Atmos. Chem. Phys., 9, 8377-8412, 2009
www.atmos-chem-phys.net/9/8377/2009/
doi:10.5194/acp-9-8377-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
NOx production by lightning in Hector: first airborne measurements during SCOUT-O3/ACTIVE
H. Huntrieser1, H. Schlager1, M. Lichtenstern1, A. Roiger1, P. Stock1, A. Minikin1, H. Höller1, K. Schmidt2, H.-D. Betz2,3, G. Allen4, S. Viciani5, A. Ulanovsky6, F. Ravegnani7, and D. Brunner8
1Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany
2nowcast GmbH, München, Germany
3Physics Department, University of Munich, Germany
4School of Earth, Atmospheric & Environmental Sciences, University of Manchester, UK
5Istituto Nazionale di Ottica Applicata (CNR-INOA), Firenze, Italy
6Central Aerological Observatory, Moscow, Russia
7Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy
8Laboratory for Air Pollution and Environmental Technology, Empa, Swiss Federal Laboratories for Materials Testing and Research, Dübendorf, Switzerland

Abstract. 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.

Citation: Huntrieser, H., Schlager, H., Lichtenstern, M., Roiger, A., Stock, P., Minikin, A., Höller, H., Schmidt, K., Betz, H.-D., Allen, G., Viciani, S., Ulanovsky, A., Ravegnani, F., and Brunner, D.: NOx production by lightning in Hector: first airborne measurements during SCOUT-O3/ACTIVE, Atmos. Chem. Phys., 9, 8377-8412, doi:10.5194/acp-9-8377-2009, 2009.
 
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