Modelling components (current status)
| modelling component | ALADIN | COSMO | HIRLAM | UM/JULES | ECMWF |
|---|---|---|---|---|---|
| surface energy balance | Tile approach with separate energy budgets (sea/inland water/nature). One single surface temperature for the "nature" tile (bare soil/vegetation/snow) | Surface temperature is area weighted average of temperature of snow covered and snow free surface fraction | A tiled scheme with 5 tiles : water (sea+lakes), sea-ice, bare soil, low vegetation and forest (HIRLAM) ; Tile approach with sea/inland water/nature/town (HARMONIE) | Tile scheme with 9 surfaces, or one aggregated surface. 9 tiles include 5 vegetation types, bare soil, urban, lakes and ice | Tile approach with separate temperature and energy budget for each. Up to 8 tiles : 2 vegetations (low and high), 3 snow/ice (on bare soil, low and high vegetation), 2 water (ocean/lakes and interception) |
| coupling with the atmosphere | Implicit (external) | Explicit | Explicit (HIRLAM) Implicit (HARMONIE) | Implicit | Implicit (internal) |
| Soil transfers | 3-layer force-restore method ISBA scheme : 1st layer 1 cm / 2nd layer root zone (between 1 and 3 m) / 3rd layer recharge zone (between 0.5 and 1 m) | 7-layer soil model. Layer depths between 1 cm and 14.58 m. Solution of the heat conduction equation | Force-restore formulation ISBA (HIRLAM) 3-layer ISBA scheme (HARMONIE) | 4 layer diffusion equation model for heat and Darcian flow for moisture | 4-layer scheme (bottom depth : 7, 28, 100, 289 cm), based on Richards equation for soil water and diffusion equation for heat |
| Frozen soils | 2 soil ice reservoirs (surface+deep) | Temperature and soil type dependent computation of fractional freezing/melting of total soil water content in 6 active soil layers | Explicit soil ice (HIRLAM) 2 soil ice reservoirs (HARMONIE) | 4 layer scheme with phase changes | Diagnostic function of temperature. Influences the hydraulic parameters |
| Vegetation | One layer – Canopy resistance formulation for transpiration (Jarvis type) – interception reservoir | One layer – Evapotranspiration after Dickinson (1984) – interception reservoir | Surface resistance of Jarvis type. Intercepted water | One layer – Canopy resistance formulation for transpiration (Jarvis type) – interception reservoir | One layer – Canopy resistance formulation for transpiration (Jarvis type) and ISBA-Ags formulation for carbon fluxes – interception reservoir. Separate energy balance for each tile |
| Snow model | One layer – prognostic variables : snow water equivalent, snow density, snow albedo | One layer - prognostic variables : snow temperature, snow water equivalent, snow density, snow albedo | Separate energy balance for snow pack and snow interception reservoir (HIRLAM) one layer no separate every budget (HARMONIE) | Zero layer (uses top soil layer) – snow depth, albedo interception on needleleaf trees | One layer – prognostic variable : snow water equivalent, snow albedo. Revised snow density and diagnostic liquid water storage |
| Lake model | Prescribed surface temperature (analysis) | FLake | FLake (HIRLAM) and prescribed LST (HARMONIE) | Saturated soil or high thermal inertia | Prescribed surface temperature (analysis) |
| Sea-ice | Prescribed surface temperature (analysis) | Sea-ice model | Fraction from analysis only, 2 layer ice model with prescribed depth (HIRLAM) no sea model (HARMONIE) | Single layer thermodynamic model | Fixed depth 4-layer model |
| Ocean model | Prescribed surface temperature (analysis) – Charnock formulation for roughness – ECUME transfer coefficients | Prescribed surface temperature (analysis) – Charnock formulation for roughness length | None | Prescribed surface temperature (analysis) – Adapted Charnock formulation for roughness length | Prescribed surface temperature (analysis) |
| Urban areas | Modified surface roughness, albedo, emissivity (rocks) | Modified surface roughness, leaf area index, plant coverage | Modified surface parameters (HIRLAM) and TEB model (HARMONIE) | High inertia canopy | None |
| Chemistry module | None | ART optional | None | None | None |
| Surface boundary layer | 5-layer scheme solving turbulent prognostic equations without advection | Application of the turbulence scheme at the lower boundary and interative interpolation. Roughness length for scalars implicitly considered by calculation of an additional transport resistance throughout the turbulent and laminar roughness layer |
Monin-Obukhov similarity theory (HIRLAM) CANOPY scheme (HARMONIE) | Monin-Obukhov similarity theory – explicit formulation of vertical profile | Monin-Obukhov theory |