CSIRO provides a suite of regional ocean, atmosphere, wave and littoral zone modelling systems that enable high resolution forecasts in user-configured subdomains that are nested within the global model outputs.
The Relocatable Ocean Atmosphere Model (ROAM) is a user-driven relocatable local area model used for Defence and wider community applications. The ROAM suite includes ocean, waves, atmosphere and surf modelling tools. ROAM is designed to deliver forecasts out to a few days with horizontal scales down to ~2 km for relocatable regional domains within the Australasian region using boundary and initial conditions from global models.
The ROAM tools run on a CSIRO-supported platform and are configured through an intuitive web interface. The figure below illustrates the region selection and grid definition tool for the regional ocean model. The user graphically defines the region of interest and nominates a start time for the simulation; all other aspects of model initialization and execution are automated. The methodology used to achieve this is detailed in Herzfeld (2008).
ROAM provides atmospheric forecasts for applications that require high spatial or temporal resolution data (e.g., along coasts). These forecasts are typically between 4 to 7 days long and are initialised from the ACCESS global weather forecast model. ROAM-Atmosphere is based on the CSIRO-developed Conformal Cubic Atmospheric Model (CCAM) that uses a variable resolution global grid. This means CCAM can focus over a high-resolution region of interest, but still simulate the rest of the globe at lower resolution (see figure below). As a result, there are no simulation ‘errors’ that would otherwise arise at the boundary of the high-resolution simulation (e.g., for complex terrain on the boundary).
An advantage of the CCAM stretched grid approach is that once initialised, the model runs without the need for further forcing by the global parent model, dramatically reducing the ongoing data requirements relative to other models. This makes it particularly suitable in bandwidth-limited applications such as on-board vessels at sea.
CCAM encapsulates over 20 years of development and is used routinely by the RAN for operations and for other defence related applications requiring customised high-resolution forecasts. It has also been used for other applications including several Australian Olympic Sailing teams and research into extreme weather and climate change. The ROAM interface allows for configuring and running CCAM regional forecasts from a web browser. CCAM will automatically adjust model settings for different resolutions as this scale-aware behaviour is already required for the variable resolution grid.
The core part of ROAM is a regional-scale ocean model that enables an operator to configure a high-resolution hindcast or forecast for the open ocean or shelf seas. The model provides 3 dimensional representation of the key ocean variables within the region permitting understanding of the structures and phenomena that affect important aspects of navigation, acoustic operations, and even biological processes. An important feature of ROAM is that it includes barotropic tides, as well as inertial oscillations.
The ROAM-Ocean system builds the model grid, assembles the parent model inputs (from the Bureau’s operational system), organises the observations, initialises and runs the model, provides the user with progress status and delivers the forecast. The model captures the sub-mesoscale physics, including internal tides, fine-scale fronts and filaments, re-circulations around headlands, coastal sea-level, and coastal or open-ocean upwellings.
The ROAM-Waves tool uses the mature Simulating Waves Nearshore (SWAN) spectral wave model to provide information on sea state conditions. This includes information on wave development, propagation and breaking right up to the beach face at high spatial resolutions. In combination with ROAM-Atmosphere, it enables operational decision making and risk control for marine activities, such as small vessel operations and search and rescue.
A project is underway to develop marine biogeochemical modelling capability within the ROAM modelling system. It will provide a quantitative assessment of water clarity as well as the potential for light sources such as bioluminescence. ROAM-Biovis will be underpinned by a coupled hydrodynamic–BGC model.
Defence applications of regional modelling
The Royal Australian Navy operates in a complex environment, including ocean surface, the subsurface, and the atmosphere. Understanding that environment […]
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