1. Please write down the name (and abbreviation) of your snow model or land-surface model with snow component?
ISBA (Interactions Sol-Biosphere-Atmosphere)
2. Name and address of model developer;
H. Douville (for the snow component) CNRM/GMGEC/UDC 42 av. Coriolis 31057 TOULOUSE CEDEX FRANCE
3. Name and address of model user;
Users of the ARPEGE Climate model CNRM/GMGEC 42 av. Coriolis 31057 TOULOUSE CEDEX FRANCE
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), 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);
A simple physically-based snow hydrology has been developped at Meteo-France for use in climate or NWP models, together with the ISBA land-surface scheme. A restricted number of parameters has been added, while preserving a single surface energy budget. The aging process of the snow pack has been introduced through prognostic equations for snow density and snow albedo. Snowmelt computation has been modified over partially snow-covered and vegetated areas. The new scheme has been validated against field measurements in stand-alone simulations forced by observed meteorological conditions. The results show a strong improvement in the model's performance, thereby suggesting that a simple one-layer snow model is able to reproduce the main physical mechanisms governing the snow pack evolution.
A global and coupled validation of the parameterization has been also achieved through a 3-year integration for the present-day climate within the T42L30 version of ARPEGE. Results are compared with those from a control simulation and with available observed climatologies, in order to assess the impact of the new snow parameterization on the simulated surface climate. The seasonal cycle of the Northern hemisphere snow cover is clearly improved when using the new scheme. The snow pack is still slightly overestimated in winter, but its poleward retreat is better reproduced during the melting season. As a consequence, the modified GCM performs well in simulating the springtime continental heating, which also improves some features of the general atmospheric circulation (over Europe in spring or South Asia in summer).
7. Please specify any known application range or restrictions;
8. What are the development data needs;
Local meteorological, radiative and snow measurements in open as well as forested sites ! Global (satellite ?) snow cover and snow mass data sets
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 :
surface pressure : X
11. List the state variables (e.g., snow temperature, snow water equivalent, etc) your snow model uses?
snow water equivalent snow density snow albedo (the surface temperature describes the whole soil-snow-and-vegetation system)
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?
13. What are the output data?
snow mass, snow density (and therefore snow depth), snow albedo, rate of snowmelt
14. What computer language does your model use?
15. How many subroutines (or functions) does your snow model have?
about 4 subroutines (preliminary calculations, aerodynamic resistance, energy budget and hydrology)
16. Number of lines of the snow code?
The snow code is embedded in the ISBA land-surface scheme, whose "off-line" version includes about 1350 lines.
17. What is the recommended hardware?
The "off-line" version can run on any PC or work station.
18. How does your model determine the form of precipitation (i.e., snowfall and rainfall)? Please give the formulation.
as a function of the air temperature (with a temperature threshold around 273K)
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.
21. What is your snow model time step?
between 5 and 30 minutes
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
solar zenith angle
snow depth? X
The snow albedo decrease depends on the snow age and the rate of snowmelt. The surface albedo depends on the snow cover fraction estimated as a function of snow depth.
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 a prognostic variable
27. Is heat capacity and conductivity in your snow model changing with time or fixed?
it is diagnosed from the 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?
only in its "offline" version
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?
as a function of snow depth, vegetation height and orography
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),
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)?
(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? what are their temporal and spatial scales?
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?
50. Please provide references relevant to the model description and use.
Douville H, Royer JF, Mahfouf JF (1995a): A new snow parameterization for the Meteo-France climate model, Part I: Validation in stand-alone experiments. Climate Dyn, 12, 21-35.
Douville H, Royer JF, Mahfouf JF (1995b): A new snow parameterization for the Meteo-France climate model, Part II: Validation Validation in a 3D GCM experiment. Climate Dyn, 12, 37-52.
Douville H. and J-F. Royer (1996): Sensitivity of the Asian summer monsoon to an anomalous Eurasian snow cover within the METEO-FRANCE GCM, Climate Dyn., 12, 441-448.
Douville H. and J-F. Royer (1997a): Influence of the temperate and boreal forests on the Northern Hemisphere climate in the METEO-FRANCE climate model, Climate Dyn., 13, 57-74.
Douville H. (1997b): Local and global stand-alone tests of the Meteo-France snow parameterization, Annals of Glaciology, 25 (in press)
Douville H. (1997c): Validation and sensitivity of the global hydrologic budget in stand-alone simulations with the ISBA land-surface scheme, Climate Dynamics, (in press)