Huntrieser, H. und Schlager, H. und Lichtenstern, M. und Stock, P. und Hamburger, T. und Höller, H. und Schmidt, K. und Betz, H.-D. und Ulanovsky, A. und Ravegnani, F. (2011) Mesoscale convective systems observed during AMMA and their impact on the NOx and O3 budget over West Africa. Atmospheric Chemistry and Physics (11), Seiten 2503-2536. Copernicus Publications. DOI: 10.5194/acp-11-2503-2011.
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During the "African Monsoon Multidisciplinary Analysis" (AMMA) field phase in August 2006, a variety of measurements focusing on deep convection were performed over West Africa. The German research aircraft Falcon based in Ouagadougou (Burkina Faso) investigated the chemical composition in the outflow of large mesoscale convective systems (MCS). Here we analyse two different types of MCS originating north and south of the intertropical convergence zone (ITCZ, ~10Ã�Â° N), respectively. In addition to the airborne trace gas measurements, stroke measurements from the Lightning Location Network (LINET), set up in Northern Benin, are analysed. The main focus of the present study is 1) to analyse the trace gas composition (CO, O3, NO, NOx, NOy, and HCHO) in the convective outflow as a function of distance from the convective core, 2) to investigate how different trace gas compositions in the boundary layer (BL) and ambient air may influence the O3 concentration in the convective outflow, and 3) to estimate the rate of lightning-produced nitrogen oxides per flash in selected thunderstorms and compare it to our previous results for the tropics. The MCS outflow was probed at different altitudes (~10Ã¢Â�Â�12 km) and distances from the convective core (<500 km). Trace gas signatures similar to the conditions in the MCS inflow region were observed in the outflow close to the convective core, due to efficient vertical transport. In the fresh MCS outflow, low O3 mixing ratios in the range of 35Ã¢Â�Â�40 nmol molÃ¢Â�Â�1 were observed. Further downwind, O3 mixing ratios in the outflow rapidly increased with distance, due to mixing with the ambient O3-rich air. After 2Ã¢Â�Â�3 h, O3 mixing ratios in the range of ~65 nmol molÃ¢Â�Â�1 were observed in the aged outflow. Within the fresh MCS outflow, mean NOx (=NO+NO2) mixing ratios were in the range of ~0.3Ã¢Â�Â�0.4 nmol molÃ¢Â�Â�1 (peaks ~1 nmol molÃ¢Â�Â�1) and only slightly enhanced compared to the background. Both lightning-produced NOx (LNOx) and NOx transported upward from the BL contributed about equally to this enhancement. On the basis of Falcon measurements, the mass flux of LNOx in the investigated MCS was estimated to be ~100 g(N) sÃ¢Â�Â�1. The average stroke rate of the probed thunderstorms was 0.04Ã¢Â�Â�0.07 strokes sÃ¢Â�Â�1 (here only strokes with peak currents Ã¢Â�Â¥10 kA contributing to LNOx were considered). The LNOx mass flux and the stroke rate were combined to estimate the LNOx production rate. For a better comparison with other published results, LNOx estimates per LINET stroke were scaled to Lightning Imaging Sensor (LIS) flashes. The LNOx production rate per LIS flash was estimated to 1.0 and 2.5 kg(N) for the MCS located south and north of the ITCZ, respectively. If we assume, that these different types of MCS are typical thunderstorms occurring globally (LIS flash rate ~44 sÃ¢Â�Â�1), the annual global LNOx production rate was estimated to be ~1.4 and 3.5 Tg(N) aÃ¢Â�Â�1.
|Titel:||Mesoscale convective systems observed during AMMA and their impact on the NOx and O3 budget over West Africa|
|Erschienen in:||Atmospheric Chemistry and Physics|
|In Open Access:||Ja|
|In ISI Web of Science:||Ja|
|Stichwörter:||deep convection, trace gases, lightning|
|HGF - Forschungsbereich:||Luftfahrt, Raumfahrt und Verkehr|
|HGF - Programm:||Raumfahrt, Luftfahrt|
|HGF - Programmthema:||Erdbeobachtung, ATM und Flugbetrieb|
|DLR - Schwerpunkt:||Raumfahrt, Luftfahrt|
|DLR - Forschungsgebiet:||R EO - Erdbeobachtung, L AO - Luftverkehrsmanagement und Flugbetrieb|
|DLR - Teilgebiet (Projekt, Vorhaben):||R - Vorhaben Atmosphären- und Klimaforschung, L - Klima, Wetter und Umwelt|
|Institute & Einrichtungen:||Institut für Physik der Atmosphäre > Atmosphärische Spurenstoffe|
|Hinterlegt von:||Dr.rer.nat. Heidi Huntrieser|
|Hinterlegt am:||22 Mär 2011 08:04|
|Letzte Änderung:||12 Dez 2013 21:15|
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Mesoscale convective systems observed during AMMA and their impact on the NOx and O3 budget over West Africa. (deposited 13 Okt 2010 15:46)
- Mesoscale convective systems observed during AMMA and their impact on the NOx and O3 budget over West Africa. (deposited 22 Mär 2011 08:04) [Gegenwärtig angezeigt]
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