Influence of corona discharge on the ozone budget in the tropical free troposphere: a case study of deep convection during GABRIEL

Bozem, H.; Fischer, H.; Gurk, C.; Schiller, C. L.; Parchatka, U.; Koenigstedt, R.; Stickler, A.; Martinez, M.; Harder, H.; Kubistin, D.; Williams, J.; Eerdekens, G.; Lelieveld, J.

Convective redistribution of ozone and its precursors between the boundary layer (BL) and the free troposphere (FT) influences photochemistry, in particular in the middle and upper troposphere (UT). We present a case study of convective transport during the GABRIEL campaign over the tropical rain forest in Suriname in October 2005. During one measurement flight the inflow and outflow regions of a cumulonimbus cloud (Cb) have been characterized. We identified a distinct layer between 9 and 11 km altitude with enhanced mixing ratios of CO, O 3, HO x, acetone and acetonitrile. The elevated O 3 contradicts the expectation that convective transport brings low-ozone air from the boundary layer to the outflow region. Entrainment of ozone-rich air is estimated to account for 62% (range: 33–91%) of the observed O 3. Ozone is enhanced by only 5–6% by photochemical production in the outflow due to enhanced NO from lightning, based on model calculations using observations including the first reported HO x measurements over the tropical rainforest. The "excess" ozone in the outflow is most probably due to direct production by corona discharge associated with lightning. We deduce a production rate of 5.12 × 10 28 molecules O 3 flash −1 (range: 9.89 × 10 26–9.82 × 10 28 molecules O 3 flash −1), which is at the upper limit of the range reported previously.

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Bozem, H. / Fischer, H. / Gurk, C. / et al: Influence of corona discharge on the ozone budget in the tropical free troposphere: a case study of deep convection during GABRIEL. 2014. Copernicus Publications.

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