Transcript ACRONYM Spell Out Full Name

Primitive equation models
These are the most sophisticated type of
ocean circulation model, including more of
the physics than the analysis systems and
shallow water equation models we have
discussed previously. While their increased
complexity makes them applicable to a
broader class of applications, and should
result in more accurate solutions, it can also
be more difficult to diagnose their behavior
and to understand how various model choices
affect the results.
Fixed Vertical Coordinates
• POM
• SWAFS
• POP
• NCOM
Lagrangian Vertical Coordinate
• NLOM
Hybrid Vertical Coordinate
• HYCOM
POM
Princeton Ocean Model
The first set of models we will examine
are based on the Princeton Ocean Model,
which was developed in the late 1970s
by Blumberg and Mellor (of Princeton
University), with subsequent contributions by other people. It is a very
widely used model, both for research and
operationally.
POM
http://www.aos.princeton.edu/WWWPUBLIC/htdocs.pom/
POM is a sigma coordinate, free surface,
primitive equation ocean model, which
includes a turbulence sub-model. The model
has been used for modeling of estuaries,
coastal regions and open oceans.
Physics
• It contains an imbedded second moment
turbulence closure sub-model to provide
vertical mixing coefficients. The turbulence
model does a reasonable job simulating
mixed layer dynamics, although there have
been indications that calculated mixed layer
depths are a bit too shallow (Mellor, 1998).
• Complete thermodynamics have been
implemented. (Mellor, 1998)
• The model has a free surface.
Grid and Coordinate System
• It is a  coordinate model (vertical coordinate is scaled
on the water column depth). The  coordinate system is
probably a necessary attribute in dealing with
significant topographical variability such as that
encountered in estuaries or over continental shelf
breaks and slopes. Together with the turbulence submodel, the model produces realistic bottom boundary
layers. (Mellor, 1998)
• Significant errors in the pressure gradient terms can
result when sigma coordinate models with insufficient
horizontal resolution are used with very steep
topography.
• The horizontal grid uses curvilinear orthogonal
coordinates and an "Arakawa C" differencing scheme.
(Mellor, 1998)
Time Step
• The model has a free surface and a split time step.
The external mode portion of the model is 2D and
uses a short time step based on the CFL condition
and the external wave speed. The internal mode is
three-dimensional and uses a long time step based
on the CFL condition and the internal wave speed.
(Mellor, 1998)
• The calculation of the 3D (internal) variables is
separated into a vertical diffusion time step and an
advection plus horizontal diffusion time step. The
former is implicit (to accommodate small vertical
spacing near the surface and bottom) whereas the
latter is explicit. (Mellor, 1998)
Boundary Conditions
• A number of different conditions may be
implemented along the open boundaries for the
external mode.
– Sea surface elevation
– Depth-integrated flow
– Radiation conditions
• There are also numerous options for the open
boundary conditions on the internal mode.
– Radiation conditions
– Advection of T and S
– Specified inflow
Forcing
•
•
•
•
Wind stress
Heat flux
River inflow
Tides
Output
• 3D fields of velocity, T, and S
• SSH
References
http://www.aos.princeton.edu/WWWPUBLIC/ht
docs.pom/
Mellor, G.L., Users Guide for a ThreeDimensional, Primitive Equation, Numerical
Ocean Model, Program in Atmospheric and
Oceanic Sciences, Princeton University,
Princeton, NJ, 1998.
MODAS/POM
MODAS Relocatable POM Model
Primary contacts: Dan Fox (NRLSSC);
Martin Booda (NAVO); Germana Peggion
(USM)
A relocatable version of the Princeton Ocean
Model which takes advantage of MODAS for
model initialization and data assimilation has
been developed at NRLSSC. This model has
been run operationally for a number of
domains. It is likely that in the future, NCOM
rather than POM, will be used for this
purpose.
MODAS/POM
http://www7320.nrlssc.navy.mil/modas/pom.html
• Provide short-term (2-day) forecast
• User-friendly interface
• Relocatable from deep to shallow, from open
sea to inlets
• Portability (toward PC)
• Primary clients: NAVO and Navy
operational units
Courtesy of Germana Peggion
Domain
• Fine resolution domains may be nested
inside coarser resolution domains.
• Domains in recent use include: Yellow Sea,
Arabian Gulf, Southeastern US, Strait of
Gibraltar, Taiwan Strait
• Establishment of new domains requires care
in picking boundary locations and specifying
other parameters.
• The number of domains in use is being
reduced over time with the expectation that a
new relocatable POM version, and
eventually NCOM, will be used in the
future.
Spatial Resolution
• User specifies the resolution in MODAS
• Current domains have resolution anywhere
from 0.5 km to over 20 km
• Default configuration has 25  levels in the
vertical
• User may specify up to 100  levels, and
how they are distributed in the water column
(as a percentage of depth).
Initialization
This version of POM can be initialized in various
ways using the information from the MODAS
analysis.
• Cold start: MODAS T and S grids, but not
geostrophic currents, are used.
• Diagnostic mode: POM is run for 1-2 days, holding
initial MODAS T and S fields constant so the
dynamic model develops its own currents consistent
with the user-supplied density field.
• Warm start: MODAS-estimated geostrophic
currents (default), or currents extracted from a
larger domain numerical ocean model, are used.
(Fox et al. 2002a)
• Presently, all but one POM
domains running at NAVO use
the North Pacific Ocean
Nowcast/Forecast System for
initialization.
• The area around Cadiz, Spain
uses the daily MODAS
analysis for initialization.
An example of regional finer resolution POM
models initialized from a coarser resolution basin
scale POM, North Pacific Nowcast/Forecast
follows.
