The Western Pacific: Sources of air pollution and its impact on troposphere to stratosphere transport

The Western Pacific is considered to be the main region where tropospheric trace gases enter the stratosphere. However, the composition of the Western Pacific atmosphere is not well known and the processes driving the transport of tropospheric trace gases into the stratosphere are not fully understood. In this study the composition of the Western Pacific atmosphere is analyzed based on atmospheric measurements performed aboard research vessel Sonne in autumn 2009. The observations are compared to the 3-D chemistry-transport model GEOS-Chem to test the current understanding of Western Pacific air composition. The causes of the observed contamination are analyzed using GEOS-Chem tagged-tracer simulations and trajectory-based transport studies. Finally, the lifetimes of several tropospheric trace gases in this region are calculated to analyze the significance of these gases for troposphere to stratosphere transport.