Single-layer urban surface model (SLUrb)#
Job preparation#
SLUrb is enabled by adding &slurb_parameters into p3d namelist, which is also used to define the general configuration for the model. In addition, a minimal set of model surface parameters can be set for testing purposes using only the namelist parameters (homogeneous initialization). Spatially heterogeneous initialization of surface parameters is realized through a netCDF driver, see SLUrb's model driver documentation for details. The value set using netCDF input takes priviledge over the namelist initialization. Thus, the namelist-based initialization may be amended by the netCDF input only for some grid cells.
If all the mandatory inputs are provided using the netCDF driver and the default configuration is otherwise suitable for your case, slurb_parameters must still be included in the namelist to enable the module, but can be left empty:
&slurb_parameters
/
Example#
A minimum setup with homogeneous surface and anisotropic south-north oriented street canyons could look like the following:
&slurb_parameters
urban_fraction = 0.5,
urban_roughness_length = 0.5,
building_area_fraction = 0.3,
building_frontal_fraction = 0.11,
building_height = 20.0,
window_fraction = 0.2,
street_canyon_aspect_ratio = 0.5,
building_type = 2,
pavement_type = 2,
anisotropic_street_canyons = .T.,
street_canyon_orientation = 0.,
soil_temperature = 288.0,
/
As SLUrb requires the use of the land surface model (PALM-LSM) to model the natural fluxes, land_surface_parameters has to be defined in the namelist as well. For heterogeneous surfaces, the netCDF driver must be used.
Outputs#
SLUrb provides a range of output quantities specific to the urban environment, with both instantaneous and temporally averaged outputs available. All possible outputs are listed and described as a part of the output documentation. Activating SLUrb has some side effects to the PALM's core surface outputs: shf*, qsws* and surface radiation balance outputs will become aggregated fluxes. If the user wishes to output the urban and natural surfaces separately, SLUrb provides additional output quantities to access the non-aggregated surface fluxes (e.g. slurb_shf_urban* and slurb_shf_lsm* for urban and natural sensible heat flux).
Available namelist parameters#
| Parameter | Default | Description |
|---|---|---|
| aero_roughness_heat | kanda | Parametrization for the aerodynamic roughness lengths for heat for horizontal surfaces. |
| anisotropic_street_canyons | .FALSE. | Enables anisotropic street canyons. |
| building_frontal_area_fraction | -9999.0 | Frontal area fraction of buildings. |
| building_height | -9999.0 | Mean building height within the cell. |
| building_indoor_temperature | 295.15 | Building indoor temperature. |
| building_plan_area_fraction | -9999.0 | Building plan area fraction. |
| building_type | 2 | Building type. |
| deep_soil_temperature | -9999.0 | Deep soil temperature. |
| facade_resistance_parametrization | doe-2 | Parametrization for the aerodynamic resistance between facade surfaces and the street canyon air. |
| moist_physics | .TRUE. | Enables moist dynamical processes in SLUrb. |
| n_layers_roads | 4 | Number of road layers. |
| n_layers_roofs | 4 | Number of roof layers. |
| n_layers_walls | 4 | Number of wall layers. |
| n_layers_windows | 4 | Number of window layers. |
| pavement_type | 2 | Pavement type. |
| qsws_external | 0.0 | Latent heat flux from external sources. |
| shf_external | 0.0 | Sensible heat flux from external sources. |
| shf_traffic | 0.0 | Sensible heat flux from traffic. |
| street_canyon_aspect_ratio | -9999.0 | Street canyon aspect ratio. |
| street_canyon_orientation | -9999.0 | Street canyon orientation. |
| street_canyon_wspeed_factor | surfex | Factorfor the street canyon wind speed. |
| switch_off_module | .FALSE. | Disables the module. |
| urban_fraction | -9999.0 | Urban fraction. |
| window_fraction | Depends on building_type | Window fraction. |
aero_roughness_heat#
- Fortran Type: C*20
-
Default: kanda
Parametrization for the aerodynamic roughness lengths for heat for horizontal surfaces.
Parametrization used to compute the aerodynamic roughness lengths for heat (\(z_{0,h}\)) for horizontal surfaces.
Currently 2 choices are available:
-
kanda
Parametrization by Kanda et al. (2007) where \(z_{0,h}\) is dynamically computed at every time step.
-
fixed
\(z_{0,h}\) is fixed to a material default or user input value throughout the simulation.
-
anisotropic_street_canyons#
- Fortran Type: L
-
Default: .FALSE.
Enables anisotropic street canyons.
Enables anisotropic street canyons, i.e. separtion between walls and windows A and B. When false, average radiation for walls (windows) is used and prognostic equations are computed only for wall (window) A, with outputs of wall (window) B copied from A. The street canyon orientation can be set using either street_canyon_orientation in the namelist or
theta_canin netCDF input or both. If neither is set, an isotropic canyon is used in that grid cell regardless of value of this parameter. This allows mixing isotropic and anisotropic street canyons in the same simulation.
building_frontal_area_fraction#
- Fortran Type: R
-
Default: -9999.0
Frontal area fraction of buildings.
Ratio of building frontal area to total plan area (incl. natural surfaces/pervious surfaces).
building_height#
- Fortran Type: R
- Default: -9999.0
-
SI-Unit: m
Mean building height within the cell.
Mean building height within the cell. Note that a single-layer model like SLUrb does not perform very well with deep urban canopies (>60 m).
building_indoor_temperature#
- Fortran Type: R
- Default: 295.15
-
SI-Unit: K
Building indoor temperature.
