## Summary table: Boundary Conditions

surface | top | lateral inflow | lateral outflow | |
---|---|---|---|---|

ADREA | The concept of surface layer func-tions is adopted to avoid an excessive number of meshes near the ground due to very steep parameter gradients, occurring at the region. | |||

ALADIN/A | surface pressure, orography, surface temperature and relative moisture contents, deep soil temperature and moisture contents, snow cover, albedo, emissivity, land sea mask, proportion of vegetation, roughness length, standard deviation, anisotropy and orientation of sub-grid scale orography. | wind, temperature, specific humidity | ||

ALADIN/PL | surface pressure, orography, surface temperature and relative moisure contents, snow cover, albedo, emissivity, land sea mask, proportion of vegetation, roughness lenght, standard deviation, anisotropy and orientation of sub-grid scale orography | wind, temperature, specyfic humidity | ||

ARPS | Land surface scheme De Ridder and Schayes (1997) | Rigid lid, Rayleigh damping. | Relaxation to large-scale fields (nesting) | Relaxation to large-scale fields (nesting) |

BOLCHEM | Surface model used | No vertical motion condition at the top | Relaxation condition | Relaxation condition |

CALMET/CALPUFF | ||||

CALMET/CAMx | ||||

CLM | Digital-Filter initialization of unbalanced initial states (Lynch et al., 1997) with options for adiabatic and diabatic initialization. | Options for rigid lid condition and Rayleigh damping layer. | 1-way nesting by Davies-type lateral boundary formulation. Data from several coarse-grid models can be processed (GME, IFS, LM). Option for periodic boundary conditions. | |

COSMO-2 | Friction boundary conditions boundary conditions for horiz. vel., temp. and water substances, non-penetrative for grid-scale mass fluxes, free slip for u and v, extrapolated boundary cond. for pressure disturbance. | Rayleigh damping layer,non-penetrative boundary conditions = rigid lid with free-slip condition for horiz. vel., temp. and water substances. | Interpolation from ECMWF global model IFS, with relaxation boundary condition after Davies(1976) for all prognostic variables except vert. velocity | |

COSMO-7 | Friction boundary conditions boundary conditions for horiz. vel., temp. and water substances, non-penetrative for grid-scale mass fluxes, free slip for u and v, extrapolated boundary cond. for pressure disturbance. | Rayleigh damping layer,non-penetrative boundary conditions = rigid lid with free-slip condition for horiz. vel., temp. and water substances. | Interpolation from ECMWF global model IFS, with relaxation boundary condition after Davies(1976) for all prognostic variables except vert. velocity. | |

COSMO-CLM | Digital-Filter initialization of unbalanced initial states (Lynch et al., 1997) with options for adiabatic and diabatic initialization. | Options for rigid lid condition and Rayleigh damping layer. | 1-way nesting by Davies-type lateral boundary formulation. Data from several coarse-grid models can be processed (GME, IFS, LM). Option for periodic boundary conditions. | |

COSMO-MUSCAT | Friction boundary conditions for constant-flux layer with surface budget | Free slip (vanishing vertical velocity and gradients) | Relaxation conditions forcing adaption to profiles of outer-nest model or to reanalysis data of global model GME (within a zone of few cells at each lateral boundary) | Same as lateral inflow |

ENVIRO-HIRLAM | Surface analysis | Climate files | u,v,t,q,ps | u,v,t,q,ps |

GEM-AQ | land-sea mask, roughness length, sea surface temperature, land surface temperature, deep soil temperature, soil wetness, snow fraction on the ground, sea ice, surface albedo | |||

GESIMA | no-slip, energy-budget, land-use parameters | rigid lid with sponge layer | specified values from synoptic background fields | Orlanski-type radiating b.c. |

GME | SST from analysis fixed during model integration | model top at 10hPa | none (global model) | none (global model) |

Hirlam | prescibed SST | ECMWF boundary condition files | ECMWF boundary condition files | |

