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 excluive 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 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)

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
  • 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