Model Version
Detailed information on CRCM 3.6's physics package can be found in CCCma's model section.
(http://www.cccma.bc.ec.gc.ca/models/crcm.shtml#crcm36)
A general description of CRCM3.6 and 3.7, its validation and response to increasing greenhouse-gas forcing is available in Plummer et al. (2006).
All CRCM 3.6.3 and CRCM 3.7.1 simulations shown above use the deep and shallow convection scheme from Bechtold et al. (2001).
CRCM version 3.7 differs from 3.6 in the following aspects:
- The solar radiative heating is calculated using an improved method with four bands in the visible and near-infrared (replacing an earlier two-band parameterization) and a better representation of the water vapour continuum (Puckrin et al. 2004). The updated parameterization of radiation results in increased atmospheric absorption as compared with the earlier version of the solar radiation.
- Cloud cover formulation now also takes into account the local stability within the layer, added to relative humidity that was already considered (in 3.6) (Lorant et al. 2002) ; this results in an increased reflection of incoming solar radiation.
- Vertical mixing in the boundary layer has been modified to include nonlocal mixing of heat and moisture under conditions where the buoyancy flux at the surface is upward (Jiao and Caya 2006).
- The "snow masking depth" -the specified depth of snow where surface elements are assumed to be covered by snow and the surface albedo changes from the albedo of land to that of snow- has been changed from the spatially varying field used in version 3.6 to a constant value of 3.0 m over land surfaces other than tundra, deserts and swamps. This change eliminated spurious gradients of spring snow cover found in some areas (e.g., Canadian Prairies).
- A constant soil water capacity of 10 cm for the single-layer representation of the soil is introduced, as opposed to varying soil water capacity used previously. This change increased the Bowen ratio, thereby reducing the overestimated summer surface evaporation/precipitation over land. It also shortened the freezing (and thawing) period, allowing an earlier onset of snow on the ground in the fall (Frigon et al. 2002).
- Internal water budget is now conserved every timestep over the entire free domain (Paquin et Laprise 2003).
Description of CRCM 4.1.1/4.2.0 and their physics package can be found in CCCma's model section.
(http://www.cccma.bc.ec.gc.ca/models/crcm.shtml#crcm420)
as well as in Music and Caya (2007) and Brochu and Laprise (2007).
Domain and Resolution
- AMNO : The entire AMNO domain ( topography ) covers North America with 201x193 grid points, including the 9-point surrounding sponge zone. For analysis, only the inner 182x174 grid points of the free zone are considered (without the sponge zone). The grid follows a polar-stereographic projection with a 45-km horizontal grid-size mesh (true at 60°N), 29 vertical levels (model top at 29 km) and 15-minute time step.
- AMNO (Zoom on Canada)
- AMNO (Land-sea mask)
- QC : The Quebec domain ( Topography | Land-sea mask ) contains 112x88 grid points, including the 9-point surrounding sponge zone. For analysis, only the inner 93x69 grid points of the free zone are considered (without the sponge zone). The grid follows a polar-stereographic projection with a 45-km horizontal grid-size mesh (true at 60°N), 29 vertical levels (model top at 29 km) and 15-minute time steps.
For information on polar-stereographic grid descriptors in NetCDF format, please refer to the description provided below.
Driving data (atmospheric and oceanic)
All driving data is linearly interpolated in time to CRCMs time steps. In the case of ocean data, boundary conditions for sea surface temperature (SST) and sea-ice are generated following the methodology developed by Taylor et al. (2000).
- AMIP II observational ocean dataset consists of monthly sea surface temperature (SST) and sea-ice obtained from Fiorino (1997).
- CGCM2 SST and sea-ice data are provided at daily frequency to the CRCM.
- CRCM's Great Lakes surface water conditions (SST and sea-ice):
- Are prescribed using the AMIP II observational dataset, when CRCM is driven by reanalysis.
- Are computed through the coupled lake model for the Great Lakes, when CRCM is driven by CGCM (because CGCM's coarser resolution does not resolve the Great Lakes). This mixed-layer/thermodynamic-ice lake model for the Great Lakes (Goyette et al. 2000) was coupled to the CRCM. It simulates the evolution of surface water temperature and ice cover, with mixed-layer depth that can vary spatially.
