Date: March 2020
Added several new features and fixes:
Two new cloud overlap options were added, exponential (icld=4) and
exponential-random (icld=5) that apply an exponential transition from
maximum to random through model layers. Exponential applies this
transition through all layers without regard to the cloud configuration
and exponential-random applies this transition through adjacent cloudy
layers while randomly correlating cloud layers separated by clear sky.
Both methods require calling a new subroutine, get_alpha, to define
alpha, the exponential transition parameter, prior to calling the
McICA sub-column generator. Alpha requires the specification of a
decorrelation length (in meters), and two methods for defining this
value are available that are selected using a new input control
variable, idcor, that allows the decorrelation length to be specified
either as a constant or as a value that varies by latitude and
day-of-year using the method of Oreopolous et al. (2012). See the
file doc/rrtmg_sw_instructions.txt for more information.
The three NRLSSI2 solar source component coefficients (quiet sun,
facular, and sunspot) added in v4.0 and updated in v4.1 were added to
the optional netCDF input data file (/data/rrtmg_sw.nc), and the optional
source module rrtmg_sw_read_nc.f90 was modified to input these data if
the netCDF input option is selected in the makefile. These data function
in the same way as the identical NRLSSI2 solar source coefficients that
are stored in the code by default in module rrtmg_sw_k_g.f90.
A fix was applied to source module rrtmg_sw_read_nc.f90, which
optionally reads the input data coefficients from /data/rrtmg_sw.nc if
that option is selected in the makefile, to correct the loading of the
water vapor foreign continuum data for the upper atmosphere into the
model array forrefo. This issue could impact surface downward shortwave
fluxes by as much as five percent if the netCDF option was used. The
default input coefficient data in rrtmg_sw_k_g.f90 were not affected.
Revised the calculation of zwo in rrtmg_sw_reftra.f90 to protect
against unlikely, but possible divide by zero conditions.