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| Titel |
Relationship between the NO2 photolysis frequency and the solar global irradiance |
| VerfasserIn |
I. Trebs, B. Bohn, C. Ammann, U. Rummel, M. Blumthaler, R. Königstedt, F. X. Meixner, S. Fan, M. O. Andreae |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 2, no. 2 ; Nr. 2, no. 2 (2009-11-16), S.725-739 |
| Datensatznummer |
250000579
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| Publikation (Nr.) |
 copernicus.org/amt-2-725-2009.pdf |
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| Zusammenfassung |
| Representative values of the atmospheric NO2 photolysis frequency
j(NO2) are required for the adequate calculation and interpretation of
NO and NO2 concentrations and exchange fluxes near the surface. Direct
measurements of j(NO2) at ground level are often not available in field
studies. In most cases, modeling approaches involving complex radiative
transfer calculations are used to estimate j(NO2) and other photolysis
frequencies for air chemistry studies. However, important input parameters
for accurate modeling are often missing, most importantly with regard to the
radiative effects of clouds. On the other hand, solar global irradiance
("global radiation", G) is nowadays measured as a standard parameter in
most field experiments and in many meteorological observation networks around
the world. Previous studies mainly reported linear relationships between
j(NO2) and G. We have measured j(NO2) using spectro- or filter
radiometers and G using pyranometers side-by-side at several field sites.
Our results cover a solar zenith angle range of 0–90°, and are based
on nine field campaigns in temperate, subtropical and tropical environments
during the period 1994–2008. We show that a second-order polynomial function
(intercept = 0): j(NO2)=(1+α)× (B1×G+B2×G2),
with α defined as the site-dependent UV-A surface albedo and the
polynomial coefficients: B1=(1.47± 0.03)×10-5 W−1 m2 s−1 and
B2=(-4.84±0.31)×10-9 W−2 m4 s−1 can be used to estimate ground-level
j(NO2) directly from G, independent of solar zenith angle under all
atmospheric conditions. The absolute j(NO2) residual of the empirical
function is ±6×10-4 s−1(2σ). The relationship is
valid for sites below 800 m a.s.l. and with low surface albedo
(α<0.2). It is not valid in high mountains, above snow or ice and
sandy or dry soil surfaces. |
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