Bluelink ocean forecasting session

Dr Edward King1, Commander Barbra Parker4, David Griffin1, Madeleine Cahill1, Emlyn Jones1, Ron Hoeke2, Stephanie Contardo3, Paul Branson3, Tracey Pitman1, Matthew Chamberlain1, Peter Oke1, Uwe Rosebrock1, Simon Pigot1, Gary Carroll1, Gary Brassington5, Pavel Savov5, Prasanth Divakaran5, Xinmei Huang5, Aihong Zhong5, Mirko Velic5, Justin Freeman5, Russell Fiedler1, Andy Hogg6, Andrew Kiss6

 

1CSIRO O&A, Hobart, Australia, 2CSIRO O&A, Melbourne, Australia, 3CSIRO O&A, Perth, Australia, 4Royal Australian Navy, Sydney, Australia, 5Bureau Of Meteorology, Melbourne, Australia, 6Australian National University

Bluelink is an ocean forecasting partnership between the Bureau of Meteorology, CSIRO, Department of Defence, and other collaborating partners. Its goal is to “Develop and maintain world-leading global, regional, and littoral ocean forecast systems to support Defence applications and maintain a national ocean forecasting capability for Australia.”.

 

The new Bluelink Strategic Plan to 2025 will be introduced at the start of the session. This will be followed by talks on key components of Bluelink most relevant to Australian operational oceanography i.e. global ocean forecasting (OceanMAPS), the relocatable model (ROAM), littoral forecasting, data assimilation, and downscaling.

 

The Bluelink global forecasting capability supports a category one operational system at the Bureau of Meteorology that delivers services for a range of national applications. Sustaining an internationally competitive performance from this capability into the future will require national and international collaboration to tackle the next generation developments. The current forecast system, the Ocean Model, Analysis and Prediction System (OceanMAPS) version 3.1 has been developed through successive Bluelink projects. A next generation global ocean forecast system (OceanMAPS version 4) is under development with a target for operationalization in 2020. A gap in the national operational ocean forecast service resides in finely resolved regional and coastal modelling. Some progress has been made for the majority of the Australian coastline with state-based modelling systems. Recent projects have examined the feasibility of downscaling the global system to finer scales (e.g. 1/50° resolution). With the OceanMAPS global capability maturing into an internationally competitive system, and the downscaled forecast systems achieving genuine performance gains, opportunities arise for the uptake of these products by a broader range of stakeholder applications as well as their adoption by downstream service providers and the Australian research community.

 

The Relocatable Ocean-Atmosphere Model is the component of Bluelink that sits between the global models and the littoral models, in terms of spatial and temporal scales. ‘Relocatable’ means that instead of being set up and optimised for some fixed geographic domain, ROAM can be set up wherever the user wants. In this talk, we focus on the important question of how accurate and/or realistic the simulations are, by comparing them to a wide range of IMOS observations, including various quantities recorded by gliders, moored ADCPs, Argo floats and HF radars. A particular focus is ROAM’s ability to simulate the depth of the mixed-layer, because of this quantity’s importance to 1) sound propagation in the ocean, and 2) the vertical mixing of heat, nutrients and phytoplankton near the surface of the ocean.

 

Shortcomings in littoral forecasts are being addressed so as to improve their accuracy and usefulness. Here, we present an overview of past and ongoing efforts, which fall primarily into three categories: the development of value-added forecast products; improvement of numerical prediction models and their interconnectivity; and development and ingestion of emerging data sources. In particular the recent expansion of high-resolution, (relatively) cost-effective coastal remote-sensing technologies holds significant promise to improve and inform all three categories.

 

Bluelink Reanalyses (BRAN) continue to developed and run for the ocean around Australia and the world at 0.1 degree resolution, assimilating observations such as sea surface temperature, sea level anomalies and Argo profiles of temperature and salinity. Data assimilation (DA) at multiple spatial scales is being explored as a way to improve the efficiency of the system to correct large features (diameters of several hundred km) in the deep ocean. High-resolution (0.1 degree) ocean background states are averaged onto a coarse 1-degree grid, reducing the mesoscale variability in the state. The initial DA cycle uses a coarse ensemble that has larger spatial correlation patterns. The second DA cycle is at high-resolution, based on BRAN_2015. Increments from both the low and high-resolution DA cycles are used to update the ocean state. Initial results show this approach reduces innovation errors in analysis and forecasts, especially in the deep ocean.

 

A system for automatically configuring and executing a model to predict the past, present, or future state of the ocean developed under Bluelink. This Bluelink Modelling Framework (BMF) makes it feasible to configure and execute high-resolution regional models anywhere in the world at a moment’s notice. It runs on small scale desktop or laptop and HPC environments alike, deploys execution and services into the ‘cloud’ and has a distributed service-driven architecture. Ongoing development is increasing support for more use cases and a wider range of end-user and client needs. This includes an increasing number of domains and model choices, such as relocatable atmospheric downscaling and wave modelling.

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