Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 11835-11848, 2017
https://doi.org/10.5194/acp-17-11835-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Oct 2017
The influence of deep convection on HCHO and H2O2 in the upper troposphere over Europe
Heiko Bozem1,a, Andrea Pozzer1, Hartwig Harder1, Monica Martinez1, Jonathan Williams1, Jos Lelieveld1, and Horst Fischer1 1Atmospheric Chemistry Department, Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany
anow at: Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
Abstract. Deep convection is an efficient mechanism for vertical trace gas transport from Earth's surface to the upper troposphere (UT). The convective redistribution of short-lived trace gases emitted at the surface typically results in a C-shaped profile. This redistribution mechanism can impact photochemical processes, e.g. ozone and radical production in the UT on a large scale due to the generally longer lifetimes of species like formaldehyde (HCHO) and hydrogen peroxide (H2O2), which are important HOx precursors (HOx =  OH + HO2 radicals). Due to the solubility of HCHO and H2O2 their transport may be suppressed as they are efficiently removed by wet deposition. Here we present a case study of deep convection over Germany in the summer of 2007 within the framework of the HOOVER II project. Airborne in situ measurements within the in- and outflow regions of an isolated thunderstorm provide a unique data set to study the influence of deep convection on the transport efficiency of soluble and insoluble trace gases. Comparing the in- and outflow indicates an almost undiluted transport of insoluble trace gases from the boundary layer to the UT. The ratios of out : inflow of CO and CH4 are 0.94 ± 0.04 and 0.99 ± 0.01, respectively. For the soluble species HCHO and H2O2 these ratios are 0.55 ± 0.09 and 0.61 ± 0.08, respectively, indicating partial scavenging and washout. Chemical box model simulations show that post-convection secondary formation of HCHO and H2O2 cannot explain their enhancement in the UT. A plausible explanation, in particular for the enhancement of the highly soluble H2O2, is degassing from cloud droplets during freezing, which reduces the retention coefficient.

Citation: Bozem, H., Pozzer, A., Harder, H., Martinez, M., Williams, J., Lelieveld, J., and Fischer, H.: The influence of deep convection on HCHO and H2O2 in the upper troposphere over Europe, Atmos. Chem. Phys., 17, 11835-11848, https://doi.org/10.5194/acp-17-11835-2017, 2017.
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Short summary
We present a case study of deep convection over Germany in July 2007 within the framework of the HOOVER II project. Airborne in situ measurements within the in- and outflow regions of an isolated thunderstorm provide a unique data set to study the influence of deep convection on the transport efficiency of soluble and insoluble trace gases. Despite their high solubility HCHO and H2O2 show enhanced concentrations in the outflow presumably due to degassing from cloud droplets during freezing.
We present a case study of deep convection over Germany in July 2007 within the framework of the...
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