6.3. switches.nml

This file sets up the switches that control model behaviour. It contains a single namelist named JULES_SWITCHES.

6.3.1. JULES_SWITCHES namelist members

JULES_SWITCHES::l_aggregate

Type:logical Default:F

Switch controlling number of tiles for each gridbox.

This is used to set the number of surface energy balances that are solved for each gridbox (ntiles).

TRUE

Aggregate parameter values are used to solve a single energy balance per gridbox. This option sets ntiles = 1.

FALSE

A separate energy balance is calculated for each surface type. This option sets ntiles = ntype.

JULES_SWITCHES::can_model

Type:integer Permitted:1-4 Default:4

Choice of canopy model for vegetation:

1. No canopy.
2. Radiative canopy with no heat capacity.
3. Radiative canopy with heat capacity. This option is deprecated, with 4 preferred.
4. As 3 but with a representation of snow beneath the canopy. This option is preferred to 3.

Note

can_model = 1 does not mean that there is no vegetation canopy. It means that the surface is represented as a single entity, rather than having distinct surface and canopy levels for the purposes of radiative processes.

JULES_SWITCHES::can_rad_mod

Type:integer Permitted:1-5 Default:4

Switch for treatment of canopy radiation.

1. A single canopy layer for which radiation absorption is calculated using Beer’s law. Leaf-level photosynthesis is scaled to the canopy level using the ‘big leaf’ approach. Leaf nitrogen, photosynthetic capacity, i.e the Vcmax parameter, and leaf photosynthesis vary exponentially through the canopy with radiation.
2. Multi-layer approach for radiation interception following the 2-stream approach of Sellers et al. (1992). This approach takes into account leaf angle distribution, zenith angle, and differentiates absorption of direct and diffuse radiation. Leaf-level photosynthesis is calculated using a vertically-varying light-limited rate, and constant Rubisco and export velocities, consistent with the assumption of constant leaf N through the canopy. Canopy photosynthesis and conductance are calculated as the sum over all layers.
3. As 2, but photosynthesis calculated separately for sunlit and shaded leaves for the whole canopy (i.e. not at each layer). The definition of sunlit and shaded leaves is based on a threshold of absorbed radiation at each layer.
4. This is a modification of option 2. Instead of constant leaf N through the canopy, it has an exponential decline of leaf N with canopy height. Additionally includes inhibition of leaf respiration in the light.
5. This is an improvement of option 4, including:
   • Sunfleck penetration though the canopy.
   • Division of sunlit and shaded leaves within each canopy level.
   • A modified version of inhibition of leaf respiration in the light.

Note

When using can_rad_mod = 4 or 5, it is recommended to use driving data that contains direct and diffuse radiation separately rather than a constant diffuse fraction.

See also

Descriptions 1, 2 and 3 can be found in Jogireddy et al. (2006), and an application of option 4 can be found in Mercado et al. (2007) and all are described in Clark et al (2011).

JULES_SWITCHES::ilayers

Type:integer Permitted:>= 0 Default:10

Number of layers for canopy radiation model.

These layers are used for the calculations of radiation interception and photosynthesis.

Only used if can_rad_mod is 2 or 3.

JULES_SWITCHES::l_cosz

Type:logical Default:T

Switch for calculation of solar zenith angle. For land points, this switch is only relevant if l_spec_albedo = TRUE.

TRUE

Calculate zenith angle.

FALSE

Assume constant zenith angle of zero, meaning sun is directly overhead.

JULES_SWITCHES::l_spec_albedo

Type:logical Default:T

Switch for albedo model.

TRUE

Use spectral albedo.

FALSE

Use a single (averaged) waveband albedo.

JULES_SWITCHES::l_snow_albedo

Type:logical Default:T

Switch for using prognostic snow properties in model albedo.

Requires l_spec_albedo = TRUE.

TRUE

Use prognostic snow properties for albedo.

FALSE

Calculate albedo of snow using only snow depth.

JULES_SWITCHES::l_albedo_obs

Type:logical Default:F

Switch for applying a scaling factor to the albedo values, on tiles, so that the resultant aggregate albedo matches observations.

TRUE

Scale the albedo values on tiles.

Note

Observed albedo(s) must be prescribed in prescribed_data.nml.

FALSE

Do not scale the albedo values on tiles.

JULES_SWITCHES::l_phenol

Type:logical Default:F

Switch for vegetation phenology model.

TRUE

Use phenology model.

FALSE

Do not use phenology model.

JULES_SWITCHES::l_triffid

Type:logical Default:F

Switch for dynamic vegetation model (TRIFFID) except for competition.

TRUE

Use TRIFFID. In this case soil carbon is modelled using four pools (biomass, humus, decomposable plant material, resistant plant material).

FALSE

Do not use TRIFFID. A single soil carbon pool is used.

JULES_SWITCHES::l_veg_compete

Type:logical Default:T

Switch for competing vegetation.

Only used if l_triffid = TRUE.

TRUE

TRIFFID will let the different PFTs compete against each other and modify the vegetation fractions.

FALSE

Vegetation fractions do not change.

JULES_SWITCHES::l_trif_eq

Type:logical Default:T

Switch for equilibrium vegetation model (i.e., an equilibrium solution of TRIFFID).

