Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia
In this study, we characterize the transport of ozone from Africa to Asia through the analysis of the simulations of a global chemical transport model, GEOS-Chem, from 1987 to 2006. The receptor region Asia is defined within 5–60° N and 60–145° E, while the source region Africa is within 35° S–1...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/4251/2018/acp-18-4251-2018.pdf |
| _version_ | 1819087349709012992 |
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| author | H. Han J. Liu J. Liu H. Yuan B. Zhuang Y. Zhu Y. Zhu Y. Wu Y. Yan A. Ding |
| author_facet | H. Han J. Liu J. Liu H. Yuan B. Zhuang Y. Zhu Y. Zhu Y. Wu Y. Yan A. Ding |
| author_sort | H. Han |
| collection | DOAJ |
| description | In this study, we characterize the transport of ozone from Africa to Asia
through the analysis of the simulations of a global chemical transport model,
GEOS-Chem, from 1987 to 2006. The receptor region Asia is defined within
5–60° N and 60–145° E, while the
source region Africa is within 35° S–15° N and
20° W–55° E and within 15–35° N and 20° W–30° E. The ozone generated in the African troposphere
from both natural and anthropogenic sources is tracked through tagged ozone
simulation. Combining this with analysis of trajectory simulations using the
Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we
find that the upper branch of the Hadley cell connects with the subtropical
westerlies in the Northern Hemisphere (NH) to form a primary transport
pathway from Africa to Asia in the middle and upper troposphere throughout
the year. The Somali jet that runs from eastern Africa near the equator to
the Indian subcontinent in the lower troposphere is the second pathway that
appears only in NH summer.
<br><br>
The influence of African ozone mainly appears over Asia south of
40° N. The influence shows strong seasonality, varying with
latitude, longitude, and altitude. In the Asian upper troposphere, imported
African ozone is largest from March to May around 30° N (12–16 ppbv)
and lowest during July–October around 10° N ( ∼ 2 ppbv). In the Asian middle and lower troposphere, imported African ozone
peaks in NH winter between 20 and 25° N. Over 5–40° N, the
mean fractional contribution of imported African ozone to the overall ozone
concentrations in Asia is largest during NH winter in the middle troposphere
( ∼ 18 %) and lowest in NH summer throughout the tropospheric
column ( ∼ 6 %).
<br><br>
This seasonality mainly results from the collective effects of the ozone
precursor emissions in Africa and meteorology and chemistry in Africa, in Asia and along the transport pathways. The seasonal swing of the Hadley
circulation and subtropical westerlies along the primary transport pathway
plays a dominant role in modulating the seasonality. There is more imported
African ozone in the Asian upper troposphere in NH spring than in winter.
This is likely due to more ozone in the NH African upper troposphere generated from
biogenic and lightning NO<sub><i>x</i></sub> emissions in NH spring. The influence of
African ozone on Asia appears larger in NH spring than in autumn. This can
be attributed to both higher altitudes of the elevated ozone in Africa and
stronger subtropical westerlies in NH spring. In NH summer, African ozone
hardly reaches Asia because of the blocking by the Saharan High, Arabian High,
and Tibetan High on the transport pathway in the middle and upper
troposphere, in addition to the northward swing of the subtropical
westerlies. The seasonal swings of the intertropical convergence zone (ITCZ)
in Africa, coinciding with the geographic variations of the ozone precursor emissions, can
further modulate the seasonality of the transport of African ozone, owing to
the functions of the ITCZ in enhancing lightning NO<sub><i>x</i></sub> generation and
uplifting ozone and ozone precursors to upper layers. The strength of the
ITCZ in Africa is also found to be positively correlated with the
interannual variation of the transport of African ozone to Asia in NH
winter.
