GSTDTAP  > 气候变化
DOI10.1175/JCLI-D-16-0696.1
Weakening and Shifting of the Saharan Shallow Meridional Circulation during Wet Years of the West African Monsoon
Shekhar, Ravi; Boos, William R.
2017-09-01
发表期刊JOURNAL OF CLIMATE
ISSN0894-8755
EISSN1520-0442
出版年2017
卷号30期号:18
文章类型Article
语种英语
国家USA
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.


领域气候变化
收录类别SCI-E
WOS记录号WOS:000408613400017
WOS关键词IDEALIZED 2-DIMENSIONAL FRAMEWORK ; INTERTROPICAL CONVERGENCE ZONE ; SAHEL RAINFALL VARIABILITY ; HEAT LOW ; SEASONAL EVOLUTION ; MOIST CONVECTION ; WATER-VAPOR ; DYNAMICS ; PRECIPITATION ; DROUGHT
WOS类目Meteorology & Atmospheric Sciences
WOS研究方向Meteorology & Atmospheric Sciences
引用统计
文献类型期刊论文
条目标识符http://119.78.100.173/C666/handle/2XK7JSWQ/20932
专题气候变化
作者单位Yale Univ, New Haven, CT 06520 USA
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GB/T 7714
Shekhar, Ravi,Boos, William R.. Weakening and Shifting of the Saharan Shallow Meridional Circulation during Wet Years of the West African Monsoon[J]. JOURNAL OF CLIMATE,2017,30(18).
APA Shekhar, Ravi,&Boos, William R..(2017).Weakening and Shifting of the Saharan Shallow Meridional Circulation during Wet Years of the West African Monsoon.JOURNAL OF CLIMATE,30(18).
MLA Shekhar, Ravi,et al."Weakening and Shifting of the Saharan Shallow Meridional Circulation during Wet Years of the West African Monsoon".JOURNAL OF CLIMATE 30.18(2017).
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