| 索马里急流与南亚高压年代际变化的可能联系 |
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| 引用本文： | 石文静,肖子牛,孙杭媛.索马里急流与南亚高压年代际变化的可能联系[J].大气科学,2017,41(3):561-577. |
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| 作者姓名： | 石文静 肖子牛 孙杭媛 |
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| 作者单位： | 中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室 (LASG), 北京 100029 |
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| 基金项目： | 国家自然科学基金项目91637208、41375069、41175051，云南省重点基金项目2016FA041 |
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| 摘 要： | 索马里急流是北半球夏季最为强盛的越赤道气流，南亚高压则是出现在对流层高层、平流层低层最大最稳定的反气旋环流系统，基于近60年NECP/NCAR再分析资料，本文研究了年代际尺度上夏季索马里急流与南亚高压的联系。研究结果表明:年代际尺度上，索马里急流与南亚高压存在显著的正相关关系，当索马里急流偏弱(强)时，夏季南亚高压偏弱西退(偏强东进)。对不同年代际背景下南亚高压东西部的经向垂直环流的分析发现，当索马里急流处于偏弱位相时，南亚高压西半部(20°~70°E)经向垂直环流偏强，而其东半部(75°~120°E)经向垂直环流减弱；反之亦然。南亚高压南北两侧的纬向垂直环流的变化也有差异，索马里急流偏弱(强)时，北部南亚高压(27.5°~35°N)的青藏高原上空纬向垂直环流显著减弱(增强)，而南部南亚高压(20°~27.5°N)的伊朗高原上空纬向垂直环流减弱(增强)明显。进一步的研究发现，年代际尺度上索马里急流与南亚高压的联系受到PDO(Pacific Decadal Oscillation)年代际变化的调制。PDO正负位相的转折，首先改变了对流层高层副热带西风急流的强弱变化，从而使得位于其南部的南亚高压强度和热带东风急流发生相应的改变，热带东风急流的变化又通过热带印度洋上空的局地纬向垂直环流将异常信号传递到对流低层，改变热带地区索马里急流的强弱变化。
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| 关 键 词： | 索马里急流强度 南亚高压 年代际变化 太平洋年代际振荡 纬向东风 |
| 收稿时间： | 2016/4/14 0:00:00 |
| 修稿时间： | 2016/9/22 0:00:00 |
The Correlation of Somali Jet Strength with South Asia High on Interdecadal Timescale |
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| SHI Wenjing,XIAO Ziniu and SUN Hangyuan.The Correlation of Somali Jet Strength with South Asia High on Interdecadal Timescale[J].Chinese Journal of Atmospheric Sciences,2017,41(3):561-577. |
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| Authors: | SHI Wenjing XIAO Ziniu and SUN Hangyuan |
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| Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | The relationship between the Somali jet strength and the summertime South Asia high on interdecadal timescale is analyzed using the nearly 60-y NCEP/NCAR reanalysis data. The results are shown as follows. On interdecadal timescale, positive correlation between Somali jet strength and South Asia high is found. If the Somali jet strength is weak (strong), the summertime South Asia high is also weak (strong) and retreats westward (advances eastward). In different interdecadal backgrounds of Somali jet strength, meridional circulations of the eastern (75°-120°E) and western (20°-70°E) South Asia high are just opposite. During the period when the Somali jet is weak, the meridional circulation of the western South Asia high is strong, whereas the meridional circulation of the eastern South Asia high is dramatically weak, and vice versa. Meanwhile, zonal circulations to the south (20°-27.5°N) and north (27.5°-35°N) of the South Asia high also change differently. The zonal circulation of the northern South Asia high over the Tibetan Plateau is weaker (stronger) than normal, while the zonal circulation of the southern South Asia high over Iranian Plateau is significantly weaker (stronger) than normal during the stronger (weaker) Somali jet period.Further studies verify that the interdecadal relationship between the Somali jet strength and South Asia high is related to the Pacific Decadal Oscillation (PDO). The phase transition of PDO first changes the subtropical westerly jet on interdecadal time scale, which causes the interdecadal variation in the strength of the South Asia high and the tropical easterly jet over the tropical northern Indian Ocean. The tropical easterly jet then sends signals of anomalies to lower level of the atmosphere by the zonal circulation over the tropical Indian Ocean. Finally, the strength of the Somali jet changes. |
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| Keywords: | Somali jet strength South Asia high Interdecadal variability Pacific Decadal Oscillation (PDO) Zonal easterlies |
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