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

Layered snow model for climate study (SAST)

2. Name and address of model developer;

  Shufen Sun,  Jiming Jin
  LASG, Institute of Atmospheric Physics,
  Chinese Academy of Sciences,
  P.O. 2718, Beijing 100080, P.R. China

3. Name and address of model user;

  Shufen Sun,  Jiming Jin
  LASG, Institute of Atmospheric Physics,
  Chinese Academy of Sciences,
  P.O. 2718, Beijing 100080, P.R. China

4. Please indicate whether your model is developed for application

   in understanding snow processes,     X   
   in a runoff forecasting model,	X 
   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;


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

It is a layerd model, which can be used for stand-alone experiment now as well as be implemented with atmospheric model. The key process described in the model are: 1) compaction of snow layer due to several effects; 2) describe mass and energy balancve by considering many internal process such as liquid water transmission, heat conduction, melting/freezing/runoff and so on; 3) snow pack is layered with different thicknesses.

7. Please specify any known application range or restrictions;

8. What are the development data needs;

Observation data of snowdepth, snow surface temperature, snow surface albedo, snow water equvilent.

9. What are the operational data needs?

initial data and atmospheric data and soil surface data.

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                : X 

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

     snow temperature
     snow water equivalent
     dry snow density
     liquid water content

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?

    snow surface aerodynamic roughness
    maximum snow holding capacity
    proportion of rain to dry snow in precipitation
    effective thermal conductivity

13. What are the output data?

    snow temperature
    snowdepth and snow water equivalent
    run off

14. What computer language does your model use?


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

28 subroutines and functions

16. Number of lines of the snow code?

more than 2000 lines

17. What is the recommended hardware?

any type of hardware

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

use Jordan's scheme in CRREL Special Report 91-16

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.

six layers,the three for snow and the three for soil

21. What is your snow model time step?

1800.0 seconds

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                 X
      grain size                  
      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?


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?

Changing with snow density.

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?


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?

Not now but try to do later

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?

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

snowmelting water infitrates into soil at a speed with saturation hydraulic conductivity

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

if liquid water excesses the infiltration capacity, the remaining part becomes runoff.

42. How is frozen soil treated in your model?

if soil temperature is below 273.15, soil is frozen. However it is not true, we will modify later.

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


If so, what data?

what are their temporal and spatial scales?

Russian and French data. Maximum temporal scale is 6 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?


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?

plan to consider the interaction effect between snow falling and vegetation first and then improve the frozen soil scheme under snow cover second. finally hope to put all together into a exsisting land surface model in order to use it for climate study.

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

Sun, S.F., Jin, J.M., and Xue, Y. 1999. A simple Snow-Atmosphere-Soil Transfer (SAST) Model, J. Geophys. Res., (submitted).

Jin, J.M., X. Gao, S. Sorooshian, Z.-L. Yang, R.C. Bales, R.E. Dickinson, S.-F. Sun and G.-X. Wu, 1999: One-dimensional snow water and energy balance model for vegetated surfaces, Hydrological Processes, (in press). [Abstract]

Jin, J.M., X. Gao, Z.-L. Yang, R.C. Bales, S. Sorooshian, R.E. Dickinson, S.-F. Sun and G.-X. Wu, 1999: Comparative analyses of physically based snowmelt models for climate simulations. Journal of Climate, (in press). [Abstract]

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