Globale Auswirkung des Straßenverkehrs auf die chemische Zusammensetzung der Atmosphäre

Road traffic represents one of the main sources of emissions to the
atmosphere. This work determines the impact of road traffic
emissions on the chemical composition of the atmosphere by a
numerical modelling study with ECHAM4/CBM-IV. For the first time,
global impact of non-methane-hydrocarbon-emissions (NMHCs) from
road traffic is presented. Annual, global emissions from road
traffic following a consumption-based approach amount to (8.8 +/-
1.8) Tg [N] nitrogen oxides, (206 +/- 86) Tg [CO] carbonmonoxide,
and (34.4 +/- 18.9) Tg NMHCs. Road traffic emissions cause an
increase of ozone, which is an important trace gas for the
oxidizing capacity and the radiative budget of the atmosphere. In
industrialized regions of the northern hemisphere the increase
exceeds more than 20%. In remote regions an increase of more than
10% is calculated. Tropical latitudes show a relative contribution
of more than 6% due to road traffic up to 10km. NOx-emissions
account for about 70% of this ozone increase. Further, road traffic
increases and decreases the concentration of hydroxyl radicals (OH)
depending on geographical region and season. This again affects the
oxidizing capacity and the lifetime of methane. In summer, road
traffic causes in northern extratropics a 3% increase of OH, and in
winter a decrease of 10%. These changes in chemical composition
cause an indirect radiative forcing to the atmosphere. Ozone
increases due to road traffic emissions (NOx, CO, NMHCs) result in
an annual and global mean radiative forcing of 0.058 W/m^2. The
indirect forcing due to road traffic-induced changes in the
lifetime of methane amounts to 0.006 W/m^2. This forcing is
temporal and spatial inhomogeneous, and can even possess a positive
sign (e.g. in spring). Results show that NMHC-emissions
considerably contribute to the global impact of road traffic
emissions.