Nesting Strategy
- For all CRCM 3.6.3 and CRCM 3.7.1 simulations shown above, a spectral nudging technique (Riette and Caya 2002) is applied within the regional domain to the large-scale horizontal winds (>1400 km wavelength). The nudging varies in the vertical, starting just above 500 hPa and reaching a characteristic relaxation time of 10 hours at the model top (~10 hPa).
GHG+A Evolution
- The A2 GHG evolution follows SRES from IPCC (2000).
Period
- Prior to all CRCM 3.6.3, CRCM 3.7.1 and CRCM 4.1.1/4.2.0 time-slice simulations shown above, a two-year spin-up has been performed for the modeled climate system to reach equilibrium.
A guide to CRCM's polar stereographic grid output in NetCDF format
- Polar stereographic GRID DESCRIPTORS
- straight_vertical_longitude_from_pole : longitude at which the y-axis (of the polar stereographic grid) and the meridian are parallel.
- standard_parallel : parallel in degrees to which the polar stereographic grid is projected, with its hemispheric location defined by "hemisphere_of_standard_parallel".
- false_easting : distance in meters in x-direction from pole to inferior-left corner of regional domain. The pole is defined by "hemisphere_of_standard_parallel" (either North or South).
- false_northing : distance in meters in y-direction from pole to inferior-left corner of regional domain. The pole is defined by "hemisphere_of_standard_parallel" (either North or South).
- hemisphere_of_standard_parallel : location of "standard_parallel", either North (with value of 1) or South (with value of 2).
- resolution_at_standard_parallel : resolution in meters of the polar stereographic grid at the "standard_parallel".
For example, CRCM's AMNO grid (182x174) is defined in netCDF format by (where ".f" indicates "floating point values"):
polar_stereographic:straight_vertical_longitude_from_pole = 245.f ;
polar_stereographic:standard_parallel = 60.f ;
polar_stereographic:false_easting = -3240000.f ;
polar_stereographic:false_northing = -6358500.f ;
polar_stereographic:hemisphere_of_standard_parallel = 1.f ;
- Polar stereographic GRID COORDINATES
- xc : x-coordinate of the center of each CRCM tile as distance (in meters) from the "false_easting" value.
- yc : y-coordinate of the center of each CRCM tile as distance (in meters) from the "false_northing" value.
- lat(xc,yc) : corresponding latitude (in degrees north) of the center coordinates (xc,yc) of each CRCM tile.
- lon(xc,yc) : corresponding longitude (in degrees east) of the center coordinates (xc,yc) of each CRCM tile.
REFERENCES
- Bechtold, P., E. Bazile, F. Guichard, P. Mascart et E. Richard, 2001: A Mass Flux Convection Scheme for Regional and Global Models. Quart. J. Roy. Meteorol. Soc., vol.127, 869-886.
- Fiorino, M, 1997: AMIP II sea surface temperature and sea ice concentration observations. http://www-pcmdi.llnl.gov/amip/AMIP2EXPDSN/BCS_OBS/amip2_bcs.htm
- Frigon, A., D. Caya, M. Slivitzky and D. Tremblay, 2002: Investigation of the hydrologic cycle simulated by the Canadian Regional Climate Model over Québec/Labrador territory. In: Advances in Global Change Research, vol. 10, Climatic Change: Implications for the Hydrological Cycle and for Water Management, Ed. M. Beniston, Kluwer Academic Publishers (Dordrecht et Boston) 31-55.
- Goyette, S., N.A. McFarlane, and G. Flato, 2000: Application of the Canadian Regional Climate Model to the Laurentian Great Lakes Regions. Implementation of a Lake Model. Atmos.-Ocean, vol.38, 481-503.
- IPCC (Intergovernmental Panel on Climate Change): 2000. Special Report on Emissions Scenarios, A Report of the Working Group III. Nakicenovic, N. and Swart, R. (eds.),Cambridge University Press, Cambridge, United Kingdom. 612 pp.
- Jiao, Y., and D. Caya, 2006: An investigation of the summer precipitation simulated by the Canadian Regional Climate Model. Mon. Wea. Rev., In Press.
- Lorant V, N. McFarlane and R. Laprise, 2002. A numerical study using the Canadian Regional Climate Model for the PIDCAP period. Boreal Environment Research, vol.7(3), 203-210.
