DOI: 10.1007/s00382-017-3628-7
Scopus记录号: 2-s2.0-85015690930
论文题名: Mesoscale convective systems and nocturnal rainfall over the West African Sahel: role of the Inter-tropical front
作者: Vizy E.K. ; Cook K.H.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2018
卷: 50, 期: 2018-01-02 起始页码: 587
结束页码: 614
语种: 英语
英文关键词: Diurnal cycle of precipitation
; Dryline
; Inter-tropical front
; MCS genesis
; Mesoscale convective system
; Sahel
; West Africa
Scopus关键词: atmospheric front
; convective system
; diurnal variation
; mesoscale meteorology
; monsoon
; orography
; precipitation (climatology)
; rainfall
; vertical mixing
; West Africa
英文摘要: A convection-permitting regional model simulation for August 2006 and observations are evaluated to better understand the diurnal cycle of precipitation over the Sahel. In particular, reasons for a nocturnal rainfall maximum over parts of the Sahel during the height of the West African monsoon are investigated. A relationship between mesoscale convective system (MCS) activity and inter-tropical front (ITF)/dryline dynamics is revealed. Over 90% of the Sahel nocturnal rainfall derives from propagating MCSs that have been associated with topography in earlier studies. In contrast, in this case study, 70–90% of the nocturnal rainfall over the southern Sahel (11°N–14°N) west of 15°E is associated with MCSs that originate less than 1000 km upstream (to the north and east) in the afternoon, in a region largely devoid of significant orography. This MCS development occurs in association with the Sahel ITF, combined with atmospheric pre-conditioning. Daytime surface heating generates turbulent mixing that promotes planetary boundary layer (PBL) growth accompanied by a low-level reversal in the meridional flow. This enhances wind convergence in the low-level moist layer within 2°–3° of latitude of the equatorward side of the ITF. MCSs tend to form when this vertical mixing extends to the level of free convection and is accompanied by a mid-tropospheric African easterly wave disturbance to the east. This synoptic disturbance enhances the vertical wind shear and atmospheric instability over the genesis location. These results are found to be robust across the region. © 2017, The Author(s). Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109509
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, United States
Recommended Citation:
Vizy E.K.,Cook K.H.. Mesoscale convective systems and nocturnal rainfall over the West African Sahel: role of the Inter-tropical front[J]. Climate Dynamics,2018-01-01,50(2018-01-02)