气候变化领域集成服务门户(CCPortal): A quasi-geostrophic diagnosis of the zonal flow associated with cut-off lows over South Africa and surrounding oceans

CCPortal

DOI	10.1007/s00382-020-05401-4
	A quasi-geostrophic diagnosis of the zonal flow associated with cut-off lows over South Africa and surrounding oceans
	Ndarana T.; Rammopo T.S.; Chikoore H.; Barnes M.A.; Bopape M.-J.
发表日期	2020
ISSN	0930-7575
起始页码	2631
结束页码	2644
卷号	55
英文摘要	The zonal flow associated with cut-off lows (COLs) comprises two jet streaks of different spatial extents. The smaller scale jet streak, located north of the COLs, forms as a result of meridional divergence of vorticity advection and it is quasi-stationary, relative to the COLs. It dissipates as the COLs do the same. The larger scale jet streak gives rise to anticyclonic and equatorward Rossby wave breaking (RWB) as it propagates southeasterly to the base of the ridge, south of the COL and then northeasterly beyond that point. As the jet streak propagates it brings with it the anticyclonic barotropic shear that causes the Rossby waves to break. Its propagation is caused by zonal momentum advection by the zonal flow from jet streak entrance to its exit. As it propagates, its northwesterly/southeasterly orientation changes to one that is more zonal to become south-westerly/northeasterly at the end of the COL life cycle. This change in orientation is due to meridional advection of zonal momentum,where the meridional flow advects momentum southward (northward) at the jet streak entrance (exit). The jet streaks form a split jet structure and the winds between the streaks is decelerated by vorticity advection convergence. Because the flow and COL (and RWB) life cycle are coupled, understanding the dynamics that underlie the changes in the COL ambient flow contributes to resolving the outstanding RWB/COL causality problem. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
英文关键词	Cut-off low; Geostrophic flow; Jet streak; Rossby wave breaking
语种	英语
scopus关键词	advection; anticyclone; barotropic motion; geostrophic flow; jet stream; meridional circulation; Rossby wave; vorticity; wave breaking; zonal flow; South Africa
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/145277
作者单位	Geography, Geoinformatics and Meteorology, University of Pretoria, Hatfield, South Africa; Unit for Environmental Sciences and Management, North-West University, Vanderbijlpark, South Africa; Marine Research Unit, South African Weather Service, Cape Town, South Africa; Department of Research and Innovation, South African Weather Service, Centurion, South Africa
推荐引用方式 GB/T 7714	Ndarana T.,Rammopo T.S.,Chikoore H.,et al. A quasi-geostrophic diagnosis of the zonal flow associated with cut-off lows over South Africa and surrounding oceans[J],2020,55.
APA	Ndarana T.,Rammopo T.S.,Chikoore H.,Barnes M.A.,&Bopape M.-J..(2020).A quasi-geostrophic diagnosis of the zonal flow associated with cut-off lows over South Africa and surrounding oceans.Climate Dynamics,55.
MLA	Ndarana T.,et al."A quasi-geostrophic diagnosis of the zonal flow associated with cut-off lows over South Africa and surrounding oceans".Climate Dynamics 55(2020).