DudhiaSWParameters

Scheme constants of the Dudhia (1989) shortwave radiation scheme, transcribed from the in-line literals of SUBROUTINE SWPARA in phys/module_ra_sw.F (WRF 4.8). Mounted by the DudhiaSW component as subsystem `par` so that no tuning constant is written inline in the physics. The clear-sky scattering coefficient (namelist swrad_scat, stored by swinit as cssca = swrad_scat * 1e-5 m^2/kg) is a run-time namelist choice and therefore a parameter of the component itself, not of this table. Values are the nominal decimal values of the Fortran source; the real64 kernel build used for the reference tests promotes these default-real literals to binary64 (-fdefault-real-8), so no single-precision rounding note applies here.

Domain: atmospheric_radiation
Subdomain: dudhia_sw
Type: model
.esm schema: 1.2.0
Source: components/atmospheric_radiation/dudhia_sw/dudhia_sw_parameters.esm
Tags: #atmospheric_radiation #dudhia_sw #model #wrf #radiation #shortwave #dudhia #scheme-constants

Description

Scheme constants of the Dudhia (1989) shortwave radiation scheme, transcribed from the in-line literals of SUBROUTINE SWPARA in phys/module_ra_sw.F (WRF 4.8). Mounted by the DudhiaSW component as subsystem par so that no tuning constant is written inline in the physics. The clear-sky scattering coefficient (namelist swrad_scat, stored by swinit as cssca = swrad_scat * 1e-5 m^2/kg) is a run-time namelist choice and therefore a parameter of the component itself, not of this table. Values are the nominal decimal values of the Fortran source; the real64 kernel build used for the reference tests promotes these default-real literals to binary64 (-fdefault-real-8), so no single-precision rounding note applies here.

Reference

Dudhia, J. (1989). Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model. J. Atmos. Sci. 46, 3077-3107.
Lacis, A. A. and Hansen, J. E. (1974). A parameterization for the absorption of solar radiation in the Earth’s atmosphere. J. Atmos. Sci. 31, 118-133.
wrf-model/WRF v4.8.0 phys/module_ra_sw.F, SUBROUTINE SWPARA.

Parameters

Name	Units	Default	Description
`lacis_a`	`1`	`2.9`	Numerator coefficient of the Lacis and Hansen (1974) water-vapour absorptance fit A(u) = a u / ((1 + b u)^p + c u), u the vapour path in g/cm^2 (SWPARA: 2.9).
`lacis_b`	`1`	`141.5`	Coefficient b of the Lacis-Hansen fit (SWPARA: 141.5).
`lacis_p`	`1`	`0.635`	Exponent p of the Lacis-Hansen fit (SWPARA: 0.635).
`lacis_c`	`1`	`5.925`	Coefficient c of the Lacis-Hansen fit (SWPARA: 5.925).
`w_ice`	`1`	`0.1`	Weight of cloud ice in the effective liquid water path (SWPARA: 0.1*QI, ‘reduce effects of ice clouds’).
`w_rain`	`1`	`0.05`	Weight of rain water in the effective liquid water path (SWPARA: 0.05*QR).
`w_snow`	`1`	`0.02`	Weight of snow in the effective liquid water path (SWPARA: 0.02*QS).
`w_graupel`	`1`	`0.05`	Weight of graupel in the effective liquid water path (SWPARA: 0.05*QG, ‘assumed same as rain’).
`w_ref`	`kg/m^2`	`0.001`	Unit of the Stephens (1978) table argument: 1 g/m^2 of slant liquid water path (SWPARA works in g/m^2 and takes log10(WGM + 1)).
`u_ref`	`kg/m^2`	`10.0`	Unit of the Lacis-Hansen fit argument: 1 g/cm^2 of slant water-vapour path (SWPARA: UGCM = UV * 0.0001 / XMU with UV in g/m^2).
`alw_max`	`1`	`3.999`	Upper clamp of log10(slant liquid water path / (1 g/m^2) + 1), keeping the table argument inside the last tabulated interval (SWPARA: IF(ALW.GT.3.999) ALW=3.999).
`mu_min`	`1`	`1e-09`	Cosine of the solar zenith angle below which SWPARA returns without computing (night): IF(CSZA.LE.1.E-9) GOTO 7.
`soltop_min`	`W/m^2`	`1e-09`	Top-of-atmosphere irradiance below which SWPARA returns without computing (total eclipse): IF(SOLTOP.LE.1.E-9) GOTO 7.
`tau_min`	`1`	`0.01`	Lower bound of a layer’s beam transmissivity: when the raw depletion fractions of one layer would leave less than tau_min of the entering beam (SWPARA: IF(TRANS0.LT.1.) with TRANS0 in per cent), the four fractions are rescaled to sum to 1 - tau_min and the transmissivity is set to tau_min (TRANS0 = 1.). Its value, 1 %, is the literal 1. / 99. of SWPARA.
`S_min`	`W/m^2`	`1e-09`	Floor of the downward beam at every interface, SDOWN(K+1) = AMAX1(1.E-9, …) in SWPARA; reached only after several consecutive renormalised layers (each leaves 1 % of the beam).

