1. Please write down the name (and abbreviation) of your snow model or land-surface model with snow component?


2. Name and address of model developer;

Eric Brun
Centre national de recherches meteorologiques
Centre d'etudes de la neige
1441 rue de la piscine
38406 St Martin d'Heres CEDEX  FRANCE

3. Name and address of model user;

Eric Martin
Centre national de recherches meteorologiques
Centre d'etudes de la neige
1441 rue de la piscine
38406 St Martin d'Heres CEDEX  FRANCE

4. Please indicate whether your model is developed for application

   in understanding snow processes,     X
   in a runoff forecasting model,	
   in a weather forecasting model,       
   in a global climate model (GCM),     X
   or other (please specify)?           X
   operational avalanche forecasting in France 

5. The first year when the model was used;


6. One paragraph description of your model (e.g. abstract from report or paper);

CROCUS is a one-dimensional model. The snow cover is represented as a pile of layers parallel to the ground. Energy exchanges are projected orthogonally to the slope. The model describes the evolution of the internal state of the snow cover as a function of meteorological conditions. The variables describing the snow cover are temperature, density, liquid water content, snow type of each layer. The thickness and number of layers are adjusted by the model in order that the numerical layers match the natural layers. The model simulate the heat conduction, melting/refreezing of snow layers, settlement, metamorphism, percolation. The originality of the model is that it simulates the snow metamorphism with experimental laws from cold laboratory. The snow grains are characterized by their sizes and types. This allows to calculate an accurate albedo of the snow cover.

7. Please specify any known application range or restrictions;

8. What are the development data needs;

9. What are the operational data needs?

10. Please indicate with an "x" for those meteorological variables used to DRIVE your snow model?

   precipitation                   : X
   air temperature                 : X
   wind speed                      : X
   wind direction                  : 
   humidity                        : X
   downwelling shortwave radiation : X
   downwelling longwave  radiation : X
   cloud cover                     : X
   surface pressure                :  

11. List the state variables (e.g., snow temperature, snow water equivalent, etc) your snow model uses?

snow temperature, snow density, liquid water content, grain type for each layer of snow (maximum 50 layers)

12. List the measurable/adjustable parameters (e.g., snow surface aerodynamic roughness, maximum albedo at visible wavelength, etc, excluding initial conditions) your snow model uses?

13. What are the output data?

CROCUS can produce hourly snow profiles, one may obtain also hourly or daily snow depth, snow water equivalent, bottom runoff, surface temperature.....

14. What computer language does your model use?


15. How many subroutines (or functions) does your snow model have?


16. Number of lines of the snow code?

1800 effective lines

17. What is the recommended hardware?

CROCUS runs on most unix workstation

18. How does your model determine the form of precipitation (i.e., snowfall and rainfall)? Please give the formulation.

this must be given as input data

19. Is your snow model one dimensional or multi-dimensional? Please specify.


20. If one dimensional, how many layers are there in your snow model? Please specify layering structure.

a maximum of 50 layers are used (variable depth)

21. What is your snow model time step?

900 seconds

22. Does your model snow albedo allow its

    spectral differences    (visible vs. near-IR)? Yes.
    directional differences (direct  vs. diffuse)? No.

23. Is your model snow albedo a function of

      snow age                 X
      grain size               X  and GRAIN TYPE
      solar zenith angle        
      snow depth?               

24. Does your snow model explicitly treat liquid water retention and percolation within the snowpack?


25. Does your snow model account for changes in the hydraulic and thermal properties of snow due to meltwater refreezing?


26. Is snow density in your snow model changing with time or fixed?

Changing with time.

27. Is heat capacity and conductivity in your snow model changing with time or fixed?

Changing with time.

28. Does your snow model simulate vapor transfer in the snowpack?

NOT EXPLICITELY, "effective conduction" used.

29. Does your snow model account for the heat transfer between the bottom of the snowpack and the underlying soil?


30. In snow energy balance, does your model consider heat convected by rain or falling snow?


31. Does your snow model include snow drifting and redistribution by wind (or avalanche)? If so, how?


32. How is areal snow distribution treated?

33. Does your snow model account for sub-grid (or sub-watershed) effects of topography? If so, how is temperature distributed?


how is precipitation (spatial, elevation and corrections) distributed?


how is solar radiation distributed?


how is wind distributed?


how are other meteorological variables distributed?


34. Does your snow model consider snow-vegetation interaction?


35. Does the snow-vegetation interaction account for

 different vegetation types     (grass vs. forest),            
 different vegetation heights   (short vs. tall),             
 different vegetation densities (small vs. large LAI),        
 different vegetation coverages (sparse vs. dense vegetation)?

36. Are snow interception, drip and melt on canopy surface allowed in your model?


37. How is the upper limit of the canopy interception determined?

38. In the presence of vegetation, how is snow surface albedo altered?

39. In the presence of vegetation, how is snow surface roughness altered?

40. In the presence of forest, does your snow model allow spatial variability of snow depth and water equivalent on forest floor?

41(a). How does your model deliver snowmelt to the soil system (e.g. affecting soil moisture)?

(b). Once snowmelt is generated, how does your model relate it to runoff?

percolation in the snowpack is simulated

42. How is frozen soil treated in your model?

no soil in the model

43. Has your snow model been tested with the field data?

    If so, what data?
    what are their temporal and spatial scales?

Yes. Data recorded in the experimental site of CEN. Several winters at an hourly time step.

44. Has your snow model been used together with remote sensing data as input? If so, how?


45. If your snow model is coupled with a numerical weather forecasting model or climate model, has the model snow product been compared with satellite data? If so, what satellite data were used?

Not yet.

46. Please list any other previous applications.

47. Please specify verification criteria, if any?

snow depth, snow water equivalent, snow profiles, bottom runoff...

48. What are the model fitting procedures, if any?

no fitting procedure

49. What are future plans for using/improving the model?

    operational avalanche forecasting in France
    coupling CROCUS with a soil and a vegetation model
    coupling CROCUS with distributed hydrological models
    use CROCUS in a GCM
    use CROCUS for modelling of polar snow
    calculate a snow climatology of the Alps and the Pyrenes

50. Please provide references relevant to the model description and use.

Brun E., Martin E., Simon V., Gendre C., Coleou C. (1989): "An energy and mass model of snow cover suitable for operational avalanche forecasting", J. of Glaciol., 35, 121, 333-342.

Durand Y., Brun E., Merindol L., Guyomarc'h G., Lesaffre B., Martin E. (1993): "A meteorological estimation of relevant parameters for snow models", Annals of Glaciol., 18, 65-71.

Braun L., Brun E., Durand Y., Martin E. Tourasse P (1994): "Simulation of discharge using different method of meteorological data distribution, basin discretization and snow modelling", Nordic Hydrology, 25, No. 1/2, 129-144.

Martin E., Brun E., Durand Y. (1994): "Sensitivity of the French Alps snow cover to the variation of climatic variables", Annales Geophysicae, 12, 469-477.

Brun E., Durand Y., Martin E., Braun L. (1994): "Snow modelling as an efficient tool to simulate snow cover evolution at different spatial scales", IAHS publication, No. 223, 163-176.

Martin E., Timbal B., Brun E. (1997): "Downscaling of general circulation Sensitivity to climate changes", Climate Dynamics, 13, 45-56.

-- Last updated Fri Oct 8 12:47:54 MST 1999 by Zong-Liang Yang.
For questions and comments, please contact Zong-Liang Yang