| Ozone is an important oxidant and a greenhouse gas. While the highest mixing ratios are
found in the stratosphere, significant changes of ozone at tropopause levels can
have significant climate effects. Furthermore ozone is the main precursor of the
hydroxyl radical OH, thus strongly affecting the oxidation power of the atmosphere.
Convective transport of ozone and its precursors between low altitudes near the
surface and the middle and upper troposphere influences ozone in the tropopause
region.
Data from the airborne measurement campaigns, GABRIEL 2005 (Suriname, South
America) and HOOVER 2006 and 2007 (Europe) are presented. We investigate the ozone
budget in the free troposphere in cases of deep convection and in background conditions.
Steady state model calculations, based on in-situ measurements of O3, NO, OH, HO2 and
actinic radiation are used to calculate the net O3 tendency for background and convectively
processed air. In the extratropics the net ozone production rate (OPR) in convective outflow
amounts to 1.85 ppbv/h (Range: 0.26 to 8.21 ppbv/h, depending on the mixing ratio of
NO and HO2), while the background atmosphere shows no clear tendency. In the
tropics an OPR of 0.23 ppbv/h (0.01 to 1.13 ppbv/h) in the outflow and 0.08 ppbv/h
(-0.01 to 0.47 ppbv/h) for the background atmosphere was calculated. Convective
outflow in both regimes is able to produce ozone in high amounts. For background
conditions no clear tendency for the extratropics compared to the tropics is found. |