Raw .esm

Raw .esm JSON (this component)

{
  "variables": {
    "lacis_a": {
      "type": "parameter",
      "units": "1",
      "default": 2.9,
      "description": "Numerator coefficient of the Lacis and Hansen (1974) water-vapour absorptance fit A(u) = a u / ((1 + b u)^p + c u), u the vapour path in g/cm^2 (SWPARA: 2.9)."
    },
    "lacis_b": {
      "type": "parameter",
      "units": "1",
      "default": 141.5,
      "description": "Coefficient b of the Lacis-Hansen fit (SWPARA: 141.5)."
    },
    "lacis_p": {
      "type": "parameter",
      "units": "1",
      "default": 0.635,
      "description": "Exponent p of the Lacis-Hansen fit (SWPARA: 0.635)."
    },
    "lacis_c": {
      "type": "parameter",
      "units": "1",
      "default": 5.925,
      "description": "Coefficient c of the Lacis-Hansen fit (SWPARA: 5.925)."
    },
    "w_ice": {
      "type": "parameter",
      "units": "1",
      "default": 0.1,
      "description": "Weight of cloud ice in the effective liquid water path (SWPARA: 0.1*QI, 'reduce effects of ice clouds')."
    },
    "w_rain": {
      "type": "parameter",
      "units": "1",
      "default": 0.05,
      "description": "Weight of rain water in the effective liquid water path (SWPARA: 0.05*QR)."
    },
    "w_snow": {
      "type": "parameter",
      "units": "1",
      "default": 0.02,
      "description": "Weight of snow in the effective liquid water path (SWPARA: 0.02*QS)."
    },
    "w_graupel": {
      "type": "parameter",
      "units": "1",
      "default": 0.05,
      "description": "Weight of graupel in the effective liquid water path (SWPARA: 0.05*QG, 'assumed same as rain')."
    },
    "w_ref": {
      "type": "parameter",
      "units": "kg/m^2",
      "default": 0.001,
      "description": "Unit of the Stephens (1978) table argument: 1 g/m^2 of slant liquid water path (SWPARA works in g/m^2 and takes log10(WGM + 1))."
    },
    "u_ref": {
      "type": "parameter",
      "units": "kg/m^2",
      "default": 10.0,
      "description": "Unit of the Lacis-Hansen fit argument: 1 g/cm^2 of slant water-vapour path (SWPARA: UGCM = UV * 0.0001 / XMU with UV in g/m^2)."
    },
    "alw_max": {
      "type": "parameter",
      "units": "1",
      "default": 3.999,
      "description": "Upper clamp of log10(slant liquid water path / (1 g/m^2) + 1), keeping the table argument inside the last tabulated interval (SWPARA: IF(ALW.GT.3.999) ALW=3.999)."
    },
    "mu_min": {
      "type": "parameter",
      "units": "1",
      "default": 1e-09,
      "description": "Cosine of the solar zenith angle below which SWPARA returns without computing (night): IF(CSZA.LE.1.E-9) GOTO 7."
    },
    "soltop_min": {
      "type": "parameter",
      "units": "W/m^2",
      "default": 1e-09,
      "description": "Top-of-atmosphere irradiance below which SWPARA returns without computing (total eclipse): IF(SOLTOP.LE.1.E-9) GOTO 7."
    },
    "tau_min": {
      "type": "parameter",
      "units": "1",
      "default": 0.01,
      "description": "Lower bound of a layer's beam transmissivity: when the raw depletion fractions of one layer would leave less than tau_min of the entering beam (SWPARA: IF(TRANS0.LT.1.) with TRANS0 in per cent), the four fractions are rescaled to sum to 1 - tau_min and the transmissivity is set to tau_min (TRANS0 = 1.). Its value, 1 %, is the literal 1. / 99. of SWPARA."
    },
    "S_min": {
      "type": "parameter",
      "units": "W/m^2",
      "default": 1e-09,
      "description": "Floor of the downward beam at every interface, SDOWN(K+1) = AMAX1(1.E-9, ...) in SWPARA; reached only after several consecutive renormalised layers (each leaves 1 % of the beam)."
    }
  },
  "equations": []
}