- Plummer, D.A., D. Caya, A. Frigon, H. Côté, M. Giguère, D. Paquin, S. Biner, R. Harvey, and R. de Elia, 2006: Climate and Climate Change over North America as Simulated by the Canadian RCM. J. Clim., vol.19(13), 3112-3132.
- Paquin D. et R. Laprise, 2003: Traitement du bilan d'humidite interne au MRCC. Rapport interne. 26 pp.
- Puckrin, E., W.F.J. Evans, J. Li, and H. Lavoie, 2000: Comparison of clear-sky surface radiative fluxes simulated with radiative transfer models. Canadian Journal of Remote Sensing, vol.30, 903-912.
- Riette, S. and D. Caya, 2002: Sensitivity of short simulations to the various parameters in the new CRCM spectral nudging. Research activities in Atmospheric and Oceanic Modelling, edited by H. Ritchie, WMO/TD - No 1105, Report No. 32: 7.39-7.40.
- Taylor, K.E., D. Williamson, and F. Zwiers: 2000. The Sea Surface Temperature and Sea-Ice Concentration Boundary Conditions for AMIP II Simulations. PCMDI Report No. 60, 28 pp.
Notes and updates
- In CRCM 3.6.3, 3.6.4 and 3.7.1, the simulation of snow cover over glacier grid points (mostly located over Greenland) shows a monotonic increase directly linked to the treatment of snow cover, which does not increase underlying glacier mass, simply remaining as snow cover. (7 June 2006)
- In CRCM 3.7.1, a bug was found in the implementation of the mixed-layer/thermodynamic-ice lake model for the Great Lakes (Goyette et al., 2000) into the CRCM. This produced Great Lakes surface water temperatures that remain around zero degrees C throughout the year, getting much too cold in the summer/fall seasons. Surface water temperatures and ice cover are therefore considered erroneous over the Great Lakes. One must not forget that these lake surface fields influence many other meteorological fields that are simulated by the CRCM such as evaporation and hence precipitation, snow water content (usually present over lake ice), screen values (temperature, humidity and winds) and surface radiation fields, etc. over the Great Lakes and over surrounding land grid points. (7 June 2006)
- In CRCM4.1.1 and 4.2.0, the snow cover data over glacier grid points (can be identified by values of 5 in the ground cover data) shows either a monotonic increase (directly linked to the treatment of snow cover, which does not increase underlying glacier mass, simply remaining as snow cover) or just reaches a maximum value near 100 kg m-2 (as is the case over Groenland).
- In CRCM4.1.1 and 4.2.0, known bugs from CLASS 2.7, the multi-layer surface scheme suggests:
- Water content phase changes are overestimating liquid water over frozen water due to a missing soil thickness parameter in their computation. This seems to affect mostly soil-layer liquid/frozen water contents and soil temperatures. In some areas, the liquid soil water content becomes too important in winter (i.e. lower frozen water content) and hence drainage appears relatively higher. Though surface fluxes (i.e. precipitation, evaporation, runoff) are also affected, particularly in spring and early summer, they do not seem significantly different.
- There is a small bug in surface turbulent flux calculations.
- An additional set of bugs in the CRCM4.1.1/4.2.0 were recently fixed but their effect has not yet been evaluated:
- An error in the computation of canopy mass for crops can lead to its overestimation in the presence of snow cover during transition periods and in winter.
- Soil water matric potentials are systematically computed as being saturated (i.e., too low potentials in general) possibly causing as underestimation of the suction force in soil layers.
- Incorrectly computes soil temperature in the bottom layer when bedrock is present due to an error in the heat flux calculations between the second and third layers.
- Potential problem with the CRCM data from the experiment ade. This CRCM 4.1.1 experiment, driven by the ERA40 reanalyses and the AMIP sea surface temperatures, runs from 1961 to 2005. The AMIP data that were used to drive this experiment are in error form August 2002 and beyond. Note that that no problems were found prior to that month. It is difficult to evaluate the impact of this problem to the results of the simulation, but it is important that all the users be aware of this potential problem.
- Regular updates and notes on this model version are also available in the CCCMa web site (http://www.cccma.bc.ec.gc.ca/data/crcm42/crcm420_adj_1co2.shtml).
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