Global impact of road traffic emissions on tropospheric ozone S. Matthes1, V. Grewe1, R. Sausen1, and G.-J. Roelofs2 1Institut für Physik der Atmosphäre, DLR-Oberpfaffenhofen, Wessling, Germany 2Institut for Marine Research, University of Utrecht, Utrecht, The Netherlands
Abstract. Road traffic is one of the major anthropogenic emission sectors for NOx, CO and
NMHCs (non-methane hydrocarbons). We applied ECHAM4/CBM,
a general circulation model coupled to a chemistry module,
which includes higher hydrocarbons, to investigate
the global impact of 1990 road traffic emissions on the atmosphere.
Improving over previous global modelling studies, which concentrated on
road traffic NOx and CO emissions only, we assess the impact of
NMHC emissions from road traffic.
It is revealed that NMHC emissions from road traffic
play a key role for the impact on ozone. They are responsible for
(indirect) long-range transport of NOx from road traffic via
the formation of PAN, which is not found in a simulation without NMHC emissions from road
Long-range transport of NMHC-induced PAN
impacts on the ozone distribution in Northern Hemisphere regions far away from the sources,
arctic and remote maritime regions.
In July total road traffic emissions (NOx, CO and NMHCs) contribute to
the zonally averaged ozone distribution by more than 12%
near the surface in the Northern Hemisphere
midlatitudes and arctic latitudes. In January road traffic emissions contribute near the
surface in northern and southern extratropics more than 8%.
Sensitivity studies for regional emission show that effective transport of road traffic
emissions occurs mainly in the free troposphere.
In tropical latitudes of America
up to an altitude of 200 hPa, global road traffic emissions contribute about 8%
to the ozone concentration.
In arctic latitudes NMHC emissions from road transport are responsible for about 90%
of PAN increase from road transport, leading to a contribution to ozone concentrations
of up to 15%.
Citation: Matthes, S., Grewe, V., Sausen, R., and Roelofs, G.-J.: Global impact of road traffic emissions on tropospheric ozone, Atmos. Chem. Phys., 7, 1707-1718, doi:10.5194/acp-7-1707-2007, 2007.