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The correlated k-distribution (CKD) method is widely used in the radiative transfer schemes of atmospheric models, and involves dividing the spectrum into a number of bands and then reordering the gaseous absorption coefficients within each one. The fluxes and heating rates for each band may then be computed by discretizing the reordered spectrum into of order 10 quadrature points per major gas, and performing a pseudo-monochromatic radiation calculation for each point. In this paper it is first argued that for clear-sky longwave calculations, sufficient\ud accuracy for most applications can be achieved without the need for bands: reordering may be performed on the entire longwave spectrum. The resulting full-spectrum correlated k (FSCK) method requires significantly fewer pseudo-monochromatic calculations than standard CKD to achieve a given accuracy. The concept is first demonstrated by comparing with line-by-line calculations for an atmosphere containing only water vapor, in which it is shown that the accuracy of heating-rate calculations improves approximately in proportion to the square of the number of quadrature points. For more than around 20 points, the root-mean-squared error flattens out at around 0.015 K d−1 due to the imperfect rank correlation of absorption spectra at different pressures in the profile. The spectral overlap of m different gases is treated by considering an m-dimensional hypercube where each axis corresponds to the reordered spectrum of one of the gases. This hypercube is then divided up into a number of volumes,\ud each approximated by a single quadrature point, such that the total number of quadrature points is slightly fewer\ud than the sum of the number that would be required to treat each of the gases separately. The gaseous absorptions\ud for each quadrature point are optimized such they minimize a cost function expressing the deviation of the heating\ud rates and fluxes calculated by the FSCK method from line-by-line calculations for a number of training profiles. This approach is validated for atmospheres containing water vapor, carbon dioxide and ozone, in which it is found that in the troposphere and most of the stratosphere, heating-rate errors of less than 0.2 K d−1 can be achieved using a total of 23 quadrature points, decreasing to less than 0.1 K d−1 for 32 quadrature points. It would be relatively straightforward to extend the method to include other gases.
Ambartzumian, V., 1936: The effect of the absorption lines on the radiative equilibrium of the outer layers of the stars. Publ. Obs. Astron. Univ. Leningrad, 6, 7-18.
Cahalan, R. F., W. Ridgeway, W. J. Wiscombe, T. L. Bell and J. B. Snider, 1994: The albedo of fractal stratocumulus clouds. J. Atmos. Sci., 51, 2434- 2455.
Curry, C. L., N. A. McFarlane and J. F. Scinocca, 2006: Relaxing the well-mixed greenhouse gas approximation in climate simulations: Consequences for stratospheric climate. J. Geophys. Res., 111, doi:10.1029/2005JD006670.
Edwards, J. M., 1996: Efficient calculation of infrared fluxes and cooling rates using the two-stream equations. J. Atmos. Sci., 53, 1921-1932.
Elsasser, W. M., 1942: Heat transfer by infrared radiation in the atmosphere. Harvard Meteorol. Studies, Vol. 6, Harvard Univ. Press, 106 pp.
Eymet, V., J. L. Dufresne, P. Ricchiazzi, R. Fournier and S. Blanco, 2004: Long-wave radiative analysis of cloudy scattering atmospheres using a net exchange formulation. Atmos. Res., 72, 239-261.
Fomin, B. A., 2004: A k-distribution technique for radiative transfer simulation in inhomogeneous atmosphere - 1. FKDM, fast k-distribution model for the longwave. J. Geophys. Res., 109, D02110, doi:10.1029/2003JD003802.
Fu, Q., and K. N. Liou, 1992: On the correlated kdistribution method for radiative transfer in nonhomogenous atmospheres. J. Atmos. Sci., 49, 2139- 2156.
Fu, Q., K. N. Liou, M. C. Cribb, T. P. Charlock and A. Grossman, 1997: Multiple scattering parameterization in thermal infrared radiative transfer. J. Atmos. Sci., 54, 2799-2812.
Green, J. S. A., 1967: Division of radiative streams into internal transfer and cooling to space. Quart. J. Roy. Meteorol. Soc., 93, 371-372.
Hansen, J., G. Russell, D. Rind, P. Stone, A. Lacis, S. Lebedeff, R. Ruedy, and L. Travis, 1983: Efficient three-dimensional global models for climate studies: Models I and II. Mon. Weath. Rev., 111, 609-662.
