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DOI | 10.1002/joc.5214 |
Simulations of the observed 'jump' in the West African monsoon and its underlying dynamics using the MIT regional climate model | |
Im, Eun-Soon1,2,3; Eltahir, Elfatih A. B.4 | |
2018-02-01 | |
发表期刊 | INTERNATIONAL JOURNAL OF CLIMATOLOGY
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ISSN | 0899-8418 |
EISSN | 1097-0088 |
出版年 | 2018 |
卷号 | 38期号:2页码:841-852 |
文章类型 | Article |
语种 | 英语 |
国家 | Singapore; Peoples R China; USA |
英文摘要 | The observed seasonal migration of rainfall associated with the West African monsoon (WAM) is characterized by two regimes of relatively intense rainfall: an early, intense peak over the Guinean Coast during late May to early July; and a late, less-intense peak over the Sahel during mid-July to mid-September. The transition between these two rainfall regimes occurs relatively quickly around the beginning of July. This quick transition can be described as a jump' of the WAM into the continent. Eltahir and Gong (1996) proposed a theory for the WAM whereby the solar radiation forcing during the summer shapes a distribution of boundary-layer entropy that peaks over the continent. By assuming a quasi-equilibrium balance between moist convection and the large-scale radiative forcing, the distribution of boundary-layer entropy can be linked to the absolute vorticity at the tropopause. According to this analytical theory, the onset of the monsoon, characterized by the jump', reflects of a nonlinear shift from a radiative-convective equilibrium regime to an angular momentum conserving regime that would only occur when the value of absolute vorticity in the upper troposphere approaches a threshold of zero. It is because, when the absolute vorticity is significantly different from zero, then the air as a rotating fluid is too rigid to exhibit a meridional overturning. Here, we use the MIT regional climate model (MRCM) to test this theory further and reach a couple of conclusions. First, MRCM succeeds in reproducing the main features of the observed rainfall distribution, including the jump'. Second, analysis of the rainfall, vorticity, entropy, and wind fields simulated by the model reveals a dynamical picture consistent with the proposed theory. |
英文关键词 | West African monsoon jump regional climate model absolute vorticity boundary-layer entropy |
领域 | 气候变化 |
收录类别 | SCI-E |
WOS记录号 | WOS:000423816900023 |
WOS关键词 | SEASONAL EVOLUTION ; PART II ; RAINFALL ; VARIABILITY ; REGCM3 ; PARAMETERIZATION ; ONSET ; REANALYSIS ; MULTIYEAR ; FIELDS |
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/37519 |
专题 | 气候变化 |
作者单位 | 1.Singapore MIT Alliance Res & Technol, Ctr Environm Sensing & Modeling, Singapore, Singapore; 2.Hong Kong Univ Sci & Technol, Dept Civil & Environm Engn, Kowloon, Hong Kong, Peoples R China; 3.Hong Kong Univ Sci & Technol, Div Environm & Sustainabil, Kowloon, Hong Kong, Peoples R China; 4.MIT, Ralph M Parsons Lab, Dept Civil & Environm Engn, Cambridge, MA 02139 USA |
推荐引用方式 GB/T 7714 | Im, Eun-Soon,Eltahir, Elfatih A. B.. Simulations of the observed 'jump' in the West African monsoon and its underlying dynamics using the MIT regional climate model[J]. INTERNATIONAL JOURNAL OF CLIMATOLOGY,2018,38(2):841-852. |
APA | Im, Eun-Soon,&Eltahir, Elfatih A. B..(2018).Simulations of the observed 'jump' in the West African monsoon and its underlying dynamics using the MIT regional climate model.INTERNATIONAL JOURNAL OF CLIMATOLOGY,38(2),841-852. |
MLA | Im, Eun-Soon,et al."Simulations of the observed 'jump' in the West African monsoon and its underlying dynamics using the MIT regional climate model".INTERNATIONAL JOURNAL OF CLIMATOLOGY 38.2(2018):841-852. |
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