A Prototype Storm Response Monitoring and Forecast System for the Western Gulf of Maine

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Project Type: 
Research
Project Number: 
R/CE-122
Inception Date: 
1998
Completion Date: 
2001
Theme Area: 
Coastal Ecosystem and Public Health
Coastal Communities and Economics

Participants:

Wendell Brown University of Massachusetts - Dartmouth Principal Investigator
Frank Bub UNH - Institute for the Study of Earth, Oceans and Space Co-Principal Investigator

Students Involved:

Yalin Fan UNH - Department of Earth Sciences
Prashant Mupparapu UNH - Department of Earth Sciences
Abstract: 

This proposed research addresses the issue of the importance of ocean waves and hydrodynamic nonlinearities for the accurate prediction of the response of the western Gulf of Maine to storm forcing. Here, "response" means the added rise in sea level (above normal tides) due to the combined effects of storm-related waves, high winds and decreased atmospheric pressure.

We hypothesize that both the nonlinear interaction between storm-wind-induced surface gravity wave currents and the relatively large tidal and wind-induced currents in the coastal ocean significantly alter the response of coastal Gulf of Maine sea level to storm forcing.

To test this hypothesis, we propose to add a surface wave model to the three-dimensional, nonlinear Dartmouth numerical circulation model and to evaluate the accuracy of the combined model hindcasts (past scenarios) in terms of archived data sets. The resulting model system will be the core element of a prototype ocean sea level monitoring and forecast system that will be forced by an appropriate suite of real-time operational government meteorological, sea level, surface wave and river discharge data and their products.

We will adapt an existing regional data and information management system to:

1) Link the operational forcing data and the ocean model system

2) Serve useful products to regional emergency management officers

Objectives: 

The specific objectives of the proposed Sea Grant research are to:

1) Couple a combined surface gravity wave/current bottom friction model to the Dartmouth nonlinear circulation model, called QUODDY

2) Implement a suitable scheme for specifying a space/time variable sea level pressure along the open ocean boundary of QUODDY

3) Implement a scheme for the near-realtime forcing of QUODDY with realistic atmospheric pressure and wind stress

4) Conduct hindcast studies of the storm response of the western Gulf, with a focus on the winter 1987, spring 1994 and winter 1995-96 periods of existing measurements

5) Assess the quality of the model system storm response through comparison with existing observations

6) Develop storm response model products suitable for emergency management office use

Methodology: 

Our approach is to adapt the Dartmouth three-dimensional (3-D), finite-element, nonlinear hydrodynamic model of the extended Gulf of Maine circulation (called QUODDY; Lynch and Werner 1991) to the proposed task. The model will be run on a composite of the two meshes shown in Lynch et al. 1997.

The seaward open ocean boundary of the large scale mesh goes to a depth of about 2000 meters to be somewhat remote from the part of the Gulf's wind-forced response located on the continental slope (see Greenberg et al. 1997). The more refined coastal mesh will be embedded in the large scale mesh so that the details of the coastal sea level response to storm forcing can be resolved adequately.

To more accurately model the storm response of sea level in the coastal Gulf of Maine, we will:

1) Force the model with both space/time variable atmospheric pressure and wind stress

2) Account for the anomalous friction caused by the nonlinear interaction between surface waves and currents (Grant and Madsen 1979).

To simplify the diagnosis of new effects due to wave/current-induced bottom friction and nonlinearities, we will run the model with constant density. Our experiments will focus primarily on the late fall/winter/spring time periods, when storm-forced effects are strong and natural density stratification is relatively weak. Biological productivity rates are high during late winter/early spring, and the model will simulate realistic coastal ocean response during this important time of year.

Rationale: 

There is increasing pressure on federal, state and local government agencies to find more effective tools for environmental hazard management because of:

1) Accelerated aquaculture development

2) Increased pollution of the coastal ocean and estuaries due to oil spills and other toxic inputs

3) A greater frequency in shellfish bed closures due to noxious phytoplankton blooms.

Although the complexity of the coastal ocean system poses great challenges to such developments, recent research results are providing direction to such efforts. It now appears that coastal ocean management tools of the future will consist of seamlessly blended suites of atmospheric, ocean, estuarine and ecosystem models, all fed by the necessary operational observations via distributed data and information management systems. Specially packaged sets of observations, model outputs and other information will be delivered in a timely and useful form to the desks of the appropriate environmental managers.

