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RRTM_LW is a rapid radiative transfer model for the longwave which utilizes the correlated-k approach to calculate fluxes and heating rates efficiently and accurately.

Key features of RRTM_LW are:

1) K-distributions are obtained directly from a line-by-line radiative transfer code, [LBLRTM]
   (https://www.github.com/AER-RC/LBLRTM), which has been extensively validated against observations, 
   principally at the ARM climate research facilities
2) Water vapor continuum absorption coefficients are consistent with those in [MT_CKD 2.5.]
   (https://www.github.com/AER-RC/MT_CKD)
3) Fluxes and cooling rates can be calculated over sixteen bands contiguous bands in the longwave 
   (10-3250 cm-1)
4) Scattering capability is available through the radiative transfer solver DISORT
5) Modeled molecular absorbers are:  water vapor, carbon dioxide, ozone, nitrous oxide, methane, 
   oxygen, nitrogen and halocarbons.
6) Fluxes calculated by RRTM agree with those computed by LBLRTM within 1.5 W/m2 at all levels, and 
   the computed cooling rates agree to within 0.1 K/day in the troposphere and 0.3 K/day in the 
   stratosphere (see above plot).
7) Water clouds:
   The optical properties of water clouds are calculated for each spectral band from the Hu and Stamnes 
   parameterization. The optical depth, single-scattering albedo, and asymmetry parameter are 
   parameterized as a function of cloud equivalent radius and liquid water path.  Reference: Hu, Y. X., 
   and K. Stamnes, An accurate parameterization of the radiative properties of water clouds suitable for 
   use in climate models, J. Climate, Vol. 6, 728-742, 1993.
8) Ice clouds:
   The optical properties of ice clouds are calculated for each spectral band from the ice particle 
   parameterization from Fu, Yang, and Sun (J. Climate, Vol 11, 1998, pp. 2223 - 2237) or from the ice 
   particle parameterization available from the STREAMER model v3.0.