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

Division of Atmospheric Research Snow and Soil Model - DARSSM

2. Name and address of model developer;

 Eva Kowalczyk                                Telephone: (+61 3) 9239 4524
 Division of Atmospheric Research,            Fax:       (+61 3) 9239 4444
 CSIRO,                                email: eva.kowalczyk@dar.csiro.au
 PMB 1, Aspendale, Victoria 3195,               or      eak@dar.csiro.au

3. Name and address of model user;

  CSIRO, Division of Atmospheric Research
  PMB 1, Aspendale, Victoria 3195,

4. Please indicate whether your model is developed for application

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

5. The first year when the model was used;


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

A simple four layer snow model is based on the energy and mass conservation and includes the diffusion of temperature through the pack, the extinction of short wave radiation, melting and freezing, and physically based snow albedo. The variables describing each snow layer are: depth in snow water equivalent, temperature and density. Discretization of the snowpack depth into layers changes with snowfall, melting, sublimation, densification etc... . The snow density changes with time due to compaction, settling and melting and refreezing processes.

7. Please specify any known application range or restrictions;

8. What are the development data needs;

mean snow cover thickness, water equivalent snow cover, air temperature, soil freezing depth, snow melt, ground temperature...

9. What are the operational data needs?

atmospheric forcing

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                  : X
   downwelling shortwave radiation : X
   downwelling longwave  radiation : X
   cloud cover                     : 
   surface pressure                : X

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

snow water equivalent, snow density, snow temperature, snow age

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?

maximum albedo at visible and near-infrared wavelength, snow surface aerodynamic roughness,

13. What are the output data?

snow water equivalent,  snow temperature

14. What computer language does your model use?


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

As it is combined with the soil model there are about 7 routines.

16. Number of lines of the snow code?


17. What is the recommended hardware?

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

In the CSIRO GCM snowfall or rainfall fractions are determined within the cloud scheme, hence this information is given to the snow model.

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

Model operates in GCM, however a one dimensional version of the model exist.

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

4 layers, discretization of the snowpack depth into layers changes with snowfall, melting, sublimation, densification etc... .

21. What is your snow model time step?

20 to 30 min

22. Does your model snow albedo allow its

    spectral differences    (visible vs. near-IR)?  X
    directional differences (direct  vs. diffuse)? 

23. Is your model snow albedo a function of

      snow age                 X
      grain size                  
      solar zenith angle       X
      pollution                X
      snow depth?              X

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?

prognostic variable

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

heat capacity and conductivity are function of snow density which is a prognostic variable

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


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

yes, this is the combined snow and soil model

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)? 
yes, in a limited way

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?

surface albedo is a combination of snow and vegetation albedo

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

Snow cover decreases the roughness length depending on snow depth and vegetation height.

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)?

Snowmelt increases soil moisture reservoir when soil surface temperature is above the freezing point and soil moisture is below the saturation.

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

Snowmelt is treated as surface runoff when soil moisture reservoir is full or when soil surface temperature is below the freezing point.

42. How is frozen soil treated in your model?

Soil ice starts to form if a layer temperature cools to the freezing point. During the freezing latent heat is released and the layer temperature drops below freezing after all the water turned into ice. Opposite process is taking place when the temperature of a layer with ice is increasing to 0 C.

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

If so, what data? (areas)

what are their temporal and spatial scales?

The observation data from six russian stations were used ( Schlosser, Roboc and Vinnikov ). Also, the model took part in the latest PILPS snow experiment.

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?


46. Please list any other previous applications.

47. Please specify verification criteria, if any?

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

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

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

a paper is being written up describing model physics and validation

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