| DOI: | 10.1175/JCLI-D-11-00232.1
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| Scopus记录号: | 2-s2.0-84862059116
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| 论文题名: | The influence of the MJO on upstream precursors to African easterly waves |
| 作者: | Alaka G.J.; Maloney E.D.
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| 刊名: | Journal of Climate
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| ISSN: | 8948755
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| 出版年: | 2012
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| 卷: | 25, 期:9 | | 起始页码: | 3219
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| 结束页码: | 3236
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| 语种: | 英语
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| Scopus关键词: | Africa
; Intraseasonal variability
; Kelvin waves
; Madden-Julian oscillation
; Rossby wave
; Heat convection
; Moisture
; Ocean currents
; Climate change
; advection
; atmospheric convection
; brightness temperature
; easterly wave
; Kelvin wave
; Madden-Julian oscillation
; monsoon
; precipitation (climatology)
; Rossby wave
; seasonal variation
; temperature anomaly
; Indian Ocean
; Pacific Ocean
; Pacific Ocean (West)
; West Africa
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| 英文摘要: | The Madden-Julian oscillation (MJO) produces alternating periods of increased and reduced precipitation and African easterly wave (AEW) activity in West Africa. This study documents the influence of the MJO on the West African monsoon system during boreal summer using reanalysis and brightness temperature fields. MJO-related West African convective anomalies are likely induced by equatorial Kelvin and Rossby waves generated in the Indian Ocean and West Pacific by the MJO, which is consistent with previous studies. The initial modulation of tropical African convection occurs upstream of West Africa, near the entrance of the African easterly jet (AEJ). Previous studies have hypothesized that an area to the east of Lake Chad is an initiation region for AEWs. Called the "trigger region" in this study, this area exhibits significant intraseasonal convection and wave activity anomalies prior to the wet and dry MJO phases in the West African monsoon region. In the trigger region, cold tropospheric temperature anomalies and high precipitable water, as well as an eastward extension of the African easterly jet, appear to precede and contribute to the wet MJO phase in West Africa. An anomalous stratiform heating profile is observed in advance of the wet MJO phase with anomalous PV generation maximized at the jet level. The opposite behavior occurs in advance of the dry MJO phase. The moisture budget is examined to provide further insight as to how the MJO modulates and initiates precipitation and AEW variability in this region. In particular, meridional moisture advection anomalies foster moistening in the trigger region in advance of the wet MJO phase across West Africa. © 2012 American Meteorological Society. |
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| 资源类型: | 期刊论文
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/52430
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| Appears in Collections: | 气候变化事实与影响
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作者单位: | Department of Atmospheric Science, Colorado State University, Fort Collins, CO, United States
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| Recommended Citation: | |
Alaka G.J.,Maloney E.D.. The influence of the MJO on upstream precursors to African easterly waves[J]. Journal of Climate,2012-01-01,25(9)
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