1 / 36

ENSO sensitivity to change in stratification in CMIP3

ENSO sensitivity to change in stratification in CMIP3. Boris Dewitte Sulian Thual, Sang-Wook Yeh, Soon-Il An, Ali Belmadani. CLIVAR Workshop, Paris, France, 17-19 November 2010 New strategies for evaluating ENSO processes in climate models .

kanan
Download Presentation

ENSO sensitivity to change in stratification in CMIP3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ENSO sensitivity to change in stratification in CMIP3 Boris Dewitte Sulian Thual, Sang-Wook Yeh, Soon-Il An, Ali Belmadani CLIVAR Workshop, Paris, France, 17-19 November 2010 New strategies for evaluating ENSO processes in climate models

  2. Impact of climate change on the mean stratification in ensemble models ΔT (2xCO2 – PI) Dinezio et al. (2009) Yeh et al. (2009)

  3. Conclusions/Perspectives • The characteristics of the thermocline (depth, sharpness, intensity) needs to be taken into account for determining the stability of ENSO • SODA tells us that an increased stratification leads to more energetic and low-frequency ENSO (Climate change paradox..) • Need to understand the impact of stratification changes on ENSO non-linearities.

  4. Motivation Understand the physical mechanism associated to the ‘rectification’ of ENSO variability/stability by the change in mean state? ? t~6 months η~10-20 years t2~? k~? Cf. Battisti and Hirst (1989)

  5. Change in thermocline depth at decadal timescales On thermocline depth: small amplitude (Wang and An, 2001) Levitus data

  6. T(1960-2001) T(1980-1997)-T(1960-1975) D20 (1980-1997) D20 (1960-1975) (Moon et al., 2004; Dewitte et al., 2009) Change in mean temperature associated to the 1976/77 climate shift

  7. (modes 1 to 3) • The ‘Moon pattern’ indicates that change in mean state cannot be account for just one baroclinic mode..! T(1980-1997)-T(1960-1975)

  8. Sensitivity of ENSO to stratification • Ocean dynamics perspective Shallow-water equations Stratification defined by (c, H) Multimode context Stratification defined by (cn, Pn)

  9. A ‘finer’ representation of the thermocline allows for taking into account the ‘loss’ of energy associated to vertical propagation: Implication for ENSO energetics and feedbacks Interannual variability of vertical displacements in a OGCM simulation (1985-1994) (Dewitte and Reverdin, 2000)

  10. Nonlinear Dynamical Heating Thermocline Feedback Sensitivity of ENSO to stratification • Thermodynamics perspective Zonal Advective Feedback

  11. Mean circulation ( , ) in CMIP3 1 : BCCR-BCM2.0 2 : CCCMA-CGCM3.1 3 : CCCMA-CGCM3.1 (t63) 4 : CNRM-CM3 5 : CSIRO-MK3.0 6 : CSIRO-MK3.5 7 : GFDL-CM2.0 8 : GFDL-CM2.1 9a : GISS-AOM (run1) 9b : GISS-AOM (run2) 11 : GISS-MODEL-E-R 12 : IAP-FGOALS1.0-g 13 : INGV-ECHAM4 14 : INM-CM3.0 15 : IPSL-CM4 16 : MIROC3.2-HIRES 17 : MIROC3.2-MEDRES 18 : MIUB-ECHO-g 19 : MPI-ECHAM5 20 : MRI-CGCM2.3.2A 21 : NCAR-CCSM3.0 22 : UKMO-HadCM3 23 : UKMO-HadGem1 Belmadani et al. (2010)

  12. Thermocline depth bias in CMIP3 1 : BCCR-BCM2.0 2 : CCCMA-CGCM3.1 3 : CCCMA-CGCM3.1 (t63) 4 : CNRM-CM3 5 : CSIRO-MK3.0 6 : CSIRO-MK3.5 7 : GFDL-CM2.0 8 : GFDL-CM2.1 9a : GISS-AOM (run1) 9b : GISS-AOM (run2) 11 : GISS-MODEL-E-R 12 : IAP-FGOALS1.0-g 13 : INGV-ECHAM4 14 : INM-CM3.0 15 : IPSL-CM4 16 : MIROC3.2-HIRES 17 : MIROC3.2-MEDRES 18 : MIUB-ECHO-g 19 : MPI-ECHAM5 20 : MRI-CGCM2.3.2A 21 : NCAR-CCSM3.0 22 : UKMO-HadCM3 23 : UKMO-HadGem1