LAMI | friction boundary conditions for horiz. vel., temp. and water substances, non-penetrative for grid-scale mass fluxes, extrapolated boundary cond. for pressure disturbance. | Rayleigh damping layer,non-penetrative boundary conditions = rigid lid with free-slip condition for horiz. vel., temp. and water substances. | interpolation from DWD's global model GME,with relaxation boundary condition after Davies(1976) for all prognostic variables. | |

LME | friction boundary conditions boundary conditions for horiz. vel., temp. and water substances, non-penetrative for grid-scale mass fluxes, free slip for u and v, extrapolated boundary cond. for pressure disturbance. | interpolation from DWD's global model GME,with relaxation boundary condition after Davies(1976) for all prognostic variables except vert. velocity. | ||

LME_MH | see LME model documentation | see LME model documentation | see LME model documentation | see LME model documentation |

M-SYS | Several options (constant values, surface energy budgets, constant fluxes) | rigid lid, damping layers; towards forcing data | Towards forcing data (relaxation area) or modified radiation boundary condition | Towards forcing data (relaxation area) or modified radiation boundary condition |

MC2-AQ | various geophysical and climatological fields (land-sea mask, roughness length, sea surface temperature, land surface temperature, deep soil temperature, soil wetness, snow fraction on the ground, sea ice, surface albedo) | rigid lid with no vertical motion at the model top | time varying meteorological fields coming either from global model (GEM-AQ) results or from objective anaysis | |

MCCM | Soil model | |||

MEMO (UoT-GR) | The lower boundary coincides with the ground (or, more precisely, a height above ground corresponding to its aerodynamic roughness). For the nonhydrostatic part of the mesoscale pressure perturbation, inhomogeneous Neumann conditions are imposed. All othe | Neumann for the horizontal velocity components and the potential temperature. To ensure non-reflectivity, a radiative condition is used for the hydrostatic part of the mesoscale pressure perturbation. For the nonhydrostatic part of the mesoscale pressure | Radiation conditions for u,v,w, potential temperature and pressure. For the nonhydrostatic mesoscale pressure perturbation, homogeneous Neumann conditions are used. | see above |

MEMO (UoA-PT) | The lower boundary coincides with the ground. For mesoscale pressure perturbation, inhomogeneous Neumann consitions are imposed. All other consitions at the lower boundary follow the onin-Obukhov similarity theory. | Neumann boundary conditions are imposed for horizontal velocity components and potential temperature. For the mesoscale pressure perturbation homogeneous staggered Dirichlet conditions are impose. | Homogeneous Neumann boundary conditions. | Homogeneous Neumann boundary conditions. |

MERCURE | surface exchange parameterization (two layer model; cf. above) | - prescribed large scale flow - optional absorbing layer | - standard Dirichlet - optional absorbing layer | - standard Neuman - optional absorbing layer |

METRAS | Several options (constant values, surface energy budgets, constant fluxes) | rigid lid, damping layers; towards forcing data | Towards forcing data (relaxation area) or modified radiation boundary condition | Towards forcing data (relaxation area) or modified radiation boundary condition |

METRAS-PCL | constant values or budget equation | rigid with damping layers | ||

MM5 (UoA-GR) | The LOWBDY_DOMAINx file provides sea-surface temperature, substrate temperature, and optionally snow cover and sea-ice. The switch ISSTVAR allows multiple times in this file (created by INTERPF) to be read in as the model runs, which is the method of updating these fields in long-term simulations. | - No upper boundary condition - Rigid lid with no vertical motion at the model top. This may be preferable for very coarse mesh simulations (50 km or more grids). 1. Upper radiative condition - Top vertical motion calculated to reduce reflection of energy from the model top preventing some spurious noise or energy build-up over topography. This is recommended for grid-lengths below 50 km. It works better for hydrostatic gravity wave scales, rather than inertial or nonhydrostatic scales. | 1 - Fixed 2 - Time-dependent/Nest Outer two rows and columns have specified values of all predicted fields. Recommended for nests where time-dependent values are supplied by the parent domain. Not recommended for coarse mesh where only one outer row and column would be specified. 3 - Relaxation/inflow-outflow Outer row and column is specified by time-dependent value, next four points are relaxed towards the boundary values with a relaxation constant that decreases linearly away from the boundary. | several options are available: fixed; Sponge Boundary Conditions;Nudging Boundary Conditions |

