The correlated-k method for radiation calculations in nonhomogeneous atmospheres

Goody, R. M.; West, Robert A.; Chen, Liming; Crisp, David

doi:10.1016/0022-4073(89)90044-7

Cited by 478 publications

(235 citation statements)

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“…If the absorption coefficient decreases with height at one wavelength and increases with height at a different wavelength within the same band, the two wavelengths will no longer correspond to the same value of g. A pseudo-monochromatic calculation where g is kept constant is therefore not equivalent to a proper monochromatic calculation except in a very few special cases, see e.g. Goody et al (1989) for more details.…”

Section: The Correlated-k Methodsmentioning

confidence: 99%

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

Amundsen

Baraffe

Tremblin

et al. 2014

A&A

167

229

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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 ∼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 ∼100%, and should thus be used with caution.

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Section: The Correlated-k Methodsmentioning

confidence: 99%

“…Thomas & Stamnes 2002) and correlated-k method (Lacis & Oinas 1991;Goody et al 1989) implemented in the Edwards-Slingo (ES) radiation scheme (Edwards & Slingo 1996) currently used in the UM. This scheme has been widely used in the meteorological community, see e.g.…”

Section: The Edwards-slingo Radiation Scheme and Atmomentioning

confidence: 99%

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

Amundsen

Baraffe

Tremblin

et al. 2014

A&A

167

229

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“…MODTRAN solves the radiative transfer equation by including the effects of molecular and particulate absorption/emission and scattering, surface reflections and emission, solar/lunar illumination, and spherical refraction. The absorption and scattering processes, considering the atmospheric extinction both for aerosols and molecules, are rigorously calculated using DISORT [60] and Correlated-k [61] algorithms. In addition, MODTRAN uses a spherically symmetric atmosphere, consisting of homogeneous layers, each one characterized by its temperature, pressure and concentration of atmospheric compounds.…”

Section: Modtran5mentioning

confidence: 99%

Emulation of Leaf, Canopy and Atmosphere Radiative Transfer Models for Fast Global Sensitivity Analysis

et al. 2016

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Abstract:Physically-based radiative transfer models (RTMs) help understand the interactions of radiation with vegetation and atmosphere. However, advanced RTMs can be computationally burdensome, which makes them impractical in many real applications, especially when many state conditions and model couplings need to be studied. To overcome this problem, it is proposed to substitute RTMs through surrogate meta-models also named emulators. Emulators approximate the functioning of RTMs through statistical learning regression methods, and can open many new applications because of their computational efficiency and outstanding accuracy. Emulators allow fast global sensitivity analysis (GSA) studies on advanced, computationally expensive RTMs. As a proof-of-concept, three machine learning regression algorithms (MLRAs) were tested to function as emulators for the leaf RTM PROSPECT-4, the canopy RTM PROSAIL, and the computationally expensive atmospheric RTM MODTRAN5. Selected MLRAs were: kernel ridge regression (KRR), neural networks (NN) and Gaussian processes regression (GPR). For each RTM, 500 simulations were generated for training and validation. The majority of MLRAs were excellently validated to function as emulators with relative errors well below 0.2%. The emulators were then put into a GSA scheme and compared against GSA results as generated by original PROSPECT-4 and PROSAIL runs. NN and GPR emulators delivered identical GSA results, while processing speed compared to the original RTMs doubled for PROSPECT-4 and tripled for PROSAIL. Having the emulator-GSA concept successfully tested, for six MODTRAN5 atmospheric transfer functions (outputs), i.e., direct and diffuse at-surface solar irradiance (E di f , E dir ), direct and diffuse upward transmittance (T dir , T di f ), spherical albedo (S) and path radiance (L 0 ), the most accurate MLRA's were subsequently applied as emulator into the GSA scheme. The sensitivity analysis along the 400-2500 nm spectral range took no more than a few minutes on a contemporary computer-in comparison, the same analysis in the original MODTRAN5 would have taken over a month. Key atmospheric drivers were identified, which are on the one hand aerosol optical properties, i.e., aerosol optical thickness (AOT), Angstrom coefficient (AMS) and scattering asymmetry variable (G), mostly driving diffuse atmospheric components, E di f and T di f ; and those affected by atmospheric scattering, L 0 and S. On the other hand, as expected, AOT, AMS and columnar water vapor (CWV) in the absorption regions mostly drive E dir and T dir atmospheric functions. The presented emulation schemes showed very promising results in replacing costly RTMs, and we think they can contribute to the adoption of machine learning techniques in remote sensing and environmental applications.

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“…We used a direct sorting method to calculate the k-distribution from line-by-line spectra within each spectral bin (e.g., Goody et al 1989b). For the continuum fitting, we initially used a triangular function as an approximation to the SPIRE instrument function.…”

Section: Saturn Continuum Modelling: Temperatures Ph 3 and Nhmentioning

confidence: 99%

Sub-millimetre spectroscopy of Saturn’s trace gases fromHerschel/SPIRE

Fletcher

Swinyard

Salji

et al. 2012

A&A

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Aims. We provide an extensive new sub-millimetre survey of the trace gas composition of Saturn's atmosphere using the broad spectral range (15-51 cm −1 ) and high spectral resolution (0.048 cm −1 ) offered by Fourier transform spectroscopy by the Herschel/SPIRE instrument (Spectral and Photometric Imaging REceiver). Observations were acquired in June 2010, shortly after equinox, with negligible contribution from Saturn's ring emission. Methods. Tropospheric temperatures and the vertical distributions of phosphine and ammonia are derived using an optimal estimation retrieval algorithm to reproduce the sub-millimetre data. The abundance of methane, water and upper limits on a range of different species are estimated using a line-by-line forward model. Results. Saturn's disc-averaged temperature profile is found to be quasi-isothermal between 60 and 300 mbar, with uncertainties of 7 K due to the absolute calibration of SPIRE. Modelling of PH 3 rotational lines confirms the vertical profile derived in previous studies and shows that negligible PH 3 is present above the 10-to 20-mbar level. The upper tropospheric abundance of NH 3 appears to follow a vapour pressure distribution throughout the region of sensitivity in the SPIRE data, but the degree of saturation is highly uncertain. The tropospheric CH 4 abundance and Saturn's bulk C/H ratio are consistent with Cassini studies. We improve the upper limits on several species (H 2 S, HCN, HCP and HI); provide the first observational constraints on others (SO 2 , CS, methanol, formaldehyde, CH 3 Cl); and confirm previous upper limits on HF, HCl and HBr. Stratospheric emission from H 2 O is suggested at 36.6 and 38.8 cm −1 with a 1σ significance level, and these lines are used to derive mole fractions and column abundances consistent with ISO and SWAS estimations a decade earlier.

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The correlated-k method for radiation calculations in nonhomogeneous atmospheres

Cited by 478 publications

References 1 publication

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

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

Emulation of Leaf, Canopy and Atmosphere Radiative Transfer Models for Fast Global Sensitivity Analysis

Sub-millimetre spectroscopy of Saturn’s trace gases fromHerschel/SPIRE

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