Building indoor temperature. Kept constant throughout the simulation.
building_plan_area_fraction#
- Fortran Type: R
-
Default: -9999.0
Building plan area fraction.
Ratio of building plan area to total plan area incl. natural surfaces. Cannot exceed
urban_fraction.
building_type#
- Fortran Type: I
-
Default: 2
Building type.
Building type corresponding to building types as described in the SLUrb's model driver documentation. The building material properties are set according to the type.
deep_soil_temperature#
- Fortran Type: R
- Default: -9999.0
-
SI-Unit: K
Deep soil temperature.
Deep soil temperature to be used as a bottom boundary condition for the road model.
facade_resistance_parametrization#
- Fortran Type: C*20
-
Default: doe-2
Parametrization for the aerodynamic resistance between facade surfaces and the street canyon air.
Parametrization used to compute the aerodynamic roughness resistances for heat (\(r_{ah}\)) for facade surfaces (i.e. walls and windows).
Currently 3 choices are available:
-
doe-2
DOE-2 parametrization from the EnergyPlus building energy simulation system (EnergyPlus(TM) version 23.2.0 Engineering Reference, 2023), which is a function of natural convection strength, local surface roughness and street canyon effective wind speed. An average of windward and leeward parametrization are used.
-
krayenhoff&voogt
Parametrization following Krayenhoff & Voogt (2007), which is a function of local surface roughness and the street canyon effective wind speed.
-
rowley
Parametrization following Rowley (1932), which is a simple function of the street canyon effective wind speed.
-
moist_physics#
- Fortran Type: L
-
Default: .TRUE.
Enables moist dynamical processes in SLUrb.
Enables condensation/evaporation processes on roofs and roads as well as prognostic equation for street canyon mixing ratio. Only effective if humidity = .T., otherwise ignored.
n_layers_roads#
- Fortran Type: I
-
Default: 4
Number of road layers.
Number of road layers to be modelled. Non-default configuration requires setting of all road material parameters manually using the netCDF input. A minimum of three layers is required.
n_layers_roofs#
- Fortran Type: I
-
Default: 4
Number of roof layers.
Number of roof layers to be modelled. Non-default configuration requires setting of all roof material parameters manually using the netCDF input. A minimum of three layers is required.
n_layers_walls#
- Fortran Type: I
-
Default: 4
Number of wall layers.
Number of wall layers to be modelled. Non-default configuration requires setting of all wall material parameters manually using the netCDF input. A minimum of three layers is required.
n_layers_windows#
- Fortran Type: I
-
Default: 4
Number of window layers.
Number of window layers to be modelled. Non-default configuration requires setting of all window material parameters manually using the netCDF input. A minimum of three layers is required.
pavement_type#
- Fortran Type: I
-
Default: 2
Pavement type.
Pavement type corresponding to pavement types as described in the SLUrb's model driver documentation. The pavement material properties are set according to the type.
qsws_external#
- Fortran Type: R
- Default: 0.0
-
SI-Unit: W m-2
Latent heat flux from external sources.
Additional latent heat flux from sources external to the model (e.g. industry or HVAC exhaust) per unit area. The flux is internally scaled to unit urban area and aggregated to atmospheric fluxes.
shf_external#
- Fortran Type: R
- Default: 0.0
-
SI-Unit: W m-2
Sensible heat flux from external sources.
Additional sensible heat flux from sources external to the model (e.g. industry or HVAC exhaust) per unit area. The flux is internally scaled to unit urban area and aggregated to atmospheric fluxes.
shf_traffic#
- Fortran Type: R
- Default: 0.0
-
SI-Unit: W m-2
Sensible heat flux from traffic.
Additional sensible heat flux from traffic per unit urban area. The flux is internally scaled and entered into the prognostic equation for street canyon air temperature.
street_canyon_aspect_ratio#
- Fortran Type: R
-
Default: -9999.0
Street canyon aspect ratio.
Street canyon aspect ratio (height-to-width ratio, \(H/W\)).
street_canyon_orientation#
- Fortran Type: R
- Default: -9999.0
-
SI-Unit: degrees
Street canyon orientation.
Only effective when anisotropic_street_canyons = .T. .
street_canyon_wspeed_factor#
- Fortran Type: C*20
-
Default: surfex
Factorfor the street canyon wind speed.
Parametrization for the factor used to compute street canyon wind speed from first atmospheric grid level wind speed.
Currently 3 choices are available:
-
surfex
The street canyon wind speed is computed as in the SURFEX model v8.1.
-
krayenhoff&voogt
The street canyon wind speed is computed following Krayenhoff and Voogt (2007).
-
masson
The street canyon wind speed is computed following Masson (2000).
-
switch_off_module#
- Fortran Type: L
-
Default: .FALSE.
Disables the module.
Switch to turn off the module without having to remove slurb_parameters from the namelist.
urban_fraction#
- Fortran Type: R
-
Default: -9999.0
Urban fraction.
The plan area fraction of buildings and streets combined. The remaining surface area will be modelled as vegetation, water or open pavement surface by PALM-LSM depending on the user's setup. Any pervious or water surfaces should be included in the non-urban fraction, irregardless if they are part of urban fabric or not. As SLUrb's physical formulation is based on a street canyon, large paved areas without buildings (e.g. large parking lots) are better to be omitted from this fraction as well and modelled with PALM-LSM instead (surface type
pavement).
window_fraction#
- Fortran Type: R
-
Default: Depends on building_type
Window fraction.
Area fraction of windows of the total facade area. Setting the fraction to zero disables the window model.