Journal Article

PreJuSER-6241

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Lightning-produced NOx during the Northern Australian monsoon - Results from the ACTIVE campaign

Labrador, L. ; Vaughan, G. ; Heyes, W. ; Waddicor, D. ; Volz-Thomas, A.FZJ* ; Pätz, H.-W.FZJ* ; Höller, H.

2009
EGU Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/10130  doi:10.5194/acp-9-7419-2009

Abstract: Measurements of nitrogen oxides onboard a high altitude aircraft were carried out for the first time during the Northern Australian monsoon in the framework of the Aerosol and Chemical Transport in Tropical Convection (ACTIVE) campaign, in the area around Darwin, Australia. During one flight on 22 January 2006, average NOx volume mixing ratios (vmr) of 984 and 723 parts per trillion (ppt) were recorded for both in and out of cloud conditions, respectively. The in-cloud measurements were made in the convective outflow region of a storm 56 km south-west of Darwin, whereas those out of cloud were made due south of Darwin and upwind from the storm sampled. This storm produced a total of only 8 lightning strokes, as detected by an in-situ lightning detection network, ruling out significant lightning-NOx production. 5-day backward trajectories suggest that the sampled airmasses had travelled over convectively-active land in Northern Australia during that period. The low stroke count of the sampled storm, along with the high out-of-cloud NOx concentration, suggest that, in the absence of other major NOx sources during the monsoon season, a combination of processes including regional transport patterns, convective vertical transport and entrainment may lead to accumulation of lightning-produced NOx, a situation that contrasts with the pre-monsoon period in Northern Australia, where the high NOx values occur mainly in or in the vicinity of storms. These high NOx concentrations may help start ozone photochemistry and OH radical production in an otherwise NOx-limited environment.

Keyword(s): J

Note: We thank the pilots and ground staff of the Egrett and Dornier aircraft for ensuring a successful campaign, and thank Peter May for particularly useful discussions and insight into the general meteorological condition over Northern Australia during ACTIVE, as well as the staff of the Bureau of Meteorology (BoM) Regional Centre in Darwin for their support in forecasting and logistics; also the Royal Australian Air Force for hosting the aircraft experiment, and Marcel Berg and Norbert Houben for maintenance of the CO and NOx instruments. James Lee provided the Dornier NOx estimates. We would also like to thank the editor as well as three anonymous referees, whose useful comments and suggestions have contributed to improving this manuscript. Finally, we thank the UK Natural Environment Research Council (Grant NE/C512688/1) for supporting ACTIVE.

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Research Program(s):

1. Atmosphäre und Klima (P22)

Appears in the scientific report 2009

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