6.7. jules_radiation.nml

This file sets the radiation options. It contains one namelist called JULES_RADIATION.

6.7.1. JULES_RADIATION namelist members

JULES_RADIATION::l_cosz
Type:

logical

Default:

T

Switch for calculation of solar zenith angle.

TRUE

Calculate zenith angle.

FALSE

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

n.b. assuming that the sun is directly overhead may overestimate primary productivity if l_triffid = TRUE (see GPP on JULES Output variables).

JULES_RADIATION::l_spec_albedo
Type:

logical

Default:

F

Switch for the two-stream spectral land-surface albedo model.

TRUE

Use spectral albedo with VIS and NIR components.

FALSE

Use a single (averaged) waveband albedo.

JULES_RADIATION::l_spec_alb_bs
Type:

logical

Default:

F

Switch for albedo model, when spectral albedo is being used.

Requires l_spec_albedo = TRUE.

TRUE

Produces a single albedo for use by both the direct and diffuse beams (a ‘blue’ sky albedo). This currently copies the diffuse beam albedo for the direct beam.

FALSE

Produces both a direct (‘black’ sky) and a diffuse (‘white’ sky) albedo.

JULES_RADIATION::l_niso_direct
Type:

logical

Default:

F

Switch for using full non-isotropic expression for direct scattering in plant canopies when using the two-stream canopy radiation model.

Requires l_spec_albedo = TRUE.

TRUE

Use full non-isotropic expression for scattering in plant canopies.

FALSE

Use the original isotropic expression.

JULES_RADIATION::l_snow_albedo
Type:

logical

Default:

F

Switch for using prognostic snow properties, which represents the effect of snow aging and soot deposition, 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_RADIATION::l_embedded_snow
Type:

logical

Default:

F

Switch to account for pft LAI and pft height in calculation of snow albedo.

TRUE

Use the embedded canopy snow albedo model. This is exclusive of l_snow_albedo.

FALSE

No effect.

JULES_RADIATION::l_mask_snow_orog
Type:

logical

Default:

F

Switch for orographic masking of snow, which decreases the albedo of snow in mountainous regions.

TRUE

Include orographic masking of snow in calculating albedo.

FALSE

No effect.

JULES_RADIATION::l_albedo_obs
Type:

logical

Default:

F

Switch for applying a scaling factor to the albedo values, on surface tiles, so that the resultant aggregate albedo matches observations. The supplied albedos should be from an observed climatology or analysis system and be supplied via an ancillary file.

TRUE

Scale the albedo values on tiles within the physical limits supplied in JULES_PFTPARM and JULES_NVEGPARM. When l_spec_albedo = TRUE, VIS and NIR components are required and when l_spec_albedo = FALSE the single (averaged) waveband albedo is required.

Note

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

FALSE

Do not scale the albedo values on tiles.

JULES_RADIATION::l_spec_sea_alb
Type:

logical

Default:

F

Switch to use spectrally varying open sea albedos

TRUE

When i_sea_alb_method = 1 or 2, spectrally varying sea albedos are produced only when the spectral file contains 6 SW bands identical to those used in HadGEM1.

When i_sea_alb_method = 3, the spectral variability is calculated as per the Jin et al. (2011) parameterisation.

FALSE

Uses the calculated broadband sea albedo instead.

JULES_RADIATION::i_sea_alb_method
Type:

integer

Default:

None

Choice of model for the Ocean Surface Albedo (open water, ice free)

  1. Diffuse albedo constant (0.06), direct albedo from Briegleb and Ramanathan (1982).

  2. Diffuse albedo constant (0.06), direct albedo from Barker and Li (1995).

  3. Direct and diffuse albedo from Jin et al. (2011).

  4. Fixed global value, defined by fixed_sea_albedo.

  5. Fixed global value, defined by fixed_sea_albedo, above 271K and variable below this to simulate sea-ice following Liu et al. (2007), Joshi & Haberle (2012) and Turbet et al. (2016).

