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


For all of the below answers, see Rachel Jordan's reply, except where
I have made modifications

2. Name and address of model developer;

Rachel Jordan, CRREL, Hanover, NH, USA

3. Name and address of model user;

Graham Glendinning, IMGI, University of Innsbruck, 
Innrain 52, Innsbruck 6020, Austria

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),     
   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);

Modifying SNTHERM (energy-budget model) to include a full discrete ordinate radiative transfer. Extra data required for surface boundary; direct/ diffuse and spectral split in each (nine bands). This derived from measured global radiation and predicted clear sky radiation using a derived 'cloudiness' factor

7. Please specify any known application range or restrictions;

spherical snow grains, clean snow

8. What are the development data needs;

extra data to normal SNTHERM; direct, difuse and spectral split of direct and diffuse light (nine bands). Obtained from runs of 6S atmospheric code

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                     :  
   surface pressure                :   

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

Extra; Henyey-greenstein assymetry paramter, single scattering albedo,
optical depth

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?

SNTHERM: FORTRAN , calls shellscript which calculates parameters for DISORT radiative transfer program (Stamnes et al. 1988); UNIX

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

Extra; 2 + DISORT (many)

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.

One-dimensional, with three D radiative transfer

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

ca. 20

21. What is your snow model time step?

variable. Hourly data

22. Does your model snow albedo allow its

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

23. Is your model snow albedo a function of

      snow age                (with grain size variations)
      grain size               X
      solar zenith angle       X 
      snow depth?             assumed semi-infinite, but function of layering

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?

assumed semi-infinite snow. Deep enough for no transfer at bottom boundary

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?

42. How is frozen soil treated in your model?

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

If so, what data? (areas)

URANUS Glacier, Alexander Island, Antarctica
1994 Dec - Feb 1995.
weathter station with temperature, wind, humidity, temperatures in the
snowpack, solar radiation, net radiation
Snow pits with temperature, grain size, density.
Reflectance measurements; SPECTRON SE590 on A-frame.

what are their temporal and spatial scales?

90 minute data, 1 dimensional

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?

measured data

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

Varying radiative transfer parameterisations and minimising errors with measured snowpack temperatures over the season.

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

Spectral split for diffuse light conditions improved

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

Jordan R., 1991, A one-dimensional temperature model for a snow cover; Technical documentation for SNTHERM.89. U.S. Army Corps of Engineers, CRREL Special Report 91-16.

Stamnes K, Tsay S-C, Wiscombe W & Jayaweera K. 1988. Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. Applied Optics, 27, no.12, 2502-2509.

Vermote E, Tanri D., Deuzi J.L., Herman M., Morcette J.J., Second Simulation of the Satellite Signal in the Solar Spectrum (6S), Version 3.2, User Manual , FTP site: kratmos.gsfc.nasa.gov

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