University of Rhode Island (URI)

Domains

Horizontal

• 1/2 deg (75 deg by 75 deg) / 1/6 deg (11 deg by 11 deg) / 1/12 deg (5 deg by 5 deg)
• URI1: 15 deg by 15 deg domain at 1/12 deg resolution.
  Post-processed grids: 1/12 deg grid over 15 deg by 15 deg domain, where domain that extends beyond innermost grid is filled with appropriate outer domain interpolated to 1/12 deg resolution.
• 1/2 deg (75 deg by 75 deg) / 1/6 deg (11 deg by 11 deg) / 1/18 deg (5 deg by 5 deg)
• URI2: 15 deg by 15 deg domain at 1/18 deg resolution.
  Post-processed grids: 1/18 deg grid over 15 deg by 15 deg domain, where domain that extends beyond innermost grid is filled with appropriate outer domain interpolated to 1/18 deg resolution.

Vertical

42 levels with model top at

Atmosphere

Model: GFDL/URI Coupled Hurricane-Ocean Model

Overview

GFDL/URI is a primitive equation coupled atmosphere-ocean model formulated in latitude, longitude and sigma coordinates. The model domain consists of a triply nested grid configuration, in which the two inner grids are moveable and two-way interactive. For more detailed information on the GFDL model, please see Bender et al, 2007.

Initialization

NCEP GFS (Global Forecast System) global analysis and the storm message provided by NHC are used to generate initial conditions for hurricane model. An axisymmetric version of the prediction model is used to create an axisymmetric vortex based on the initial storm structure that is estimated from the data in the storm message. The initial conditions are calculated by adding back the model simulated vortex to the environmental fields that are determined from the GFS analysis.

Lateral Boundary Conditions

6-h GFS forecast output on 1/2 deg grid

Physics

Cumulus	Simplified Arakawa-Schubert
Microphysics	Ferrier
PBL	Troen and Mahrt (1986)
Surface Layer	Monin-Obukov
Land Surface	Tuleya (1994)
Radiation	Schwarzkopf and Fels (1991) (longwave) Lacis and Hansen (1974) (shortwave)

Ocean

Model: Princeton Ocean Model (POM)

Domains

Horizontal:
• 1/6 deg resolution
Vertical:
• 23 sigma levels

Initialization

Diagnostic and prognostic spinup of the ocean circulations using available climatological ocean data in combination with real-time sea surface temperature and sea surface height data. During the ocean spinup realistic representations of the structure and positions of the Loop Currents, Gulf Stream and warm- and cold-core eddies are incorporated.

Air-Sea Coupling

During one ocean model time step, the atmospheric model is integrated with its own time steps, keeping the SST constant. The computed wind stress, heat, moisture and radiative fluxes are passed into ocean model, which is then integrated one step, and a new SST is calculated. The new SST is used in the ensuing time steps of the atmospheric model.

Archival

Plan to archive forecast fields in the grib format at URI depending on available resources.

References

Bender, M.A., I. Ginis, R. Tuleya, B. Thomas, and T. Marchok, 2007: The operational GFDL coupled hurricane-ocean prediction system and summary of its performance. Mon. Wea. Rev., 135, 3965-3989.

Lacis, A. A., and J. E. Hansen, 1974: Parameterization for the absorption of solar radiation in the earth's atmosphere, J. Atmos. Sci., 31, 118-133.

Schwarzkopf, M.D., and S.B. Fels, 1991: The simplified exchange method revisited: An accurate, rapid method for computation of infrared cooling rates and fluxes. J. Geophys. Res., 96, 9075-9096.

Troen, I.B. and Mahrt, L., 1986: A Simple Model of the Atmospheric Boundary Layer: Sensivity to Surface Evaporation. Bound.-Layer Meteor. 37, pp. 129-148.

Tuleya, R.E., 1994: Tropical storm development and decay: Sensitivity to surface boundary conditions. Mon. Wea. Rev., 122, 291-304.

Yablonsky, R. M., and I. Ginis, 2008: Improving the ocean initialization of coupled hurricane-ocean models using feature-based data assimilation. Mon. Wea. Rev., 136, 2592-2607.