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ECMWF update 2011-2: NEMOVAR

ECMWF update 2011-2: NEMOVAR. ORA-S4 (Ocean Re-Analysis System 4) implemented operationally Based on NEMO/NEMOVAR ORCA1 configuration It provides initial conditions for EPS and Seasonal. Value for climate: Ocean Re-analysis, initialization of decadal forecasts by EC-EARTH Validation of ORA-S4

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ECMWF update 2011-2: NEMOVAR

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  1. ECMWF update 2011-2: NEMOVAR • ORA-S4 (Ocean Re-Analysis System 4) implemented operationally • Based on NEMO/NEMOVAR ORCA1 configuration • It provides initial conditions for EPS and Seasonal. Value for climate: Ocean Re-analysis, initialization of decadal forecasts by EC-EARTH • Validation of ORA-S4 • Can we learn any lessons? Is there room for improvement? • What is the value of the assimilation? [ OSES, comparison with CONTROL] • Identifiy and Assess robustness of climate signals • Ocean Heat Content, Thermocline trends, MOC variability • The heat budget in NEMOVAR. • Dissemination of Results • Web Pages for ORAS4. Almost there http://www.ecmwf.int/products/forecasts/d/charts/oras4/reanalysis/ • Report (tech-memo): description and summary of performance. Ongoing • Maybe some papers. Abstract to WCRP conference on reanalysis • Data in community servers (EasyInit). To do • Several data requests already. ”

  2. ORAS4: 5 ens members 195709 to present • Other information • Bias correction scheme estimated from Argo Period. • Delayed reanalysis suite and real time suite

  3. Assessment of ORAS4 • Fit to assimilated data: Improvement. Importance of bias correction. • Comparison with independent data: • Velocity: Improvement in general, but not always. • Success stories: Eastern Pacific, Atlantic • No so successful: Central/West Pacific, Upper Indian Ocean. • MOC: Degradation of Florida Strait current. • Time variability • Comparison with SL altimeter: Improvement in general. • Problems with the Mediterranean Outflow?? TO BE DIAGNOSED farther • Comparison with OSCAR currents: Improvement • Impact on Seasonal Forecasts: Improvement • Aspects that need improvement • Covariance estimation: spatial and time dependence. Assim near coast (MOC) • T/S balance (Mediterranean Outflow) • Altimeter assim (Better tuning of Unbal eta, include Sunbal) • More diagnostic tools required: Balanced and unbalanced increments.

  4. Fit to Observations Temperature • Assim shows better fit than Control • Error decreases with time in both, indicative of improvement of forcing fluxes. • Bias is more stable in Assim. Salinity

  5. Fit to ADCP Velocity Observations TAO (Pacific) PIRATA (Atlantic) Obs ORAS4 CNTL

  6. More on Ocean currents: Time and variability Central Pac: -ve impact Eastern Pac: +ve impact

  7. Correlation with Altimeter • General Improvement • Little impact of altimeter at high latitudes • Very little weight to the unbalance component • Decrease of correlation West Iberian • Under study. Possible problem • How to improve further the assimilation of altimeter? • Include effect of unbalance salinity • Better definition of mixed layer depth (rho=0.01 criteria underestimate MLD) • MDT from observations (Dan’s work) • Better tuning of balance/unbalance covariances.

  8. Med Outflow problem and Assimilation We should look at the balanced/unbalanced separation of increments

  9. Plans • Transition to NEMO/NEMOVAR 3.4 (discussion tomorrow) • New Ocean configurations: ORCA025_L75 as well as ORCA1_L75 • Tuning of background/obs errors • Revise analysis cycle? • LIM2 sea-ice model • Assimilation of sea-ice in NEMOVAR? • Any relevant data sets for the obs-operator and diagnostics? • MyOcean2 ocean re-analysis: 2 years starting ~ April 2012 • ORCA025+NEMOVAR+Up-to-date datasets (OSTIA, SL ECV,MDT…) • Hopefully other improvements. • CERA project: Weakly coupled DA using for reanalysis applications. • ESA funded. 2 years x 2 positions. Starting ~ April 2012 • 4 Stages: CERA-S, CERA-O, CERA-A, CERA

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