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

Best Approximation of Surface Exchange (BASE)

2. Name and address of model developer;

C.E. Desborough, A.J. Pitman and (w.r.t. snow) A.G. Slater

3. Name and address of model user;

many users - point of contact is

Prof A.J.Pitman
School of Earth Sciences
Macquarie University
North Ryde, 2109, NSW, Australia
Phone +61 2 9850 8425, Fax +61 2 9850 8428

4. Please indicate whether your model is developed for application

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

5. The first year when the model was used;

1995 but its parents go back to 1986

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

7. Please specify any known application range or restrictions;

Not sure what this means. If you mean spatial scale, I'd guess 0.1 x 0.1 degrees to 4 x 4 degrees. Time scale from 5 minutes to say 100 years (we don't do biome developments)

8. What are the development data needs;

Not sure I understand the question - any observational data of any quantity in BASE is useful

9. What are the operational data needs?

As per Question 10 + soil and vegetation parameters

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 temperature
snow water equivalent
snow density

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?

an initial density
a parameter controlling densification
a temperature dependence for albedo

13. What are the output data?

snow density
snow water equivalent and snow temperature. 
If this means snow model output, there is also 
snow-cover fractions for the ground and foliage

14. What computer language does your model use?


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


16. Number of lines of the snow code?

357 including comments

17. What is the recommended hardware?

anything - runs on SGi, PCs, Suns, CRAY etc.

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

Derived by the GCM based on temperatures in atmosphere

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

1D in space

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

1 layer at the moment

21. What is your snow model time step?

Host model determined - 20-30 mins usually

22. Does your model snow albedo allow its

    spectral differences    (visible vs. near-IR)? 
      not in the latest version
    directional differences (direct  vs. diffuse)? 

23. Is your model snow albedo a function of

      snow age                   
      grain size               X (effectively through temperature)  
      solar zenith angle        
      snow depth?              X

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?

yes (optional)

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?

changes (optional)

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?

can do (doesn't seem to really matter)

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


32. How is areal snow distribution treated?

fractional area is represented as a function of vegetation roughness and snow depth

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),  
            YES (but coupled in with type).
 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?

doesn't intercept snow

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

it affects fractiona extent of snow cover and therefore albedo

39. In the presence of vegetation, how is snow surface roughness altered?

It isn't - the grid area roughness is, but the snow roughness is not

40. In the presence of forest, does your snow model allow spatial variability of snow depth and water equivalent on forest floor?

no although there is a fractional snow-cover for the forest floor

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

water melting is available for infiltration

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

If it cannot infiltrate it runs off

42. How is frozen soil treated in your model?

Explicitly as a prognostic variable

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


If so, what data? (areas)

Valdai and half a dozen Russian sites

what are their temporal and spatial scales?

spatial is small - tens of metres. Temporal is up to 16 years

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?

Its been coupled but not compared (carefully)

46. Please list any other previous applications.


47. Please specify verification criteria, if any?

compared to available data

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


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

re snow - we have just finished extensive testing and are not likely to focus on snow again in the near future

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

Desborough, C.E. and A.J. Pitman, 1998: The BASE land surface model, Global and Planetary Change, 19(1-4), 3-18.

Slater, A.G., A.J. Pitman, and C.E. Desborough, 1998a: The validation of a snow parameterization designed for use in General Circulation Models, International Journal of Climatology, 18(6), 595-617.

Slater, A.G., A.J. Pitman, and C.E. Desborough, 1998b: Simulation of freeze-thaw cycles in a general circulation model land surface scheme, J. Geophys. Res. (Atmospheres), 103 (D10), 11303-11312.

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