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

SPECIAL SENSOR MICROWAVE IMAGER (SATELLITE) DERIVED SNOW COVER MODEL

2. Name and address of model developer;

NORMAN GRODY AND ALAN BASIST
abasist@ncdc.noaa.gov

3. Name and address of model user;

DEFENSE DEPARTMENT, NESDIS, NOAA USE IT OPERATIONALLY, PLUS NUMEROUS
OTHER RESEARCH AND OPERATIONAL FACILITIES.

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,      X
   in a global climate model (GCM),     X
   or other (please specify)?           X      
CLIMATE MONITORING

5. The first year when the model was used;

1995

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

1996: IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING GRODY AND BASIST V. 34, 237-249.

7. Please specify any known application range or restrictions;

CAN NOT IDENTIFY SNOW DEPTH, OR SNOW THAT IS UNDERGOING SIGNIFICANT MELTING.

8. What are the development data needs;

BETTER INSITU SNOW STRATIGRAPHY TO DEVELOP A ALOGRITHM THAT IDENTIFIES SNOW WATER EQUIVALENT FROM SATELLITES

9. What are the operational data needs?

DAILY CHANNEL MEASUREMENTS FROM THE SSMI INSTRUMENT

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?

MICROWAVE SPECTRUM

13. What are the output data?

A DAILY GLOBAL SNOW COVER PRODCUT IN NEAR REAL TIME. THE ARCHIVE GOES
BACK TO 1987.

14. What computer language does your model use?

Fortran

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

4

16. Number of lines of the snow code?

25 LINES

17. What is the recommended hardware?

A DESCENT PC

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

DERIVED SURFACE TEMPERATURE IS BELOW FREEZING, AND PRECIPITAION OR SNOW 
ON THE SURFACE IS OBSERVED.

OUR ALGORITHM IS PUBLISHED IN THE ARTICLE.

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

TWO. WE IDENTIFY SNOW AT 1/3 DEGREE PIXEL RESOLUTION.

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?

DAILY

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?

YES

25. Does your snow model account for changes in the hydraulic and thermal properties of snow due to meltwater refreezing?

YES

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?

YES, WE MEASURE IT

32. How is areal snow distribution treated?

OBSERVATIONS

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

NO

        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?

YES, BUT IT COULD BE BETTER

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?

WE OBSERVE THE SNOW SIGANTURE FROM THE RADIATING SURFACE, EVEN IF IT IS THE CANOPY.

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)

what are their temporal and spatial scales?

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

IT IS REMOTE SENSING DATA

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?

SERVES AS INPUT

If so, what satellite data were used?

SSMI

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?

WE ARE DEVELOPING A TECHNIQUE TO DERIVE SNOW WATER EQUAVALENT FROM THE SSMI INSTRUEMENT, USING THE POLARIZATION AND FREQUENCY INFORAMTION TO IDENTIFY THE FIRNAFICATION, AND CORRECT FOR IT IN THE SCATTERING SIGNATURE.

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

GRODY AND BASIST, 1996: IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, V. 34, 237-249.