BLUElink ROAM Project

SHOC is the hydrodynamic model implemented in ROAM (Relocatable Ocean and Atmospheric Model) as a component of BLUElink (www.cmar.csiro.au/bluelink/). ROAM is a tactical tool developed for the Royal Australian Navy to improve prediction of sonar range in the ocean and radar in the atmosphere. This model is coupled to the global ocean operational model OceanMAPS: (www.bom.gov.au/bluelink/products/prod_oceanmaps.html), operated by BOM (Bureau of Meteorology). OceanMAPS is a data assimilating, eddy resolving model with 10 km resolution in the region surrounding Australia. Atmospheric fluxes are supplied to the ocean model in ROAM by the relocatable atmospheric model RAMS (Pielke et. al., 1992). ROAM is designed to deliver forecasts out to 3 days for relocatable regional domains within the Australasian region (including New Zealand and Indonesia), down to scales of ~2 km using the OceanMAPS products as boundary and initial conditions. Furthermore, the system is to be operated by non-specialist users with minimum user input. The user graphically defines the region of interest and nominates that 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 is designed to deliver forecasts on a first-time-every-time basis; i.e. model instability and optimisation of model parameters via iterative simulations cannot be accepted. This makes the automated parameterisation of SHOC a challenge;  the model must be robust enough to deliver a stable simulation, but accurate enough to provide meaningful results. The open boundaries are particularly challenging in this regard, and alternative velocity forced boundaries in conjunction with a local flux adjustment have been developed, which appear superior to traditional radiating open boundary conditions. ROAM has been successfully trialled on numerous domains within the Australasian region (Figure 1). The added skill of ROAM in comparison to the global model is illustrated in Figures 2 and 3, where most of the added value is due to the inclusion of the tide in this case. The higher resolution used in ROAM results in the added spatial detail illustrated in Figure 4.

 

Figure 1 : Some resgions ROAM has been applied to.

 

Figure 2 : Surface currents and salinity comparison between OFAM and ROAM for the south-east Australian coast. OFAM (an implementation of the MOM4 ocean code) is the underlying global ocean model used in BlueLINK.

 

Figure 3 : Detail of the surface salinity comparison between OFAM and ROAM on the south-east coast of Australia.

 

Figure 4 : Surface temperature comparison between OFAM and ROAM on the North West Shelf of Australia.

 

Herzfeld, M. (2008) Improving stability of regional numerical ocean models. Ocean Dynamics, 59, 21-46. http://dx.doi.org/10.1007/s10236-008-0158-1

Pielke, R.A., Cotton, W.R. Walco, R.L., Tremback, C.J., Lyons, W.A., Grasso, L.D., Nicholls, M.E., Moran, M.D., Wesley, D.A., Lee, T.J., Copeland, J.H. (1992) A comprehensive meteorological modelling system - RAMS. Meteorol. Atmos. Phys., 49, 69-91.

 


 








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