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

Experimental snow-frozen ground parameterization of the       
        NCEP/OH/OSU land-surface model

2. Name and address of model developer;

    Victor Koren (Victor.Koren@noaa.gov, tel. 301-713-0640, ext. 114)
    NOAA/NWS/OH, 1325 East-West Highway, Silver Spring, MD 20910
    NCEP:   Kennneth Mitchell
    OH:     Q.-Y. Duan
    OH:     John Schaake
    NCAR:   Fei Chen

3. Name and address of model user;

    NOAA/NWS Office of Hydrology (address as in Question 2)

    Environmental Modeling Center
            National Centers for Environmental Prediction
        Environmental Modeling Center
            National Centers for Environmental Prediction
            W/NP2, Room 204
            4700 Silver Hill Road
            Stop 9910
            Washington DC 20233-9910

4. Please indicate whether your model is developed for application

   in understanding snow processes,     
   in a runoff forecasting model,                        X
      (There is a plan to make a version of the                  
       parameterization for a runoff forecasting model)
   in a weather forecasting model,                       X
      (i.e. in the NCEP Mesoscale Eta Model)
   in a global climate model (GCM),     
   or other (please specify)?                 

5. The first year when the model was used;

Off-line tests started in 1997

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

Snow parameterization is based on the energy and mass balance of snowpack with snow compaction and subgrid variability components. The frozen ground component is based on the layer- integrated form of heat and water diffusion equations, and it simulates total ice content of each soil layer rather than the freezing depth. Infiltration reduction under frozen ground conditions is estimated based on probabilistic averaging of spatially variable ice content of the soil profile.

7. Please specify any known application range or restrictions;


8. What are the development data needs;

    Surface forcing (PILPS2d) and soil and snowpack properties.   
        Snow depth, soil moisture, soil temperature, and runoff       
        (streamflow) are used for validation.

9. What are the operational data needs?

Surface forcing data (precipitaion, surface radiation, air temperature, humidity, wind speed, pressure) usually with 30-minutes interval.

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                : X

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

    Snow water equivalent
    Snow depth
    Liquid water in snow
    Skin (snow surface) temperature
    Total soil moisture at each layer (2-4)
    Unfrozen soil moisture at each layer (2-4)
    Soil temperature at each layer (2-4)

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 of snow surface, 0.75
    Snowmelt temperature threshold, 273.16K
    Threshold snow water equivalent of 100% coverage
    Critical value of ice content to generate frost heave

13. What are the output data?

    Snow water equivalent
    Snow depth, density, and conductivity
    Liquid water in snow
    Snow covered fraction
    Snow albedo
    Total soil moisture content
    Unfrozen soil moisture content
    Soil temperature

14. What computer language does your model use?


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

9 subroutines

16. Number of lines of the snow code?

About 700 lines

17. What is the recommended hardware?

UNIX workstation

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

If air temperature is above snowmelt temperature threshold    
        (see item 12) it is raining
    and if it's below it is snowing

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

One dimensional

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

Snow model uses one layer, and frozen ground is multilayer type model. Four layers are usually used, however, more or less layer can be easily accomodated

21. What is your snow model time step?

Snow-frozen ground model time step depends on a land surface required time step that is usually 30 minutes

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      X
      snow depth?             X (It is function of snow coverage)

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 in time depending on snow compaction and melting

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

It is changing

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?

It accounts for heat convected by rain

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


32. How is areal snow distribution treated?

Exponential distribution function with upper bound

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?

It accounts for the shade factor of vegetation to estimate albedo

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),         X 
 different vegetation coverages (sparse vs. dense vegetation)? X

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?

See item 36

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

Albedo is reduced depending on vegetation shade fraction

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)?

Snowmelt water is a direct input to the soil surface

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

Snowmelt water is combined with rainfall and partitioned into infiltration and runoff depending on total soil moisture and ice content

42. How is frozen soil treated in your model?

It simulates total and unfrozen water contents at each soil layer

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

If so, what data? (areas)

what are their temporal and spatial scales?

It was tested using point measurement and areal averaged experimental field data

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?

It is coupled with Eta model, however, no tests were done in on- line mode.

46. Please list any other previous applications.


47. Please specify verification criteria, if any?

Comparison of simulated and observed time series of snow water equivalent, soil temperature, and soil moisture

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

Automatic/manual calibration using available observed hydrometeorological data

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

Improve calculation/estimation of albedo Testing using river basin data, and on-line tests

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

Koren, V., Q.-Y. Duan, J. Schaake, and K. Mitchell, 1999: Validation of a snow-frozen ground parameterization of the Eta model. Preprints, 14th Conference on Hydrology, 10-15 January, 1999, Dallas, TX., pp. 410-413.

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