Thunderstorms and trace gas distribution
Convective transport is a major pathway for rapidly moving chemical constituents
and water from the boundary layer to the upper troposphere and in some cases to
the lower stratosphere. Deep convection is an important mechanism in the
transport of planetary boundary layer (PBL) air into the upper troposphere (UT) and
lower stratosphere (LS, UTLS). It only takes a few minutes to about an hour to
transport an air parcel from the surface to the UT. Measurements from field
campaigns and satellites have demonstrated that deep convective transport affects
the moisture and the chemical composition of the UTLS.
The plumes of convective outflow in the upper troposphere are often rich in ozone
precursors. Nitrogen oxides are formed from lightning, while volatile organic
compounds, peroxides, and formaldehyde are transported from the boundary layer.
The mechanism of deep convective transport is complex. Vertical transport
processes in thunderstorms have become an issue of increasing interest in recent
years. A better quantitative knowledge of the re-distribution of pollutants from the
boundary layer to the upper troposphere is important for regional and global climate
studies. Measurements and theoretical investigations have shown that deep
convective processes are important means for vertical trace gas transport.
Different trace gases have different vertical distribution, which might affect the
vertical transport pattern.Thus, CO, NOx, water vapour and O3 have been studied
as example tracers, which have different and opposite vertical distributions and
gradients. The lightning NOx source has been investigated recently by field
experiments mainly in mid-latitudes. Growing interest is now in the role of tropical
thunderstorms for NOx production.
Several case studies have been conducted for determining vocative the impact of
above mentioned trace gases w.r.t. individual cases of convective activities.