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| Titel |
Ultraviolet actinic flux in clear and cloudy atmospheres: model calculations and aircraft-based measurements |
| VerfasserIn |
G. G. Palancar, R. E. Shetter, S. R. Hall, B. M. Toselli, S. Madronich |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-14), S.5457-5469 |
| Datensatznummer |
250009812
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| Publikation (Nr.) |
 copernicus.org/acp-11-5457-2011.pdf |
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| Zusammenfassung |
| Ultraviolet (UV) actinic fluxes measured with two Scanning Actinic Flux
Spectroradiometers (SAFS) aboard the NASA DC-8 aircraft are compared with
the Tropospheric Ultraviolet-Visible (TUV) model. The observations from 17
days in July-August 2004 (INTEX-NA field campaign) span a wide range of
latitudes (28° N–53° N), longitudes (45° W–140° W),
altitudes (0.1–11.9 km), ozone columns (285–353 DU), and solar zenith
angles (2°–85°). Both cloudy and cloud-free conditions were
encountered. For cloud-free conditions, the ratio of observed to
clear-sky-model actinic flux (integrated from 298 to 422 nm) was 1.01±0.04,
i.e. in good agreement with observations. The agreement improved to
1.00±0.03 for the down-welling component under clear sky conditions.
In the presence of clouds and depending on their position relative to the
aircraft, the up-welling component was frequently enhanced (by as much as a
factor of 8 relative to cloud-free values) while the down-welling component
showed both reductions and enhancements of up to a few tens of percent.
Including all conditions, the ratio of the observed actinic flux to the
cloud-free model value was 1.1±0.3 for the total, or separately
1.0±0.2 for the down-welling and 1.5±0.8 for the up-welling
components. The correlations between up-welling and down-welling deviations
are well reproduced with sensitivity studies using the TUV model, and are
understood qualitatively with a simple conceptual model. This analysis of
actinic flux observations illustrates opportunities for future evaluations
of photolysis rates in three-dimensional chemistry-transport models. |
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