Journal
ASTRONOMY & ASTROPHYSICS
Volume 564, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201323169
Keywords
radiative transfer; opacity; planets and satellites: atmospheres; planets and satellites: gaseous planets
Categories
Funding
- European Research Council under the European Community's Seventh Framework Programme (FP7) [247060]
- STFC grant [ST/J001627/1]
- Royal Society [WM090065]
- STFC
- Large Facilities Capital Fund of BIS
- University of Exeter
- STFC [ST/J001627/1, ST/H008535/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H008535/1, ST/J001627/1] Funding Source: researchfish
- Royal Society [WM090065] Funding Source: Royal Society
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The treatment of radiation transport in global circulation models (GCMs) is crucial for correctly describing Earth and exoplanet atmospheric dynamics processes. The two-stream approximation and correlated-k method are currently state-of-the-art approximations applied in both Earth and hot Jupiter GCM radiation schemes to facilitate the rapid calculation of fluxes and heating rates. Their accuracy have been tested extensively for Earth-like conditions, but verification of the methods' applicability to hot Jupiter-like conditions is lacking in the literature. We are adapting the UK Met Office GCM, the Unified Model (UM), for the study of hot Jupiters, and present in this work the adaptation of the Edwards-Slingo radiation scheme based on the two-stream approximation and the correlated-k method. We discuss the calculation of absorption coefficients from high-temperature line lists and highlight the large uncertainty in the pressure-broadened line widths. We compare fluxes and heating rates obtained with our adapted scheme to more accurate discrete ordinate (DO) line-by-line (LbL) calculations ignoring scattering effects. We find that, in most cases, errors stay below 10% for both heating rates and fluxes using similar to 10 k-coefficients in each band and a diffusivity factor D = 1.66. The two-stream approximation and the correlated-k method both contribute non-negligibly to the total error. We also find that using band-averaged absorption coefficients, which have previously been used in radiative-hydrodynamical simulations of a hot Jupiter, may yield errors of similar to 100%, and should thus be used with caution.
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