Rutgers Ocean Modeling Group Regional Ocean Modeling System ROMS forecasts for SW06

The ROMS forecast will be nested within the NRL NCOM ocean forecast, and forced with RU WRF high-resolution nested atmospheric model forcing

Observation links:

Surface current data from AVHRR sequence maximum cross correlations
(Ian Crocker, CU)

AVHRR satellite imagery for SW06
(Jen Bosch, RU-COOL)

Active Glider data

See the discussion of ocean synoptic conditions at: NJ Shelf blog

The ROMS Ocean forecast data will be accessible by OPeNDAP server. Contact John Wilkin if you wish to access data directly.

WRF meteorology data are also available via OPENDAP but access is restricted. Contact John Wilkin.

 

Ocean Model links:

ROMS 4DVAR assimilation analysis/forecast

 NCOM nest1 analysis/forecast results:

 

 

Forecast model configuration summary:

The Regional Ocean Modeling System (ROMS) SW06 model covers the Mid-Atlantic Bight from the center of Long Island southward to south of the mouth of the Delaware River, from the coast to beyond the shelf break and shelf/slope front.

The inner and mid-shelf domain coincides with the domain used for forecasting and analysis for the LaTTE program.

The prototype system is a 5-km horizontal, 30-level ROMS model with Incremental Strong Constraint 4DVAR assimilation of all glider observations (RU COOL), shipboard CTDs and XBTs of opportunity on the transit legs, scanfish profiles from RV Endeavor (Gawarkiewicz), underway thermosalinograph data from the first two RV Knorr legs, daily composite SST (RU COOL) and gridded altimeter SSH anomalies (AVISO).

Initial conditions were the Linder and Gawarkiewicz NJ shelf climatology adjusted by simple relaxation to the kinematic constraints of the model domain.

Meteorological forcing is NCEP/NAM 12-km 3-hourly forecast data.

Hudson River discharge is from daily average observations.

Tide boundary conditions are from the Oregon State OTPS harmonic analysis.

We assimilated data over 2-day intervals iterating the initial conditions to minimize the model-data misfit over each cycle. Each 2-day cycle begins with first guess initial conditions being the conclusion of the preceding interval.

Climatology was a poor estimator of the initial state in 2006 given the extreme precipitation and Hudson River discharge in mid-July. Assimilation results show the model quickly adjusts to in situ observations in the central SW06 region, influenced strongly by the low salinities observed by the gliders. However, in the absence of other data in the far field, the adjustment is unsatisfyingly local. Efforts to redress this bias will be pursued during future reanalysis.

As the model simulation proceeded, the salinity-corrected region advanced slowly northward and eastward consistent with the adjoint model propagating the model-data misfit information upstream. The barotropic transport of the shelf/slope front is not well constrained by the assimilation of predominantly temperature and salinity data from gliders, ships and satellites, arguing in favor of the value of complementary observing systems (CODAR, ship ADCP, moored current meters) to constrain ocean velocities.

Open boundary conditions are simple gradient conditions because the Orlanksi-type radiation conditions typically preferred in this type of application are not well-posed in the adjoint model formulation. Air-sea heat and momentum fluxes are calculated by the bulk formulae of Fairall et al. (1996,2002) using the model sea surface temperature and sea level air temperature, pressure, relative humidity, and 10-meter winds.

The inflow of the Hudson River is specified using a simple estimate computed as 2 times the sum of the daily mean observations at the Mohawk and Fort Edward USGS gauges. The Delaware River is included with a monthly climatological flow rate and the model solution for the Delaware should not be trusted.