Only used if l_triffid = TRUE.

TRUE

Use equilibrium TRIFFID.

FALSE

Do not use equilibrium TRIFFID.

JULES_SWITCHES::l_top

Type:logical Default:F

Switch for a TOPMODEL-type model of runoff production.

TRUE

Use a TOPMODEL-type scheme. This is based on Gedney and Cox (2003); see also Clark and Gedney (2008).

FALSE

No TOPMODEL scheme.

See also

References:

• Gedney, N. and P.M.Cox, 2003 , The sensitivity of global climate model simulations to the representation of soil moisture heterogeneity, J. Hydrometeorology, 4, 1265-1275.
• Clark and Gedney, 2008, Representing the effects of subgrid variability of soil moisture on runoff generation in a land surface model, Journal of Geophysical Research - Atmospheres, 113, D10111, doi:10.1029/2007JD008940.

JULES_SWITCHES::l_pdm

Type:logical Default:F

Switch for a PDM-type model of runoff production.

PDM is the Probability Distributed Model (Moore, 1985), implemented in JULES following Clark and Gedney (2008).

TRUE

Use a PDM scheme.

FALSE

No PDM scheme.

See also

References:

• Moore, R. J. (1985), The probability-distributed principle and runoff production at point and basin scales, Hydrol. Sci. J., 30, 273-297.
• Clark and Gedney, 2008, Representing the effects of subgrid variability of soil moisture on runoff generation in a land surface model, Journal of Geophysical Research - Atmospheres, 113, D10111, doi:10.1029/2007JD008940.

JULES_SWITCHES::l_anthrop_heat_src

Type:logical Default:F

Switch for inclusion of anthropogenic contribution to the surface heat flux from urban tiles.

TRUE

Add anthropogenic effect.

FALSE

No effect.

JULES_SWITCHES::l_o3_damage

Type:logical Default:F

Switch for ozone damage.

TRUE

Ozone damage is on.

Note

Ozone concentration in ppb must be prescribed in prescribed_data.nml.

FALSE

No effect.

JULES_SWITCHES::l_imogen

Type:logical Default:F

Switch for IMOGEN.

TRUE

IMOGEN is used to generate driving data.

FALSE

No effect.

JULES_SWITCHES::l_epot_corr

Type:logical Default:T

TRUE

Use correction to the calculation of potential evaporation.

FALSE

No effect.

JULES_SWITCHES::l_snowdep_surf

Type:logical Default:F

TRUE

Use equivalent canopy snow depth for surface calculations on tiles with a snow canopy.

FALSE

No effect.

JULES_SWITCHES::Iscrntdiag

Type:integer Permitted:0 or 1 Default:0

Switch controlling method for diagnosing screen temperature.

0. Use surface similarity theory.
1. Use surface similarity theory but allow decoupling in very stable conditions based on the quasi-equilibrium radiative solution.

JULES_SWITCHES::l_360

Type:logical Default:F

Switch indicating use of 360 day years.

TRUE

Each year consists of 360 days. This is sometimes used for idealised experiments.

FALSE

Each year consists of 365 or 366 days.

JULES_SWITCHES::l_q10

Type:logical Default:T

Switch for use of Q10 approach when calculating soil respiration.

TRUE

Use Q10 approach.

Note

This is always used if TRIFFID is switched off (l_triffid = FALSE) and was used in JULES2.0.

FALSE

Use the approach of the RothC model.

JULES_SWITCHES::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

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

FALSE

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_SWITCHES::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 [*].

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_SWITCHES::soilhc_method

Type:integer Permitted:1 or 2 Default:1

Switch for soil thermal conductivity model.

1. Use approach of Cox et al (1999), as in JULES2.0.
2. Use approach of Johansen (1975).

JULES_SWITCHES::l_point_data

Type:logical Default:F

Flag indicating if driving data are point or area-average values. This affects the treatment of precipitation input and how snow affects the albedo.

TRUE

Driving data are point data. Precipitation is not distributed in space (see FALSE below) and is all assumed to be large-scale in origin. The albedo formulation is suitable for a point.

FALSE

Driving data are area averages. The precipitation inputs are assumed to be exponentially distributed in space, as in UMDP25, and can include convective and large-scale components. The albedo formulation is suitable for a gridbox.

JULES_SWITCHES::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_SWITCHES::l_land_ice_imp

Type:logical Default:F

Switch to control the use of implicit numerics to update land ice temperatures.

TRUE

Use implicit numerics to update land ice temperatures.

FALSE

Use explicit numerics to update land ice temperatures.

JULES_SWITCHES::l_bvoc_emis

Type:logical Default:F

Switch to enable calculation of BVOC emissions.

TRUE

BVOC emissions diagnostics will be calculated.

FALSE

BVOC emissions diagnostics will not be calculated.

Footnotes

[*]

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 (Toby Marthews, pers comm.). There has been confusion in the literature and in past documentation of MOSES/JULES, resulting in these differences often being ignored, but JULES uses the Brooks and Corey model. Hopefully this confusion will be removed from future releases. Reference: Clapp, R.B. and G.M.Hornberger, 1978, Empirical Equations for Some Soil Hydraulic Properties. Water Resources Research 14:601-604.