NPACNFS consists of a data assimilative dynamic
ocean model based on POM, with 1/4o horizontal
resolution and 26 sigma levels in the vertical, the
MODAS 3D ocean temperature/salinity analysis, and
a real-time data stream from NRL/NAVO satellite
data fusion center and NOGAPS from FNMOC.
The North Pacific Ocean Nowcast/Forecast System
(NPACNFS) is an automated real-time ocean prediction
system for the North Pacific Ocean. It produces daily
nowcast/forecast sea level variation, 3D current, temperature
and salinity for the North Pacific Ocean.
Relocatable Princeton Ocean Model (POM)
(evolving to applying NCOM in this mode and within COAMPS)
Buoy
Gauge
26 km
6 km
1.5 km
Global NCOM provides boundary conditions for regional model which provides BC for local model
TIDE GAUGE: sea surface
elevation time series at tide
gauge station
BUOY DATA: comparison
of sea surface temperature
From Harding et al.’s 2001 GRC poster
Tidal heights
Grenoble
NRLPOM
Tide Station
Model salinity
Model vs Buoy
Surface Temperature
Boundary Conditions
• Radiation-like open boundary condition requiring
reference velocities.
• Reference velocity values are held constant during
the forecast.
• MODAS T and S are used to calculate baroclinic
geostrophic reference velocity.
• Barotropic reference velocity (transport)
is
derived from MODAS or a numerical ocean
model.
• Tidal heights (the same solutions from the
Grenoble tidal model as are used in PCTides and
ADCIRC) applied at open boundaries every
baroclinic mode time step
(Fox et al. 2002a)
Forcing
• NOGAPS or COAMPSTM winds
• Tidal forcing may be included as a
boundary condition. Product Info should
indicate whether or not tidal forcing has
been included.
Location: Strait of Gibralter
Type: Princeton Ocean Model
Description: Currents Surface Series (U)
POC: NAVO - Princeton Ocean Model Library Custodian
COMM: 228-688-5176 DSN: 828-5176 or E-mail Us
Update Cycle: 24 hour(s) Typical File Size: 35(K)
Level-of-Confidence: This product is unvalidated and fully beyond
the control of NMOC to ensure the quality of
the underlying data and/or availability of product.
Current File Statistics:
i.cadvelpom000_0000.gif Size: 48 (Kbytes) Last Update:
19-Jul-12:50 CDT (U)
ii.cadvelpom024_0000.gif Size: 51 (Kbytes) Last Update:
19-Jul-12:50 CDT (U)
iii.cadvelpom048_0000.gif Size: 56 (Kbytes) Last Update:
19-Jul-12:50 CDT (U)
Location: Taiwan Strait
Type: Princeton Ocean Model
Description: Currents over
Temperature Surface Series (U)
POC: NAVO - Princeton Ocean Model Library
Custodian
COMM: 228-688-5176 DSN: 828-5176 or
E-mail Us
Update Cycle: 24 hour(s) Typical File Size:
73(K)
Level-of-Confidence: This product is unvalidated
and fully beyond the control of NMOC to ensure the
quality of
the underlying data and/or availability of product.
Current File Statistics:
i.taivelsstpom024_0000.gif Size: 99
(Kbytes) Last Update: 19-Jul-13:06 CDT (U)
ii.taivelsstpom048_0000.gif Size: 95
(Kbytes) Last Update: 19-Jul-13:06 CDT (U)
Additional Information:
i.Product reflects geostrophic influence on
model. (U)
Additional Information:
ii.Product reflects wind-driven influence on
i.Product reflects geostrophic
model. (U)
influence on model. (U)
iii.Product reflects tidal influence on model. (U)
ii.Product reflects wind-driven
iv.Product does NOT reflect Sea Surface Height
influence on model. (U)
influence on model. (U)
iii.Product does NOT reflect
tidal influence on model. (U)
Data Assimilation
• Data assimilation is through MODAS, so in
areas where MODAS doesn’t use satellite
SSH, that won’t be in relocatable POM
either.
• No new data is assimilated during the
forecast.
Implementation
• Relocatable POM is included in the full
MODAS2.1 version (at NRLSSC) and
MODAS-Heavy (at NAVO). Presently it is
not implemented at any of the METOC
regional centers.
Output
• Nowcast, and 24 and 48 hr forecasts
• Velocity, T, MLD, critical depth, deep and shallow
sound channel axes, depth excess
• Depths for which V and T are shown vary by
domain
• Graphical format
• Animations (of the same 3 pictures as in series)
available for some domains
• No byte-encoded or wavelet compressed SV fields
• Some fields for some domains output for REACTs
(viewed with ArcExplorer)
Above is as of 7/19/02
Example Implementation
•Updates once per day.
•24 and 48 h forecasts.
•Currents, and currents over temperature, at
surface and selected subsurface layers are
displayed.
•Critical depth, shallow sound channel axis,
deep sound channel axis, depth excess, mixed
layer depth, sonic layer depth, and sea surface
temperature are output.
•Products may be output in graphical, ArcView
(for REACTS), EOF-compacted, NetCDF or
other formats
POM
Velocity scale arrow is same as in
Taiwan
Strait
Gulf of Cadiz
POM SST and Sfc. Currents Relative to Satellite SST
Unclassified NAVOCEANO MCSST
Arabian Gulf – Gulf of Oman
NAVO IR Composite 24 Feb98
Courtesy of John Harding, NRL-SSC
References
http://www7320.nrlssc.navy.mil/modas/
Fox, D.N., C.N. Barron, M.R. Carnes, M. Booda, G.
Peggion, and J. Gurley, The Modular Ocean Data
Assimilation System, Oceanography, 15 (1), 22-28,
2002a.