| 高空西风急流东西向形态变化对梅雨期降水空间分布的影响 |
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| 引用本文： | 杜银,张耀存,谢志清.高空西风急流东西向形态变化对梅雨期降水空间分布的影响[J].气象学报,2008,66(4):566-576. |
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| 作者姓名： | 杜银 张耀存 谢志清 |
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| 作者单位： | 南京大学大气科学系，南京，210093;南京大学大气科学系，南京，210093;江苏省气象科学研究所，南京，210008 |
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| 基金项目： | 国家自然科学基金，江苏省自然科学基金 |
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| 摘 要： | 利用40年的NCEP/NCAR再分析候平均资料和同期长江中下游地区逐日降水资料,使用合成方法分析了梅雨期东亚副热带高空西风急流的东西位置和形态变化特征,探讨了高空西风急流对梅雨期降水空间分布的影响.分析结果表明,梅雨期东亚大陆上空西风急流强度减弱且持续维持、西太平洋上空西风急流核分裂减弱直至出梅后消失,这是梅雨期200 hPa东亚高空西风急流东西向位置变化的主要特征.梅雨期,200 hPa副热带西风急流中心呈现东西向位置变化和海陆分布形态差异,西风急流中心东西向位置变化对梅雨起讫有着较好的指示意义.梅雨期东亚副热带高空西风急流东西形态分布差异不仅影响到长江中下游地区降水空间集中区的位置而且还影响到降水中心强度.进一步分析表明,当东亚西风急流主体位于西太平洋上空时,在长江下游地区形成高低空急流耦合的环流形势,强烈的辐合上升运动加上充足的水汽条件供应,有利于在长江下游形成集中的强降水区域.当高空西风急流位于东亚大陆上空时,在长江中下游地区高低空急流无耦合形势存在,长江中下游地区也没有强的集中降水区域.因此,东亚副热带高空西风急流东西向形态变化对长江中下游地区的高低空环流结构、地面集中降水区域的空间分布具有重要的影响.
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| 关 键 词： | 高空西风急流 东西位置和形态变化 降水空间分布 梅雨 |
Impacts of longitude location changes of East Asian westerly jet core on the precipitation distribution during meiyu period in middle-lower reaches of Yangtze River valley |
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| DU Yin,ZHANG Yaocun,XIE Zhiqing.Impacts of longitude location changes of East Asian westerly jet core on the precipitation distribution during meiyu period in middle-lower reaches of Yangtze River valley[J].Acta Meteorologica Sinica,2008,66(4):566-576. |
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| Authors: | DU Yin ZHANG Yaocun XIE Zhiqing |
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| Abstract: | The longitude location change characteristic of the East Asia Westerly Jet (EAWJ) core at the upper troposphere during meiyu period and its impacts on the spatial distribution of precipitation in the middle-lower reaches of the Yangtze River valley are investigated by using the 40 year's NCEP/NCAR reanalysis mean pentad data and observed daily precipitation data from 1958 to 1997. The results show that there are two areas, where the 200 hPa East Asia westerly jet center appears frequently during meiyu periods: one is located over the western Pacific and the other over the Asian continent. During the meiyu period, the intensity of the westerly jet over Asian continent weakens and the core of the westerly jet over western Pacific splits up and its intensity reduces, and disappears after the end of meiyu, which is the main characteristic of the longitude location change of the 200 hPa westerly jet over East Asian. The change in the location and intensity of the westerly jet is not only associated with the start and end of meiyu period, but also with the spatial distribution and intensity of precipitation in the middle-lower reaches of the Yangtze River valley. The further analysis suggests that when the westerly jet core at upper troposphere is located over the western Pacific, and coupled with an 850 hPa southwesterly jet, the heavy precipitation occurs in the lower reaches of the Yangtze River valley, where the convergence is strong and the water vapor supply sufficient. While the 200 hPa westerly jet core is located over the East Asian continent, and not coupled with an 850 hPa southwesterly jet, only the weaker precipitation occurs in the middle and lower reaches. Therefore, the longitude location changes of the East Asian westerly jet core play important roles in determining the upper-low level circulation structure and the spatial distribution of heavy precipitation in the middle and lower reaches of the Yangtze River valley during the meiyu period. |
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| Keywords: | East Asia subtropical westerly jet Longitude location change of the westerly jet core Precipitation distribution meiyu |
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