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| Titel |
How well can we quantify the actinic flux driving catalytic ozone chemistry at high solar zenith angles? |
| VerfasserIn |
M. von Hobe, O. Sumińska-Ebersoldt, C. Emde, F. Stroh |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065811
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| Zusammenfassung |
| When chlorine has been heterogeneously activated in the polar stratosphere in winter, two
catalytic cycles, the ClO dimer cycle and the ClO-BrO cycle, are largely responsible for the
chemical destruction of ozone leading to the so-called ozone hole. These cycles cannot
proceed in the absence of light, because they involve photolysis reactions, which are rate
limiting at low solar zenith angles typical for the polar regions in late winter/early
spring.
The ClOOCl and BrCl photolysis rates are given by the wavelength integrated
product of the respective species’ photolysis cross section and the actinic flux. While
tremendous efforts have been made over the past 25 years to reduce the uncertainties in
the photolysis cross sections, in particular for ClOOCl, the focus on variability
and uncertainties in the actinic flux, and endeavors to correctly represent them in
photochemical models simulating ClOx partitioning and ozone loss, have been surprisingly
small.
Using the radiative transfer model LibRadTran, we quantify the influence of column
ozone, surface albedo, clouds (presence, microphysical properties and altitude) and aerosol
loading on the actinic flux in the spectral region relevant to ClOOCl and BrCl photolysis. We
go on to investigate how our results may influence the interpretation of several studies that
use a photochemical model to constrain kinetic parameters from observed ClOx partitioning
and ozone loss. |
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