Scientific Results

NOx production by lightning in Hector: first airborne measurements during SCOUT-O3/ACTIVE

Year: 2009

Authors: 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., Brunner D.

Autors Affiliation: Institut fur Physik der Atmosphare, Deutsches Zentrum fur Luft-und Raumfahrt (DLR), Oberpfaffenhofen, Germany; Nowcast GmbH, Munchen, Germany; Physics Department, University of Munich, Germany; School of Earth, Atmospheric & Environmental Sciences, University of Manchester, UK; Istituto Nazionale di Ottica Applicata (CNR-INOA), Firenze, Italy; Central Aerological Observatory, Moscow, Russia; Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy; Laboratory for Air Pollution and Environmental Technology, Empa, Swiss Federal Laboratories for Materials Testing and Research, Dubendorf, 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, O-3) 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 similar to 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 similar to 11.5-12.5 km altitude. The mean NOx (=NO+NO2) mixing ratios during these penetrations (similar to 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 similar to 44 s(-1)), the annual global LNOx production rate based on Hector would be similar to 5.7-6.6 Tg(N) a(-1) and based on the continental thunderstorms developing in subtropical and tropical airmasses similar to 7.6 and similar to 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.

Journal/Review:

Volume: 9 (21)      Pages from: 8377  to: 8412

More Information: The measurements presented here from the Integrated Project SCOUT-O3 were partially funded by the European Commission under the contract (505390-GOCE-CT-2004) and partly by the DLR (Deutsches Zentrum fur Luft- und Raumfahrt) and other SCOUT-O3 partners. ACTIVE was supported by NERC Airborne Remote Sensing Facility and the U.S. Natural Environment Research Council (Grant NE/C512688/1). We thank C. Schiller (Forschungszentrum Julich), R. MacKenzie (Lancaster University), T. Peter (ETH Zurich), and G. Vaughan ( University of Manchester) for the coordination of the SCOUT-O3 and ACTIVE field campaigns. We thank the Falcon, Geophysica and Dornier-228 pilots, the engineers and scientists of the flight departments for the excellent support during the field phase and A. Lewis (University of York) for performing the CO measurements on the Dornier-228 aircraft used in this paper. The LINET system was installed in the Darwin area as a joint effort between DLR and the Bureau of Meteorology Research Center (BMRC) which is now part of the Centre for Australian Weather and Climate Research (CAWCR) and by support from the U.S. DOE-ARM (Department of Energy – Atmospheric Radiation Measurement Program) for TWPICE (Tropical Warm Pool International Cloud Experiment). We greatly acknowledge B. Atkinson, A. Noonan (Bureau of Meteorology), and L. Oswald (DLR) for making the LINET system operations possible, and M. Zich (nowcast GmbH) for the system support. We thank P. May (CAWCR) for providing the C-POL radar data which were of great help for interpreting the airborne data and the lightning evolution. We express our gratitude to the lightning team at MSFC-NASA for the access to the LIS data. ECMWF is acknowledged for permitting access to their data archives. Finally, we thank L. Labrador (University of Manchester) and E. Defer (Observatoire de Paris – LERMA) for helpful discussions on ACTIVE trace gas and LINET lightning measurements, respectively, and N. Dotzek (DLR), V. Grewe (DLR), K. Pickering (NASA Goddard Space Flight Center Greenbelt) and the two anonymous reviewers for their comments and suggestions, which greatly helped to improve the manuscript.
KeyWords: air mass; airborne sensing; annual variation; atmospheric chemistry; boundary layer; convective system; formation mechanism; in situ measurement; lightning; mesoscale meteorology; mixing ratio; nitrogen oxides; thunderstorm; trace gas; tropical meteorology; wind shear, Australasia; Australia, Falconidae
DOI: 10.5194/acp-9-8377-2009

Citations: 24
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