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

NWSRFS SNOW-17

2. Name and address of model developer;

   Dr. Eric A. Anderson, formerly of Hydrologic Research Lab, NWS/NOAA,
   1325 East-West Highway, Silver Spring, MD 20910

3. Name and address of model user;

13 River Forecast Centers of the National Weather Service and others

Response by      Qingyun Duan
     GCIP Climate Project
     NWS/NOAA, W/OHx3            Tel:    301-713-1018
     1325 East-West Highway      Fax:    301-713-1051
     Silver Spring, MD 20910     Email:  qingyun.duan@noaa.gov

For further information, contact
Dr. Lee Larson of Hydrologic Research Lab of NWS at 301-713-0640

4. Please indicate whether your model is developed for application

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

5. The first year when the model was used;

1973

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

The SNOW-17 model is one of operations available in the National Weather Service River Forecast System (NWSRFS). It is a conceptual model in which each of the significant physical processes affecting snow accumulation and snowmelt is mathematically respresented. The model uses air temperature as the sole index to energy exchange across the snow-air interface and was developed to run in conjunction with a rainfall-runoff model. For more detail, see NOAA Technical Memorandum NWS HYDRO-17 (Anderson, 1973) and NOAA Technical Report NWS 19 (Anderson, 1976).

7. Please specify any known application range or restrictions;

This model can be used at a point or over an area. The time step of the model ranges from hours upto a day.

8. What are the development data needs;

9. What are the operational data needs?

Air temperature and precipitation time series are the only data needed to run the model. Optional data include snowfall percentage, observed snow water equivalent and observed areal snow coverage.

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

   precipitation                   : X
   air temperature                 : X
   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?

Snow water equivalent

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?

Rain + Snowmelt

14. What computer language does your model use?

Fortran

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        
      pollution                 
      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?

Snow depth is assumed to be distributed spatially according to a
predetermined curve.

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?

Since this is a conceptual model, many of these effects are implicitly accounted for in the model parameters. This answer applie to many of other questions.

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?

Snow depth is assumed to be distributed spatially according to a predetermined curve.

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

Rain + snowmelt is treat as the input to a rainfall/runoff model. Therefore the snowmelt only indirectly influence soil moisture.

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

see above

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)

what are their temporal and spatial scales?

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.

Anderson, Eric A., 1973: "National Weather Service River Forecast System -- Snow Accumulationa and Ablation Model", NOAA Technical Memorandum NWS HYDRO-17, US Dept. of Commerce, Silver Spring, MD, 217p.

Anderson, Eric, A., 1976: "A Point Energy and Mass Balance Model of a Snow Cover", NOAA Technical Report 19, U.S. Dept. of Commerce, Silver Spring, MD, 150p.