JULES_RADIATION::fixed_sea_albedo
Type:

real

Default:

None

The global value of sea albedo to use if i_sea_alb_method = 4, 5

JULES_RADIATION::wght_alb
Type:

real(4)

Default:

MDI

Weights to form the overall albedo from its components (VIS direct, VIS diffuse, NIR direct, NIR diffuse) (Ideally, if l_partition_albsoil = T, wght_alb and swdn_frac_albsoil should be consistent, with swdn_frac_albsoil equal to \sum_{3,4} wght_alb / \sum_1^4 wght_alb. However, swdn_frac_albsoil is applied only to bare soil and having a single parameter is more transparent to the user, while wght_alb is used only in diagnostics in standalone JULES and may have historical settings. Hence, the consistency of these two variables is not enforced.)

JULES_RADIATION::l_hapke_soil
Type:

logical

Default:

F

Switch to enable Hapke’s model of soil albedo to include a zenith-angle dependence

TRUE

Apply a zenith-angle dependence to the direct albedo.

FALSE

Use the diffuse albedo for the direct beam as well.

JULES_RADIATION::l_partition_albsoil
Type:

logical

Default:

F

Switch to apply a spectral partitioning to the soil albedo.

TRUE

Partition the soil albedo between the visible and near infrared parts of the spectrum using ratio_albsoil and swdn_frac_albsoil.

FALSE

Apply the broadband albedo in both spectral regions.

JULES_RADIATION::ratio_albsoil
Type:

real

Default:

MDI

Ratio of the NIR to the VIS albedo of bare soil. Used if l_partition_albsoil = T.

JULES_RADIATION::swdn_frac_albsoil
Type:

real

Default:

MDI

The fraction of the total downward SW radiation assumed to be in the NIR part of the spectrum for partitioning the soil albedo. Used if l_partition_albsoil = T. (Ideally, wght_alb and swdn_frac_albsoil should be consistent, with swdn_frac_albsoil equal to \sum_{3,4} wght_alb / \sum_1^4 wght_alb. However, swdn_frac_albsoil is applied only to bare soil and having a single parameter is more transparent to the user, while wght_alb is used only in diagnostics in standalone JULES and may have historical settings. Hence, the consistency of these two variables is not enforced.)

See also

References:

  • Barker, H.W. and Li, Z. (1995), Improved Simulation of Clear-Sky Shortwave Radiative Transfer in the CCC-GCM. J. Climate, 8, 2213–2223, doi:10.1175/1520-0442(1995)008<2213:ISOCSS>2.0.CO;2

  • Briegleb, B. and Ramanathan, V. (1982), Spectral and Diurnal Variations in Clear Sky Planetary Albedo. J. Appl. Meteor., 21, 1160–1171, doi:10.1175/1520-0450(1982)021<1160:SADVIC>2.0.CO;2

  • Liu, J. , Zhang, Z. , Inoue, J. and Horton, R. M. (2007), Evaluation of snow/ice albedo parameterizations and their impacts on sea ice simulations. Int. J. Climatol., 27: 81-91. doi:10.1002/joc.1373

  • Zhonghai Jin, Yanli Qiao, Yingjian Wang, Yonghua Fang, and Weining Yi, “A new parameterization of spectral and broadband ocean surface albedo”, Opt. Express 19, 26429-26443 (2011), doi:10.1364/OE.19.026429

  • B. Hapke, “Bidirectional reflectance spectroscopy: 1. Theory”, J. Geophys. Res. 86(B4), 3039-3054 (1981), doi:10.1029/JB086iB04p03039

  • Manoj M. Joshi and Robert M. Haberle. Astrobiology. Jan 2012. ahead of print doi:10.1089/ast.2011.0668

  • Martin Turbet, Jérémy Leconte, Franck Selsis, Emeline Bolmont, François Forget, Ignasi Ribas, Sean N. Raymond and Guillem Anglada-Escudé (2016), The habitability of Proxima Centauri b - II. Possible climates and observability, A&A, 596, A112, doi:10.1051/0004-6361/201629577