an overview of nested regions using hycomhycom nesting in hycom • currently off-line • boundary...
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![Page 1: An Overview of Nested Regions Using HYCOMHYCOM NESTING in HYCOM • Currently off-line • Boundary info comes from archive files • Exact boundary condition for depth averaged (barotropic)](https://reader035.vdocuments.us/reader035/viewer/2022071410/61052f65d4605550722c6362/html5/thumbnails/1.jpg)
An Overview of Nested Regions Using HYCOM
Patrick Hogan Alan WallcraftLuis ZamudioSergio DeRadaPrasad Thoppil
Naval Research LaboratoryStennis Space Center, MS
10th HYCOM Consortium Meeting
COAPS, Florida State University, 7-9 November 2006
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Outline•Motivation
•Open boundary nesting techniques
•Different nested regions
•Need generic and accurate horizontal and vertical interpolation
•Need to cover wide range of flow regimes
East Asian Seas region – shallow isopycnalsJapan/East Sea – Intrathermocline EddiesGulf of California – sensitivity to BC paramsGulf of Mexico – cross-shelf exchangeCalifornia Current System – HYCOM-NCOM couplingNorwegian Coastal Current – buoyancy driven currentPersian Gulf – contaminant dispersion
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NavalGlobalOcean
Prediction
Navy Ocean Circulation PredictionExpected Evolution
1/32°NLOM, 1/8°NCOM
NavyCoastalOcean
Prediction
SWAFS, Relocatable NCOM, associated updates ??
HYCOM(Hybrid
Coordinate Ocean Model)
Through FY07 FY 08 & Beyond
HYCOM
NCOM
OPERATIONAL
ADCIRC
Note: Coastal component does not include nearshore environment
Boundary Conditions
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3.5 km East Asian Seas HYCOMNested inside 16 km North Pacific HYCOM
open boundaryconditions from 1/6°North Pacific HYCOM
Same vertical structure as Pacific Ocean model (20 layers)
HYCOM NESTING in HYCOMHYCOM NESTING in HYCOM
• Currently off-line • Boundary info comes from archive files• Exact boundary condition for depth
averaged (barotropic) component• Relaxation in buffer zone for T,S,P,u,v
Current Status of NestingCurrent Status of Nesting
Off-line:• Boundary information comes from
archive files• Updating frequency limited by
archive file frequency• Don’t need to know nest area in advance
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1/25° HYCOM East Asian Seas Model(nested inside 1/6° North Pacific Model
North-south cross-section along 124.5°E
Snapshot on Oct. 14
Isopycnals overshelf region
density frontassociated withsharp topo feature(can’t resolve withsigma coordinates)
red=eastward flowblue=westward flow
Yellow Sea flowreversal with depth
Snapshot on April 12
z-levels and sigmasover shelf and in mixed layer
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RMS error map (wrt Pacific model over GoC domain)
Time series of domain-wide RMS error
Same geometrySame horz. res.Same vert. res.
Barotropic BCS are updated every 1-dayBaroclinic BCS are updated every 6-day 10 grid-point wide relaxation zone1-10 day relaxation e-folding time
Starting Point
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Sensitivity to:Updating frequency
3 hours, 1, 2, 4, 6 days
10 grid-point1-10 e-foldingBarotropic + baroclinic
E-folding time in BZ
1-10, 1-5, .1-1, .1-.5, .1-.2
10 grid-point3 hoursBarotropic + baroclinic
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Sensitivity to:
Barotropic/baroclinic mode Width of buffer zone
Barotropic or baroclinic only
10 gridpoints0.1-1.0 e-folding3 hourly
1,2,3,4,5,10 grid-point
3 hourly0.1-1.0 e-foldingBarotropic + baroclinic
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Lowest Error Nesting Parameters
Time series of domain-wide RMS errorRMS error map
10 grid points.1-1 day e-folding3 hour updatingBaroclinic+barotropic
*
Mazatlán
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Noto Pen.
