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

MAPS/RUC soil/vegetation model with snow physics
  (MAPS = Mesoscale Analysis and Prediction System)
  (RUC = Rapid Update Cycle)

2. Name and address of model developer;

Tanya Smirnova
  (assisted by John Brown and Stan Benjamin)
325 Broadway
Boulder, CO  80303

3. Name and address of model user;



National Centers for Environmental Prediction
Camp Springs, MD
  (where RUC is run operationally)

4. Please indicate whether your model is developed for application

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

5. The first year when the model was used;

starting in 1997

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

Accumulation of snow is derived from explicitly predicted fallout of snow and graupel from atmospheric model. Surface energy balance derived by considering a layer that spans the lowest few meters of the atmosphere and the top half of the snow layer; if the temperature of this layer is computed to be warmer than 0C, the excess heat is used to melt snow. For other details, see answers to questions below.

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

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

snow temp, 
snow water equivalent, 
snow density, 
snow thermal conductivity

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?

The parameters in soil model are fixed

13. What are the output data?

Snow depth, snow water equivalent, snowmelt, accumulation of fresh snow, energy flux consumed to melt snowcover

14. What computer language does your model use?

Fortran (F77 with extensions)

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

Three subroutines

16. Number of lines of the snow code?

Approximately 500

17. What is the recommended hardware?

No special requirements.

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

Explicit precipitation: NCAR/PSU MM5 model level 4 explicit cloud microphysics (Reisner et al. 1997 QJRMS). Rain, snow and graupel fallout explicitly predicted. Convective parameterization: Grell (1994, Mon. Wea. Rev.). All parameterized convective precipitation assumed to fall as rain.

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.

Snow cover is the first layer of 6-layer soil model

21. What is your snow model time step?

5-min time step is used in MAPS/RUC forecast model

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?               
It is fixed

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?

It is 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?

The model considers 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?

If snow height at the grid point is more than 2 cm then this grid box is considered to be 100% covered by snow

33. Does your snow model account for sub-grid (or sub-watershed) effects of topography? If so, how is temperature distributed?

No sub-grid effects

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?

In snow covered areas roughness length is defined by the type of vegetation.

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 together with liquid precipitation is the source of water in soil

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

The excess of snowmelt over maximum possible infiltration rate goes into runoff

42. How is frozen soil treated in your model?

No frozen soil physics

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


If so, what data? (areas)

what are their temporal and spatial scales?

It is tested in 1-d mode on Valdai data set (PILPS-2d) with 19-year duration, and data from several Russian stations (6-year duration).

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?

Yes, visual comparison with satellite image of snow cover. Visible GOES and polar orbiter imagery from NOAA/NESDIS.

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?

Snow model will be used in MAPS/RUC forecasting model. Improvements will include development of parameterization of frozen soil physics, introducing of land-use and snow properties dependence on snow age, and explicit treatment of liquid water retention and percolation within the snowpack.

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

General description of MAPS/RUC and soil model can be found in:

Benjamin, S.G., J.M. Brown, K.J. Brundage, D. Devenyi, D. Kim, B.E. Schwartz, T.G. Smirnova, T.L. Smith, and A. Marroquin, 1997: Improvements in aviation forecasts from the 40-km RUC. Preprints, 7th Conference on Aviation, Range, and Aerospace Meteorology, Long Beach, February, 411-416.

Smirnova, T. G., J. M. Brown, and S. G. Benjamin, 1997: Performance of different soil model configurations in simulating ground surface temperature and surface fluxes. Mon. Wea. Rev., 125, 216-261.

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