DOI: 10.1175/JCLI-D-17-0221.1
Scopus记录号: 2-s2.0-85047090901
论文题名: On the likelihood of tropical-extratropical cloud bands in the South Indian convergence zone during ENSO events
作者: Hart N.C.G. ; Washington R. ; Reason C.J.C.
刊名: Journal of Climate
ISSN: 8948755
出版年: 2018
卷: 31, 期: 7 起始页码: 2797
结束页码: 2817
语种: 英语
英文关键词: Africa
; ENSO
; Jets
; Seasonal cycle
; Southern Hemisphere
; Teleconnections
Scopus关键词: Jets
; Rain
; Tropics
; Africa
; ENSO
; Seasonal cycle
; Southern Hemisphere
; Teleconnections
; Fighter aircraft
英文摘要: The Southern Hemisphere subtropical convergence zones are important regions of rainfall in the subtropics. The south Indian Ocean convergence zone (SICZ) has the strongest seasonality and exhibits substantial interannual variability in strength and position during austral summer. On synoptic time scales, the SICZ is a preferred region for the formation of tropical-extratropical (TE) cloud bands with local maxima over the southern African mainland and Madagascar. This study investigates how the seasonality in satellite-observed cloud band frequency emerges from the interplay between the asynchronous seasonal cycles in convective instability and upper-level flow, as represented by reanalysis data. These atmospheric mean states are diagnosed with a gross convective instability metric and a method to distinguish between subtropical and eddy-driven jet axes. Month-by-month analysis of these diagnostics elucidates how mean-state perturbations during ENSO events modify cloud band likelihood. Typically, 150%-200% more cloud bands develop during La Niña seasons supported by 5°-10° latitudinal separation between the local subtropical and eddy-driven jets and higher values of convective instability, especially in semiarid parts of mainland southern Africa. During El Niño events, fewer cloud bands develop over southern Africa in a more convectively stable environment without a distinct subtropical jet. However, east of Madagascar cloud bands are 150% more likely. Plausible teleconnection pathways based on these ENSO-related perturbations are discussed. The paper concludes with a conceptual framing of the seasonal cycle in the mean-state pertinent to TE cloud band likelihood. © 2018 American Meteorological Society. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/111605
Appears in Collections: 气候减缓与适应
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作者单位: School of Geography and the Environment, University of Oxford, Oxford, United Kingdom; Department of Oceanography, University of Cape Town, Cape Town, South Africa
Recommended Citation:
Hart N.C.G.,Washington R.,Reason C.J.C.. On the likelihood of tropical-extratropical cloud bands in the South Indian convergence zone during ENSO events[J]. Journal of Climate,2018-01-01,31(7)