 |
| Titel |
Constraining the N2O5 UV absorption cross section from spectroscopic trace gas measurements in the tropical mid-stratosphere |
| VerfasserIn |
L. Kritten, A. Butz, M. P. Chipperfield, M. Dorf, S. Dhomse, R. Hossaini, H. Oelhaf, C. Prados-Roman, G. Wetzel, K. Pfeilsticker |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-16), S.9555-9566 |
| Datensatznummer |
250119027
|
| Publikation (Nr.) |
 copernicus.org/acp-14-9555-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| The absorption cross section of N2O5,
σN2O5(λ, T), which is known from laboratory
measurements with the uncertainty of a factor of 2 (Table 4-2 in (Jet
Propulsion Laboratory) JPL-2011; the spread in laboratory data, however,
points to an uncertainty in the range of 25 to 30%, Sander et al., 2011),
was investigated by balloon-borne observations of the relevant trace gases in
the tropical mid-stratosphere. The method relies on the observation of the
diurnal variation of NO2 by limb scanning DOAS (differential optical
absorption spectroscopy) measurements (Weidner et al., 2005;
Kritten et al., 2010), supported by detailed photochemical modelling of
NOy
(NOx(= NO + NO2) + NO3 + 2N2O5
+ ClONO2 + HO2NO2 + BrONO2 + HNO3)
photochemistry and a non-linear least square fitting of the model result to
the NO2 observations. Simulations are initialised with O3
measured by direct sun observations, the NOy partitioning
from MIPAS-B (Michelson Interferometer for Passive Atmospheric Sounding –
Balloon-borne version) observations in similar air masses at night-time, and
all other relevant species from simulations of the SLIMCAT (Single Layer
Isentropic Model of Chemistry And Transport) chemical transport model (CTM).
Best agreement between the simulated and observed diurnal increase of
NO2 is found if the σN2O5(λ, T) is scaled by
a factor of 1.6 ± 0.8 in the UV-C (200–260 nm) and by a factor of
0.9 ± 0.26 in the UV-B/A (260–350 nm), compared to current
recommendations. As a consequence, at 30 km altitude, the
N2O5 lifetime against photolysis becomes a factor of 0.77 shorter at
solar zenith angle (SZA) of 30° than using the recommended
σN2O5(λ, T), and stays more or less constant at
SZAs of 60°. Our scaled N2O5 photolysis frequency slightly
reduces the lifetime (0.2–0.6%) of ozone in the tropical mid- and upper
stratosphere, but not to an extent to be important for global ozone. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|