Oki Spur
Japan Basin
Subpolar Front
EKW
C
Tsushima Warm Current
Tsushima Strait
Soya Strait
TsugaruStrait
NKCC
Lim
anCu
rrent
Ulleung eddy/basin
15 layer 1/25° Japan/East Sea HYCOM
Mean Sea Surface Height
2 Sverdrup barotropic straits forcingRelaxation to climatology for baroclinic part
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Observed JES Intrathermocline Eddies (Gordon et al., 2002)
May 1999 January 2000
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Intra-ThermoclineEddies
NotoPeninsula
Oki Spur
Layer thickness between the 8°-11° isotherm
Location of JES Intrathermocline Eddies (Gordon et al., 2002)
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33.5 33.6 33.7 33.8 33.9 34.0 34.1 34.2 34.3 34.4 34.5
4(a)January
4(b)March
4(c)May
4(d)July
4(e)September
4(f)November
Layer 6 salinity (color) and layer 7 thickness
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5(a)Jan.
Temperature (°C)
salinity salinity
Temperature (°C) temperature (°C)
salinity salinity
salinity
5(b)Mar.
5(c)May
Temperature (°C)
5(d)Jul.
5(e)Sep.
5(f)Nov.
Temperature (°C) Temperature (°C)
salinity salinity salinity
0 2 4 6 8 10 12 14 16 18
Temperature (°C) Salinity (PSU)
33.7 33.9 34.1 34.3
0 m
500 m
1000 m
1000 m
1000 m
1000 m
500 m
500 m
500 m
0 m
0 m
0 m
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1000 m
January 04 temperature along 131.7°E
6(a)
1000 m
January 04 salinity along 131.7°E
6(b)From Gordon et al. (2002)
Secondary JES ITE Formation Mechanism:Frontal subduction along the subpolar front
1/25° JES HYCOM
Hogan and Hurlburt (2006)
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20 layer 1/25° Gulf of Mexico Model (~4 km)
Method of Characteristics usedTo update the barotropic mode
20 gridpoint buffer zone for baroclinicmode with e-folding time .1 to 10 days
Atlantic boundary data provided daily
Open boundary locations
Bathy from NRL-DBDB2
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Sensitivity of boundary forcing updating
Climatologicalforcing
1-day forcing
Monthly climatology formed from 1-day archives
Allows for long-term integrations over any timeframe
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1/25° (~4 km) Nested Gulf of Mexico
SSH
SST
Lots of cycloniccold core eddies(impact of 2x res.)
Local upwelling
Snapshot of SSHand SST on June, 13
2000
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Global NCOMto
CCS NCOM
PAC HYCOMto
CCS NCOM
PAC HYCOMto
CCS HYCOM
(σ-z) to (σ-z)
(σ-z-ρ) to (σ-z)
(σ-z-ρ) to (σ-z-ρ)
Vertical Remapping and Nesting Different Ocean Models
1/8°-1/12°
1/12°-1/12°
1/12°-1/12°
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NCOM CCS 9 km
NCOM-NCOM 1-4 km
NCOM-NCOM 0.5-1.5 km
Triple nesting in the California Current System
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1 km Persian Gulf HYCOM
•Boundary conditions from 1/12° Global HYCOM
•Includes rivers, bottom boundary layer
•Requires remapping from σ2000 to σθ
unclassified
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1 km Persian Gulf HYCOM
Surface Temperature Surface Tracer
Forced with 0.5° NOGAPS and lateral boundary conditions from 1/12° Global HYCOM
unclassified
Besheur*
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Summary and Future Plans
• Add wetting and drying (inudation) capability to HYCOM• Add tidal forcing to standard version• Improve river plume dynamics• More quantitative HYCOM-NCOM-Observations comparisons• Evaluation of nested boundary placement (on or off-shelf)• Implementation and evaluation of other boundary conditions• Additional evaluation of coastal HYCOM
• A Robust capability exists for nesting HYCOMwithin HYCOM and HYCOM within NCOM
• Sensitivity studies reveal the most accurate nesting params• HYCOM successfully simulates JES Intrathermocline eddies• HYCOM successfully simulates Loop Current eddy shedding
Future Plans
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Supplemental Slides Follow
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July 27, 20001/25° Nested Gulf of Mexico HYCOM
Initial eastward along-shelf break currentin geostrophic balance
Barotropic u-velocity Barotropic v-velocity
red=east blue=west red=north blue=south
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August 12, 2000 (+ ~2 weeks)
1/25° Nested Gulf of Mexico HYCOM
A reversal in the barotropic currents triggers a transition of the along-shelf break currents to flow onto the shelf
red=east blue=west red=north blue=south
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August 18, 2004 (+ ~1 week)
Significant cross-shelf flow exists after the reversal
1/25° Nested Gulf of Mexico HYCOM
red=east blue=west red=north blue=south