Abstract
Abstract. Rotational Raman scattering in the Earth's atmosphere explains the filling-in of Fraunhofer lines in the solar spectrum. A new model including first-order rotational Raman scattering has been developed, based on a reimplementation of the versatile discrete ordinate radiative transfer (DISORT) solver in the C computer language. The solver is fully integrated in the freely available libRadtran radiative transfer package. A detailed description is given of the model including the spectral resolution and a spectral interpolation scheme that considerably speeds up the calculations. The model is used to demonstrate the effect of clouds on top and bottom of the atmosphere filling-in factors and differential optical depths. Cloud effects on vertical profiles of the filling-in factor are also presented. The spectral behaviour of the model is compared against measurements under thunderstorm and aerosol loaded conditions.
Highlights
Rotational Raman scattering (RRS) explains the filling-in of Fraunhofer lines in solar spectra measured both from the Earth’s surface and onboard satellites (Kattawar et al, 1981)
They found that the inclusion of polarization on Raman scattering is of minor importance for most applications. van Deelen et al (2005) developed a doubling-adding code including multiple elastic scattering and multiple inelastic RRS
The aerosol case was based on a situation that occurred during the Actinic flux determination from measurements of irradiance (ADMIRA) measurement campaign, August 2000 at Nea Michaniona, Greece (Webb et al, 2002)
Summary
Rotational Raman scattering (RRS) explains the filling-in of Fraunhofer lines in solar spectra measured both from the Earth’s surface and onboard satellites (Kattawar et al, 1981). Vountas et al (1998) described a first-order RRS finite difference model that treated clouds and aerosols explicitly This model was used by de Beek et al (2001) to study the effect of RRS on both ground-based and satellite measurements. Spurr et al (2008) described a discrete ordinates method model for first-order RRS and presented model simulations of fillingin factors due to RRS in cloudy situations Results for both satellite geometries and vertical profiles of filling-in factors were shown. Landgraf et al (2004) presented a first-order RRS vector radiative transfer model based on the Gauss-Seidel approximation They found that the inclusion of polarization on Raman scattering is of minor importance for most applications. This is followed by a comparison of model results and measurements for a thunderstorm situation and an aerosol case
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