| On the Mechanism of the Locking of the El Nino Event Onset Phase to Boreal Spring |
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| 作者姓名： | YAN Bangliang |
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| 作者单位： | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080 |
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| 基金项目： | This work was supported by The National Key Basic Reserch and Development Project of China，国家自然科学基金，中国科学院资助项目 |
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| 摘 要： | The mechanism of the locking of the E1 Nino event onset phase to boreal spring （from April to June） in an intermediate coupled ocean-atmosphere model is investigated. The results show that the seasonal variation of the zonal wind anomaly over the equatorial Pacific associated with the seasonal variation of the ITCZ is the mechanism of the locking in the model. From January to March of the E1 Nino year, the western wind anomaly over the western equatorial Pacific can excite the downwelling Kelvin wave that propagates eastward to the eastern and middle Pacific by April to June. From April to December of the year before the E1 Nifio year, the eastern wind anomaly over the equatorial Pacific forces the downwelling Rossby waves that modulate the ENSO cycle. The modulation and the reflection at the western boundary modulate the time of the transition from the cool to the warm phase to September of the year before the E1 Nifio year and cause the strongest downwelling Kelvin wave from the reflected Rossby waves at the western boundary to arrive in the middle and eastern equatorial Pacific by April to June of the E1 Nino year. The superposition of these two kinds of downwelling Kelvin waves causes the El Nino event to tend to occur from April to June.
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| 关 键 词： | 北半球 春季 ENSO循环 大气环境 |
| 收稿时间： | 2004-03-16 |
| 修稿时间： | 2005-06-06 |
On the mechanism of the locking of the El Niño event onset phase to boreal spring |
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| YAN Bangliang.On the Mechanism of the Locking of the El Nino Event Onset Phase to Boreal Spring[J].Advances in Atmospheric Sciences,2005,22(5):741-750. |
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| Authors: | Yan Bangliang |
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| Institution: | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080 |
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| Abstract: | The mechanism of the locking of the El Nino event onset phase to boreal spring (from April to June)in an intermediate coupled ocean-atmosphere model is investigated. The results show that the seasonal variation of the zonal wind anomaly over the equatorial Pacific associated with the seasonal variation of the ITCZ is the mechanism of the locking in the model. From January to March of the El Nino year, the western wind anomaly over the western equatorial Pacific can excite the downwelling Kelvin wave that propagates eastward to the eastern and middle Pacific by April to June. From April to December of the year before the El Nino year, the eastern wind anomaly over the equatorial Pacific forces the downwelling Rossby waves that modulate the ENSO cycle. The modulation and the reflection at the western boundary modulate the time of the transition from the cool to the warm phase to September of the year before the El Nino year and cause the strongest downwelling Kelvin wave from the reflected Rossby waves at the western boundary to arrive in the middle and eastern equatorial Pacific by April to June of the El Nino year. The superposition of these two kinds of downwelling Kelvin waves causes the El Nino event to tend to occur from April to June. |
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| Keywords: | ENSO cycle locking of the El Nino event onset phase ocean-atmosphere interaction |
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