6.6. jules_surface.nml
¶
This file sets the surface options. It contains one namelist called JULES_SURFACE
.
6.6.1. JULES_SURFACE
namelist members¶

JULES_SURFACE::
all_tiles
¶ Type: integer Permitted: 0,1 Default: 0 Perform calculations of tile properties on all tiles (except land ice) for all gridpoints even when the tile fraction is zero.
 Off
 On

JULES_SURFACE::
cor_mo_iter
¶ Type: integer Permitted: 14 Default: 1 Corrections to MoninObukhov surface exchange calculation. Please see also UMDP24 “The Parametrization of Boundary Layer Processes” (section 8.4.1).
 Correct convective gustiness in low winds
 Correct U* in dust scheme,
 Limit Obukhov length in low winds
 Improve the initialisation of the iteration
Note
Option 4 should be the preferred option.

JULES_SURFACE::
beta_cnv_bl
¶ Type: real Permitted: >=0.0 Dimensionless coefficient scaling the boundary layer convective gustiness contribution to surface exchange. Historically this was set to 0.08 but is recommended to be reduced to 0.04 when gustiness from convective downdraughts is included, either from the convection parametrization or when convection is resolved (so resolutions ~1km or finer). Please see also UMDP24 “The Parametrization of Boundary Layer Processes” (section 8.1).

JULES_SURFACE::
l_aggregate
¶ Type: logical Default: F Switch controlling number of surface tiles for each gridbox.
This is used to set the number of surface energy balances that are solved for each gridbox (
nsurft
). TRUE
 Aggregate parameter values are used to solve a single energy balance per gridbox. This option sets
nsurft = 1
.  FALSE
 A separate energy balance is calculated for each surface type. This option sets
nsurft = ntype
.

JULES_SURFACE::
i_aggregate_opt
¶ Type: integer Permitted: 01 Default: 0 Option for aggregating surface properties to surface tiles:
 Aggregate momentum roughness lengths and set the thermal roughness length as a given fraction of this (in practice the ratio of roughness lengths for the first surface type).
 Aggregate the thermal roughness lengths separately from the momentum roughness lengths using an analogous algorithm.
Note
This option is ignored unless
l_aggregate
is true.

JULES_SURFACE::
l_epot_corr
¶ Type: logical Default: F  TRUE
 Use correction to the calculation of potential evaporation.
 FALSE
 No effect.

JULES_SURFACE::
l_point_data
¶ Type: logical Default: F Flag indicating if driving data are point or areaaverage 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 largescale 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 largescale components. The albedo formulation is suitable for a gridbox.

JULES_SURFACE::
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_SURFACE::
l_anthrop_heat_src
¶ Type: logical Default: F Switch for inclusion of anthropogenic contribution to the surface heat flux from urban surface types. If
l_urban2t
then the anthropogenic heat will be distributed between theurban_canyon
andurban_roof
according toanthrop_heat_scale
, otherwise it is added tourban
only. TRUE
 Add anthropogenic effect.
 FALSE
 No effect.

JULES_SURFACE::
iscrntdiag
¶ Type: integer Permitted: 03 (standalone: 0 or 1 only) Default: 0 Switch controlling method for diagnosing screen temperature.
 Use surface similarity theory (no decoupling).
 Use surface similarity theory but allow decoupling in very stable conditions based on the quasiequilibrium radiative solution.
 Diagnose the screen temperature including transient effects and radiative cooling.
 Diagnose the screen temperature and humidity including transient effects and radiative cooling. The diagnosis of the screen temperature follows option 2. This is an experimental option and is undergoing development and additional testing.
Note
Option 0 should be the preferred option in standalone i.e. no decoupling until the decoupled options are fully tested in standalone scenarios.

JULES_SURFACE::
l_elev_lw_down
¶ Type: logical Default: false If surface tiles are set to be at an elevation offset from the gridbox mean altitude (see
JULES_SURF_HGT
) this switch controls whether downwelling longwave radiation is adjusted along with surface air temperature and relative humidity.If true, the downwelling longwave for each surface tile not at the gridbox mean height is adjusted by an amount proportional to the fourth power of the adjustment that has been made to the surface air temperature. The adjustments are then scaled such that the sum over all surface tiles conserves the gridbox mean energy in the original forcing.

