Improving transmission calculations for the Edwards–Slingo radiation scheme using a correlated-k distribution method
✍ Scribed by Zhian Sun
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 359 KB
- Volume
- 137
- Category
- Article
- ISSN
- 0035-9009
- DOI
- 10.1002/qj.880
No coin nor oath required. For personal study only.
✦ Synopsis
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 collision‐induced 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 © 2011 Royal Meteorological Society