Investigating <i>k</i> distribution methods for parameterizing gaseous absorption in the Hadley Centre Climate Model

Cusack, Stephen; Edwards, John M.; Crowther, John

doi:10.1029/1998jd200063

Cited by 100 publications

(72 citation statements)

References 19 publications

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“…For all other gases absorption is based on HITRAN92. Gaseous absorption is represented according to Cusack et al (1999) using a correlatedk method.…”

Section: A20 Models #20-23 University Of Reading Edwards Andmentioning

confidence: 99%

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

et al. 2013

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Abstract. In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly −10 to 20%, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

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“…For all other gases absorption is based on HITRAN92. Gaseous absorption is represented according to Cusack et al (1999) using a correlatedk method.…”

Section: A20 Models #20-23 University Of Reading Edwards Andmentioning

confidence: 99%

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

et al. 2013

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“…Estimates of the anthropogenic SO 2 emissions were taken from Orn et al (1996) for 1860-1970, the Global Emissions Inventory Activity (GEIA) 1B dataset for 1985, and the preliminary SRES datasets for 1990 and 2000 (Nakićenović and Swart 2000) and linearly interpolated between these times. The distribution of atmospheric sulfate aerosol was then passed to the model's radiation scheme (Edwards and Slingo 1996;Cusack et al 1999) for computation of its direct radiative effect.…”

Section: B Sulfatesmentioning

confidence: 99%

Do Models Underestimate the Solar Contribution to Recent Climate Change?

Stott¹,

Jones²,

Mitchell³

2003

J. Climate

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Current attribution analyses that seek to determine the relative contributions of different forcing agents to observed near-surface temperature changes underestimate the importance of weak signals, such as that due to changes in solar irradiance. Here a new attribution method is applied that does not have a systematic bias against weak signals.It is found that current climate models underestimate the observed climate response to solar forcing over the twentieth century as a whole, indicating that the climate system has a greater sensitivity to solar forcing than do models. The results from this research show that increases in solar irradiance are likely to have had a greater influence on global-mean temperatures in the first half of the twentieth century than the combined effects of changes in anthropogenic forcings. Nevertheless the results confirm previous analyses showing that greenhouse gas increases explain most of the global warming observed in the second half of the twentieth century.

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“…The number of k-terms can be adjusted to give the desired trade-off between accuracy and efficiency that is required for a given application. For example, the Met Office currently uses a scheme with a total of 115 k-terms for climate and global forecasting applications, and a scheme with 55 k-terms for short-term local area modelling (Edwards and Slingo, 1996;Cusack et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Two fast radiative transfer methods to improve the temporal sampling of clouds in numerical weather prediction and climate models

Manners

Thelen

Petch

et al. 2009

Quart J Royal Meteoro Soc

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ABSTRACT:The high computational cost of calculating the radiative heating rates in numerical weather prediction (NWP) and climate models requires that calculations are made infrequently, leading to poor sampling of the fast-changing cloud field and a poor representation of the feedback that would occur. This paper presents two related schemes for improving the temporal sampling of the cloud field. Firstly, the 'split time-stepping' scheme takes advantage of the independent nature of the monochromatic calculations of the 'correlated-k' method to split the calculation into gaseous absorption terms that are highly dependent on changes in cloud (the optically thin terms) and those that are not (optically thick). The small number of optically thin terms can then be calculated more often to capture changes in the grey absorption and scattering associated with cloud droplets and ice crystals. Secondly, the 'incremental time-stepping' scheme uses a simple radiative transfer calculation using only one or two monochromatic calculations representing the optically thin part of the atmospheric spectrum. These are found to be sufficient to represent the heating rate increments caused by changes in the cloud field, which can then be added to the last full calculation of the radiation code. We test these schemes in an operational forecast model configuration and find a significant improvement is achieved, for a small computational cost, over the current scheme employed at the Met Office. The 'incremental time-stepping' scheme is recommended for operational use, along with a new scheme to correct the surface fluxes for the change in solar zenith angle between radiation calculations.

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Investigating k distribution methods for parameterizing gaseous absorption in the Hadley Centre Climate Model

Cited by 100 publications

References 19 publications

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

Do Models Underestimate the Solar Contribution to Recent Climate Change?

Two fast radiative transfer methods to improve the temporal sampling of clouds in numerical weather prediction and climate models

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