| Convective redistribution of ozone and its precursors between the boundary layer (BL) and
the free troposphere (FT) influences the photochemistry, in particular the ozone production in
the middle and upper troposphere (UT). We present a case study of convective transport
during the GABRIEL campaign over the tropical rainforest in Suriname in October 2005. On
the last part of a measurement flight on October 12 the inflow and outflow regions of a nearly
completely developed cumulonimbus cloud (Cb) have been characterized, providing clear
indications of convective transport. We identified a distinct layer between 9 and 11 km
altitude with enhanced mixing ratios of CO, O3, HOx, acetone and acetonitrile. The
elevated O3 contradicts to the expectation of convective transport of low ozone air
from the boundary layer. The high mixing ratio of ozone in the outflow has mainly
dynamical reasons. Entrainment of ozone rich air into the convective outflow accounts
for 64Â % of the observed O3 value. Ozone is further enhanced by photochemical
production in the outflow, with enhanced NO, that is most likely due to lightning activity.
The contribution of photochemical ozone production to the elevated mixing ratio
amounts to 2-3Â % based on steady state model calculations, using in-situ observations
including the first reported HOx measurements over the tropical rainforest. The
missing ozone in the outflow might be attributed to an additional dynamical or
photochemical source, whereas the most probable source is direct production from
lightning by cold corona discharge. We present a production rate of 5.19 Ã1028
molecules O3/flash (range: 4.19 Ã1027 - 9.96 Ã1028 molecules O3/flash) which
is one order of magnitude higher compared to known values from the literature. |