6.17. urban.nml

This file contains three namelists called URBAN_SWITCHES, URBAN2T_PARAM and URBAN_PROPERTIES.

This section reads in model configuration choices, geometry & material characteristics data for the urban schemes URBAN-2T and MORUSES. Both these schemes must have an urban_roof tile and an urban_canyon tile. Values from this section are only used if either of the two-tile urban schemes are enabled by specifying an urban_roof tile.

For parameters that MORUSES does not parameterise, and for any MORUSES parametrisations that are turned off, values from nveg_params.nml will be used. See the switches below for more information.

Further information on MORUSES, including references, can be found in the technical documentation and under l_moruses.

6.17.1. URBAN_SWITCHES namelist members

URBAN_SWITCHES::l_moruses

Type:logical Default:F

Note

Not used unless an urban_roof tile is present.

Switch for turning on MORUSES.

TRUE

Use MORUSES parameterisations.

FALSE

Do not use MORUSES parameterisations. Use urban tile parameters, set in nveg_params.nml, instead.

See also

References:

• Porson, A., et al. (2010), Implementation of a new urban energy budget scheme in the MetUM. Part I: Description and idealized simulations, Quarterly Journal of the Royal Meteorological Society, 136: 1514-1529. doi: 10.1002/qj.668
• Porson, A., et al. (2010), Implementation of a new urban energy budget scheme into MetUM. Part II: Validation against observations and model Intercomparison, Quarterly Journal of the Royal Meteorological Society, 136: 1530-1542. doi: 10.1002/qj.572

URBAN_SWITCHES::l_urban_empirical

Type:logical Default:T

Switch to use empirical relationships for urban geometry, based on total urban fraction. Dimensions calculated are W/R, H/W & H.

URBAN-2T uses W/R only.

Used in calculation of the canyon and roof fractions and also to distribute anthropogenic heat between roof and canyon if l_anthrop_heat_src = TRUE.

TRUE

Use empirical relationships for urban geometry.

FALSE

Appropriate data needs to be supplied instead.

Warning

These are only valid for high resolutions (~1 km).

See also

References:

• Bohnenstengel SI, Evans S, Clark P, Belcher SE (2010). Simulations of the London urban heat island, Quarterly Journal of the Royal Meteorological Society (submitted)

URBAN_SWITCHES::l_moruses_macdonald

Type:logical Default:T

MORUSES switch for using MacDonald et al. (1998) to calculate effective roughness length of urban areas and displacement height from urban geometry.

TRUE

Use MacDonald et al. (1998) formulations.

FALSE

Appropriate data needs to be supplied instead.

Note

If l_urban_empirical = TRUE then l_moruses_macdonald = TRUE, which the code enforces.

See also

References:

• Macdonald RW, Griffiths RF, Hall D. 1998. An improved method for the estimation of surface roughness of obstacle arrays. Atmos. Env. 32: 1857-1864

URBAN_SWITCHES::l_moruses_albedo

Type:logical Default:T

MORUSES switch for effective canyon albedo parameterisation.

TRUE

Use MORUSES parameterisation. Requires that l_cosz = TRUE, which the code automatically enables.

FALSE

The canyon albedo is taken from albsnf_nvg_io and albsnc_nvg_io.

In all cases, the roof albedo is taken from albsnf_nvg_io and albsnc_nvg_io.

URBAN_SWITCHES::l_moruses_emissivity

Type:logical Default:F

MORUSES switch for effective canyon emissivity parameterisation.

TRUE

Use MORUSES parameterisation.

FALSE

The canyon emmissivity is taken from emis_nvg_io.

In all cases, the roof emissivity is taken from emis_nvg_io.

URBAN_SWITCHES::l_moruses_rough

Type:logical Default:T

MORUSES switch for effective roughness length for heat parameterisation.

TRUE

Use MORUSES parameterisation for canyon and roof.

FALSE

Values for canyon and roof are taken from z0_nvg_io and z0hm_nvg_io.

URBAN_SWITCHES::l_moruses_storage

Type:logical Default:T

MORUSES switch for thermal inertia and coupling with underlying soil parameterisation.

