DOI: 10.1175/JCLI-D-16-0696.1
Scopus记录号: 2-s2.0-85028504441
论文题名: Weakening and shifting of the Saharan shallow meridional circulation during wet years of the West African monsoon
作者: Shekhar R. ; Boos W.R.
刊名: Journal of Climate
ISSN: 8948755
出版年: 2017
卷: 30, 期: 18 起始页码: 7399
结束页码: 7422
语种: 英语
Scopus关键词: Atmospheric movements
; Atmospheric thermodynamics
; Climate change
; Oceanography
; Precipitation (meteorology)
; Rain
; Surface waters
; Climate variability
; Deep convection
; Interannual variability
; Meridional overturning circulations
; Monsoons
; Climate models
英文摘要: The correlation between increased Sahel rainfall and reduced Saharan surface pressure is well established in observations and global climate models and has been used to imply that increased Sahel rainfall is caused by a stronger shallow meridional circulation (SMC) over the Sahara. This study uses two atmospheric reanalyses to examine interannual variability of Sahel rainfall and the Saharan SMC, which consists of northward near-surface flow across the Sahel into the Sahara and southward flow near 700 hPa out of the Sahara. During wet Sahel years, the Saharan SMC shifts poleward, producing a drop in low-level geopotential and surface pressure over the Sahara. Statistically removing the effect of the poleward shift from the low-level geopotential eliminates significant correlations between this geopotential and Sahel precipitation. As the Saharan SMC shifts poleward, its midtropospheric divergent outflow decreases, indicating a weakening of its overturning mass flux. The poleward shift and weakening of the Saharan SMC during wet Sahel years is reproduced in an idealized model of West Africa; a wide range of imposed sea surface temperature and land surface albedo perturbations in this model produce a much larger range of SMC variations that nevertheless have similar quantitative associations with Sahel rainfall, as in the reanalyses. These results disprove the idea that enhanced Sahel rainfall is caused by strengthening of the Saharan SMC. Instead, these results are consistent with the hypothesis that a stronger SMC inhibits Sahel rainfall, perhaps by advecting midtropospheric warm and dry air into the precipitation maximum. © 2017 American Meteorological Society.
资助项目: NSF, National Science Foundation
; Yale University
Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/48732
Appears in Collections: 气候减缓与适应 气候变化与战略
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作者单位: Yale University, New Haven, CT, United States
Recommended Citation:
Shekhar R.,Boos W.R.. Weakening and shifting of the Saharan shallow meridional circulation during wet years of the West African monsoon[J]. Journal of Climate,2017-01-01,30(18)