Extension of the weak-line approximation and application to correlated-k methods
Conley, A. J., & Collins, W. D. (2011). Extension of the weak-line approximation and application to correlated-k methods. Journal Of Quantitative Spectroscopy &Amp; Radiative Transfer, 112, 1525-1532. doi:10.1016/j.jqsrt.2011.02.008
Global climate models require accurate and rapid computation of the radiative transfer through the atmosphere. Correlated-k methods are often used. One of the approximations used in correlated-k models is the weak-line approximation. We introduce an approximation Tγ which reduces to the weak-line... Show moreGlobal climate models require accurate and rapid computation of the radiative transfer through the atmosphere. Correlated-k methods are often used. One of the approximations used in correlated-k models is the weak-line approximation. We introduce an approximation Tγ which reduces to the weak-line limit when optical depths are small, and captures the deviation from the weak-line limit as the extinction deviates from the weak-line limit. This approximation is constructed to match the first two moments of the gamma distribution to the k-distribution of the transmission. We compare the errors of the weak-line approximation with Tγ in the context of a water vapor spectrum. The extension Tγ is more accurate and converges more rapidly than the weak-line approximation. Show less