JULES_SURFACE::
l_elev_land_ice
¶ Type: logical Default: false Allows multiple ice surface tiles to exist in an ice gridbox, usually with each representing a different elevation (
JULES_SURF_HGT
) band on in icesheet areas so that a subgridscale surface mass balance term (a strong function of altitude) can be derived for forcing icesheet/glacier models. When enabled, ice tiles in a gridbox do not use the usual (gridbox mean) JULES soil/ice subsurface model, but each tile has an independent single layer bedrocktype solid ice boundary condition under the snowpack.In addition, when selected, dense snowpacks on elevated ice gridboxes are parameterised to behave more like firn in two ways: 1) The meltwaterholding capacity of snow layers reduces as a linear function of their density, becoming zero above the poreclosure density of 850 kg/m^2 so as to restrict retention of melt within the snowpack. 2) Where the top few centimetres of the pack has a density appropriate to firn/bare ice and the grainsize physics otherwise used for snow albedo become less appropriate, surface albedo becomes a function of density, tending towards that of bare ice as density increases (see
rho_firn_albedo
,amax
,aicemax
).If this scheme is enabled, a depth for the bedrock layer must be provided (
dzsoil_elev
) and the new tile numbers must be specified (JULES_SURFACE_TYPES
) as either typeelev_ice
(for fully glaciated areas) orelev_rock
(for nonglaciated areas where the bedrock may become exposed under a thin snow layer). The total number of nonvegetated surface tiles, and their surface properties (JULES_NVEGPARM
, usually set to be the same as the normal ice tile) must be set accordingly, as with any surface tile.

JULES_SURFACE::
l_flake_model
¶ Type: logical Default: false Switch for using the freshwater lake model ‘FLake’ on the lake/inlandwater surface tile. More information on the FLake model can be found on the FLake website. A description of how FLake is coupled to JULES can be found in Rooney and Jones 2010.
When using FLake, it is not necessary to use a canopy representation of lake properties so
catch_nvg_io
,ch_nvg_io
andvf_nvg_io
should all be set to zero for the lake tile.

JULES_SURFACE::
l_urban2t
¶ Type: logical Default: false Switch for using the twotile urban schemes (including MORUSES). This allows two urban surface tiles (
urban_canyon
andurban_roof
) to be used instead of one. Additional parameters must be supplied viaJULES_NVEGPARM
, with some able to be provided by MORUSES (seeJULES_URBAN
).

JULES_SURFACE::
l_mo_buoyancy_calc
¶ Type: logical Default: false Default JULES (l_mo_buoyancy_flux = false) uses the buoyancy from the previous timestep to calculate the surface transfer coefficients. In coupled simulations this can lead to unrealistic surface temperatures if the stability suddenly switches from stable to unstable, due to the low turbulence determined by the stable buoyancy flux.
With the interactive buoyancy flux option (l_mo_buoyancy_flux = true) the surface energy balance and buoyancy flux are calculated within the iterative calculation for the MoninObukhov similarity theory for the surface exchange coefficients. On occations when the stability is around neutral it is possible that the iterative calculation does not converge. In this case the larger of the last two calculated transfer coefficients is then used to prevent any unrealistic surface temperatures.
Surface parameters

JULES_SURFACE::
hleaf
¶ Type: real Default: 5.7e4 Specific heat capacity of leaves (J K^{1} per kg carbon).
See Hadley Centre Technical Note 30, p6, available from the Met Office Library.

JULES_SURFACE::
hwood
¶ Type: real Default: 1.1e4 Specific heat capacity of wood (J K^{1} per kg carbon).
See Hadley Centre Technical Note 30, p6, available from the Met Office Library.

JULES_SURFACE::
beta1
¶ Type: real Default: 0.83 Coupling coefficient for colimitation in photosynthesis model.
See Cox et al. (1999), Eq.61.

JULES_SURFACE::
beta2
¶ Type: real Default: 0.93 Coupling coefficient for colimitation in photosynthesis model.
See Cox et al. (1999), Eq.61.

JULES_SURFACE::
fwe_c3
¶ Type: real Default: 0.5 Constant in expression for limitation of photosynthesis by transport of products, for C3 plants.
See Cox et al. (1999) Eq.60.

JULES_SURFACE::
fwe_c4
¶ Type: real Default: 20000.0 Constant in expression for limitation of photosynthesis by transport of products, for C4 plants.
See Cox et al. (1999) Eq.60.