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| Titel |
Atmospheric pollutant outflow from southern Asia: a review |
| VerfasserIn |
M. G. Lawrence, J. Lelieveld  |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-25), S.11017-11096 |
| Datensatznummer |
250008910
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| Publikation (Nr.) |
 copernicus.org/acp-10-11017-2010.pdf |
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| Zusammenfassung |
| Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea,
is one of the most heavily populated regions of the
world. Biofuel and biomass burning play a disproportionately large
role in the emissions of most key pollutant gases and aerosols there,
in contrast to much of the rest of the Northern Hemisphere, where
fossil fuel burning and industrial processes tend to dominate. This
results in polluted air masses which are enriched in carbon-containing
aerosols, carbon monoxide, and hydrocarbons. The outflow and
long-distance transport of these polluted air masses is characterized
by three distinct seasonal circulation patterns: the winter monsoon,
the summer monsoon, and the monsoon transition periods. During
winter, the near-surface flow is mostly northeasterly, and the
regional pollution forms a thick haze layer in the lower troposphere
which spreads out over millions of square km between southern Asia and
the Intertropical Convergence Zone (ITCZ), located several degrees
south of the equator over the Indian Ocean during this period. During
summer, the heavy monsoon rains effectively remove soluble gases and
aerosols. Less soluble species, on the other hand, are lifted to the
upper troposphere in deep convective clouds, and are then transported
away from the region by strong upper tropospheric winds, particularly
towards northern Africa and the Mediterranean in the tropical easterly
jet. Part of the pollution can reach the tropical tropopause layer,
the gateway to the stratosphere. During the monsoon transition
periods, the flow across the Indian Ocean is primarily zonal,
and strong pollution plumes originating from both
southeastern Asia and from Africa spread across the central Indian
Ocean. This paper provides a review of the current state of knowledge
based on the many observational and modeling studies over the last
decades that have examined the southern Asian atmospheric pollutant
outflow and its large scale effects. An outlook is provided as a guideline for future research, pointing
out particularly critical issues such as: resolving discrepancies
between top down and bottom up emissions estimates; assessing the
processing and aging of the pollutant outflow; developing a better
understanding of the observed elevated pollutant layers and their
relationship to local sea breeze and large scale monsoon circulations;
and determining the impacts of the pollutant outflow on the Asian
monsoon meteorology and the regional hydrological cycle, in particular
the mountain cryospheric reservoirs and the fresh water supply, which
in turn directly impact the lives of over a billion inhabitants of
southern Asia. |
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