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CMIP5 decadal experiments at CERFACS: Initialisation and preliminary results

Christophe Cassou, Emilia Sanchez-Gomez Elodie Fernandez Laurent Terray. CMIP5 decadal experiments at CERFACS: Initialisation and preliminary results. Aspen CMIP5 workshop ,Colorado , June 2011. Prediction or forecast?. Forecast = prévision. Prediction = prédiction.

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CMIP5 decadal experiments at CERFACS: Initialisation and preliminary results

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  1. Christophe Cassou, Emilia Sanchez-Gomez Elodie Fernandez Laurent Terray CMIP5 decadalexperimentsat CERFACS: Initialisation and preliminaryresults Aspen CMIP5 workshop,Colorado, June 2011

  2. Prediction or forecast? Forecast = prévision Prediction = prédiction Meteorologist, climatologist Miss Sun, astrologist

  3. Outline OUTLINE Description of the CERFACS model and CERFACS contribution to CMIP5 database 2. Impact of the initialisation technique upon model initial shock and drift 3. Verypreliminaryresults about AMO predictability

  4. The Cerfacs-CNRM contribution to the CMIP5 database Coreexperiments « Tier 1 »: Increase ensemble sizesfrom 3 to 10 members 2. Forecastwith 2010 Pinatubo eruptions (10 members) 3. Work on initialization techniques « Bonus »: 10 more dates starting one yearbefore the requested CMIP5 experiments All simulations are completed and model outputs have been posted last week end on ESG nodes (exceptsea-ice data)

  5. The decadal forecast initialization The coupled model = CNRM-CM5 Atmosphere ARPEGE-Climat v5.2 T127 (1.4°), 31 levels Full Initialization: Ocean Only In a coupled mode from 1958 To 2008 SURFEX Interface Land surface, ISBA The COMBINE ECMWF Ocean Reanalysis OASIS v3 (24h coupling) Sea Ice GELATO v5 Ocean NEMO v3.2 1° 42 levels River Routing TRIP 24h

  6. 3D Nudging as a function of depth and space β = f(depth, space) Reanalysis In the mixed layer (1/ β) =0 Below thermocline β = 10 days Deep Ocean β = 360 days Current No 3D nudgingwithin the Equatorial band (1oN-1oS) and nearthe coast (300km) (1/ β) =0

  7. Sea surface restoring At the surface Heat flux: Feedback coefficient = -40W/m2/K feedback term. SSTobs= observations Heat flux at the surface Fresh water flux: Feedback parameter = -167 mm/day Fresh water budget at the surface Feedback term. SSSobs= observations

  8. Outline Sensitivity of the initial shock and drift to the 3D-nudging domain of application

  9. Two types of CMIP5 experiments • Nudging to the ECMWF ocean reanalysis NEMOVAR (ORCA1°) 1958 -2008 • Several tests have been performed to set the optimal parameters for • dQ/Dt and b GLOB No 3D nudging within the 1°S–1°N band EXTROP No 3D nudging Within the 15°S–15°N band

  10. Ocean Heat Content Mean 1960-2005 NEMOVAR DH GLOB EXTROP Mean 1960-2005

  11. Along the equatorial thermocline Mean [1960-2005] Temperature difference averaged over the 2oN-2oS band (GLOB-EXTROP) (HIST-NEMOVAR) D20

  12. Impact of initialization on mean ocean heat transport GLOB: perturbation of the Northward heat transport around 10o Of latitude GLOB: perturbation of the Northward heat transport around 10o Of latitude in the Atlantic EXTROP: close to HIST up to 20oN close to NEMOVAR northward

  13. Impact of initialization on prediction Global Mean SST Strong warm initial shock mainlydue to veryrapid austral oceanwarming GLOB / EXTROP Annualmean SST biases (HIST-ERSST (1960-2005) > 10 years 2-3 years 6 months

  14. Impact of the initialization on predictions Global Mean SST (from 35oS to 90oN) GLOB / EXTROP 1-yr warmingmuch drift lesspronounced GLOB warm shockstrongerthanEXTROP

  15. Thermocline depth prediction GLOB/EXTROP HIST 3-member ensemble Mean D20 isotherm depth over the 2oN-2oS band 1 spaghetti = 1 forecast date

  16. ENSO variability Yr1 Yr2 Yr3 Yr4 NINO34 SST Ensemble mean (dates+members) Nino34 SST index Perturbation of the tropical climate up to 4yr (systematic NINO the 1st and 3rd year in GLOB)

  17. Teleconnection Color=precip / contour=Z500 (significance hatching) Difference between GLOB and EXTROP ensemble mean (dates+members) Z500 and precipitation for the 1yr-forecast winter Strong difference in rainfall drift between GLOB and EXTROP, presence of ENSO Teleconnection in Z500 drift

  18. Does the drift affect skills? 2 questions: 1. Do the strength and physical structures of the initial shock and subsequent drift affect the skill of the forecastatdecadaltime-scale (yr 2-5?) 2. Whatis the relevance of lineardebiasingmethods in presence of drifts that DO project onnatural modes of variability that are clearlynonlinear (convection and teleconnection associated with ENSO)?

  19. Outline Preliminaryresults on model skill and AMO predictability

  20. SST Correlation skill (with trend) Historical 20th simulations Decadal Forecast

  21. SST Correlation skill (without trend) Historical 20th simulations Decadal Forecast

  22. Global (60°S-60°N) SST Predictability OBS=ERSST3 DEC HIST

  23. Detrended global (60°S-60°N) SST OBS=ERSST3 DEC HIST

  24. AMO Predictability OBS=ERSST3 DEC HIST

  25. Conclusions • Weneed to beextremelycautious in the wayocean 3D fields • are initialized • Model drift correction is a central question (interaction with the forcing • and the naturalvariability modes) • Weneed to beverycautiouswith the estimation of the decadalforecast • skill (choice of the statistics etc.) and with the wayusers are going to deal • with the decadalforecasts The Cerfacs-CNRM data are available! Feel free to use them!

  26. IPO/PDO ERSST3 1890-2010

  27. IPO/PDO Predictability

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