Post on 04-Apr-2015
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
Variabilité interannuelle
2L20NCEP
Pas assez de réponse en vent aux anomalies de SST
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QuickTime™ and aTIFF (LZW) decompressor
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Variabilité interannuelle
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2L20
Obs
HH20
Higher atmosphere resolution(2.5x1.8 vs. 3.75x2.5)
A"HiRes"
NCEP
ACTRL
Clear improvement of wind variability (Niño 4)
Higher atmosphere resolution
1. Larger El Niño variability (+ 15% amplitude)2. Slightly larger ICS, larger non-linearity
CTRL "HiRes"
<SST>
ICS
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
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
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
Impact of U*(Passage du courant)
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
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)
Impact on mean state
IPSL
INGV
SST Taux
Impact on mean state SST errorsDiff. with obs
IPSL
INGV
CTRL U* run
Impact on interannual variability (IPSL)CTRL U* run
Oce
anA
tmos
Impact on interannual variability (INGV)CTRL U* run
Oce
anA
tmos
• 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
Impact on seasonal cycle at equator
IPSL
INGV
SST Taux
Impact on SST seasonal cycle at equator
IPSL
INGV
Diff. with obsCTRL U* run