气候变化领域集成服务门户(CCPortal): A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau

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DOI	10.5194/acp-19-6535-2019
	A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau
	Škerlak B.; Pfahl S.; Sprenger M.; Wernli H.
发表日期	2019
ISSN	16807316
起始页码	6535
结束页码	6549
卷号	19 期号:9
英文摘要	Upper-level fronts are often associated with the rapid transport of stratospheric air along tilted isentropes to the middle or lower troposphere, where this air leads to significantly enhanced ozone concentrations. These plumes of originally stratospheric air can only occasionally be observed at the surface because (i) stable boundary layers prevent an efficient vertical transport down to the surface, and (ii) even if boundary layer turbulence were strong enough to enable this transport, the originally stratospheric air mass can be diluted by mixing, such that only a weak stratospheric signal can be recorded at the surface. Most documented examples of stratospheric air reaching the surface occurred in mountainous regions. This study investigates two such events, using a passive stratospheric air mass tracer in a mesoscale model to explore the processes that enable the transport down to the surface. The events occurred in early May 2006 in the Rocky Mountains and in mid-June 2006 on the Tibetan Plateau. In both cases, a tropopause fold associated with an upper-level front enabled stratospheric air to enter the troposphere. In our model simulation of the North American case, the strong frontal zone reaches down to 700 hPa and leads to a fairly direct vertical transport of the stratospheric tracer along the tilted isentropes to the surface. In the Tibetan Plateau case, however, no near-surface front exists and a reservoir of high stratospheric tracer concentrations initially forms at 300-400 hPa, without further isentropic descent. However, entrainment at the top of the very deep boundary layer (reaching to 300 hPa over the Tibetan Plateau) and turbulence within the boundary layer allows for downward transport of stratospheric air to the surface. Despite the strongly differing dynamical processes, stratospheric tracer concentrations at the surface reach peak values of 10 %-20 % of the imposed stratospheric value in both cases, corroborating the potential of deep stratosphere-to-troposphere transport events to significantly influence surface ozone concentrations in these regions. © Author(s) 2019.
语种	英语
scopus关键词	air mass; atmospheric chemistry; boundary layer; concentration (composition); mountain region; ozone; stratosphere; troposphere; China; Qinghai-Xizang Plateau; Rocky Mountains
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144406
作者单位	Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland; Institute of Meteorology, Freie Universität Berlin, Berlin, Germany
推荐引用方式 GB/T 7714	Škerlak B.,Pfahl S.,Sprenger M.,et al. A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau[J],2019,19(9).
APA	Škerlak B.,Pfahl S.,Sprenger M.,&Wernli H..(2019).A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau.Atmospheric Chemistry and Physics,19(9).
MLA	Škerlak B.,et al."A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau".Atmospheric Chemistry and Physics 19.9(2019).