TRUE

Use MORUSES parameterisation.

FALSE

Values are taken from ch_nvg_io and vf_nvg_io.

URBAN_SWITCHES::l_moruses_storage_thin

Type:logical Default:T

MORUSES switch to use a thin roof to simulate the effects of insulation.

Only used if l_moruses_storage = TRUE.

TRUE

Use thin, insulated roof.

FALSE

Use damping depth diffusivity of roofing materials.

6.17.2. URBAN2T_PARAM namelist members

URBAN2T_PARAM::anthrop_heat_scale

Type:real Default:1.0

Distribution scaling factor, which allows the anthropogenic heat flux to be spread between the urban_canyon and urban_roof tiles such that:

• H_roof = anthrop_heat_scale x H_canyon
• H_canyon x (W/R) + H_roof x ( 1.0 - W/R ) = anthrop_heat

Has a value between 0.0 and 1.0 where the extremes correspond to:

• 0.0 = all released within the canyon.
• 1.0 = evenly spread between canyon and roof.

Only used if l_anthrop_heat_src = TRUE.

6.17.3. URBAN_PROPERTIES namelist members

URBAN_PROPERTIES::file

Type:character Default:None

The file to read urban properties from.

If use_file (see below) is FALSE for every variable, this will not be used.

This file name can use variable name templating.

URBAN_PROPERTIES::nvars

Type:integer Permitted:>= 0 Default:0

The number of urban property variables that will be provided.

The required variables depend on whether MORUSES is used or not:

• If MORUSES is on, all variables must be given. However, depending on the configuration of MORUSES, not all given variables will be used. Those that will not be used could be set to constant values to avoid setting them from file.
• If MORUSES is not on, only wrr is required.

URBAN_PROPERTIES::var

Type:character(nvars) Default:None

List of urban property variable names as recognised by JULES (see List of urban properties). Names are case sensitive.

Note

For ASCII files, variable names must be in the order they appear in the file.

URBAN_PROPERTIES::use_file

Type:logical(nvars) Default:T

For each JULES variable specified in var, this indicates if it should be read from the specified file or whether a constant value is to be used.

TRUE

The variable will be read from the file.

FALSE

The variable will be set to a constant value everywhere using const_val below.

URBAN_PROPERTIES::var_name

Type:character(nvars) Default:None

For each JULES variable specified in var where use_file = TRUE, this is the name of the variable in the file containing the data.

This is not used for variables where use_file = FALSE, but a placeholder must still be given.

Note

For ASCII files, this is not used - only the order in the file matters, as described above.

URBAN_PROPERTIES::tpl_name

Type:character(nvars) Default:None

For each JULES variable specified in var, this is the string to substitute into the file name in place of the variable name substitution string.

If the file name does not use variable name templating, this is not used.

URBAN_PROPERTIES::const_val

Type:real(nvars) Default:None

For each JULES variable specified in var where use_file = FALSE, this is a constant value that the variable will be set to at every point in every layer.

This is not used for variables where use_file = TRUE, but a placeholder must still be given.

6.17.3.1. List of urban properties

All of the urban property variables listed below are expected to have no levels dimensions and no time dimension.

Variable name	Decription [*]	Notes
wrr	Repeating width ratio (or canyon fraction, W/R)	If l_urban_empirical = TRUE then this is updated with calculated values.
The following apply to MORUSES only
hwr	Height-to-width ratio (H/W)	See for wrr above.
hgt	Building height (H)	See for wrr above.
ztm	Effective roughness length of urban areas	If l_moruses_macdonald = TRUE (or l_urban_empirical = TRUE), then this is updated with calculated values.
disp	Displacement height	See for ztm above.
albwl	Wall albedo	Data only used if l_moruses_albedo = TRUE.
albrd	Road albedo	See for albwl above.
emisw	Wall emissivity	Data only used if l_moruses_emissivity = TRUE.
emisr	Road emissivity	See for emisw above.

Footnotes

[*]	For more information on the urban geometry used please see the JULES technical documentation.