气候变化领域集成服务门户(CCPortal): Is the subtropical jet shifting poleward?

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DOI	10.1007/s00382-019-05084-6
	Is the subtropical jet shifting poleward?
	Maher P.; Kelleher M.E.; Sansom P.G.; Methven J.
发表日期	2020
ISSN	0930-7575
起始页码	1741
结束页码	1759
卷号	54
英文摘要	The tropics are expanding poleward at about 0.5 ∘ per decade in observations. This poleward expansion of the circulation is consistently reported using Hadley cell edge metrics and lower-atmospheric tropical edge metrics. However, some upper-atmospheric tropical metrics report smaller trends that are often not significant. One such upper-atmospheric metric is the subtropical jet latitude, which has smaller trends compared to the Hadley cell edge. In this study we investigate the robustness of the weak trends in the subtropical jet position by introducing a new method for locating the subtropical jet, and examining the trends and variability of the subtropical jet latitude. We introduce the tropopause gradient method based on the peak gradient in potential temperature along the dynamic tropopause. Using this method we find the trends in the subtropical jet latitude are indeed much smaller than 0.5 ∘ per decade, consistent with previous studies. We also find that natural variability within the subtropical jet latitude would not prevent trends from being detected if they were similar to the Hadley cell edge, as trends greater than 0.24∘ per decade could reliably be detected using monthly data or 0.09∘ per decade using daily data. Despite the poleward expansion of the tropics, there is no robust evidence to suggest the subtropical jet is shifting poleward in either hemisphere. Neither the current diagnostic methods nor natural variability can account for the small subtropical jet trends. The most likely explanation, which requires further investigation, is that the subtropical jet position is not tied dynamically to the Hadley cell edge. © 2019, The Author(s).
英文关键词	Subtropical jet stream; Tropical expansion; Tropopause gradient method
语种	英语
scopus关键词	current velocity; geostrophic flow; gradient analysis; Hadley cell; jet stream; numerical model; temperature profile; trend analysis; tropopause
来源期刊	Climate Dynamics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/145613
作者单位	Department of Mathematics, University of Exeter, Exeter, United Kingdom; Department of Meteorology, University of Reading, Reading, United Kingdom; Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, United States
推荐引用方式 GB/T 7714	Maher P.,Kelleher M.E.,Sansom P.G.,et al. Is the subtropical jet shifting poleward?[J],2020,54.
APA	Maher P.,Kelleher M.E.,Sansom P.G.,&Methven J..(2020).Is the subtropical jet shifting poleward?.Climate Dynamics,54.
MLA	Maher P.,et al."Is the subtropical jet shifting poleward?".Climate Dynamics 54(2020).