Abstract
Abstract. A comprehensive inter-comparison of seven radiative transfer models in the limb scattering geometry has been performed. Every model is capable of accounting for polarization within a spherical atmosphere. Three models (GSLS, SASKTRAN-HR, and SCIATRAN) are deterministic, and four models (MYSTIC, SASKTRAN-MC, Siro, and SMART-G) are statistical using the Monte Carlo technique. A wide variety of test cases encompassing different atmospheric conditions, solar geometries, wavelengths, tangent altitudes, and Lambertian surface reflectances have been defined and executed for every model. For the majority of conditions it was found that the models agree to better than 0.2 % in the single-scatter test cases and better than 1 % in the scalar and vectorial test cases with multiple scattering included, with some larger differences noted at high values of surface reflectance. For the first time in limb geometry, the effect of atmospheric refraction was compared among four models that support it (GSLS, SASKTRAN-HR, SCIATRAN, and SMART-G). Differences among most models with multiple scattering and refraction enabled were less than 1 %, with larger differences observed for some models. Overall the agreement among the models with and without refraction is better than has been previously reported in both scalar and vectorial modes.
Highlights
The limb scattering measurement technique involves viewing through the side, the limb, of the atmosphere while measuring scattered sunlight
Both SASKTRAN (HR and Monte Carlo (MC)) and Gauss– Seidel limb scattering (GSLS) make the assumption that V is exactly 0, which reduces the size of the phase matrix to speed up the computation, and it does not appear that this approximation affects the results in a noticeable way
A systematic comparison has been performed between seven radiative transfer models operating in the limb scatter geometry
Summary
The limb scattering measurement technique involves viewing through the side, the limb, of the atmosphere while measuring scattered sunlight (see Fig. 1). Vertical profiles of limb scattering spectra can be inverted to obtain distributions of atmospheric constituents with spectral absorption or scattering features These include but are not limited to stratospheric aerosol (Bourassa et al, 2007; von Savigny et al, 2015), ozone (Roth et al, 2007; Degenstein et al, 2009; Rault and Spurr, 2010; Arosio et al, 2018), nitrogen dioxide (Butz et al, 2006; Sioris et al, 2017), water vapor (Rozanov et al, 2011b), and bromine oxide (McLinden et al, 2010; Rozanov et al, 2011a).
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