hh20 vs. 2l20 dans les tropiques etat moyen sst vs. obs
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![Page 1: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/1.jpg)
HH20 vs. 2L20 dans les tropiques
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Etat moyen SST vs. obs
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Etat moyen Taux vs. obs
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Diff etat moyen SST/Taux HH20-2L20
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Variabilité interannuelle
2L20NCEP
Pas assez de réponse en vent aux anomalies de SST
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Variabilité interannuelle
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2L20
Obs
HH20
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Higher atmosphere resolution(2.5x1.8 vs. 3.75x2.5)
A"HiRes"
NCEP
ACTRL
Clear improvement of wind variability (Niño 4)
![Page 7: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/7.jpg)
Higher atmosphere resolution
1. Larger El Niño variability (+ 15% amplitude)2. Slightly larger ICS, larger non-linearity
CTRL "HiRes"
<SST>
ICS
![Page 8: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/8.jpg)
HH20 vs 2L20 conclusions
• Pas de révolution dans état moyen et SC (mais légères améliorations)
• Nette amélioration de la variabilité en vent dans le Pacifique central (même si progrès encore possibles !
• Du coup, El Niño est plus fort (+15% - trop fort en fait)
• Suite:• regarder VV20 et 1 degré• comprendre trop faible variabilité en vent (runs IFC)• analyse feedback flux de chaleur
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Impact of correction on wind stress variability (IFC)
1. Anot much corrected (via SSTA)
2. Over correction O as « non-linearity » added during
growing phase via
AIFC
ACTRL
ONCEP
SC SC
SC SC
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Radiative feedbacks
Analysis of 9 AMIP forced AGCM (IPCC AR4) (Sun al. 2006)
• Too weak negative net feedback from atmosphere leads to unrealistically high sensitivity to small flux errors
• Main contributors: cloud albedo and atmosphere transport feedbacks
• Linked to a too strong water vapour feedback (underestimation of equatorial precipitation response)
Response of net surface heating to ENSO warming
El Niño in coupled GCMs – Eric Guilyardi – WGNE/PCMDI, San Francisco – Feb 2007
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Impact of U*(Passage du courant)
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Tropical Instability Waves
U*=0 U*0
T30
T106
SST (shading) + wind div.• TIW “seen” by T106
• U* (TIW) “seen” by wind stress calculation
Navarra et al. 2006
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U*=0 vs. U*0• Impact on tropical variability shown in SINTEX-F (T106)
U*=0
U*0
Reduced CS and Tau variability,Slightly reduced El Niño amplitude
SST correlation with nino3 SST
(Luo, Masson et al., 2006)
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Impact on mean state
IPSL
INGV
SST Taux
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Impact on mean state SST errorsDiff. with obs
IPSL
INGV
CTRL U* run
![Page 16: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/16.jpg)
Impact on interannual variability (IPSL)CTRL U* run
Oce
anA
tmos
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Impact on interannual variability (INGV)CTRL U* run
Oce
anA
tmos
![Page 18: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/18.jpg)
• Including U* in wind stress computation:– slightly slows down trade winds, mostly in
spring (good)– slightly warms west Pacific (good)– slightly reduces El Niño amplitude (why ?)
Preliminary conclusions of U* runs
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Impact on seasonal cycle at equator
IPSL
INGV
SST Taux
![Page 20: HH20 vs. 2L20 dans les tropiques Etat moyen SST vs. obs](https://reader035.vdocuments.site/reader035/viewer/2022062307/551d9db6497959293b8db3d1/html5/thumbnails/20.jpg)
Impact on SST seasonal cycle at equator
IPSL
INGV
Diff. with obsCTRL U* run