Modelling

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Global Environmental Modelling Systems

Expertise in the development and application of high-resolution computer models to realistically predict atmospheric and oceanographic behaviour in riverine, coastal and oceanic settings.

GEMMS applies this expertise to a wide range of marine issues:

3D Ocean Modelling Studies

The GEMMS Coastal Ocean Model:GCOM3D was developed for the simulation of ocean circulation and sea level variation under ambient and extreme weather conditions.
GCOM3D was first developed by Dr Hubbert in the early 1980s and was the first 3D ocean model to be used for ocean discharge studies in Australia (Geelong Ocean Outfall, 1984).

GCOM3D has been validated extensively in many verification studies (particularly by the Australian Maritime Safety Authority and the major oil companies) and has gained wide acceptance for accurate modelling of coastal ocean currents and tides. GCOM3D has also undergone a wide range of testing by the U.S. Navy Research Laboratories, which uses the model as part of their ocean forecasting system.

GCOM3D is an advanced, fully three-dimensional, ocean-circulation model that simulates horizontal and vertical ocean or river circulation due to wind stress, atmospheric pressure gradients, astronomical tides, quadratic bed friction (as a function of bed type) and ocean thermal structure. The system will run on Windows or UNIX platforms. GCOM3D is a fully functional anywhere in the world using tidal constituent and bathymetric data derived from global, regional and local databases. The model scale is freely adjustable, and nesting to any number of levels is supported in order to suit the complexity of the physics of the study area. As the model is fully three-dimensional, output can include current data at any or all levels in the water column. A 2-dimensional version of the model that includes a stable flood/tidal inundation algorithm is also available to simulate storms surges and inter-tidal behaviour in coastal and river systems. The model can be used for simulations under seasonal, real time, or extreme weather conditions.

GCOM3D has been used in a wide range of ocean environmental studies including prediction of the fate of oil spills, sediments, hydrotest chemicals, drill cuttings, produced formation water and cooling waters as well as in other coastal ocean modelling studies such as storm surges and search and rescue.

Example of the GCOM3D simulation of the flood tide moving onto the North West Shelf of Australia

  • Forecasting, now-casting or hindcasting ambient and extreme water currents and sea levels (eg. for advice to maritime operations or for return-period calculations);

  • Determining affects of proposed river or coastal modifications;

  • Determining affects of seasonal wind conditions on circulation;

  • Specification of ambient and extreme currents for the design of surface and undersea facilities;

  • Development of criteria for the design of undersea pipelines for stability and fatigue analysis;

  • As input to modelling the fate of spills, leaks, discharges and other marine discharge activities.

Environmental forcing for GCOM3D includes input of winds, tides and geostrophic currents (subject to applicability). The wind input may be single station or gridded winds from numerical weather prediction models. GEMMS strongly recommends that close attention be paid to the analysis of environmental forcing, as the results of any plume modelling will not be usable if the model is subjected to incorrect meteorological or oceanographic data.

Discharge Modelling

GEMMS have the expertise in modelling the transport, settlement and resuspension of conservative particles, such as sediment or other inert material.

GEMMS uses its three dimensional ocean model, GCOM3D, and its associated 3D plume model PLUME3D to assess the fates of the discharge. GCOM3D has been extensively tested across a wide range of applications on the North West Shelf and throughout the world.

PLUME3D is the integrated, high-resolution 3D dispersion model developed by GEMMS for modelling a wide variety of discharge materials including sediments, sewerage, thermal discharges, oils and chemical releases. Our oil spill prediction model, OILTRAK3D, is a sub-model of PLUME3D.

PLUME3D can be used stochastically to simulate a large number of random events over time or can be used for specific case studies. Again, the selection of the forcing for the case studies needs to be carefully considered.

The model suite quantifies the distribution of each substance spilled or released under controlled conditions. The model reports mass and concentration levels on the water surface, on shorelines, in the sediments or through the water column as required. Horizontal and vertical cross-sections are available to better illustrate the three dimensional distributions. Where multiple chemical constituents are involved, the model can report the distribution of each constituent individually.

Example of the discharge plume dispersion simulations with PLUME3D at Palm Island, Jumeirah in Dubai, UAE

  • Forecasting, now-casting or hindcasting ambient and extreme water currents and sea levels (eg. for advice to maritime operations or for return-period calculations);

  • Determining affects of proposed river or coastal modifications;

  • Determining affects of seasonal wind conditions on circulation;

  • Specification of ambient and extreme currents for the design of surface and undersea facilities;

  • Development of criteria for the design of undersea pipelines for stability and fatigue analysis;

  • As input to modelling the fate of spills, leaks, discharges and other marine discharge activities.

