1. Coordinated CESM/CanESM Large Ensembles for the CanSISE Community
Paul Kushner
Department of Physics
University of Toronto

2. Purpose of this Discussion
CanSISE Theme B and Deliverable 3:
Attribution of Climate/Cryospheric Events (ACE/ACRE)
Quantify probability of extremes in presence or absence of anthropogenic influence (FAR).
E.g. what is the fraction of risk attributable to human influence of the 2007 vs. the 2012 sea ice minimum?
Create large initial condition ensembles of historical and projected forcing simulations.
Coordinated between CanESM (CCCma) and NCAR CESM1 (Toronto).
Carry out attribution runs with selected radiative forcings.
Ensemble size large enough to simultaneously estimate
forced response and
probability distribution associated with internal variability.
Don’t forget to ask if we coordinate on ozone forcing. Use WACCM.

3. Purpose of this Discussion
But we can use such runs for many other purposes than ACE/ACRE!
Let’s look on them as a community resource.
Consider the design and diagnostic aims.
To jog ideas I will review some applications of the large ensemble approach, then talk about our proposed experiments.
Don’t forget to ask if we coordinate on ozone forcing. Use WACCM.

4. Distribution of Global Temperature Trends in CESM Large Ensemble
(Kay et al. 2014, submitted to BAMS)

5. (Fischer et al. 2014, Nature Climate Change)
Attributing changes in extreme temperatures to model uncertainty versus internal variability
(Fischer et al. 2014, Nature Climate Change)

6. (Deser et al. 2012, Nature Climate Change)
Communicating uncertainty in regional trends arising from internal variability
(Deser et al. 2012, Nature Climate Change)

7. (Mudryk et al. 2013, Climate Dynamics)
Analyzing cryospheric trends in context of internal variability and observational uncertainty.
(Mudryk et al. 2013, Climate Dynamics)

8. Several Large Ensemble Projects
Model
Time Period
Forcing N
Projects
CCSM3
A1B Projection 40
Deser et al., Teng/Branstator
CCSM4
Historical
Mudryk et al.
CESM1-CAM5
Historical/rcp8.5 21
Fischer et al.
30 (NCAR)
1 + 6 (UofT)
Kay et al.
CanESM and NCAR CESM (U of T)
Historical-ALL FORCE 50
CanSISE Theme B
Historical-NAT
In red are shown runs to be done this year.

9. Design Discussion Model version CanESM – which version?
CESM1 – CAM5: 2 degree atmosphere, 1 degree ocean
Forcing
Generally, use each model’s forcings.
But CESM has specially developed stratospheric ozone from WACCM with realistic Antarctic Ozone Hole.
Should this be used for CanESM?
pictrl spin-up
Does this exist for CanESM version used?
To be done in 2014 for CESM1 2 degree on SciNET (Compute Canada allocation)
Initialization and generation of realizations
, branch at 1950, analysis
To be done in 2014 for CESM1 on SciNet
Standard perturbation methods to generate realizations.
Data saved
Diagnostic set developed for CESM project.
Extensive, but a good starting point.
NetCDF data compression reduces data by factor of 2-4.
Each 3-D variable saved monthly requires ~15-20GB for 2 degree model resolution on 30 levels.
What output should be saved and where should it be saved?

10. Design Discussion Model version CanESM – which version?
CESM1 – CAM5: 2 degree atmosphere, 1 degree ocean
Forcing
Generally, use each model’s forcings.
But CESM has specially developed stratospheric ozone from WACCM with realistic Antarctic Ozone Hole.
Should this be used for CanESM?
pictrl spin-up
Does this exist for CanESM version used?
To be done in 2014 for CESM1 2 degree on SciNET (Compute Canada allocation)
Initialization and generation of realizations
, branch at 1950, analysis
To be done in 2014 for CESM1 on SciNet
Standard perturbation methods to generate realizations.
Data saved
Diagnostic set developed for CESM project.
Extensive, but a good starting point.
NetCDF data compression reduces data by factor of 2-4.
Each 3-D variable saved monthly requires ~15-20GB for 2 degree model resolution on 30 levels.
What output should be saved and where should it be saved?

11. Design Discussion Model version CanESM – which version?
CESM1 – CAM5: 2 degree atmosphere, 1 degree ocean
Forcing
Generally, use each model’s forcings.
But CESM has specially developed stratospheric ozone from WACCM with realistic Antarctic Ozone Hole.
Should this be used for CanESM?
pictrl spin-up (multi century)
Does this exist for CanESM version used?
To be done in 2014 for CESM1 2 degree on SciNET (Compute Canada allocation)
Initialization and generation of realizations
, branch at 1950, analysis
To be done in 2014 for CESM1 on SciNet
Standard perturbation methods to generate realizations.
Data saved
Diagnostic set developed for CESM project.
Extensive, but a good starting point.
NetCDF data compression reduces data by factor of 2-4.
Each 3-D variable saved monthly requires ~15-20GB for 2 degree model resolution on 30 levels.
What output should be saved and where should it be saved?

12. Design Discussion Model version CanESM – which version?
CESM1 – CAM5: 2 degree atmosphere, 1 degree ocean
Forcing
Generally, use each model’s forcings.
But CESM has specially developed stratospheric ozone from WACCM with realistic Antarctic Ozone Hole.
Should this be used for CanESM?
pictrl spin-up (multi century)
Does this exist for CanESM version used?
To be done in 2014 for CESM1 2 degree on SciNET (Compute Canada allocation)
Initialization and generation of realizations
, branch at 1950, analysis
To be done in 2014 for CESM1 on SciNet
Standard perturbation methods to generate realizations.
Data saved
Diagnostic set developed for CESM project.
Extensive, but a good starting point.
NetCDF data compression reduces data by factor of 2-4.
Each 3-D variable saved monthly requires ~15-20GB for 2 degree model resolution on 30 levels.
What output should be saved and where should it be saved?

13. Design Discussion Model version CanESM – which version?
CESM1 – CAM5: 2 degree atmosphere, 1 degree ocean
Forcing
Generally, use each model’s forcings.
But CESM has specially developed stratospheric ozone from WACCM with realistic Antarctic Ozone Hole.
Should this be used for CanESM?
pictrl spin-up (multi century)
Does this exist for CanESM version used?
To be done in 2014 for CESM1 2 degree on SciNET (Compute Canada allocation)
Initialization and generation of realizations
, branch at 1950, analysis
To be done in 2014 for CESM1 on SciNet
Standard perturbation methods to generate realizations.
Data saved
Diagnostic set developed for CESM project.
Extensive, but a good starting point.
NetCDF data compression reduces data by factor of 2-4.
Each 3-D variable saved monthly requires ~15-20GB for 2 degree model resolution on 30 levels.
What output should be saved and where should it be saved?

14. Conclusion
Large initial condition ensembles involve work to coordinate, significant computation, data resources.
They can add value to traditional CMIP sets, but this requires good planning/coordination. Let’s make sure to coordinate well.
Tentative timeline:
June 2014: finalize design
August 2014: pictrl done
December 2014: 5-10 realizations done, initial comparisons.
April 2015: full sets done.

15. Discussion