! path: $Source: /storm/rc1/cvsroot/rc/rrtmg_lw/README,v $ ! author: $Author: mike $ ! revision: $Revision: 1.8 $ ! created: $Date: 2008/04/24 16:17:25 $ ! --------------------------------------------------------------------- RRTMG_LW: Longwave Radiative Transfer Model for GCMs Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, MA 02421 Original version: E. J. Mlawer, et al. (AER) Revision for GCMs: Michael J. Iacono (AER) Contact: Michael J. Iacono (E-mail: miacono@aer.com) Web Site: www.rtweb.aer.com References (RRTMG_LW/RRTM_LW): Iacono, M.J., J.S. Delamere, E.J. Mlawer, M.W. Shephard, S.A. Clough, and W.D. Collins, Radiative forcing by long- lived greenhouse gases: Calculations with the AER radiative transfer models, accepted by J. Geophys. Res., 2008. 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. Iacono, M.J., J.S. Delamere, E.J. Mlawer, and S.A. Clough, Evaluation of upper tropospheric water vapor in the NCAR Community Climate Model (CCM3) using modeled and observed HIRS radiances. J. Geophys. Res., 108(D2), 4037, doi:10.1029/ 2002JD002539, 2003. Iacono, M.J., E.J. Mlawer, S.A. Clough, and J.-J. Morcrette, Impact of an improved longwave radiation model, RRTM, on the energy budget and thermodynamic properties of the NCAR Community Climate Model, CCM3, J. Geophys. Res., 105, 14873-14890, 2000. Mlawer, E.J., S.J. Taubman, P.D. Brown, M.J. Iacono, and S.A. Clough: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102, 16663-16682, 1997. Reference (McICA): Pincus, R., H. W. Barker, and J.-J. Morcrette, A fast, flexible, approximation technique for computing radiative transfer in inhomogeneous cloud fields, J. Geophys. Res., 108(D13), 4376, doi:10.1029/2002JD003322, 2003. ****************************************************************************** This package contains the source code and sample makefiles necessary to run the latest version of RRTMG_LW, a correlated k-distribution longwave radiative transfer model developed at AER, Inc for application to GCMs. This version of RRTMG_LW has been modified from the standard RRTM_LW distributed by AER to enhance its performance for use within general circulation models. This code has also been modified to utilize FORTRAN90 coding features. Two modes of operation are possible. RRTMG_LW can be run in stand-alone mode using the input files and source modules described below, or it can be attached to an atmospheric general circulation model or single column model. The version of RRTMG_LW provided here has been modified from the standard RRTM_LW to enhance performance with little effect on the accuracy. The total number of g-points used has been reduced from 256 to 140. Fluxes are accurate to within 0.5 W/m2 and cooling rate within 0.1 K/day relative to the standard RRTM_LW, which is itself accurate to within 1 W/m2 of the data-validated line-by-line radiative transfer model, LBLRTM. This model can also utilize McICA, the Monte-Carlo Independent Column Approximation, to represent sub-grid scale cloud variability such as cloud fraction and cloud overlap. If the McICA option is selected to model a cloudy profile in column mode, then the model will run stochastically, and the output fluxes and heating rates will be an average over 200 samples. ************************* RRTMG_LW : Column Version ************************* DOCUMENTATION: The following text files (some in /column_model/doc directory) provide information on using and running RRTMG_LW: README : Basic code package information (this file) README.release_notes : Code archive update information rrtmg_lw_instructions : Input instructions for files INPUT_RRTM, IN_CLD_RRTM and IN_AER_RRTM SOURCE CODE: The following source files (in /column_model/src directory) must be used to run RRTMG_LW in stand-alone mode as a column model: rrtmg_lw.1col.f90 : RRTMG_LW main module rrtmg_lw_cldprop.f90 : Calculation of cloud optical properties rrtmg_lw_cldprmc.f90 : Calculation of cloud optical properties (McICA) rrtmg_lw_init.f90 : RRTMG_LW initialization routine; reduces g-intervals from 256 to 140 rrtmg_lw_k_g.f90 : Absorption coefficient data file rrtmg_lw_rtrn.f90 : Calculation of clear and cloudy radiative transfer using random cloud overlap rrtmg_lw_rtrnmr.f90 : Calculation of clear and cloudy radiative transfer using maximum-random cloud overlap rrtmg_lw_rtrnmc.f90 : Calculation of clear and cloudy radiative transfer using McICA (with selectable overlap method) rrtmg_lw_setcoef.f90 : Set up routine rrtmg_lw_taumol.f90 : Calculation of optical depths and Planck fractions for each spectral band mcica_random_numbers.f90 : Random number generator for McICA mcica_subcol_gen_lw.1col.f90 : Sub-column generator for McICA rrtatm.f : Process user-defined input data files extra.f : Process input data files util_**.f : Utilities (available for multiple platforms) The following module files (in /column_model/modules directory) must be used to run RRTMG_LW in stand-alone mode as a column model (these must be compiled before the source code files): parkind.f90 : real and