Parameter Sensitivity of aCoupled Climate Model Estimated Through Data Assimilation
Xueyuan Liu A. Köhl, D. Stammer
CEN (Center für Erdsystemfurschung und Nachhaltigkeit) Hamburg University
The highlights of decadal climate predictions up to date:
1)initialization 2)uncertainties
3) minimizing the influence of systematic model biases
4)measurements of the skill of hindcasts
Approach: A fully-coupled data assimilation was used to get the
optimal oceanic initial conditions and control variables(JAMSTEC).
Based on those, ensembles of hindcasts with implimentation of
greenhouse gas forcing are carried out every one year to assess how
the strategy works. A 20C run from 1913 shall also be done. Extra
ensembles might be necessary in order to give statistics. Ensembles
of decadal prediction is expected to give information on the climate
of the coming century.
Decadal Prediction
Contribution of Control Variables
alphas=0 against alphas=climatologyhindcasts (alphas=0) against HadISST
The two patterns of mean bias of SST(1980-1989) are almost opposite. Despite the differences in the amplitude, we can come to a conclusion that control alphas contribute to the improvement of a hindcast.
Annual-mean SST over 9 Years
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10.04.23
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• Coupled Model---CFES (Coupled model for the Earth Simulator)
● T42L24 AFES (Atmospheric GCM for the Earth Simulator) for AGCM
● 1*1 degree, 45 vertical layers MOM3 for OGCM
● IARC (International Arctic Research Center) Sea-ice model
● MATSIRO (Minimal Advanced Treatments of Surface Interaction and Runoff)
Model for land
• Assimilation Method-----4D-VAR
K7 System from Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Assimilation period
forwardbackward
First guess field
Best guess trajectory
Obs
ObsObs
Schematic view of the experimental configuration:
Improving Decadal Predictions
9 mon
9 mon
… …
1970 1980 1990 2000Spinup run by IAU
……First guess I.C.
First guess I.C. First guess I.C.
Assimilation Exp.by 4D-VAR
optimized
optimized
optimized optimized
First guess Exp.(Free run)
1.5 month
Jan 1980 Jan 1981 Jan 1982
Ensemble Exp.(each with 3 members-
shifted atmosphere)
10 yr
10 yr
10 yr
In all:1980-2007
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299
NACLIM www.naclim.eu
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