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Abstract:
Carbon monoxide (CO) and ozone (O3) have been measured in the Western Pacific (43 N to 35 S) during
a ship campaign with Research Vessel Sonne in fall 2009.
Observations have been performed using ship-based solar absorption
Fourier Transform infrared spectrometry, flask sampling,
balloon sounding, and in-situ Fourier Transform infrared
analysis. The results obtained are compared to the
GEOS-Chem global 3-D chemistry transport model for atmospheric
composition. In general, a very good agreement is
found between the GEOS-Chem model and all instruments.
The CO and O3 distributions show a comparable variability
suggesting an impact from the same source regions.
Tagged-CO simulations implemented in the GEOS-Chem
model make it possible to differentiate between different
source processes and source regions. The source regions are
verified with HYSPLIT backward trajectory calculations. In
the Northern Hemisphere fossil fuel combustion in Asia is
the dominant source. European and North American fossil
fuel combustion also contribute to Northern Hemispheric CO
pollution. In the Southern Hemisphere contributions from
biomass burning and fossil fuel combustion are dominant;
African biomass burning has a significant impact on Western
Pacific CO pollution. Furthermore, in the tropical Western
Pacific enhanced upper tropospheric CO within the tropical
tropopause layer mainly originates from Indonesian fossil
fuel combustion and can be transported into the stratosphere.
The source regions of the measured O3 pollution are
simulated with a tagged-O3 simulation implemented in the
GEOS-Chem model. Similar source regions compared to the
tagged-CO simulations are identified by the model. In the
Northern Hemisphere contributions from Asia, Europe, and
North America are significant. In the Southern Hemisphere
emissions from South America, south-east Africa, and Oceania
significantly contribute to the measured O3 pollution.
