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| Titel |
Relationship between the NO2 photolysis frequency and the global broadband irradiance |
| VerfasserIn |
I. Trebs, U. Rummel, C. Ammann, R. Koenigstedt, B. Bohn, M. Blumthaler, F. X. Meixner, M. O. Andreae |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026625
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| Zusammenfassung |
| Direct measurements of the nitrogen dioxide (NO2) photolysis rate (j(NO2)) at ground level
are often not available from field experiments. Modeling approaches are mainly used to
estimate j(NO2) for air chemistry studies, involving complex radiative transfer algorithms
based on e.g., actinic flux, absorption cross sections, solar zenith angle, aerosol optical
thickness, ozone column concentration and cloud cover. Bahe et al., 1980 empirically found a
near-linear relationship between global broadband irradiance (G) and j(NO2) on top
of a laboratory building in Germany, which has been applied to estimate j(NO2)
from G. We have measured incoming j(NO2) using spectral/filterradiometers and G
using pyranometers side-by-side at several field sites. In this study, we will show
that a second-order polynomial function can be used to accurately estimate j(NO2)
solely from G, independent of latitude and longitude, solar zenith angle, aerosol
optical thickness and cloud cover. Our results include solar zenith angels smaller than
30° and are based on nine field observations in temperate, subtropical and tropical
environments. This approach can be applied to calculate chemical timescales of the
NO-NO2-O3 triad in order to evaluate the potential influence of chemical reactions on
surface-atmosphere exchange fluxes. Furthermore, the relationship represents a simple
tool to evaluate the photochemical steady state (PSS) assumption of NOx in the
absence of j(NO2) measurements, subsequently being useful for examining the local
photochemistry.
Bahe, F.C., Schurath, U. and Becker, K.H., 1980. The Frequency of NO2 Photolysis at
Ground-Level, as Recorded by a Continuous Actinometer. Atmospheric Environment, 14(6):
711-718. |
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