MM5 (UoA-PT) | The LOWBDY_DOMAINx file provides sea-surface temperature, substrate temperature, and optionally snow cover and sea-ice. The switch ISSTVAR allows multiple times in this file (created by INTERPF) to be read in as the model runs, which is the method of updating these fields in long-term simulations. | - No upper boundary condition - Rigid lid with no vertical motion at the model top. This may be preferable for very coarse mesh simulations (50 km or more grids). 1. Upper radiative condition - Top vertical motion calculated to reduce reflection of energy from the model top preventing some spurious noise or energy build-up over topography. This is recommended for grid-lengths below 50 km. It works better for hydrostatic gravity wave scales, rather than inertial or nonhydrostatic scales. | 1 - Fixed 2 - Time-dependent/Nest Outer two rows and columns have specified values of all predicted fields. Recommended for nests where time-dependent values are supplied by the parent domain. Not recommended for coarse mesh where only one outer row and column would be specified. 3 - Relaxation/inflow-outflow Outer row and column is specified by time-dependent value, next four points are relaxed towards the boundary values with a relaxation constant that decreases linearly away from the boundary. | |

MM5 (UoH-UK) | Many options are available: single slab with fixed-temperature substrate or five layer soil model base on the 'force-restore' method developed by Blackadar;Pleim-Xiu Land-Surface Model;Noah Land-Surface Model | Radiative boundary conditions | several options are available: fixed; Sponge Boundary Conditions;Nudging Boundary Conditions | several options are available: fixed; Sponge Boundary Conditions;Nudging Boundary Conditions |

MM5(GKSS-D) | 4 options avalaible. AT GKSS NOAH land surface model with 4 layers is used. | radiative boundary conditions | time dependent values in one outer row and column for the coarse mesh. Two outer rows and columns are used for nests. Several outer meteorology data sets can be used for lateral boundary conditions. At GKSS, ERA40 data is used. | Depends on variables prescribed at the boundaries. Variables which are not specified by the outer meteorology fields are zero on inflow and zero grdaient on outflow. |

Meso-NH | Given by the externalized surface model | Rigid | For the coarser model, open boundary conditions with radiative properties from the LS coupling model. For the inner models, interpolation from the coarser grid. | Radiative open boundary conditions |

NHHIRLAM | no condition or weak sponge | Davies, 1976 | Davies, 1976 | |

RAMS | SVAT model (LEAF-2) | Rayleigh friction absorbing layer. | Klemp and Wilhelmson scheme. | Klemp and Wilhelmson |

RCG | ||||

SAIMM | no-slip condition (u=v=0) is specified for the horizontal velocities. For the vertical velocity, the lower boundary condition is always w*=0. The temperature at the ground surface is predicted from an energy balance through a Newton-Raphson iterative technique. | the upper boundary is an isentropic surface with no horizontal velocity perturbation from the basic state. | zero-gradient lateral boundary conditions are imposed on all prognostic variables | -- |

TAPM | The soil and vegetation parameterisations are based on those from Kowalczyk et al. (1991). | At the model top boundary, all variables are set at their synoptic values. | One-way nested lateral boundary conditions are used for the prognostic equations. | |

UM | No slip or free slip in dynamics, no slip via PBL. | w=0 | Davies relaxation | Davies relaxation |

WRF-ARW | ||||

WRF/Chem | SST's | mass coordinate | Analysis data from operational centers, or 1-way nesting, also forecasts from operational centers |

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