Application of FVCOM to the Gulf of Maine/Georges Bank:

Simulated and Assimilated Modeling Studies of Stratification and Sub-tidal Circulation

Chen, C, H. Liu, R. C. Beardsley, G. Cowles, J. Pringle, R. Schlitz and B. Rothschild

The FVCOM GOM/GB

Physical Model

Wind stress, heat flux

GOM/GB MM5

• Real-time tidal forcing

• River discharges

• Scotian shelf water input

• North Atlantic open boundary condition ??

• SST

• Hydrographic survey CTD

• ADCP

• Moored current meter data

• CODAR??

Assimilation Boundary forcings

Meteorological forcing

: H, , , D, s, , q2, q2l, Am, Kh I : u, v,

The Finite-Volume Coastal Ocean Model (FVCOM)

6 ADCPs 3-6, 1999

NECE

The 1995 and 1999 Experiments

1. Run the model with tidal forcing only from December 1-15;

2. Re-start the model on December 15 with the initial condition of T and S given by December climatologic hydrographic field;

3. Add real-time wind stress, heat flux, river discharge, etc on January 1

Simulating

Assimilating: SST, Current

Re-start with the assimilated field

January February

Observed Calculated CalculatedObserved

M2

N2

S2

Observed ObservedCalculated Calculated

K1

O1

The 1995 Simulation and Assimilation

Jan

Feb

March

Observed Simulated Assimilated

SimulatedObserved Assimilated

April

May

June

Observed Simulated Assimilated

July

Aug

Sept

Observed Simulated Assimilated

Oct

Nov

Dec

23 m

99 m

191 m

Site: NECE

Site: NECE

23 m

99 m

191 m

February 1995

July 1995

The 1999 Summer Simulation and Assimilation

Observed Simulated Assimilated

Times (day) May 1999

Observed Simulated Assimilated

Ob

serv

edS

imu

late

dA

ssim

ilat

ion

Site2 Site4 Site6

Comparison between observed and simulated currents at an ADCP site

May 1999

May 1999Simulated subtidal surface water temperature and currents

Summary

1. Both simulation and assimilation clearly show that the seasonal variation of clockwise subtidal gyre on GB and also cyclonic circulation around the Jordon basin. The cyclonic circulation forming around the Jordon basin could cause a significant on-bank water transport to GB during summer.

2. Good agreement between model-predicted and observed currents was found on the southern flank of GB, but not in the Northeast Channel (NEC). This suggests that the subtidal circulation on GB is mainly controlled by local forcing, while the currents in the eastern GOM/GB are strongly influenced by water input from the Scotian Shelf.

3. Nudging assimilation is used to merge the model-computed and observed currents in the NEC. This approach produces a more realistic pattern of subtidal currents and on-bank transport on the northeastern flank of GB.