The Bluelink ReANalysis (BRAN) is a multi-year integration of OFAM that assimilates observations using an Ensemble Optimal Interpolation (EnOI) data assimilation system called BODAS (Bluelink Ocean Data Assimilation System). The goal of BRAN is to provide a realistic quantitative description of the three-dimensional time-varying ocean circulation of all physical variables (temperature, salinity, sea-level and three components of velocity) for the last few decades.
Results from the latest Bluelink reanalysis – BRAN3 – are described in:
Oke, P. R., P. Sakov, M. L. Cahill, J. R. Dunn, R. Fiedler, D. A. Griffin, J. V. Mansbridge, K. R. Ridgway, A. Schiller, 2012: Towards a dynamically balanced eddy-resolving ocean reanalysis: BRAN3, Ocean Modelling, 67, 52-70, dx.doi.org/10.1016/j.ocemod.2013.03.008.
The following model runs without data assimilation (called spinup runs) and BRAN experiments have been performed:
- SPINUP1: based on OFAM1 – suffered from a warm bias and a trend that has been traced to an error in the surface fluxes.
- BRAN1p0: based on OFAM1 and the first version of BODAS – the first version of BRAN that assimilated along-track sea-level anomalies (SLA) from altimeters, in situ temperature and salinity (from Argo, XBT, TAO etc). BRAN1.0 spanned the period October 1992 to December 2004. Results from BRAN1p0 are described by Okeet al. (2005), and demonstrated the potential of the Bluelink system to realistically represent the mesoscale ocean circulation. BRAN1.0 suffered from a warm bias, as in SPINUP1.
- SPINUP4/5: based on OFAM1 – tuning of the mixed-layer scheme and corrections to the surface fluxes significantly improved the simulation compared to SPINUP1; the warm bias and trend were eliminated.
- BRAN1p5: based on OFAM1 and the second version of BODAS – the second version of BRAN assimilated along-track SLA, SST from AMSR-E and in situ temperature and salinity. BRAN1p5 spanned the period January 2003 to June 2006. BRAN1.5 realistically reproduced the mesoscale circulation around Australia with errors of ~5-10 cm for sea-level, ~0.6o for SST; <1o for sub-surface T and <0.15 psu for salinity. Results are described by Oke et al. (2008).
- BRAN2p1: based on OFAM1 and the third version of BODAS – used a similar configuration to BRAN1p5 that is described by Oke et al. (2008). BRAN2p1 also assimilated Pathfinder SST before 2002, when AMSR-E observations became available. Results from BRAN2p1 are described by Schiller et al. (2008).
- BRAN2p2: based on OFAM1 and the fourth version of BODAS – used a similar configuration to BRAN2p1, except in the way the model is initialised. The latest series of test runs use incremental analysis updating, where U, V, T, S and eta are explicitly updated over a number of time-steps. These experiments provide smooth, realistic fields that fit the observations better than all previous experiments.
- SPINUP6p8: based on OFAM2 – spanning 1/1992-12/2008.
- BRAN3p5: based on OFAM2 and version 8.2 of BODAS – spanning 1/1992-7/2012 – includes many changes to the model, the data assimilation, and the pre-processing of observations. Results are described by Oke et al. (2013). Compared to BRAN2p1, BRAN3p5 fits observations 10-30% closer.
BRAN1p0: Oke, P. R., A. Schiller, G. A. Griffin, G. B. Brassington 2005: Ensemble data assimilation for an eddy-resolving ocean model. Quarterly Journal of the Royal Meteorological Society, 131, 3301-3311.
BRAN1p5: Oke, P. R., G. B. Brassington, D. A. Griffin and A. Schiller, 2008: The Bluelink Ocean Data Assimilation System (BODAS), Ocean Modelling,21, 46-70,doi:10.1016/j.ocemod.2007.11.002.
BRAN2p1: Schiller, A., P. R. Oke, G. B. Brassington, M. Entel, R. Fiedler, D. A. Griffin, and J. V. Mansbridge, 2008: Eddy-resolving ocean circulation in the Asian-Australian region inferred from an ocean reanalysis effort. Progress in Oceanography, 76, 334-365.
BRAN3p5: Oke, P. R., P. Sakov, M. L. Cahill, J. R. Dunn, R. Fiedler, D. A. Griffin, J. V. Mansbridge, K. R. Ridgway, A. Schiller, 2012: Towards a dynamically balanced eddy-resolving ocean reanalysis: BRAN3, Ocean Modelling, 67, 52-70, dx.doi.org/10.1016/j.ocemod.2013.03.008.