Radiation Scheme in CCPP
Cloud Optical Property in LW

SUBROUTINE cldprop in module_radlw_main computes the cloud optical depth(s) for each cloudy layer and g-point interval.
Usage:
call cldprop
! — inputs:
& ( cfrac,cliqp,reliq,cicep,reice,cdat1,cdat2,cdat3,cdat4, &
& nlay, nlp1, ipseed, &
! — outputs:
& cldfmc, taucld &
& )

Parameters
[in]cfrac- real, (0:nlp1), layer cloud fraction
..... for ilwcliq > 0 (prognostic cloud scheme) - - -
[in]cliqp- real, (nlay), layer in-cloud liq water path ( \(g/m^2\))
[in]reliq- real, (nlay), mean eff radius for liq cloud (micron)
[in]cicep- real, (nlay), layer in-cloud ice water path ( \(g/m^2\))
[in]reice- real, (nlay), mean eff radius for ice cloud (micron)
[in]cdat1- real, (nlay), layer rain drop water path ( \(g/m^2\))
[in]cdat2- real, (nlay), effective radius for rain drop (micron)
[in]cdat3- real, (nlay), layer snow flake water path( \(g/m^2\))
[in]cdat4- real, (nlay), mean eff radius for snow flake(micron)
..... for ilwcliq = 0 (diagnostic cloud scheme) - - -
[in]cliqp- real, (nlay), not used
[in]cicep- real, (nlay), not used
[in]reliq- real, (nlay), not used
[in]reice- real, (nlay), not used
[in]cdat1- real, (nlay), layer cloud optical depth
[in]cdat2- real, (nlay), layer cloud single scattering albedo
[in]cdat3- real, (nlay), layer cloud asymmetry factor
[in]cdat4- real, (nlay), optional use
[in]nlay- integer, 1, number of layer number
[in]nlp1- integer, 1, number of veritcal levels
[in]ipseed-permutation seed for generating random numbers (isubclw>0)
[out]cldfmc- real,ngptlw*nlay, cloud fraction for each sub-column
[out]taucld- real,nbands*nlay, cloud optical depth for bands (non-mcica)

General Algorithm

  1. Compute cloud radiative properties for a cloudy column
    • Compute cloud radiative properties for rain and snow (tauran,tausnw)
    • Calculation of sbsorption coefficients due to water clouds (tauliq)
    • Calcultaion of absorption coefficients due to ice clouds (tauice): Fu's approach for ice effective radius between 4.8 and 135 microns (generalized effective size from 5 to 140 microns)
    • For prognostic cloud scheme: sum up the cloud optical property:
      \( taucld=tauice+tauliq+tauran+tausnw \)
  2. Distribute cloud properties to each g-point (isubclw > 0, for mcica sub-col clouds approx)