<br><br>
Ozone from NH Africa makes up over 80 % of the total imported African
ozone over Asia in most altitudes and seasons. The interhemispheric
transport of ozone from southern hemispheric Africa (SHAF) is most evident in
NH winter over the Asian upper troposphere and in NH summer over the Asian
lower troposphere. The former case is associated with the primary transport
pathway in NH winter, while the latter case is associated with the second transport
pathway. The intensities of the ITCZ in Africa and the Somali jet can
each explain ∼ 30 % of the interannual variations in
the transport of ozone from SHAF to Asia in the
two cases. |
| first_indexed | 2024-12-21T21:34:44Z |
| format | Article |
| id | doaj.art-dd81b5c2718e49cebdb85c9d99f1baa4 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-21T21:34:44Z |
| publishDate | 2018-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-dd81b5c2718e49cebdb85c9d99f1baa42022-12-21T18:49:31ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-03-01184251427610.5194/acp-18-4251-2018Characteristics of intercontinental transport of tropospheric ozone from Africa to AsiaH. Han0J. Liu1J. Liu2H. Yuan3B. Zhuang4Y. Zhu5Y. Zhu6Y. Wu7Y. Yan8A. Ding9School of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaDepartment of Geography and Planning, University of Toronto, Toronto, CanadaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaShanghai Public Meteorological Service Centre, Shanghai, ChinaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaChinese Academy of Science, Institute of Atmospheric Physics, Beijing, ChinaSchool of Atmospheric Sciences, Jiangsu Collaborative Innovation Center for Climate Change, CMA-NJU Joint Laboratory for Climate Prediction Studies, Nanjing University, Nanjing, ChinaIn this study, we characterize the transport of ozone from Africa to Asia through the analysis of the simulations of a global chemical transport model, GEOS-Chem, from 1987 to 2006. The receptor region Asia is defined within 5–60° N and 60–145° E, while the source region Africa is within 35° S–15° N and 20° W–55° E and within 15–35° N and 20° W–30° E. The ozone generated in the African troposphere from both natural and anthropogenic sources is tracked through tagged ozone simulation. Combining this with analysis of trajectory simulations using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we find that the upper branch of the Hadley cell connects with the subtropical westerlies in the Northern Hemisphere (NH) to form a primary transport pathway from Africa to Asia in the middle and upper troposphere throughout the year. The Somali jet that runs from eastern Africa near the equator to the Indian subcontinent in the lower troposphere is the second pathway that appears only in NH summer. <br><br> The influence of African ozone mainly appears over Asia south of 40° N. The influence shows strong seasonality, varying with latitude, longitude, and altitude. In the Asian upper troposphere, imported African ozone is largest from March to May around 30° N (12–16 ppbv) and lowest during July–October around 10° N ( ∼ 2 ppbv). In the Asian middle and lower troposphere, imported African ozone peaks in NH winter between 20 and 25° N. Over 5–40° N, the mean fractional contribution of imported African ozone to the overall ozone concentrations in Asia is largest during NH winter in the middle troposphere ( ∼ 18 %) and lowest in NH summer throughout the tropospheric column ( ∼ 6 %). <br><br> This seasonality mainly results from the collective effects of the ozone precursor emissions in Africa and meteorology and chemistry in Africa, in Asia and along the transport pathways. The seasonal swing of the Hadley circulation and subtropical westerlies along the primary transport pathway plays a dominant role in modulating the seasonality. There is more imported African ozone in the Asian upper troposphere in NH spring than in winter. This is likely due to more ozone in the NH African upper troposphere generated from biogenic and lightning NO<sub><i>x</i></sub> emissions in NH spring. The influence of African ozone on Asia appears larger in NH spring than in autumn. This can be attributed to both higher altitudes of the elevated ozone in Africa and stronger subtropical westerlies in NH spring. In NH summer, African ozone hardly reaches Asia because of the blocking by the Saharan High, Arabian High, and Tibetan High on the transport pathway in the middle and upper troposphere, in addition to the northward swing of the subtropical westerlies. The seasonal swings of the intertropical convergence zone (ITCZ) in Africa, coinciding with the geographic variations of the ozone precursor emissions, can further modulate the seasonality of the transport of African ozone, owing to the functions of the ITCZ in enhancing lightning NO<sub><i>x</i></sub> generation and uplifting ozone and ozone precursors to upper layers. The strength of the ITCZ in Africa is also found to be positively correlated with the interannual variation of the transport of African ozone to Asia in NH winter. <br><br> Ozone from NH Africa makes up over 80 % of the total imported African ozone over Asia in most altitudes and seasons. The interhemispheric transport of ozone from southern hemispheric Africa (SHAF) is most evident in NH winter over the Asian upper troposphere and in NH summer over the Asian lower troposphere. The former case is associated with the primary transport pathway in NH winter, while the latter case is associated with the second transport pathway. The intensities of the ITCZ in Africa and the Somali jet can each explain ∼ 30 % of the interannual variations in the transport of ozone from SHAF to Asia in the two cases.https://www.atmos-chem-phys.net/18/4251/2018/acp-18-4251-2018.pdf |
| spellingShingle | H. Han J. Liu J. Liu H. Yuan B. Zhuang Y. Zhu Y. Zhu Y. Wu Y. Yan A. Ding Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia Atmospheric Chemistry and Physics |
| title | Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia |
| title_full | Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia |
| title_fullStr | Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia |
| title_full_unstemmed | Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia |
| title_short | Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia |
| title_sort | characteristics of intercontinental transport of tropospheric ozone from africa to asia |
| url | https://www.atmos-chem-phys.net/18/4251/2018/acp-18-4251-2018.pdf |
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