  13. Nonlinear Dynamical Heating Thermocline Feedback Sensitivity of ENSO to stratification • Thermodynamics perspective Zonal Advective Feedback

  14. ~3°N Equator Rossby waves (hn) y=yn y=0° he=rWhn hn=rEhe Kelvin waves (he, ue) y=0°-> y=yn-> The Jin two-strip model(An and Jin, 2001) Hmix

  15. =1 =0 (basin mode) ~4 yrs ~ 9 months Solution of the mode [Xµ=X0.ea.t.cos(β.t +φ)] as a function of coupling efficiency  The Jin two-strip model(An and Jin, 2001) α β

  16. Stability of ENSO as a function of thermocline depth Period Increased thermocline depth -------->lower frequency stronger ENSO Growth rate Federov and Philander (2001)

  17. Defining thermocline… • Depth (P1) • Intensity, Sharpness (Pn, n>1) Gent and Luyten (1985)

  18. dD20<0 thermocline dD20>0 180° 90°W dD20>0 dD20<0 CNRM-CM3 N3VAR Decadal variability of Pn – CNRM-CM3 Dewitte et al. (2007) <P1>=0.5, <P2>=0.5, <P3>=0.2 dPn(t)

  19. Conceptual Model (Thual et al., 2010) comparable to the Jin two-strip model (Jin 1997b, An & Jin 2001) except for the ocean dynamics. Atmospherical component : Statistical relationship (SVD) with a coupling coefficient µ. Ocean dynamics : Kelvin and Rossby wave on 3 baroclinic modes : Kn, Rn Thermodynamics : Thermocline depth and zonal currents : H, U Variables :

  20. Thermodynamical feedbacks Thermocline feedback Adimentionalised feedback intensity Zonal advective feedback SODA dataset (1958-2008)

  21. Stability Analysis Find eigenvalues (a+ ib) of from Each eigenmode (a,b) has the form Dominant eigenmode=ENSO mode Eigenvectors of the ENSO mode (µ=1)

  22. Sensitivity to Stratification δ P1(1-δ), P2(1+δ/2), P3(1+δ/2) Stratification acts as a coupling parameter, but with physical meaning.

  23. Sensitivity of ENSO mode to stratification in the TD model Model parameters: P1(1-δ), P2(1+δ/2), P3(1+δ/2) frequency Growth rate

  24. The 1976/77 Climate shifts: Pre-70s to Post-70s : Strong increase in stratification (δ =120%). => Stronger, lower frequency ENSO Data: SODA

  25. The 2000 shifts: Post-2000 : Slight decrease in stratification (δ =95%). => ENSO variability displaced toward the west. Processes ? Data: SODA

  26. Change in ENSO stability in the GFDL model

  27. « Metrics » for the sensitivity to stratification change using the extended Jin’s two-strip model

  28. 2xCO2 - PI EOF1 of low-passed filtered T(x,z,y=0) (PI runs) Change in feedback processes MRI GFDL Yeh et al. (2010)

  29. Sensitivity of ENSO to a warming climate: GFDL versus MRI Yeh et al. (2010) Change in feedback processes

  30. Conclusions/Perspectives • The characteristics of the thermocline (depth, sharpness, intensity) needs to be taken into account for determining the stability of ENSO • SODA tells us that an increased stratification leads to more energetic and lower-frequency ENSO (Climate change paradox.?.) • Need to understand the impact of stratification changes on ENSO non-linearities.

  31. « Metrics » for the sensitivity to stratification change using the extended Jin’s two-strip model

  32. Low frequency change of temperature (EOF1) in the MRI and GFDL models MRI GFDL Change in stratification does project on the gravest modes (n=1,3)  Impact ENSO stability Change in stratification tends to project on the high-order or « very slow » modes (n>3)  impact Ekman layer physics

  33. Change in feedback processes Yeh et al. (2010)

  34. Change in feedback processes Yeh et al. (2010)

  35. Low frequency change of temperature (EOF1) in CMIP3 MIROC3_3_HIRES MIROC3_3_MEDRES MPI_ECHAM5 MRI_CGCM2_3_2A NCAR_CCSM3_0 UKMO_HADCM3

  36. Low frequency change of temperature (EOF1) in CMIP3 CCCMA_CGCM3_1_t63 CNRM_CM3 CSIRO_MK3_5 GFDL_CM2_0 INMCM3_0 MIUB_ECHO_G CCCMA_CGCM3_1 FGOALSrun1 GFDL_CM2_1 INVG_ECHAM4 IPSL_CM4 GISS_AOMrun1

More Related