The Regional Ocean Forecast System (ROFS) has been developed jointly by
the Ocean Modeling Branch of the National Weather Service's
Environmental Modeling Center, the National Ocean Service's Coast Survey
Development Lab, Princeton University, and Naval Oceanographic Office
(NAVOCEANO). ROFS is based on a hydrodynamic, three-dimensional ocean
circulation model (Princeton Ocean Model) which simulates 
temperature, salinity, surface elevation, and currents for a region off
the U.S. East Coast from ~30 to 47N and out to 50W. The model is driven
at the ocean surface boundary by heat, moisture, and momentum fluxes
provided by NCEP's Eta mesoscale atmospheric forecast model. The ocean
model is driven along its open (i.e. southern and eastern) boundaries by
climatological estimates of temperature, salinity, and transport. The
spatial resolution of the model varies from approximately 20km offshore
to about 10km nearshore. The coastal boundary corresponds to the
location of the 10m isobath. In the vertical, an 18-layer sigma
(terrain-following) coordinate system is used with at least half the
layers concentrated in the upper 100m. Tidal forcing is included in the
model. 

At 24-hour intervals, Gulf Stream north-wall-location data and satellite
altimeter data are assimilated with an OI-based algorithm from Princeton
University. Gulf Stream location data are provided by NAVOCEANO and sea
surface height anomalies (SSHAs) derived from satellite altimeter data
are provided by the NOAA Laboratory for Satellite Altimetry. These data
are input for correction of the model's sea surface height field and
assimilation into the subsurface temperature and salinity fields using
correlation functions statistically derived from the model itself. Gulf
Stream location data for the current day and TOPEX data from the prior
10-day orbital cycle, are used in this analysis step, which provides the
input fields for the second analysis step. 

Sea surface temperature (SST) data from in-situ and satellite observing
platforms are assimilated into the updated fields from the first data
assimilation step, in a nowcast/data assimilation cycle producing
initial conditions for the 48-h forecast. In-situ observations are from
fixed and drifting buoys, C-MAN stations, and ships. Remotely sensed
observations are MCSST retrievals from the AVHRR sensor onboard the NOAA
polar orbiting satellites. Surface atmospheric forcing is obtained from
3-hourly analyses of the NCEP's Eta Data Assimilation System
(EDAS). 

The forecast cycle generates regional ocean forecasts out to 48 hours.
Surface forcing is obtained from the 3-hourly surface fields from NCEP's
Eta mesoscale atmospheric prediction model. [This abstract was obtained
from the ROFS website at
http://polar.wwb.noaa.gov/cofs/Description.html#OM on June 23, 2004.]