| Model Components | ||||||
| Lake Model? | Frozen Soils? | Vegetation? | ||||
| Yes | No | Yes | No | Lumped | Mosaic | |
| CHASM | ||||||
| SEWAB | ||||||
| MECMWF | ||||||
| Snow Model Structure | |||||
| Zero Order | Implicit | Composite | Bulk Layer | Multi-layer | |
| CHASM | |||||
| SEWAB | |||||
| MECMWF | |||||
| Runoff Generation | ||
| Surface Runoff | Subsurface Runoff | |
| CHASM | None | Free drainage |
| SEWAB | No surface runoff before upper soil layer is saturated; 'topmodel' approach | Free drainage; 'topmodel' approach |
| MECMWF | variable infiltration capacity | Free drainage following Van Genuchten (1980) |
| Calibration? | Apply knoweldge? | Input TS? | Output TS? | |
| CHASM | No | No | 1 hr | 1 hr |
| SEWAB | Yes | Yes | 0.5 hr | 1 hr |
| MECMWF | Yes | Yes | 1 hr | 0.5 hr |
| Calibration | |
| CHASM | No calibration performed. |
| SEWAB | Applied a logarithmic profile for the saturated conductivity of the soil (topmodel approach). |
| MECMWF | Depth of the soil over which the relative soil water content is calculated was tuned. |
| Soil Parameters | ||||
| Clapp et al | Cosby et al. | Rawls et al. | Other | |
| CHASM | ||||
| SEWAB | ||||
| MECMWF | ||||
| Snow Albedo | ||
| Visible | NIR | |
| CHASM | 0.85 | 0.65 |
| SEWAB | 0.9 | 0.9 |
| MECMWF | Function of snow age and temperature | |
| General Impressions |
| We experienced large interception evaporation and inappropriate diurnal variation due to the treatment of hourly precipitation (equal to daily total precipitation/24). |
| I had the impression that the snow model suited quite well to the problem. The soil model I think had some problems in storing the large amount of water from snow and ice in the spring, which led to an unsatisfactory fitting of the discharge |
| The forcings show some very low winds and/or low atmospheric humidities, giving rise to strong peaks in evaporation. Validation data are lacking and the performance is somewhat uncertain. |
The most recent references describing model structure, as specified by the model users, are listed below:
CHASMDesborough, C.E., 1999. Surface energy balance complexity in GCM land surface models. Climate Dynamics, 15, 389-403.
Desborough, C.E., 2000. Surface energy balance complexity in GCM land surface models, Part II: coupled simulations. Climate Dynamics, in press.
SEWABMengelkamp, H.T., K. Warrach, and E. Raschke, 1997. A land surface scheme for atmospheric and hydrologic models: SEWAB (Surface Energy and Water Balance). Externer Bericht des GKSS Forschungszentrum, GKSS 97/E/69.
Warrach, K., 2000. Gefrorener boden und schneebedeckung unter besonderer beruecksichtigung des hydrologischen verhaltens der landoberflache, Dissertation GKSS 200/21.
MECMWFViterbo, P. and A.C.M. Beljaars, 1995. An improved land surface parameterization scheme in the ECMWF model and its validation. Journal of Climate, 8, 2716-2748.
Viterbo, P., A. Beljaars, J.F. Mahfouf and J. Teixeira, 1999. The representation of soil moisture freezing and its impacts on the stable boundary layer. Q.J.R.Meteorol. Soc., 125, 2401-2426.
Van den Hurk, B.J.J.M., P. Viterbo, A.C.M. Beljaars and A.K. Betts, 2000. Offline validation of the ERA40 surface scheme, ECMWF TechMemo 295, Journal of Climate, to be submitted.
Van den Hurk, B.J.J.M.,, P. Graham and P. Viterbo, 2000. Evaluation of simulations of runoff to the Baltic Sea by atmospheric models; KNMI Preprints 2000-04; 31 pp. (submitted to Journal of Hydrology