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| Titel |
A new numerical model to compute photolysis rates and solar heating with anisotropic scattering in spherical geometry |
| VerfasserIn |
M. Balluch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 1 ; Nr. 14, no. 1, S.80-97 |
| Datensatznummer |
250012139
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| Publikation (Nr.) |
 copernicus.org/angeo-14-80-1996.pdf |
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| Zusammenfassung |
| For calculating photolysis rates and solar
heating in the atmosphere, the radiation field has to be calculated very
accurately. Previous investigations have shown that for large solar zenith
angles a solution of the radiation equation which accounts for the Earth\'s
curvature is needed. A new simplified version of the 3D radiation equation in
spherical geometry allowing for anisotropic scattering is presented. The
horizontal variation of physical quantities, the variation of the solar zenith
angle with different longitude and latitude for the scattering calculation for
one vertical column of air and any effects of refraction are neglected. A
numerical model is introduced which efficiently solves this new 3D radiation
equation accurately. The effects of anisotropic scattering are shown to be very
important for the directional dependence of the scattered intensity. Anisotropic
scattering by aerosols and air molecules can change the intensity in certain
directions by up to 180% and 25%, respectively. However, most of these changes
cancel each other out when averaged over all angles, so that the effect of
anisotropic scattering for large solar zenith angles on the mean intensity
(actinic flux) is much smaller, i.e. less than 10%. For the heating rates, the
effect of anisotropic scattering for large solar zenith angles is even smaller,
being less than a few percent. Generally, the effects of anisotropic scattering
and the effects of including aerosols are the larger on higher altitudes the
larger the solar zenith angle is. Results of the model are shown to compare well
with results of previous investigations, including the independent work of
Dahlback and Stamnes. The agreement is especially good in the case of isotropic
scattering by air molecules and neglecting the effects of aerosols. |
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