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| Titel |
NOx production by lightning in Hector: first airborne measurements during SCOUT-O3/ACTIVE |
| VerfasserIn |
H. Huntrieser, H. Schlager, M. Lichtenstern, A. Roiger, P. Stock, A. Minikin, H. Höller, K. Schmidt, H.-D. Betz, G. Allen, S. Viciani, A. Ulanovsky, F. Ravegnani, D. Brunner |
| 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 ; 9, no. 21 ; Nr. 9, no. 21 (2009-11-05), S.8377-8412 |
| Datensatznummer |
250007732
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| Publikation (Nr.) |
 copernicus.org/acp-9-8377-2009.pdf |
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| Zusammenfassung |
| During the SCOUT-O3/ACTIVE field phase in November–December 2005, airborne in
situ measurements were performed inside and in the vicinity of thunderstorms
over northern Australia with several research aircraft (German Falcon,
Russian M55 Geophysica, and British
Dornier-228. Here a case study from 19 November is presented in
detail on the basis of airborne trace gas measurements (NO, NOy,
CO, O3) and stroke measurements from the German LIghtning
Location NETwork (LINET), set up in the vicinity of Darwin
during the field campaign. The anvil outflow from three different types of
thunderstorms was probed by the Falcon aircraft: (1) a continental
thunderstorm developing in a tropical airmass near Darwin, (2) a mesoscale
convective system (MCS), known as Hector, developing within the tropical
maritime continent (Tiwi Islands), and (3) a continental thunderstorm developing
in a subtropical airmass ~200 km south of Darwin. For the first
time detailed measurements of NO were performed in the Hector outflow. The
highest NO mixing ratios were observed in Hector with peaks up to 7 nmol mol−1
in the main anvil outflow at ~11.5–12.5 km altitude. The
mean NOx (=NO+NO2) mixing ratios during these penetrations (~100 km width)
varied between 2.2 and 2.5 nmol mol−1. The NOx
contribution from the boundary layer (BL), transported upward with the
convection, to total anvil-NOx was found to be minor (<10%). On the
basis of Falcon measurements, the mass flux of lightning-produced NOx
(LNOx) in the well-developed Hector system was estimated to 0.6–0.7 kg(N) s−1.
The highest average stroke rate of the probed thunderstorms was
observed in the Hector system with 0.2 strokes s−1 (here only strokes
with peak currents ≥10 kA contributing to LNOx were considered). The
LNOx mass flux and the stroke rate were combined to estimate the LNOx
production rate in the different thunderstorm types. For a better comparison
with other studies, LINET strokes were scaled with Lightning
Imaging Sensor (LIS) flashes. The LNOx production
rate per LIS flash was estimated to 4.1–4.8 kg(N) for the well-developed
Hector system, and to 5.4 and 1.7 kg(N) for the continental thunderstorms
developing in subtropical and tropical airmasses, respectively. If we assume,
that these different types of thunderstorms are typical thunderstorms
globally (LIS flash rate ~44 s−1), the annual global LNOx
production rate based on Hector would be ~5.7–6.6 Tg(N) a−1 and
based on the continental thunderstorms developing in subtropical and tropical
airmasses ~7.6 and ~2.4 Tg(N) a−1, respectively. The
latter thunderstorm type produced much less LNOx per flash compared to the
subtropical and Hector thunderstorms, which may be caused by the shorter mean
flash component length observed in this storm. It is suggested that the
vertical wind shear influences the horizontal extension of the charged
layers, which seems to play an important role for the flash lengths that may
originate. In addition, the horizontal dimension of the anvil outflow and the
cell organisation within the thunderstorm system are probably important
parameters influencing flash length and hence LNOx production per flash. |
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