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Why logarithmic? A note on the dependence of radiative forcing on gas concentration
Author(s) -
Huang Yi,
Bani Shahabadi Maziar
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd022466
Subject(s) - radiance , radiative forcing , radiative transfer , logarithm , forcing (mathematics) , physics , monochromatic color , perturbation (astronomy) , computational physics , atmospheric radiative transfer codes , line (geometry) , absorption (acoustics) , spectral line , mesoionic , atmospheric sciences , chemistry , optics , meteorology , mathematics , mathematical analysis , aerosol , quantum mechanics , geometry , medicinal chemistry
Line‐by‐line radiative transfer computations show that the logarithmic dependence of radiative forcing on gas concentration not only applies to broadband irradiation fluxes such as in the well‐known case of the CO 2 forcing, but also applies to the spectral radiance change due to both CO 2 and other gases, such as H 2 O. The logarithmic relationship holds for monochromatic radiance requires an explanation beyond the conventional ideas based on the spectroscopic features of the gas absorption lines. We show that the phenomenon can be explained by an Emission Layer Displacement Model, which describes the radiance response to gas perturbation under normal atmospheric conditions such as temperature linearly varying with height and gas concentration exponentially decaying with height.