Snow Model Component Questionnaire

May 12, 1997

Here is a comprehensive survey questionnaire (with 50 questions) about the snow component in your land-surface model or in your hydrological model. We would appreciate it very much if you could take a few minutes to answer them and e-mail your response back to us.

This questionnaire builds on a similar survey by World Meteorological Organization (WMO) in mid-1980s in which there were replies from 11 snowmelt-runoff model owners, whose models were hydrologically based and mainly for watershed applications. Our questionnaire extends to snow models used in numerical weather forecasting models and global climate models.

The number of questions list may be too long for some people but we would appreciate it if you could try to answer as many as possible.

The replies to this questionnaire will be summarized into a report and will be put onto a World Wide Web (WWW) site that can be assessed by you.

We hope that the completed report will serve as updated summary descriptions of snow models used in snow physics, hydrology, weather, and climate applications.

We are looking forward to your reply at your earliest convenience.

Should you have any questions regarding this questionnaire, please do not hesitate to contact Zong-Liang Yang.


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;

3. Name and address of model user;

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),
   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

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

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

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?

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?

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.

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.

21. What is your snow model time step?

22. Does your model snow albedo allow its
    spectral differences    (visible vs. near-IR)?
    directional differences (direct  vs. diffuse)?

23. Is your model snow albedo a function of 
      snow age 
      grain size
      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?

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

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?

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)

           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

42. How is frozen soil treated in your model?

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

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

44. Has your snow model been used together with remote sensing data as

    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.