Abstract
Abstract. Anthropogenic emissions from East Asia have increased over recent decades. These increases have led to changes in atmospheric composition as far afield as North America under the prevailing westerly winds. Here we show that, during Northern Hemisphere (NH) winter, pollution originating in East Asia also directly affects atmospheric composition in the deep tropics. We present observations of marked intra-seasonal variability in the anthropogenic tracer perchloroethene (C2Cl4) collected at two locations in Borneo (117.84° E, 4.98° N and 118.00° E, 4.22° N) during the NH winter of 2008/2009. We use trajectories calculated with the Numerical Atmospheric-dispersion Modelling Environment to show that the observed enhancements in C2Cl4 mixing ratio are caused by rapid meridional transport, in the form of "cold surges", from the relatively polluted East Asian land mass. In these events air masses can move from ~35° N to Borneo in 4 days. We then present data from the Monitoring Atmospheric Composition and Climate reanalysis which suggest that air masses high in C2Cl4 may also contain levels of the pollutants carbon monoxide and ozone that are approximately double the typical "background" levels in Borneo. In addition to strengthening the meridional transport from the north, cold surges can enhance convection in Southeast Asia, and further trajectory calculations indicate that the polluted air masses can subsequently be lifted to the tropical upper troposphere. This suggests a potentially important connection between midlatitude pollution sources and the very low stratosphere.
Highlights
The rapid growth of East Asian economies over recent decades has led to enhanced emissions of various pollutants, including ozone (O3) precursors (e.g. Granier et al, 2011) and halocarbons (e.g. Wan et al, 2009)
Southward transport of polluted air masses originating in East Asia, associated with the Northeast Monsoon which occurs during Northern Hemisphere (NH) winter, has been reported (e.g. Liu et al, 2003; Pochanart et al, 2003; Wang et al, 2003)
Backward trajectories calculated using NAME show that measurements of high C2Cl4 mixing ratios were associated with rapid cold surge transport towards the Equator from polluted midlatitude East Asia
Summary
The rapid growth of East Asian economies over recent decades has led to enhanced emissions of various pollutants, including ozone (O3) precursors (e.g. Granier et al, 2011) and halocarbons (e.g. Wan et al, 2009). We use trajectories calculated with the Numerical Atmospheric-dispersion Modelling Environment to show that the observed enhancements in C2Cl4 mixing ratio are caused by rapid meridional transport, in the form of “cold surges”, from the relatively polluted East Asian land mass.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
