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

Multi-layer snow model: stand-alone-model and implemented in a test version of ECHAM

2. Name and address of model developer;

   Loth, Bettina
   Max-Planck-Institute fuer Meteorologie
   Bundesstrasse 55
   D-20146 Hamburg, Germany

3. Name and address of model user;

Loth (MPI Hamburg); (future) all user of ECHAM physics

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),     
   or other (please specify)?          X 
      testing the optimal complexity of a snow cover model
      for climate studies;
      model is/ will be used in global/ regional climate models

5. The first year when the model was used;

1991 (ECHAM: 1997)

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

      efficient multi-layer snow model resolving internal snow processes
      model can be used in stand-alone-estimations as well as
      it can be coupled to a GCM (is implemented a ECHAM test
      version, will be part of a future ECHAM standard version)
      model has been tested under different climate conditions

7. Please specify any known application range or restrictions;

8. What are the development data needs;

9. What are the operational data needs?

atmospheric data, initial soil 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 (dew point temperature)
   downwelling shortwave radiation : (estimated) 
   downwelling longwave  radiation : (estimated)
   cloud cover                     : X
   surface pressure                : X 

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

       snow albedo
       for each layer: snow temperature, density, depth,
                       liquid water content
        ==> derived: total snow depth, snow water equivalent

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?

cf. 11

13. What are the output data?

cf. 11

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?

17. What is the recommended hardware?


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

in stand-alone version critical value of wet bulb temperature

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

       stand-alone version: 1D
       ECHAM-version: 1D for each grid point  (global)

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

2 to 5 layers according to vertical homogeneity of snowpack

21. What is your snow model time step?

    not fixed
    according to atmospheric model (standard ECHAM T42: 24 min.)
    or according to input data (1 h to 3h)

22. Does your model snow albedo allow its

    spectral differences    (visible vs. near-IR)? no
    directional differences (direct  vs. diffuse)? yes

23. Is your model snow albedo a function of

      snow age                 X
      grain size                
      solar zenith angle       X (in stand-alone mode)
      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?

prognostic variable

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

heat capacity fixed; conductivity: function of 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?

in the ECHAM versions: estimating the fraction of snow coverage of grid-cell area as function of snow water equivalent (critical value)

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), 
  --forest vs. non-forest for radiation
 different vegetation heights   (short vs. tall),              
 different vegetation densities (small vs. large LAI),        
 different vegetation coverages (sparse vs. dense vegetation)? 
  --indirectly for heat fluxes

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?

separately for snow-covered forest and snow over bare soil

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?

indirectly due to the parameterization of albedo and the turbulent fluxes

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

soil moisture and runoff

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

ECHAM runoff scheme

42. How is frozen soil treated in your model?

no water infitration in soil at temperatures below the freezing point

43. Has your snow model been tested with the field data? If so, what data? (areas)

what are their temporal and spatial scales?

local station measurements (snow depth, snow water equivalent, surface temperature, snow albedo); global snow depth climatology

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. SMMR.

46. Please list any other previous applications.

47. Please specify verification criteria, if any?

snow depth, snow water equivalent, surface albedo.

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

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

50. Please provide references relevant to the model description and use.
Description and use of multi-layer snow model in stand-alone-mode:

Loth, B., H. F. Graf and J. M. Oberhuber, 1993: "A Snow-Cover Model for Global Climate Simulations", J. Geophys. Res., 98, 10,451-10,464.

Loth, B. and H. F. Graf, 1997: "Modelling the Snow Cover in Climate Studies, I: "Long-Term Integrations under Different Climatic Conditions Using a Multi-Layered Snow-Cover Model"
II:"Sensitivity to Internal Snow Parameters and Interface Processes", J. Geophys. Res., (97JD014011 and 97JD014012)

Description of ECHAM standard version and verification of the global climate model ECHAM:

Roeckner, E.; K. Arpe, L. Bengtsson, M. Christoph, M. Claussen, L. Dümenil, M. Esch, M. Giorgetta, U. Schlese, U. Schulzweida, 1996: "The atmospheric circulation model ECHAM-4: Model description and simulation of present-day climate", MPI-Rep. 218, MPI für Meteorologie, Hamburg, 90 pp.
Description and verification of ECHAM&multi-layer snow model

Loth, B., L. Bengtsson, L. Dümenil, D. Jacob, 1997: "An Improved Snow Physics in the ECHAM Model", (in prep., solicited paper at EGS Meeting Apr. 1997)

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