Environmental forcing for GCOM3D includes input of winds, tides and geostrophic currents (subject to applicability). The wind input may be single station or gridded winds from numerical weather prediction models. GEMMS strongly recommends that close attention be paid to the analysis of environmental forcing, as the results of any plume modelling will not be usable if the model is subjected to incorrect meteorological or oceanographic data.

Oilspill Modelling

Dr Graeme Hubbert first began to provide ocean modelling and oil spill risk assessment services to the Australian oil industry in 1991 in response to the need for accurate ocean prediction.
Oilspill Risk Assessment on the North West Shelf of Australia 3Oilspill Risk Assessment on the North West Shelf of Australia

Example applications include:

  • Emergency oil spill trajectory and fate modelling;

  • Quantitative risk assessment for oil spills, as contingency planning for environmental risk assessment;

  • Modelling the fate of drilling mud, produced formation water, hydrotest water and other discharges from oil and gas facilities;

  • Backward trajectory modelling to define source locations of oil-slicks, flotsam and jetsam;

  • Modelling the fate of particles contaminated by hyrdrocarbons, pesticides, metals or radionuclides(eg NORMs);

  • Defining the most probable, and potential paths of larvae from and to defined locations(eg to define upstream and downstream locatons during defined seasons);

  • Defining residence times, flushing, sand scouring or deposition under existing or modified conditions (eg. for investigations of affects of channel dredging, port developments, or river and coastline modifications);

  • Modelling the fate and effects on water quality of sewage, process water or other contaminated inputs from point and diffuse sources.

  • Investigating affects on water quality from proposed or existing developments;

  • Determining sources of water quality pollutants (eg. nutrients, biological oxygen demand, turbidity, enteric bacteria).

Impact Probabilities determined by OILTRAK3D from a deep water well head blowout off North West Cape in Australia

Tide and River Flood Modelling in Coastal River Systems

Until recently, river flow and river flood modelling has been carried out with one dimensional (1D) finite difference models with analytical algorithms included to represent the flow through structures (bridges etc.). The most popular 1D model has been MIKE-11 from the Danish Hydraulics Institute (DHI). This model is used extensively around the world for river modelling for purposes such as town planning, building design, flood mitigation, sedimentation and water quality studies. However, 1D models have severe limitations as they do not represent the flow of water realistically. For this purpose GEMMS have developed an advanced 2D coastal and river flood model that simulates river flow and floods more realistically and uses high resolution graphics to better understand flow conditions.

Example applications include:

  • Investigations of flooding potential under joint probabilities of tidal and river flow conditions;

  • Investigating implications for flooding potential due to coastal, river or floodplain development;

  • Calculations of return periods for storm-induced flooding heights.

GCOM3D simulation of the ebb and flood tide in the Thames River in the region of the storm surge barrier downstream from London

Wave Studies

GEMMS have the expertise in the setup and the running of the third generation spectral wave model, WAM (Max Planck Institute). This model can be operated at variable resolution so as to capture broad-scale ocean wave energy as well as local shallow-water effects such as wave refraction and shoaling. It can be driven by synoptic scale winds derived from a range of dynamic atmospheric models or by analytical models, such as the GEMMS tropical cyclone model.
GEMMS have used the wave model in several environmental and design studies around the Australian coast. Wave model output has also been used to determine wave-induced currents over submarine pipeline routes. This has included calculation of along pipeline variation of current forces due to crest length reduction.

The GEMMS Wave Modelling System using GCOM3D and the SWAN Wave Model

Dredging Simulations

Once the physical oceanography has been simulated it is possible to study the movement of discharges into the water column (e.g. sediments, chemicals etc.) or components of the water body itself (flushing rates of harbours, bays etc.).
The GEMMS 3D Dredge Simulation Model (DREDGE3D) is used for simulating the specific fate of particles discharged during a dredging program. This model inputs the physical environmental data from GCOM3D, together with wave data from SWAN and meteorological data, to simulate the movement and deposition, of suspended particles in the water body across the study area.

DREDGE3D was used with great success in the Geraldton Port Redevelopment Project where it was compared with in-situ data, aerial photographs and satellite images.

In the past 3 years since the dredging of Geraldton Port, DREDGE3D has been used in Mermaid Sound for both the Dampier Port Authority and the Hammersley Iron port expansion projects, Chevron Gorgon dredging at Barrow Island, two projects in Queensland, several developments in the United Arab Emirates and in New Caledonia for the INCO nickel processing plant and port development.