Accomplishments: 
(1) A prototype scheme for delivering real-time waves to QUODDY consisting of coupled WAM and SWAN wave models, has been tested for storm wave radiation stress forcing on a trio of New Hampshire beaches.
(2) The I-D counterpart of the Dartmouth 3-D finite-element circulation model QUODDY called NUBBLE was coupled to the Styles (1999) continental shelf Bottom Boundary Layer Model (BBLM) and used for sensitivity testing of surface wave-induced bottom stress.
(3) QUODDY with wind stress forcing, atmospheric pressure (AP) forcing and a space/time-independent bottom drag coefficient, was used to simulate of the response of the Gulf to the 9-10 February 1987 storm. The latter model configuration explained 82% of the variance of a suite of sea level/pressure measurements: much better than the 65% explained without AP forcing, and even better than the 45% explained with surface wave induced bottom stress.
(4) We have developed a prototype near real-time (operational) version of the QUODDY model application that tested with a one-month run for July 2001.

Publications

Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant

Journal Article

  • Mupparapu, P. and W. Brown (2002). Role of convection in winter mixed layer formation in the Gulf of Maine, February 1987. Journal of Geophysical Research 107(C12):22-1 - 22-18.
  • da Silveira, I., G. Flierl and W. Brown (1999). Dynamics of separating western boundary currents. Journal of Physical Oceanography 29(2):119-144.
  • da Silveira, I., W. Brown and G. Flierl (2000). Dynamics of the north Brazil current retroflection region from the western tropical Atlantic experiment observations. Journal of Geophysical Research 105(C12):28,559-28,583.
  • Bub, F. and W. Brown (1996). Intermediate layer water masses in the western tropical Atlantic Ocean. Journal of Geophysical Research 101(C5):11,903-11,922.

Report

  • Bub, F., W. Brown and L. Smith (1999). Convective Overturn Experiment (CONVEX) Cruise #5 R/V Oceanus (OC-316) (between 02 and 12 January 1998).
  • Fan, Y., W. Brown and C. Naimie (2001). Simulations of the Gulf of Maine storm response subject to surface wave-induced effects on bottom friction. University of Massachusetts Dartmouth, School for Marine Science & Technology, SMAST Technical Report No. 01-03-21.
  • Bub, F., W. Brown and L. Smith (1999). Convective Overturn Experiment (CONVEX) Cruise #6 R/V Oceanus (OC-316) (between 29 January and 02 February 1998).
  • Fan, Y. and W. Brown (2001). The performance of a coupled 1-D circulation and bottom boundary layer model with surface wave forcing. University of Massachusetts Dartmouth, School for Marine Science & Technology, SMAST Technical Report No. 01-03-20.
  • Bub, F., W. Brown and L. Smith (1999). Convective Overturn Experiment (CONVEX) Cruise #2 R/V ENDEAVOR (EN-294) (between 31 January and 4 February 1997).
  • Miller, S., W. Brown and F. Bub (1999). CONVEX moored instruments data report. University of New Hampshire, Ocean Process Analysis Laboratory. OPAL Technical Report UNH-OPAL-1999-003.
  • Bub, F., W. Brown and P. Mupparapu (1999). Convective Overturn Experiment (CONVEX) Cruise #4 R/V ENDEAVOR (EN-306) (between 01 and 05 October 1997).
  • Bub, F., W. Brown, P. Mupparapu, K. Jacobs and B. Rogers (1999). Convective Overturn Experiment (CONVEX) Cruise #1 R/V ENDEAVOR (EN-291) (between 03 and 05 January 1997). University of New Hampshire, Ocean Process Analysis Laboratory, OPAL Technical Report UNH-OPAL-1999-001.
  • Bub, F., W. Brown, P. Mupparapu and L. Smith (1999). Convective Overturn Experiment (CONVEX) Cruise #7 R/V Oceanus (OC-323) (between 02 and 06 May 1998). University of New Hampshire Ocean Process Analysis Laboratory, OPAL Tech. Rpt. UNH-OPAL-1999-002.
  • Miller, S., P. Mupparapu, W. Brown and F. Bub (1999). CONVEX air-sea heat flux calculations. University of New Hampshire, Ocean Process Analysis Laboratory, OPAL Technical Report UNH-OPAL-1999-004.

Thesis/Dissertation

  • Mupparapu, P. (1999). Role of convection in the winter Gulf of Maine mixed layer formation. Master's Thesis, University of New Hampshire.
  • Fan, Y. (2000). The influence of combined wave and current induced bottom stress on the coastal ocean response to storm forcing. Master's Thesis, University of New Hampshire.
Keywords: 
modeling