Two of the programs, ckdlwrrtm and ckdswrrtm, are derived from the longwave and shortwave Rapid Radiative Transfer Models (RRTM) developed at Atmospheric and Environmental Research, Inc, principally by Eli Mlawer (see http://www.rtweb.aer.com). The longwave CKD program is from the original RRTM version, not the new version first released in 2002. The longwave RRTM reference is:
Mlawer, E.J., S.J. Taubman, P.D. Brown, M.J. Iacono and S.A. Clough: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102, 16,663-16,682, 1997Both the longwave and shortwave CKD programs do not exactly match the original RRTM algorithms because the SHDOM k-distribution model is different. The SHDOM model is that the temperature profile and scattering properties are independent of the "k" within each spectral band. The radiative transfer results based on ckdlwrrtm and ckdswrrtm do agree closely with the RRTM programs (fluxes within 1 - 2 W/m^2).
The third program, ckdfu, makes an SHDOM CKD file for both the shortwave and longwave, and is derived from Fu and Liou's original correlated k-distribution described in the article:
Fu, Qiang and K. N. Liou, 1992: On the Correlated k-Distribution Method for Radiative Transfer in Nonhomogeneous Atmospheres. J. Atmos. Sci., 49, 2139-2156.This version is not the much upgraded "Fu and Liou" k-distribution used by the CERES program at NASA Langley. This older k-distribution parameterization has a number of deficiencies, including using one band for the ultraviolet and the visible, using the outdated Roberts et al. (1976) water vapor continuum, and missing trace absorbing species. Thus it is considerably less accurate than the RRTM based programs, however, it is substantially cheaper to run because it has fewer k's, and is appropriate for some theoretical experiments (e.g. where differences between SHDOM runs are being investigated). The size of the k-distributions in the three programs is summarized below.
Program | Shortwave | Longwave | ||
---|---|---|---|---|
Bands | k's | Bands | k's | |
ckdlwrrtm | 16 | 256 | ||
ckdswrrtm | 14 | 224 | ||
ckdfu | 6 | 54 | 12 | 67 |
Parameter | Description |
---|---|
ATMFILE | Atmospheric profile file name |
OUTFILE | CKD file for SHDOM |
UMCO2 | Concentration of CO2 in ppmv |
UMCH4 | Concentration of CH4 in ppmv |
UMN2O | Concentration of N2O in ppmv |
Height Pressure Temperature Air_density Vapor_density Ozone_density (km) (mb) (K) (g/m^3) (g/m^3) (g/m^3)