Storm Surge, Tide and Coastal Flood Modelling

GEMMS has developed a numerical modelling system to study and predict storm surges and the resulting coastal flooding that could be expected during the passage of severe weather events such as tropical cyclones, cold fronts and other strong wind events. Atmospheric forcing is derived from the GEMMS Mesoscale Atmospheric Prediction System (MAPS) or from a tropical cyclone model. The GEMMS tides and storm surge inundation model is based on the storm surge model described in Hubbert et al (1990,1991) and in Hubbert and McInnes (1999). GEMMS have applied the storm surge system and methodology to a large number of locations around Australia (Port Hedland, Karratha, Cape Lambert, Derby, Onslow, Dampier, Cairns, Gold Coast, Darwin, Mornington Island, Port Phillip Bay).

Severe Tropical Cyclone Vance 1999

GEMSURGE simulation of TC Vance flooding at Onslow (max height of 3.3m agreed exactly with Tide Gauge)

Search and Rescue

GEMMS developed the AMSA Search and Rescue prediction software, known as Net Water Movement (NWM). NWM was first installed and became operational in 1998 and consists of:
1) GCOM3D (the GEMS 3D Coastal Ocean Model) which predicts ocean currents based on the following inputs:

  • Marine meteorology data from the operational Australian Bureau of Meteorology (BoM) forecast models, downloaded to AMSA twice daily

  • Large scale ocean currents from the joint BoM and CSIRO OceanMaps model (Bluelink)

  • Tidal data in the AMSA region from extensive tidal modelling carried out by GEMS

  • Bathymetric data from GEBCO, Geosciences Australia and other data sourced by GEMS

2) SARTRAK (the GEMS Search And Rescue Track prediction software) which predicts the search area based on a stochastic simulation of tracks which incorporates:

  • Currents from GCOM3D

  • Winds from the BoM forecast models (for leeway calculations)

  • Leeway data for different objects from the US Coast Guard studies

  • Estimate of splash down location

  • 1000 simulations randomly selecting reasonable errors on all major inputs (current speed/direction, wind speed/direction, splash down location, splash down time etc.).

SARTRAK prediction of search area for 4 young men found off Queensland in June 2015

In the 16 years since NWM became operational it has been used almost daily for search and rescue operations conducted by AMSA. The difference between the MH370 search and normal NWM operations are significant however and required deeper investigations, namely:

  • The search was in deep waters in the Indian Ocean and not on the continental shelf where most AMSA searches are conducted;

  • The duration required for the prediction of the path of drifting debris increased to well beyond the normal period needed by AMSA (2-3 days);

  • As a result of the search location being so far out in the Indian Ocean the tidal forcing would have a minimal contribution to the drift path of debris and the major contribution would come from the geostrophic and wind driven currents;

  • Therefore the main contribution to the prediction of drift paths was coming from Bluelink and the BoM atmospheric forecast model (acces_r for that region);

10 month prediction by SARTRAK of the potential fate of MH370 wreckage from the designated splash down region

Atmospheric Circulation

GEMMS have developed the Mesoscale Atmospheric Prediction System (MAPS) as a relocatable model that can be applied anywhere in the world. MAPS is a high-resolution, fully three-dimensional, atmospheric model. The scale of the model can be varied to address both regional and local scale conditions. Outputs can be predicted at all altitude levels of the model and can include wind speeds and directions, atmospheric pressure, water content, density and temperature. Outputs from the model can be used as input to the GEMMS oceanographic models for real-time or historic scenarios. For various weather dependent assessments, GEMMS have applied the model to reproduce monsoonal and other seasonal conditions or to reproduce specific weather events. After rigorous testing worldwide, the United States Navy have purchased MAPS as part of their real-time weather prediction system.

Example applications include:

  • Ambient wind field analysis;

  • Vertical wind profile analysis for structural design;

  • On site prediction of marine winds, waves and wind-inducement to currents (eg. the system was used for the past two America’s Cups and several Sydney to Hobart yacht races. The United States Navy apply the system for real-time wind forecasting)

  • Forecasts, now-casts and hindcasts of historic and extreme weather conditions as input to other atmospheric and ocean circulation studies.

Simulation during the 1991 America’s Cup Challenge of the coastal eddy in the San Diego region

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This Sliding Bar can be switched on or off in theme options, and can take any widget you throw at it or even fill it with your custom HTML Code. Its perfect for grabbing the attention of your viewers. Choose between 1, 2, 3 or 4 columns, set the background color, widget divider color, activate transparency, a top border or fully disable it on desktop and mobile.