8 stations; EFS-POM: 30 nodes)

1999 Hindcast simulation - Comparison with STACS data at 27N

standard deviationyearly average

EFS-POM (1999) STACS (1983) EFS-POM (1999) STACS (1983)

Temperature (deg.C)

Meridional velocity (m/s)

Temperature (deg.C)

Meridional velocity (m/s)

SST and SSHA daily animation

Frontal spin-off eddy event, February 1999

Eddy propagation along EFS shelf break (200m isobath)

Frontal spin-off eddy event, February 1999

Summary

Simulation Observations

alongshore diameter 60-120 km 100-200 km *

cross-shore diameter20-30 km (26N)

50-80 km (29N)

10-30 km (26N) *

30-50 km (30N) *

propagation speed 40 km/day 36 km/day #

recurrence period

(wavelength)

4-7 days

(160-210 km)

5 days #

(170 km)

* Lee et al., 1991 # Johns and Schott, 1987

Frontal spin-off eddy event, February 1999

Remaining issues

• Formation and evolution– origin– decay and growth rates– “gap closure paradox”

• Cross-shelf transport– heat, momentum– biochemical tracers

• Sensitivity to forcing and numerical parameters– seasonal transport cycle– HORCON, TPRNI– grid type and resolution

Frontal spin-off eddy event, February 1999

Dry Tortugas high-resolution nested model (DT-POM)

Domain grid - Resolution

Horizontal: 65x57 nodes (~1-2km)Vertical: 21 σ-levels (~0.1-10m) – clustering in surface and bottom layersMin. depth: 2m (no coastline)

Forcing Boundary condition

UA, VA (external)mapping from

EFS-POM

E, W: Flather radiation

N, S: Flather radiation

U, V (internal)mapping from

EFS-POM

E, W: Marchesiello radiation

N, S: Marchesiello radiation

T, Smapping from

EFS-POM

E, W: Orlanski radiation

N, S: Orlanski radiation

Wind stressC-MAN winds

(hourly, uniform)

quadratic drag law

(drag coef. = 10-3)

Heat fluxEsbensen & Kushnir

(monthly, 4ºx5º)long wave rad., latent, sensible,

(penetrating) short wave rad.

Open and surface boundary conditions - Summary

Dry Tortugas high-resolution nested model (DT-POM)

Bottom temperature and velocity

1999 Hindcast simulation - DT model

Vertical temperature and velocity structure at 24.7N

1999 Hindcast simulation - DT model

AUGUST 1999FEBRUARY 1999

February (e.g., grouper spawning) and August (e.g., coral spawning)

1999 Hindcast simulation - Tracer trajectories

• East Florida Shelf model (EFS-POM) is qualified to:

– study large scale to mesoscale processes

– investigate regional connectivity and recruitment

(i.e., long-range dispersion processes)

• Dry Tortugas model (DT-POM) is qualified to:

– study submesoscale and reef scale processes

– investigate self-seeding vs. export conditions

(i.e., local retention processes)

– relate benthic communities to flow dynamics

Conclusions

• East Florida Shelf model (EFS-POM)

– improve open boundary and surface forcing

– increase horizontal and vertical resolution

– validate further against observations

– sensitivity study (num. param., forcing, resolution)

– add ecosystem model (e.g., NPZD)

• Dry Tortugas model (DT-POM)

– improve nesting method

– increase horizontal and vertical resolution

– validate against observations

– 3-D trajectories / biological behavior

Future Work

Questions and comments