CLIRAD
Modifications made in the CLIRAD-SW solar radiation code for atmospheric
models:
1. CLIRAD-SW was developed at NASA Goddard Space Flight Center by Chou
and Suarez (1999). This code is characterized by high accuracy as
compared with line-by-line calculations and by relatively good
computational efficiency. The code is openly distributed to the
scientific community.
2. In 2000, we included the water vapor continuum of Clough et al. (1989)
in the k-distribution functions of water vapour absorption in lines
(Tarasova and Fomin, 2000). The additional absorption of solar radiation
due to water vapor continuum is noticeable and reaches 6.4% from the
water vapor absorption in lines. The error of the code obtained from the
comparison with line-by-line calculations is about 1.5 W/m2 in absorption
values and less than 0.1 K/day in heating rate values.
3. In 2007, we implemented the new parameterizations for gaseous
absorption proposed by Fomin and Correa (2005) in CLIRAD-SW (Tarasova and
Fomin, 2007). In the new version CLIRAD(FC05)-SW , the number of its
pseudomonochromatic intervals and hence its computational time is
reduced by a factor of 2.5 as compared with CLIRAD-SW without the loss of
the code accuracy. The surface and top-of-the-atmosphere flux difference
is less than 1.5 W/m2 in calculations for the standard gaseous
atmospheres and is less than 7 W/m2 in the calculations for gaseous
atmosphere with aerosols and cloudiness. The relative flux error is less
than 1%. The errors of heating rate calculations is less than 6% in the
clear-sky atmosphere and is less than 20-30% in cloud layers.
4.Analysis of errors in heating rate calculations with
broadband shortwave radiation codes (CLIRADSW-M and CLIRAD(FC05)-SW)
in cloud layers was made. The calculation results show that the HR error of both broadband codes is about 20% in cloud layers, while it is less
than 5-10% in cloud-free layers. (Analysis
of errors... .pdf )
References:
Chou, M.-D., and M.J. Suarez.
A solar radiation parameterization
(CLIRAD-SW) for atmospheric studies. NASA Tech. Memo. 10460, Vol. 15,
NASA Goddard Space Flight Center, Greenbelt, MD, 48 pp, 1999.
Fomin, B.A., and M.P. Correa.
A k-distribution technique for
radiative transfer simulation in inhomogeneous atmosphere: 2. FKDM, fast
k-distribution model for the shortwave. J. Geophys. Res., 110, D02106,
doi:10.1029/2004JD005163, 2005.
Tarasova T.A., and B.A. Fomin.
Solar radiation absorption due to
water vapor: Advanced broadband parameterizations. J. Appl. Meteor., 39,
1947-1951, 2000.
Tarasova, T.A., and B.A. Fomin,
The use of new parameterization
for gaseous absorption in the CLIRAD-SW solar radiation code for models.
J. of Atm. and Oceanic Technol., v. 24, No. 6, 1157-1162, 2007.
Intercomparison of Radiation Codes
Recently the shortwave radiation code CLIRAD(FC05)-SW (Tarasova and Fomin, 2007),
developed in Brazil for use in GCMs and climate models,
participated in the Continual Intercomparison of Radiation Codes (CIRC) (Oreopoulos et al., 2012)
where it was named as CLIRAD-SW modified. In all 7 cases, proposed in CIRC, the code demonstrated smaller
errors than the original CLIRAD-SW code (Chou and Suarez, 1999) as compared with line-by-line calculations.
The 7 cases of the CIRC (Phase I) are based on the observations of the Atmospheric Radiation
Measurement Program and describe realistic atmospheric conditions in cloud-free (5 cases) and
cloudy atmospheres with overcast liquid clouds (2 cases). The code CLIRAD-SW modified also
demonstrated good performance as compared with other 12 distinguished radiation codes, participated
in the comparison, including the codes with larger number of pseudmonochromatic intervals (Clough et al., 2005;
Iacono et al., 2008). Remind that the larger number of pseudmonochromatic intervals in the code
leads to the proportional increase of the code computational time and to the need to call
the code less frequently than dynamics or other physical processes in the climate model that
has negative effects on the model performance.
The shortwave radiation code CLIRAD(FC05)-SW you can
download (here).
References:
Chou, M.-D., and M. J. Suarez
A solar radiation parameterization
(CLIRAD-SW) for atmospheric studies. NASA Tech.
Memo. 10460, Vol. 15, NASA Goddard Space Flight Center,
Greenbelt, MD, 48 pp.,1999
Clough, S. A., M. W. Shephard, E. J. Mlawer, J. S. Delamere, M. J. Iacono,
K. Cady-Pereira, S. Boukabara, and P. D. Brown
Atmospheric radiative transfer modeling: A summary of the AER codes, J. Quant.
Spectrosc. Radiat. Transfer, 91, 233-244, 2005, doi:10.1016/j.jqsrt.2004.
05.058.
Iacono, M. J., J. S. Delamere, E. J. Mlawer, M. W. Shephard, S. A. Clough,
and W. Collins
Radiative forcing by long-lived greenhouse gases:
Calculations with the AER radiative transfer models, J. Geophys. Res.,
113, D13103, 2008, doi:10.1029/2008JD009944.
Oreopoulos, L., et al.
The Continual Intercomparison of Radiation Codes:
Results from Phase I, J. Geophys. Res., 117, D06118, 2012, doi:10.1029/2011JD016821.
Tarasova, T.A., and B.A. Fomin.
The use of new parameterization for gaseous
absorption in the CLIRAD-SW solar radiation code for models. J. of Atm. and
Oceanic Technol., v. 24, No. 6, 1157-1162, 2007,
doi:10.1175/JTECH2023.1
Fomin, B.A., and M.P. Correa.
A k-distribution tecnique for radiative transfer
simulation in inhomogeneous atmosphere: 2. FKDM, fast k-distributuion model for
the shortwave. J. Geophys. Res., 110, D02106,2005, doi:10.1029/2004JD005163 .