Norwegian Climate Prediction Model

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The Norwegian Climate Prediction Model (NorCPM) is aiming at providing prediction from seasonal-to-decadal time scale. It is based on the Norwegian Earth System Model (NorESM, [1]) and the Ensemble Kalman Filter (EnKF, [2]) data assimilation method. NorESM is a state of the art Earth system model that is based on CESM ([3]), but uses a different aerosol/chemistry scheme and ocean model (evolved from MICOM). The EnKF is a sequential data assimilation method that allows for fully multivariate and flow dependent corrections using a covariance matrix produced by a Monte-Carlo ensemble integration.

NorESM model version used in NorCPM

NorESM1-L (Zhang et al., 2012): T31 resolution in the atmosphere; ocean is bipolar gx3v7 (~3°)
NorESM1-LT: F19 atm (1.9°by 2.5°) ; ocean is tripolar 2°
BCCRFAST tripolar :F19 atm (1.9° by 2.5°) ; ocean is tripolar 1°; ocean model code equivalent to NorESM2
NorESM1-ME (Tjiputra et al., 2013) f19 for the approximately 2° finite volume grid; ocean has a 1° resolution.
NorESM1-ACPL (Toniazzon and Koseki 2018) f19 for the approximately 2° finite volume grid; ocean has a 1° resolution anomaly coupled ocean atmosphere. Anomaly coupling correct seasonally varying fluxes (SST to atm and wind to the ocean).
NorESM2-MH (Langehaug et al. 2018) 1 deg atm, 1/4 deg ocn to be used in Blue Action.

NorCPM Versions

Version 0 (V0): refers to version of NorCPM that assimilate SST only. SST is the only observational data set available in the ocean for a period of time sufficient (> 100 years) to clearly demonstrate skill of decadal prediction. Assimilation updates vertically the full ocean while the remaining components of the Earth system model (atmosphere, sea ice, land) are left unchanged but they will adjust dynamically between the monthly assimilation step (an approach referred as weakly coupled data assimilation).
:V0 was first tested in idealised twin experiment (Counillon et al. 2014). It is found that assimilation reduces error and can constrain well the variability of the ocean – with largest improvements in the near surface and sea ice with some benefit over land for temperature and precipitation. The system beats persistence forecast and shows skill for the heat content in the Nordic Seas that is close to the upper predictability limit.

Prediction activities

The optimal goal is to test the capability of our system on disparate phase of the climate in order to gain confidence on the robustnes of its accuracy. SST is the only observational data set available for a period of time sufficient (> 100 years) to clearly demonstrate skill for decadal prediction. Ideally a start date every 5 years seems achievable.

Evaluation of prediction hindcast simulations with real SST data

The observational data set used so far is the ensemble of SST data (refereed as HADISST2), which provide monthly SST for 1850--2007 with 10 members. Each member reconstructs SST using a different set of possible unknown parameters. At term we intend to perform retrospective reanalysis and decadal prediction (hindcast) over the last century, but here we have decided to focus on a shorter period (1980-2005) because the system is still premature and there are many independent observations during this period of time.

Existing runs

Following is a table that summarise the different experiment run so far:

Multiplication table

Name on Norstore	NorESM version	observation	ens size	Freq assim	full_field/anom	ocean var updated	post process	Masked coast	localisation	Atmo nudging	Prediction	Finished/Ongoing	Remark
First_Try	F19_tn21	SST	30	monthly	anom	all	fixenkf	yes	point	no	1990,1992,1995,1996	Finished	minor bug in EnKF, small drift in MSL, good SPG
Second_Try	F19_tn21	SST	30	monthly	anom	all	fixenkf	yes	point	no	1995	Finished	small drift in MSL, good SPG
Third_Try	F19_tn21	SST	30	monthly	anom	T and S	fixenkf	yes	point	no	none	Finished	weak SPG in reanalysis
Fourth_Try	F19_tn21	SST	30	monthly	anom	T and S and Barot.	micomserial	yes	point	no	none	Finished	unrealistic
Fifth_Try	F19_tn21	SST	30	monthly	anom	all	micom_serial	yes	point	no	1995	Finished	very mild improvement compare to second
ME	F19_G16	SST	30	monthly	anom	all	micom_serial	yes	point	no	no	ongoing	??
Yiguo_try	F19_tn21	SST	30	monthly	anom	All(superlayer)	micom_serial	yes	point	no	no	ongoing	??
FF_ini_try	F19_tn21	SST	30	monthly	full	all	micom_serial	yes	point	no	April and November prediction from 1981 to 2007	Finished	??

Projects using NorCPM

Current

EPOCASA, PREFACE, INCREASE, PARADIGM, STERCP, ARCPATH

Past

PRACTICE

Publications, etc.

Peer-review

• Counillon, F., Bethke, I., Keenlyside, N., Bentsen, M., Bertino, L., & Zheng, F. (2014). Seasonal-to-decadal predictions with the ensemble Kalman filter and the Norwegian Earth System Model: a twin experiment. Tellus A, 66. doi:10.3402/tellusa.v66.21074

Presentations

• NorCPM talk at the joint MiKlip/Specs meeting in Offenbach 24.-25. Feb 2015 (pdf)

User Resources

• NorCPM User Manual

Working group

• Meeting minutes of working group

Contact informations

Noel.Keenlyside@gfi.uib.no (leader); ingo.bethke@uni.no (NorESM related question); francois.counillon@nersc.no (EnKF related question); maolin.shen@gfi.uib.no (atmospheric nudging related question)