6.9. jules_soil.nml

This file sets the soil options and parameters. It contains one namelist called JULES_SOIL.

6.9.1. JULES_SOIL namelist members

JULES_SOIL::sm_levels

Type

integer

Permitted

>= 1

Default

4

Number of soil layers.

A value of 4 is often used, with soil layer depths that have been tuned using this.

Warning

If ncpft > 0, sm_levels >= 3 is required.

JULES_SOIL::l_vg_soil

Type

logical

Default

F

Switch for van Genuchten soil hydraulic model.

TRUE

Use van Genuchten model.

FALSE

Use Brooks and Corey model 1.

See also

References:

• Brooks, R.H. and A.T. Corey, 1964, Hydraulic properties of porous media. Colorado State University Hydrology Papers 3.

• van Genuchten, M.T., 1980, A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Science Society of America Journal, 44:892-898.

JULES_SOIL::l_dpsids_dsdz

Type

logical

Default

F

Switch to calculate vertical gradient of soil suction with the assumption of linearity only for fractional saturation (consistent with the calculation of hydraulic conductivity).

JULES_SOIL::l_soil_sat_down

Type

logical

Default

F

Switch for dealing with supersaturated soil layers. If a soil layer becomes supersaturated, the water in excess of saturation will be put into the layer below or above according to this switch.

TRUE (Down)

Any excess is put into the layer below. Any excess from the bottom layer becomes subsurface runoff.

FALSE (Up)

Any excess is put into the layer above. Any excess from the top layer becomes surface runoff. This option was used in JULES2.0.

JULES_SOIL::l_holdwater

Type

logical

Default

F

This switch fixes a problem in soil hydrology, whereby if a layer goes supersaturated during the implicit calulation, the excess water is pushed out of the soil column (l_holdwater = FALSE) instead of into an adjacent layer (l_holdwater = TRUE).

TRUE

Supersaturated soil moisture from implicit calculation goes into an adjacent layer (above or below depending on l_soil_sat_down). This option was added in JULES 5.1.

FALSE

Supersaturated soil moisture from implicit calculation goes out of the base of the soil column.

JULES_SOIL::soilhc_method

Type

integer

Permitted

1, 2 or 3

Default

1

Switch for soil thermal conductivity model.

1. Use approach of Cox et al (1999), as in JULES2.0.

   This is likely to predict values of soil thermal conductivity that are too low (Dharssi et al, 2009).
2. Use approach of Dharssi et al (2009), which was adapted from Johansen (1975) and described by Peters-Lidard et al. (1998).

   This is not recommended for organic soils.
3. Use approach of Chadburn et al (2015).

   This is recommended when using organic soils, which can have a much lower saturated thermal conductivity than mineral soils.

See also

References:

• Chadburn et al (2015). An improved representation of physical permafrost dynamics in a global land-surface scheme. Geoscientific Model Development

• Dharssi et al (2009). New soil physical properties implemented in the Unified Model at PS18. Met Office Technical note 528

• Johansen (1975). Thermal conductivity of soils. PhD thesis. University of Trondheim, Norway

• Peters-Lidard et al (1998). The effect of soil thermal conductivity parameterisation on surface energy fluxes and temperatures. J. Atmos. Sci. 55:1209-1224

JULES_SOIL::l_bedrock

Type

logical

Default

F

Switch for using a thermal bedrock column beneath the soil column. The bedrock has no hydrological processes - diffusion of heat is the only process represented.

Properties of the bedrock can be set using ns_deep, hcapdeep, hcondeep and dzdeep.

TRUE

An additional bedrock column is used below the soil column.

FALSE

No effect.

See also

For full details see Chadburn et al. (2015)

Bedrock parameters (only used if l_bedrock = TRUE)

JULES_SOIL::ns_deep

Type

integer

Permitted

>= 1

Default

100

The number of levels in the thermal-only bedrock.

JULES_SOIL::hcapdeep

Type

real

Default

2100000.0

The heat capacity of the bedrock (J K^-1 m^-3 ).

JULES_SOIL::hcondeep

Type

real

Default

8.6

The heat conductivity of the bedrock (W m^-2 K^-1 ).

JULES_SOIL::dzdeep

Type

real

Default

0.5

The thickness of the bedrock layers (m).

JULES_SOIL::cs_min

Type

real

Default

1.0e-6

Minimum allowed soil carbon (kg m^-2).

JULES_SOIL::zsmc

Type

real

Permitted

> 0

Default

1.0

If a depth-averaged soil moisture diagnostic is requested, the average is calculated from the surface to this depth (m).

JULES_SOIL::zst

Type

real

Permitted

> 0

Default

1.0

The depth (0.0->zst) to which the soil temperature is averaged for use in the calculation of wetland methane emissions (m).

JULES_SOIL::confrac

Type

real

Permitted

0 <= confrac <= 1

Default

0.3

The fraction of the gridbox assumed to be covered by convective precipitation.

JULES_SOIL::dzsoil_io

Type

real(sm_levels)

Default

None

The soil layer depths (m), starting with the uppermost layer.

Note that the soil layer depths (and hence the total soil depth) are constant across the domain.

It is recommended that JULES uses layer depths of 0.1, 0.25, 0.65 and 2.0m, giving a total depth of 3.0m, unless there is good reason not to.

JULES_SOIL::dzsoil_elev

Type

real

Default

None

Depth of the tiled solid-ice bedrock-type layer used underneath individual ice tiles if l_elev_land_ice is TRUE. Effectively this sets the amount of thermal buffering each surface tile has to heat fluxes penetrating through the snowpack.

JULES_SOIL::l_tile_soil

Type

logical

Default

False

Switch to set the number of soil tiles to equal the number of surface tiles. Each soil tile has independent properties.

See also l_broadcast_ancils and l_broadcast_soilt.

Note

Setting l_tile_soil = TRUE means a separate soil tile exists for each surface tile (rather than all surface tiles using the same, single soil tile). This also alters the names of many of the soil prognostic and ancillary variables that are used (see elsewhere), with the suffix “_soilt’’ being added to indicate the presence of soil tiling. The switches l_broadcast_ancils and l_broadcast_soilt allow soil tiling to be used with input files that do not contain soil tile information. Setting l_broadcast_ancils = TRUE means that a soil ancillary file that does not contain soil tiles can be used in a tiled run. Setting l_broadcast_soilt = TRUE means an initital state file that does not contain soil tiles can be used to initialise a run with soil tiles.

JULES_SOIL::l_broadcast_ancils

Type

logical

Default

False

Switch to allow non-soil tiled ancillary files to be broadcast to all soil tiles. Only active when l_tile_soil is True. When reading ancillaries from the dump file, use l_broadcast_soilt instead.

Footnotes

1

In the JULES2.0 User Manual this was described as the ‘Clapp and Hornberger’ model and the JULES code still refers to ‘Clapp and Hornberger’ rather than ‘Brooks and Corey’. In fact there are important differences between these two hydraulic models (Marthews et al. 2014,GMD). There has been confusion in the literature and in past documentation of MOSES/JULES, but JULES uses the Brooks and Corey model when l_vg_soil = FALSE .

References: * Brooks RH & Corey AT (1964). Hydraulic properties of porous media. Colorado State University Hydrology Papers 3. * Clapp RB & Hornberger GM (1978). Empirical Equations for Some Soil Hydraulic Properties. Water Resources Research 14:601-604.