Index Geophysics

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

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, O₃, HO_x, acetone and acetonitrile. The elevated O₃ 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 O₃. 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 × 10²⁸ molecules O₃ flash⁻¹ (range: 9.89 × 10²⁶–9.82 × 10²⁸ molecules O₃ flash⁻¹), which is at the upper limit of the range reported previously.

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.

2018-09-28

Text

application/pdf

10.5194/acp-14-8917-2014

https://acp.copernicus.org/articles/14/8917/2014/

eISSN: 1680-7324

eng