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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-168
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Mar 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).
Transport of Asian trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates
Suvarna Fadnavis1, Chaitri Roy1, Rajib Chattopadhyay1, Christopher E. Sioris2, Alexandru Rap3, Rolf Müller4, K. Ravi Kumar5, and Raghavan Krishnan1 1Indian Institute of Tropical Meteorology, Pune, India
2Environment and Climate Change, Toronto, Canada
3School of Earth and Environment, University of Leeds, Leeds, United Kingdom
4Forschungszentrum Jülich GmbH, IEK-7, Jülich, Germany
5King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
Abstract. The highly vibrant Asian Summer Monsoon (ASM) anticyclone plays an important role in efficient transport of Asian tropospheric air masses to the extratropical upper troposphere and lower stratosphere (UTLS). In this paper, we demonstrate long-range transport of Asian trace gases via eddy shedding events using MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) satellite observations, ERA-Interim re-analysis data and the ECHAM5–HAMMOZ global chemistry–climate model. Model simulations and observations consistently show that the Asian boundary layer trace gases are lifted to UTLS altitudes in the monsoon anticyclone and are further transported horizontally eastward and westward by eddies detached from the anticyclone. We present an event of eddy shedding during 1–8 July 2003 and discuss a 1995–2016 climatology of eddy shedding events. Our analysis indicates that eddies detached from the anticyclone are instrumental in distributing the Asian trace gases away from the Asian region to the West-Pacific (20°–30° N; 120°–150° E) and West-Africa (20°–30° N, 0°–30° E). Over the last two decades, the estimated frequency of eddy shedding is ~ 68 % towards West-Africa and ~ 25 % towards the West-Pacific.

Model sensitivity experiments for a 10 % reduction in Asian emissions of non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOx) were performed with ECHAM5–HAMMOZ to understand the impact of Asian emissions on the UTLS. The model simulations show that transport of Asian emissions due to eddy shedding significantly affects the chemical composition of the upper troposphere (~ 100–400 hPa) and lower stratosphere (~ 100–80 hPa) over West-Africa and the West-Pacific. The 10 % reduction of NMVOCs and NOx Asian emissions leads to decreases in peroxyacetyl nitrate (PAN) (2–10 % near 200–80 hPa), ozone (1–4.5 % near ~ 150 hPa) and ozone heating rates (0.001–0.004 K•day−1 near 300–150 hPa) in the upper troposphere over West-Africa and the West-Pacific.

Citation: Fadnavis, S., Roy, C., Chattopadhyay, R., Sioris, C. E., Rap, A., Müller, R., Kumar, K. R., and Krishnan, R.: Transport of Asian trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-168, in review, 2018.
Suvarna Fadnavis et al.
Suvarna Fadnavis et al.
Suvarna Fadnavis et al.

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Short summary
Rapid industrialization, traffic growth, and urbanization resulted in significant increases in the tropospheric trace gases over Asia. There is global concern about rising levels of these trace gases. The monsoon convection transports these gases to the upper-level-anticyclone. In this study, we show transport of these gases to the extra-tropics via eddy-shedding from the anticyclone. We also deliberate on changes in ozone heating rates due to the transport of Asian trace gases.
Rapid industrialization, traffic growth, and urbanization resulted in significant increases in...
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