Use of Envisat RA2 sea level observations in the Bluelink ocean modelling system

Use of Envisat RA2 sea level observations in the Bluelink ocean modelling system David Griffin, Peter Oke and Madeleine Cahill. CSIRO Marine and Atmospheric

What is Bluelink? • Goal: An ocean forecasting system to meet the needs of the entire marine sector for timely and detailed information on the physical state of the ocean • sub-systems: • Assembly and processing of observations • Global ocean model • Limited-area model • Relocatable model • Littoral-zone model • Product delivery • A partnership of three Australian Government Agencies: Royal Australian Navy, Bureau of Meteorology and CSIRO. • (cf MyOcean) • A sustained effort: 2002-2006, 2006-2010, 2010-2013. ~$5M/yr Insert presentation title

The Bluelink global ocean model • OFAM1: An implementation of MOM4p1, with 0.1ºx0.1º resolution in Australasia, grading to 2ºx2º far away, eg Norway. • Is the basis of Australia’s national operational ocean forecasting system implemented at the Bureau of Meteorology • Assimilates altimetry, SST, Argo, moorings etc using Multivariate Ensemble Optimal Interpolation Insert presentation title

Multivariate Ensemble Optimal Interpolation • run model for ~15 years → large database of realistic ocean states (u,v,t,s,eta), a.k.a ‘the Ensemble’ • commence run of model with data assimilation: • every few days: • compute model difference from available observations (u,v,t,s,eta) • use the ensemble as a set of (multivariate) basis functions to project a sparse array of model-data misfits onto the full state space of the model • apply the corrections to the model in a way that minimises shocks • integrate model forwards to the end of the forecast → Observed sea level (altimetry), SST (IR imagery) and T,S (Argo) correct all model variables in a realistic way Insert presentation title

New version of data assimilating model: smaller SLA residuals than previous version R MSLA old (loose fit) |model-obs| new (tight fit) Insert presentation title

Insert presentation title

Despite tight fit, no obvious shocksNB sparsity of obs Insert presentation title

Around Australia in 4 years, comparing the model with un-assimilated drifters Insert presentation title

Median energy flux of ocean currents Insert presentation title

Finding WWII wreck AHS Centaur (in1400m, 50km offshore Brisbane) Insert presentation title

One day of good SST: model basically right Insert presentation title

More typical: fast laminar flow Insert presentation title

Sydney Morning Herald, 22 May 2010 Insert presentation title

Conclusions • Australians are intrigued by what they hear about the ocean, especially the East Australian and Leeuwin Current. • Mariners across the spectrum from industry to recreation are all seeing opportunities to optimize their day-to-day operations by using ocean observations and forecasts • In Australia we continue to use events like hunts for shipwrecks, or periods of extreme beach temperature anomalies, to educate the population about the nature of the ocean and how knowledge of the ocean is being increased by satellites like ENVISAT. • The present constellation, however, of three nadir-sampling altimeters is only barely adequate for sampling the rapidly changing conditions over the continental margin, where most users’ interest is focused. • As Johnny Johannessen said on Tuesday: we still have to tackle the sub-mesoscale. Insert presentation title

Thankyou • Acknowledgement: Bluelink is a big project. We thank all the other team members for their contributions. • We also thank the many people and agencies (ESA, EuMetSat, CNES, NASA, NOAA, Argo, Drifter program, ECMWF,…) responsible for the many data products we use. Insert presentation title

How rare is an eddy like that? Insert presentation title

Use of Envisat RA2 sea level observations in the Bluelink ocean modelling system