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Aquatic Sciences. Application of ROMS for the Spencer Gulf and on the adjacent shelf of South Australia. Carlos Teixeira & SARDI Oceanography Group. 2009 ROMS/TOMS Asia-Pacific Workshop. Wintertime Outflow of Spencer Gulf. - PowerPoint PPT Presentation
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Application of ROMS for the Spencer Gulf
and on the adjacent shelf of South Australia
Carlos Teixeira & SARDI Oceanography Group
Aquatic Sciences
2009 ROMS/TOMS Asia-Pacific Workshop
Wintertime Outflow of Wintertime Outflow of Spencer GulfSpencer Gulf
Contours of near-bottom salinity (16-23 June 1986. Lennon et al. 1987)
During winter, the gulf waters are cooled and become denser than the shelf waters. This dense water flows out to the adjacent shelf.
Sea Surface Temperature from satellite measurements
Summertime OutflowSummertime Outflow
During summer, the gulf waters become denser due the evaporation, but the upwelled waters in the shelf block the gulf outflow.
SAIMOS
• To monitor and better understand the gulfs and shelf circulation, $6.5M invested in the Southern Australian Integrated Marine Observing System.
Planned Planned SAIMOS SAIMOS Infrastructure:Infrastructure:
Shelf/Slope Moorings
Reference Station
• Monthly CTD Stations for 2 years
HF Radar
PLUS
• Gliders
The data will be used to initialize, force and validate the hydrodynamic/bio-geochemical model for the region.
What modelling we intend to do?
• Idealized forcing to better understand the fundamental physics of the circulation within the Spencer Gulf (my PhD thesis)
• Hydrodynamic/ Biogeochemical model for the Spencer Gulf and adjacent shelf
Tides
• Barotropic Experiment
• OTPS / TP07.1 tidal forcing
• Free surface CHAPMAN BC
• 2D Momentum FLATHER BC
• Bottom Friction:– Linear– Quadratic– Logarithmic
Grid and Validation
Spencer Gulf
San Vincent
Gulf
• 3 x 3 Km grid• Amplitudes and Phases compared with Australian National Tide Tables
Amplitudes M2
West Coast
East Coast
San Vincent GulfSpencer Gulf
Phases M2
West Coast
East Coast
San Vincent GulfSpencer Gulf
Summary:• Best results with Quadratic Law scheme for Bottom friction. • Good agreement with ANTT in the stations outside the gulfs• Reasonable inside the Spencer Gulf • Poor inside San Vincente Gulf
Next Steps:• Nested model for gulfs using a high resolution grid
• Assimilation of SSH data inside the gulfs?
Local vs Remote wind?
Remote Wind =
Coastal Trapped Waves
Local
Wind
• 5 x 5 Km uniform grid• 20 Sigma levels • Analytical initial values for temperature and salinity
Same vertical profile everywhere (no horizontal gradient).
• Free surface CHAPMAN BC• 2D Momentum FLATHER BC• Gradient BC for 3D momentum and tracers• Tangent RADIATION_2D and Sponge area used in
the eastern boundary• Mellor and Yamada 2.5 turbulence closure method • 3rd-order upstream horizontal advection• 4th-order centered vertical advection
Remote wind
– Mode 1 CTW cross-shelf eigenfunction determined for the western boundary topography (Brink and Chapman,1985).
– Eigenfunction used to create SSH and external
velocities in the western boundary (Paddle).
Remote Wind – CTWResults
Paddle
Sea Level
Paddle
External Velocity
Local wind– 10 days oscillatory zonal and meridional
wind Stress (0.1 Pa)– Wind Stress tapered to the gulfs area
17.5 Days
Wind Stress
Local Wind – Cross ShoreResults
Sea Level
1
2
3
External Velocity
Diagnostics
4
7
9
COADS Wind Forcing
• Model forced with COADS monthly winds for 1 year;
• Passive Tracers used to study the connection between the Gulfs;
Summary from Wind Model• ROMS model with analytical initial conditions and
forcing was very valuable to better understand the circulation within Spencer Gulf
• Remote winds will be unimportant to the circulation within the gulfs;
• Local winds will generate a weak circulation in most
part of the gulf, with the exception of shallow areas;
• There is a strong transport from the SG to the SVG,
but not from SVG to the SG.
Next Steps….
• Use Met Stations and local atmospheric model data for better represent the wind stress inside the Gulfs and compare the results with SAIMOS data;
Summer Scenario:
• Initiate the model with realistic data and atmospheric forcing to try to reproduce summer scenario.
Thank you!