1. Forecast system version
Identifier code: cwao_CanCM4i
First operational forecast run: 31 July 2019
2. Configuration of the forecast model
Is the model coupled to an ocean model? Yes
Coupling frequency: 24 hours
2.1 Atmosphere and land surface
| Model | CanAM4 |
|---|---|
| Horizontal resolution and grid | T63 (~2.8° lat/lon) |
| Atmosphere vertical resolution | 35 hybrid levels |
| Top of atmosphere | 1 hPa |
| Soil levels (layers) | 3 Layer 1: 0-10 cm |
| Time step | 15 minutes |
Detailed documentation:
von Salzen, K., and Coauthors, 2013: The Canadian fourth generation atmospheric global climate model (CanAM4). Part I: Representation of physical processes. Atmos. -Ocean, 51, 104–125, https://doi.org/10.1080/07055900.2012.755610
2.2 Ocean and cryosphere
| Ocean model | CanOM4 |
|---|---|
| Horizontal resolution | ~1.4° (lon), ~0.94° (lat) |
| Vertical resolution | 40 levels with ~10m spacing near surface |
| Time step | 20 minutes |
| Sea ice model | CanICE |
| Sea ice model resolution | ~2.8° lat/lon |
| Sea ice model levels | 1 |
| Wave model | N/A |
| Wave model resolution | N/A |
Detailed documentation:
Merryfield, W. J., and Coauthors, 2013: The Canadian seasonal to interannual prediction system. Part I: Models and initialization. Mon. Wea. Rev., 141, 2910–2945, https://doi.org/10.1175/MWR-D-12-00216.1
3. Initialization and initial condition (IC) perturbations
3.1 Atmosphere and land
| Hindcast | Forecast | |
|---|---|---|
| Atmosphere initialization | ERA-Interim | ECCC GDPS analysis |
| Atmosphere IC perturbations | Ensemble of coupled assimilation runs begun from different initial conditions. | Ensemble of coupled assimilation runs begun from different initial conditions. |
Land Initialization | Land component forced by assimilating atmosphere. | Land component forced by assimilating atmosphere. |
| Land IC perturbations | Each ensemble member forced by slightly different atmospheric states constrained by ERA-Interim | Each ensemble member forced by slightly different atmospheric states constrained by GDPS analysis |
| Soil moisture initialization | Soil moisture forced by assimilating atmosphere. | Soil moisture forced by assimilating atmosphere. |
| Snow initialization | Snow forced by assimilating atmosphere. | Snow forced by assimilating atmosphere. |
| Unperturbed control forecast? | No (all ensemble members contain statistically equivalent perturbations). | No (all ensemble members contain statistically equivalent perturbations). |
Data assimilation method for control analysis:
Incremental Analysis Update (IAU) constrained by (re)analysis 6-hourly temperature, specific humidity and horizontal wind components, modified by inserting only 1/4 of increment on spatial scales >~1000 km.
Horizontal and vertical resolution of perturbations:
Perturbations are primarily on spatial scales <1000 km, vertical structure not directly specified.
Perturbations in +/- pairs:
No, all perturbations represent random samples from a distribution.
Detailed documentation:
Merryfield, W. J., and Coauthors, 2013: The Canadian seasonal to interannual prediction system. Part I: Models and initialization. Mon. Wea. Rev., 141, 2910–2945, https://doi.org/10.1175/MWR-D-12-00216.1
Sospedra-Alfonso, R., L. Mudryk, W. J. Merryfield, and C. Derksen, 2016: Representation of snow in the Canadian Seasonal to Interannual Prediction System: Part I. Initialization.J. Hydrometeor., 17, 1467–1488, https://doi.org/10.1175/JHM-D-14-0223.1
3.2 Ocean and cryosphere
| Hindcast | Forecast | |
|---|---|---|
| Ocean initialization |
|
|
| Ocean IC perturbations | Perturbations due to forcing of ocean surface by different realizations of assimilating atmosphere in coupled runs. | Perturbations due to forcing of ocean surface by different realizations of assimilating atmosphere in coupled runs. |
| Unperturbed control forecast? | No | No |
Detailed documentation:
Dirkson, A., W. J. Merryfield, and A. Monahan, 2017: Impacts of sea ice thickness initialization on seasonal Arctic sea ice predictions. J. Climate, 30, 1001–1017, https://doi.org/10.1175/JCLI-D-16-0437.1
Merryfield, W. J., and Coauthors, 2013: The Canadian seasonal to interannual prediction system. Part I: Models and initialization. Mon. Wea. Rev., 141, 2910–2945, https://doi.org/10.1175/MWR-D-12-00216.1
Lin, H., Merryfield, W. J., Muncaster, R., Smith, G. C., Markovic, M., Dupont, F., Roy, F., Lemieux, J.-F., Dirkson, A., Kharin, V. V., and Lee, W. S., 2020: The Canadian Seasonal to Interannual Prediction System Version 2 (CanSIPSv2), Weather and Forecasting, 35, 1317–1343, https://doi.org/10.1175/WAF-D-19-0259.1
4. Model Uncertainties perturbations:
| Model dynamics perturbations | No |
|---|---|
| Model physics perturbations | No |
If there is a control forecast, is it perturbed? | No control forecast |
Detailed documentation:
5. Forecast system and hindcasts
| Forecast frequency | 12-month forecast is produced once per month. (Hindcasts are initialized on the first day of each month, forecasts on the last day of previous month.) |
|---|---|
| Forecast ensemble size | 10 |
| Hindcast years | 1980-2010 |
| Hindcast ensemble size | 10 |
| On-the-fly or static hindcast set? | static |
6. Other relevant information
Radiative forcing is according to the CMIP5 historical specifications up to 2005, and the RCP 4.5 scenario thereafter. An exception is that CMIP5 volcanic stratospheric aerosol forcing at the start of the forecast decays with a time constant of 1 year.
7. Where to find more information
https://weather.gc.ca/saisons/index_e.html
https://climate-scenarios.canada.ca/?page=seasonal-forecasts
https://climate-scenarios.canada.ca/?page=cansips-technical-notes
