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WP 11 J. Wickert, E. Cardellach , L. Bertino , A. Camps, N. Catarino, B. Chapron,

WP 11 J. Wickert, E. Cardellach , L. Bertino , A. Camps, N. Catarino, B. Chapron, G. Foti, C. Gommenginger, J. Hatton, M. Kern, M. Martin-Neira, H. Park, A. Rius, M. Semmling, F. Soulat, A. Sousa , J. Xie. The goal: Assessing the impact on ocean forecasting systems.

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WP 11 J. Wickert, E. Cardellach , L. Bertino , A. Camps, N. Catarino, B. Chapron,

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  1. WP 11 J. Wickert, E. Cardellach, L. Bertino, A. Camps, N. Catarino, B. Chapron, G. Foti, C. Gommenginger, J. Hatton, M. Kern, M. Martin-Neira, H. Park, A. Rius, M. Semmling, F. Soulat, A. Sousa, J. Xie

  2. The goal:Assessing the impact on ocean forecasting systems

  3. Ocean Forecasting System(EnKF) Forecast Analysis Member1 Member2 …… 2 1 Member99 3 • Initial uncertainty • Model uncertainty (winds, surf. Tem) • Measurement uncertainty Member100 Observations

  4. Uncertainty of temp profiles on 5-Jul-2013 limited in 100 km2 of the Fram Strait

  5. Data Assimilation diagnostics • Degrees of Freedom for Signal (DFS=tr(KH)) • Spread Reduction Factor • Can be calculated locally • using surrounding observations • For each observation types independently • Examples from TOPAZ • Impact depends on location and time

  6. Observations-only diagnosticsgghh • CLS: Power spectra densities (PSD) • Global integrated statistics • Used to compare different satellite altimeter missions • Advantage: model-free

  7. Some numbers: Data assimilation requirements • In order to know the impact of observations a Kalman Filter needs to know • Quantified SSH accuracy • GARCA: „of 50 cm or better (goal: 20 cm)“ • For a given size or „observation support“: • „SSH scale 10 km across track, 100 km along track“ • SSH spatial coverage • (Lat, Lon) Coordinates of observations • No requirements regarding latency • But 1 week would be the oldest data assimilated in TOPAZ. • No requirement for formats (NetCDF is OK)

  8. Possible NERSC HYCOM domains Agulhas Current system South China Sea TOPAZ

  9. Foreseen Procedures • File exchange • NERSC receives pseudo-observations • Could be 10-20 possible scenarios • No specific targets • “We take what you have”. • NERSC calculates the DFS/SRF diagnostics • CLS calculates the PSD • Scenarios with or without conventional altimeters • Code exchange • NERSC provides both • A stand-alone Fortran 90 code for calculation of DFS/SRF • Input files: Ensembles • ~50-100 Gb of data • Advantage: direct coupling to GARCA simulator • Many more scenarios

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