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Data Assimilation System

Ocean State Estimation by 4D-VAR Data Assimilation using ARGO Data S. Masuda, T.Awaji,N.Sugiura,H.Igarashi,Y.Ishikawa,Q.Jiang,K.Takeuchi. Four-dimensional Variational (4D-VAR) ocean data assimilation system is used to produce time-varying model/data syntheses.

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Data Assimilation System

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  1. Ocean State Estimation by 4D-VAR Data Assimilation using ARGO DataS. Masuda, T.Awaji,N.Sugiura,H.Igarashi,Y.Ishikawa,Q.Jiang,K.Takeuchi • Four-dimensional Variational (4D-VAR) ocean data assimilation system is used to produce time-varying model/data syntheses. • The result is a dynamically self-consistent estimate of ocean state. • It has greater information and forecast potential than do models or data alone (e.g., Stammer et al., 2002; Masuda et al., 2003).

  2. Data Assimilation System Masuda et al. (2003)

  3. Cost Function

  4. Assimilated Data • Surface data ・Reynolds SST (10daily) • Subsurface data ・FNMOC; T, S (monthly) • ・TAO/TRITON/PIRATA; T, S (monthly) • from NOAA • ・ARGO buoy; T, S (monthly) • from Coriolis Data Centre • ・WOD98 climatologies; T, S (monthly)

  5. Subsurface Data without ARGO Buoys 2000 2002 T S

  6. Subsurface Data with ARGO Buoys 2000 2002 T S

  7. Subsurface Data with ARGO Buoys 2000 2002 T S

  8. Data Assimilation Experiment • Assimilation period; 2000-2002 • EXP.1 • Simulation • EXP.2 • Assimilation with whole the data • (FNMOC,ARGO,…) • EXP.3 • Assimilation with only Reynolds SST and • WOD98

  9. Salinity Distribution at 26.8sq (Jan;2002) Exp.1:Simulation Exp.2:Assimilation Exp.2-Exp.1:Difference

  10. Salinity Distribution at 26.8sq (Jan;2002) The NPIW water extends southward Exp.1:Simulation Exp.2:Assimilation ～O(0.1psu) Exp.2-Exp.1:Difference

  11. Subarctic Water Mass Distribution at 47oN (Jul;2002) Exp.1:Simulation Exp.2:Assimilation

  12. Subarctic Water Mass Distribution at 47oN (Jul;2002) Dichothermal structure Mesothermal structure Exp.1:Simulation Exp.2:Assimilation Oyashio Recirculation

  13. q47ºN P1 Revisit（1999） sq 26 27 160ºE 180ºE 160ºW 140ºW WOCE Revisit Data at 47oN Dichothermal structure Mesothermal structure Suga et al. (2002)

  14. Estimated Subsurface Circulation in the North Pacific Ocean (Jul; 2002) 26.2sq 26.6sq

  15. Estimated Subsurface Circulation in the North Pacific Ocean (Jul; 2002) 47oN 26.2sq 26.6sq

  16. HydroBase po.temp & circulation HydroBase Climatological Map at 26.6sq Suga et al. (2003)

  17. Estimated Northward Heat Transport (2000-2002 annual mean) Exp.1 Exp.1 Exp.2 Exp.2

  18. Impact of Interannual SubsurfaceObservations (ARGO,FNMOC…) Exp.2(assimilation) – Exp.3(assimilation without ARGO, FNMOC…)

  19. Impact of Interannual Subsurface Observations (ARGO,FNMOC…) Exp.2 – Exp.3

  20. 26.8sq Impact of Interannual Subsurface Observations (vertical section 30oW) Exp.2 – Exp.3

  21. Concluding Remarks • Estimates of the dynamical state for 2000-2002 . • Dynamically consistent time-varying data set with realistic features (e.g. NPIW, subarctic water masses) is obtained. • The impacts of ARGO, FNMOC…data are striking particularly in the North Atlantic region (and the Bering Sea) at 26.8sq in this assimilation experiment. • The ARGO buoy is promising. (We hope data coverage for all over the world ocean like for the North Atlantic.)

  22. Future Work • Long-term assimilation experiment • Information of recent observations can improve the quality of reanalysis data for the past.

  23. Future Work 2 • Is velocity information from ARGO buoys available as an assimilation element? Iwao et al. (2003)

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