Moana Project releases the Moana Backbone Model: A 25-year hydrodynamic hindcast model of New Zealand waters

The Moana team is pleased to announce the Moana Backbone Model: A 25-year hydrodynamic hindcast model of New Zealand coastal and shelf region is available to the public.

The Backbone is an improvement on MetOcean Solutions’ free-running Regional Ocean Modeling System (ROMS) simulation for New Zealand’s Exclusive Economic Zone. The model has high spatial resolution with horizontal resolution of approximately 5 km and 40 vertical layers, providing better representation of regional and coastal ocean processes.

MetOcean Solutions’ physical oceanographer leading the Moana Project modelling team, Dr João Marcos Souza, says advances were made in several fronts: updating the model physics; reviewing the parameterisations; improving the resolution; using a state-of-the-art vertical scheme; and upgrading the global model boundary forcing amongst others.

“In addition, with the support of project partner NIWA we were able to include climatological river fluxes and the inverse barometer effect.

“This configuration is now running to provide forecasts in Beta mode.”

Dr Ata Suanda, lecturer at the University of Otago, who has been working closely with MetOcean modelling team to validate the Moana Backbone output, says: “At the University of Otago, students and community partners are interested in understanding the coastal ocean (the region within ~10 km of the shoreline). This is the region where most of the public engages with the ocean, and it therefore holds high societal, economic and environmental value. 

“Our goal is to simulate coastal ocean processes at high spatial resolution. However, much of our understanding of coastal circulation and water quality depends on oceanic processes that occur at larger spatial scales. Without a high-fidelity nation-wide model, we will not be able to accurately simulate coastal areas. The Moana Backbone is a critical and exciting first step towards creating freely-accessible and reliable ocean forecasts for individual regions and individual communities around New Zealand.”

Daily-averaged sea surface temperature (SST) from Moana Backbone model. Black line denotes 250 m water depth. (Credit: Dr Ata Suanda, University of Otago).

Daily-averaged sea-surface current speed from Moana Backbone model. White line denotes 250 m water depth. (Credit: Dr Ata Suanda, University of Otago).

The next step for the Moana Modelling team is to include the assimilation of observations into the model to provide the best possible estimate of the ocean state - the Moana Forecast and Moana Reanalysis: A nation-wide open access coastal ocean data assimilation (25+ year hindcast) and forecast model to be released in 2020.

The reanalysis will be a vast improvement on the Moana Backbone by assimilating all available ocean observations with 4-dimensional variational data assimilation scheme. In its initial configuration, it will include the assimilation of all observations available in near-real-time. These include satellite derived sea surface temperature and sea level anomaly, and temperature and salinity profiles provided by the autonomous Argo floats. This will become a prototype for the Moana forecast system.

The Moana Backbone is part of the Ngā Ripo o te Moana research aim of the broader Moana Project. This workstream is developing advanced numerics to deliver NZ’s first nationwide, open-access, ocean modelling system. The improved model will support the understanding of ocean circulation and dynamics around New Zealand, including marine heatwaves.

The 25-year Moana Backbone model output is freely available. Please access www.moanaproject.org/data for more information.