RRTMG_SW

RRTMG_SW What's New:

RRTMG_SW v3.8

Date: May 2009

New option added to input absorption coefficient data either through original source statements or through a netCDF data file. Choice of input source is selected in the makefile. This feature was developed and contributed by Patrick Hofmann and Robert Pincus of NOAA.

The lower bound of allowable liquid droplet effective radius was changed from 1.5 to 2.5 microns for the inflag=2/liqflag=1 cloud input option.

RRTMG_SW v3.7

Date: February 2009

Modified the value of the single scattering albedo threshold (from 0.9995 to 0.9999995) that selects between the general 2-stream scattering solution (for most SSA values) and a simpler, conservative scattering solution when SSA is close to 1.0. The new more restrictive threshold generates improved results within multi-layer, highly scattering clouds when the SSA is just under one. This change will affect fluxes and will significantly affect heating rates within highly scattering clouds, especially those that extend over multiple layers. Negligible changes also occur in clear sky since the single scattering albedo can be close to this threshold when Rayleigh scattering dominates the shortwave extinction. Use of this modification is strongly recommended.

Added several code changes to the two-stream solver that prevent potential exception problems under single precision.

A new flag was installed (idelm) that is used to select between either unscaled 'true' direct and diffuse fluxes (idelm=0) or delta-scaled direct and diffuse fluxes (idelm=1). This flag is read from the input file in the column version of the model. In the code to be used in GCMs, it is set by default to 1 to provide scaled direct and diffuse fluxes. Total fluxes continue to be provided only as delta-scaled quantities.

RRTMG_SW v3.61

Date: September 2008

Modified input of ice particle effective size to require input of value appropriate for the selected ice optics parameterization. Previous scaling that was applied internally to convert ice effective radius to generalized effective size for the Fu parameterization has been removed. Any necessary scaling needed to provide the proper ice particle size must be done before input to the radiation in the GCM version of the code. This is consistent with the input requirement for the column version of the model. Note that the internal ice optics parameterizations are effective over specific ranges of particle size. Results may be different from previous versions if the Fu parameterization is used in the GCM version of the code.

RRTMG_SW v3.6

Date: August 2008

Added requirement that cloud liquid and ice water paths, or optionally the cloud optical depth, be input as in-cloud averages rather than grid-averaged values in the version of the code intended for use in a GCM. This change requires that these cloud properties be scaled by the cloud fraction on input to convert to in-cloud values if necessary. The column model version of the code continues to expect in-cloud values as before. Oxygen amount was changed from being defined internally to a required input. The forward scattering fraction for clouds was added as an input array. Several other cosmetic modifications do not affect results, but a change in the factor used to convert flux to heating rate from a fixed to a calculated quantity may produce negligible differences in heating rates.

RRTMG_SW v3.5

Date: January 2008

Corrected calculation of cloud optical property stochastic arrays in McICA sub-column generator when cloud optical properties are input directly. This change will impact calculations with clouds when McICA is used and input parameter inflag is set to 0.

RRTMG_SW v3.4

Date: September 2007

Modified use of ice particle size variables rei/reicmc to utilize separate variable names (dge/dgesmc) when units of generalized effective size are required for Fu ice parameterization (iceflag=3) option. Results may be minimally affected when ice particle radii exceed 90 microns and the iceflag=3 option is used. Also modified several local arrays in top-level subroutine module to accomodate an extra model layer at the top of the atmosphere if this feature is utilized when using the code in a GCM.

RRTMG_SW v3.3

Date: September 2007

Modified use of column dimension in some optional output arrays in subroutine version of model, and corrected intent attribute of icld flag. Also added solar constant as input value into subroutine version of model to allow scaling of solar constant from default value. Results are identical to the previous version.

RRTMG_SW v3.2

Date: August 2007

Includes changes to the makefile for AIX systems and a few minor fixes in the interface for the subroutine version of the model. Results are identical to the previous version.

RRTMG_SW v3.1

Date: August 2007

Added exponential lookup table for transmittance, similar to that used in RRTMG_LW, to improve computational performance. Improvement in speed is machine dependent, but it is typically 5-10 percent. Slight changes in results are possible, but they are generally negligible.

RRTMG_SW v3.0

Date: April 2007

Major source code reformatting to utilize modern FORTRAN90 features such as modules. Older common blocks have been removed from all but I/O related source files to retain I/O compatibility with RRTM.

Model can be run as a stand-alone column model using the same I/O format as RRTM and LBLRTM, or it can be used as a callable subroutine and implemented within a global or regional model.

McICA (Monte Carlo Independent Column Approximation) capabililty added for representation of sub-grid cloud variability such as cloud fraction and cloud overlap.

Sample input and output files and instructions for the input files are also included in the source package.