Improving transmission calculations for the Edwards–Slingo radiation scheme using a correlated‐k distribution method

Abstract

A new version of the Edwards-Slingo (ES) radiation scheme is developed using the correlated-k distribution (CKD) method. The work is conducted based on the line-by-line radiative transfer scheme GENLN2. A dataset of new ozone absorption cross-section in the ultraviolet spectrum and new oxygen collisioninduced continuum data have been implemented in both the GENLN2 and new ES schemes. In order to improve the efficiency of the ES scheme, a new technique is proposed in this work to optimize the k distribution and a new method is used to deal with the gaseous overlapping absorption in a spectral band. The accuracy of the scheme is improved by replacing the scaling function used in the ES scheme with a pre-determined look-up table for consideration of the pressure and temperature dependency of the absorption oefficients. The number of spectral bands and number of absorbing species are both increased in the new scheme for better resolution of the spectral variation of absorbing species, aerosols and clouds. However, this does not increase the computational cost. Instead, it is reduced substantially compared with the previous version of the code. The treatment of transmission in the short-wave spectrum is improved by implementing the absorbing species of CH 4 , N 2 O and O 2 collision-induced continuum absorption which are not included in the ES scheme. New O 3 absorption cross-section data in the ultraviolet spectrum measured by the European Space Agency are used to generate the CKD spectral data in the short-wave spectral bands. These data have a temperature dependency and better spectral resolution. The irradiance and heating rate determined by the new scheme are tested against the same variables determined by GENLN2. It has been shown that the new scheme produces results more accurate than the ES scheme. Copyright

Accuracy tests of radiation schemes used in hot Jupiter global circulation models

“…Currently the ES radiation scheme uses a combination of the exponential sum fitting of transmissions (ESFT) technique (Wiscombe & Evans 1977) and the correlated-k method (Lacis & Oinas 1991;Goody et al 1989) to obtain k-coefficients, some details of which can be found in Sun (2011). In each band the absorption coefficients from the line-by-line wavenumber grid are reordered according to strength in increasing order and divided into n k subintervals.…”

“…This scheme has been widely used in the meteorological community, see e.g. Sun (2011). We also describe the line-by-line discrete ordinate code Atmo used for comparisons.…”

Decadal variation of East Asian radiative forcing due to anthropogenic aerosols during 1850–2100, and the role of atmospheric moisture

“…The radiative transfer scheme used in the model is a modified version of the Edwards−Slingo scheme (Edwards & Slingo 1996, Sun 2011, and uses an approach of correlated-k distribution (Fu & Liou 1992, Li & Barker 2005 for the flux calculation. The scheme has 9 spectral intervals for solar radiation (0.25 to 5.0 µm) and 8 for thermal radiation (5.0 to 40 µm).…”

“…The scheme has 9 spectral intervals for solar radiation (0.25 to 5.0 µm) and 8 for thermal radiation (5.0 to 40 µm). When compared with line-by-line calculations, the scheme can accurately simulate gaseous absorption due to water vapor, carbon dioxide, ozone, methane, nitrous oxide, oxygen and chlorofluorocarbons (Sun 2008(Sun , 2011. The treatment of liquid cloud optical properties adopts the works of Hu & Stamnes (1993) and Sun & Rikus (2004), and the ice cloud properties follow the work of Chou (2002).…”

Evaluation of Solar Spectra and Their Effects on Radiative Transfer and Climate Simulation

“…The broad-band model used in this study is the Sun-Edwards-Slingo version 2 (SES2) scheme (Sun, 2011). It has 9 spectral bands in the shortwave region, 4 bands in the UV-VIS and 5 bands in the NIR.…”