Lacis, A., W. C. Wang and J. Hansen, 1979: Correlated k-distribution method for radiative transfer in climate models: Application to effect of cirrus clouds on climate. NASA Conf. Publ. 2076, 309- 314.
Lacis, A., and V. Oinas, 1991: A description of the correlated k-distribution method for modeling nongray gaseous absorption, thermal emission, and multiple scattering in vertically inhomogeneous atmospheres. J. Geophys. Res., 96, 9027-9063.
Manners, J., J.-C. Thelen, J. Petch, P. Hill and J. M. Edwards, 2009: Two fast radiative transfer methods to improve the temporal sampling of clouds in numerical weather prediction and climate models. Quart. J. Roy. Meteorol. Soc., 135, 457-468.
McClatchey, R. A., R. W. Fenn, J. E. A. Selby, F. E. Volz and J. S. Garing, 1972: Optical properties of the atmosphere (3rd ed.), Air Force Cambridge Research Laboratories, Rep. No. AFCRL72-0497, L. G. Hanscom Field.
Mitsel, A. A., I. V. Ptashnik, K. M. Firsov and A. B. Fomin, 1995: Efficient technique for line-by-line calculating the transmittance of the absorbing atmosphere. Atmos. Oceanic Opt., 8, 847-850.
Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J. Iacono and S. A. Clough, 1997: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J. Geophys.
Res., 102, 16663-16682.
Mlawer, E. J., D. C. Tobin and S. A. Clough, 2003: The MT-CKD water vapor continuum: A revised perspective including collision induced effects. Workshop on Atmospheric Science from Space using Fourier Transform Spectrometry II, Bad Wildbad, Germany, 8-10 October 2003.
Modest, M. F., and H. Zhang, 2002: The full-spectrum correlated-k distribution for thermal radiation from molecular gas-particulate mixtures. J. Heat Transfer, 124, 30-38.
Morcrette, J.-J., 2000: On the effects of the temporal and spatial sampling of radiation fields on the ECMWF forecasts and analyses. Mon. Weath. Rev., 128, 876-887.
Morcrette, J.-J., H. W. Barker, J. N. S. Cole, M. J. Iacono and R. Pincus, 2008: Impact of a new radiation package, McRad, in the ECMWF Integrated Forecasting System. Mon. Weath. Rev., 136, 4773-4798.
Oinas, V., A. A. Lacis, D. Rind, D. T. Shindell and J. E. Hansen, 2001: Radiative cooling by stratospheric water vapor: Big differences in GCM results. Geophys. Res. Lett., 28, 2791-2794.
Pawlak, D. T., E. E. Clothiaux, M. F. Modest and J. N. S. Cole, 2004: Full-spectrum correlated-k distribution for shortwave atmospheric radiative transfer. J. Atmos. Sci., 61, 2588-2601.
Rodgers, C. D., 2000: Inverse methods for atmospheric sounding: Theory and practice. World Scientific, pp. 238.
Rodgers, C. D., and C. D. Walshaw, 1966: The computation of infrared cooling rate in planetary atmospheres. Quart. J. Roy. Meteorol. Soc., 92, 67- 92.
Rothman, L. S., D. Jacquemart, A. Barbe, D. Chris Benner, M. Birk, L. R. Brown, M. R. Carleer, C. Chackerian Jr., K. Chance, L. H. Coudert, V. Dana, V. M. Devi, J.-M. Flaud, R. R. Gamache, A. Goldman, J.- M. Hartmann, K. W. Jucks, A. G. Maki, J.-Y. Mandin, S. T. Massie, J. Orphal, A. Perrin, C. P. Rinsland, M. A. H. Smith, J. Tennyson, R. N. Tolchenov, R. A. Toth, J. Vander Auwera, P. Varanasi and G. Wagner, 2004: The HITRAN 2004 molecular spectroscopic database. J. Quant. Spectroscopy, 96, 139- 204.
Shonk, J. K. P., and R. J. Hogan, 2008: Tripleclouds: an efficient method for representing cloud inhomogeneity in 1D radiation schemes by using three regions at each height. J. Climate, 21, 2352-2370.
Yang, G.-Y., and J. M. Slingo, 2001: The diurnal cycle in the tropics. Mon. Weath. Rev., 129, 784-801.