integer kind type parameters parrrtm.f90 : main configuration parameters rrlw_cld.f90 : cloud property coefficients rrlw_con.f90 : constants rrlw_kg**.f90 : absorption coefficient arrays for 16 spectral bands rrlw_ref.f90 : reference atmosphere data arrays rrlw_tbl.f90 : exponential look up table arrays rrlw_vsn.f90 : version number information rrlw_wvn.f90 : spectral band and g-interval array information MAKEFILES: The following files (in directory /column_model/build/makefiles) can be used to compile RRTMG_LW in stand-alone mode as a column model on various platforms. Link one of these into the /column_model/build directory to compile. make_rrtmg_lw_sgi : Sample makefile for SGI make_rrtmg_lw_sun : Sample makefile for SUN make_rrtmg_lw_linux_pgi : Sample makefile for LINUX (PGI compiler) make_rrtmg_lw_aix_xlf90 : Sample makefile for AIX (XLF90 compiler) make_rrtmg_lw_OS_X_g95 : Sample makefile for OS_X (G95 compiler) SAMPLE INPUT/OUTPUT: Several sample input (and output) files are included in the /runs_std_atm directory. Note that user-defined profiles may be used for as many as 200 layers. INPUT_RRTM : Required input file for (clear sky) atmospheric specification IN_CLD_RRTM : Required input file for cloud specification if clouds are present IN_AER_RRTM : Required input file for aerosol specification if aerosols are present OUTPUT_RRTM : Main output file for atmospheric fluxes and heating rates input_rrtm.MLS : Sample 51 layer mid-latitude summer standard atmosphere input_rrtm.MLS-cld-imca0 : Sample 51 layer mid-latitude summer standard atmosphere with cloud flag turned on (without McICA) input_rrtm.MLS-cld-imca1 : Sample 51 layer mid-latitude summer standard atmosphere with cloud flag turned on (with McICA) input_rrtm.MLS-xsec : Sample 51 layer mid-latitude summer standard atmosphere with cross-section input (CFCs, etc.) input_rrtm.MLW : Sample 51 layer mid-latitude winter standard atmosphere input_rrtm.SAW : Sample 51 layer sub-arctic winter standard atmosphere input_rrtm.TROP : Sample 51 layer tropical standard atmosphere in_cld_rrtm-cld5 : Sample cloud input file ********************* RRTMG_LW: GCM version ********************* DOCUMENTATION: README : Basic code package information (this file) SOURCE CODE: The following source files (in /gcm_model/src directory) must be used to run RRTMG_LW as a callable subroutine: rrtmg_lw.f90 : RRTMG_LW main module (with McICA) rrtmg_lw.nomcica.f90 : Optional RRTMG_LW main module (without McICA only) rrtmg_lw_cldprop.f90 : Calculation of cloud optical properties rrtmg_lw_cldprmc.f90 : Calculation of cloud optical properties (McICA) rrtmg_lw_init.f90 : RRTMG_LW initialization routine; reduces g-intervals from 256 to 140; (This has to run only once and should be installed in the GCM initialization section) rrtmg_lw_k_g.f90 : Absorption coefficient data file rrtmg_lw_rtrn.f90 : Calculation of clear and cloudy radiative transfer using random cloud overlap rrtmg_lw_rtrnmr.f90 : Calculation of clear and cloudy radiative transfer using maximum-random cloud overlap rrtmg_lw_rtrnmc.f90 : Calculation of clear and cloudy radiative transfer using McICA (with selectable overlap method) rrtmg_lw_setcoef.f90 : Set up routine rrtmg_lw_taumol.f90 : Calculation of optical depths and Planck fractions for each spectral band mcica_random_numbers.f90 : Random number generator for McICA mcica_subcol_gen_lw.f90 : Sub-column generator for McICA (must be called in GCM just before call to RRTMG) The following module files (in /gcm_model/modules directory) must be used to run RRTMG_LW as a callable subroutine (these must be compiled before the source code files) parkind.f90 : real and integer kind type parameters parrrtm.f90 : main configuration parameters rrlw_cld.f90 : cloud property coefficients rrlw_con.f90 : constants rrlw_kg**.f90 : absorption coefficient arrays for 16 spectral bands rrlw_ref.f90 : reference atmosphere data arrays rrlw_tbl.f90 : look up table arrays rrlw_vsn.f90 : version number information rrlw_wvn.f90 : spectral band and g-interval array information Notes regarding GCM version: 1) The module rrtmg_lw_init.f90 is the initialization routine that has to be called only once. The call to this subroutine should be moved to the initialization section of the host model if RRTMG_LW is called by a GCM or SCM. 2) The number of model layers and the number of columns to be looped over should be passed into RRTMG_LW through the subroutine call along with the other model profile arrays. 3) To utilize McICA, the sub-column generator (mcica_subcol_gen_lw.f90) must be implemented in the GCM so that it is called just before RRTMG. If McICA is utilized, this will run only a single statistical sample per model grid box. There are two options for the random number generator used with McICA, which is selected with the variable irnd in mcica_subcol_gen_lw.f90. When using McICA, then the main module is rrtmg_lw.f90. If McICA is not used, then the main module is rrtmg_lw.nomcica.f90 and the cloud overlap method is selected by setting flag icld.