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 fo...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/8917/2014/acp-14-8917-2014.pdf |
| Summary: | 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<sub>3</sub>, HO<sub>x</sub>, acetone and
acetonitrile. The elevated O<sub>3</sub> 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<sub>3</sub>. 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<sub>x</sub> 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<sup>28</sup> molecules O<sub>3</sub> flash<sup>−1</sup> (range:
9.89 × 10<sup>26</sup>–9.82 × 10<sup>28</sup> molecules O<sub>3</sub> flash<sup>−1</sup>),
which is at the upper limit of the range reported previously. |
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| ISSN: | 1680-7316 1680-7324 |