Fast transport from Southeast Asia boundary layer sources to northern Europe: rapid uplift in typhoons and eastward eddy shedding of the Asian monsoon anticyclone

Abstract

Abstract. Enhanced tropospheric trace gases such as CO, CH4 and H2O and reduced stratospheric O3 were measured in situ in the lowermost stratosphere over northern Europe on 26 September 2012 during the TACTS aircraft campaign. The measurements indicate that these air masses clearly differ from the stratospheric background. The calculation of 40-day backward trajectories with the trajectory module of the CLaMS model shows that these air masses are affected by the Asian monsoon anticyclone. Some air masses originate from the boundary layer in Southeast Asia/West Pacific and are rapidly lifted (1–2 days) within a typhoon up to the outer edge of the Asian monsoon anticyclone. Afterwards, the air parcels are entrained by the anticyclonic circulation of the Asian monsoon. The subsequent long-range transport (8–14 days) of enhanced water vapour and pollutants to the lowermost stratosphere in northern Europe is driven by eastward transport of tropospheric air from the Asian monsoon anticyclone caused by an eddy shedding event. We found that the combination of rapid uplift by a typhoon and eastward eddy shedding from the Asian monsoon anticyclone is a novel fast transport pathway that may carry boundary emissions from Southeast Asia/West Pacific within approximately 5 weeks to the lowermost stratosphere in northern Europe.

Quantifying pollution transport from the Asian monsoon anticyclone into the lower stratosphere

“…After a few months, however, the two distributions of anticyclone edge and core air align (Fig. 4d, f), showing that, in the long term, air masses ascending in the anticyclone core and air masses injected into the anticyclone edge (e.g., by typhoons; see Vogel et al, 2014) follow the same transport pathways. The higher fraction of air from the anticyclone edge compared to the core is likely a result of the larger area of the edge region.…”

Long-range transport pathways of tropospheric source gases originating in Asia into the northern lower stratosphere during the Asian monsoon season 2012

“…The identification and the relative importance of different transport pathways of tropospheric source gases found within the Asian monsoon anticyclone into the lower stratosphere are the subject of a longstanding debate (Dethof et al, 1999;Park et al, 2004;Randel et al, 2010;Bian et al, 2012;Bourassa et al, 2012;Ploeger et al, 2013;Fairlie et al, 2014;Fromm et al, 2014;Uma et al, 2014;Vogel et al, 2014Vogel et al, , 2015Garny and Randel, 2016;Tissier and Legras, 2016;Orbe et al, 2015). The influence of these different transport pathways on the chemical composition of the extratropical upper troposphere and lower stratosphere (ExUTLS) is important because changes in ozone and water vapor in the ExUTLS have a significant impact on surface climate, even if the perturbation is relatively small.…”

Impacts of anthropogenic and natural sources on free tropospheric ozone over the Middle East

“…The O 3 distribution in the troposphere is strongly influenced by dynamical processes, as well as by the regional chemical sources and sinks of O 3 . Previous studies (e.g., Park et al, 2007;Worden et al, 2009;Vogel et al, 2014) have demonstrated that rapid convective transport associated with the Asian monsoon anticyclone can result in significant enhancement of O 3 abundance over Asia, northern Africa and Europe. The stratosphere-troposphere exchange of O 3 also has important effects on the distribution of tropospheric O 3 (e.g., Barth et al, 2012;Neu et al, 2014).…”

“…Liu et al (2009) indicated that the enhancement of free tropospheric O 3 over the Middle East is mainly due to the influence of the Arabian anticyclone in the middle troposphere, which traps O 3 that is produced locally as well as O 3 and its precursors that are transported from rest of Asia. Recent studies (Ricaud et al, 2014;Vogel et al, 2014) demonstrated that the Asian monsoon anticyclone provides an effective pathway to redistribute Asian pollutants globally. An improved understanding about the mechanism of the summertime enhancement of free tropospheric O 3 over the Middle East is thus important as it will provide critical information about the sources and variation of tropospheric O 3 in the Northern Hemisphere.…”