| 2004年中国长江以南地区严重秋旱特征及其同期大气环流异常 |
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| 引用本文： | 牛宁,李建平.2004年中国长江以南地区严重秋旱特征及其同期大气环流异常[J].大气科学,2007,31(2):254-264. |
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| 作者姓名： | 牛宁 李建平 |
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| 作者单位： | 1.兰州大学大气科学学院,兰州,730000;中国科学院大气物理研究所大气科学与地球流体力学数值模拟国家重点实验室,北京,100029 |
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| 基金项目： | 国家自然科学基金资助项目40523001、40325015 |
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| 摘 要： | 利用2004年8～10月的中国160台站降水资料以及NCEP/NCAR再分析资料，分析了2004年秋季发生在中国长江以南地区的严重干旱（简称2004年长江以南秋旱）前兆和发展特征以及秋旱持续期间的东亚大气环流异常。结果表明:2004年长江以南秋旱是以8月在广西境内出现小范围干旱为前兆，9月扩展到长江以南中部地区，10月遍及整个长江以南地区而达到鼎盛的一个发展过程。2004年长江以南秋旱事件的发生、发展和鼎盛期都受到了同期东亚大气环流异常的很大影响:2004年秋季东南亚上空的整层经向水汽输送出现了显著的负异常，说明2004年秋季长江以南地区上空的整层水汽在经向上由南向北的输送减弱而从北向南的输送加强；850 hPa水汽输送的异常加强了从北向南的水汽输送，从而影响了秋旱的发展。结合2004年秋旱持续期间850 hPa 流场异常分析，2004年秋季850 hPa的流场在台湾海峡附近上空出现了一个气旋性的异常环流，它导致了西南水汽及其与越赤道气流和东南水汽的混合气流（10°N～20°N, 135°E～150°E）在向北的输送路径上发生改变，并且此混合气流进入内陆从而加强了大陆上空由北向南的干冷气流，进一步影响了秋旱的发展。通过分析850 hPa等压面上的垂直速度场发现:秋旱同期长江以南地区下沉气流异常，这种天气形势不利于降水的产生。2004年秋季长江以南地区受到了闭合高压——西太平洋副热带高压（简称西太副高）的长期控制，形成少雨的天气。除此之外，中高纬地区脊区前方和槽区的后方易于冷空气的南下输送， 这在很大程度上也促使了秋旱的发展。
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| 关 键 词： | 中国长江以南 秋旱 大气环流 |
| 文章编号： | 1006-9895（2007）02-0254-11 |
| 修稿时间： | 2005-07-222006-04-26 |
The Features of the Heavy Drought Occurring to the South of the Yangtze River in China as well as the Anomalies of Atmospheric Circulation in Autumn 2004 |
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| NIU Ning and LI Jian-Ping.The Features of the Heavy Drought Occurring to the South of the Yangtze River in China as well as the Anomalies of Atmospheric Circulation in Autumn 2004[J].Chinese Journal of Atmospheric Sciences,2007,31(2):254-264. |
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| Authors: | NIU Ning and LI Jian-Ping |
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| Institution: | 1 College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000; 2 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmos pheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | In order to study the features and the causes of the drought disaster, the drought occurring in the area to the south of the Yangtze River from August to October 2004 is examined by employing the monthly precipitation dataset of 160 stations in China and NCEP/NCAR reanalysis data. At the same time the atmospheric circulation anomaly over East Asia is analyzed to investigate the causes of the drought. The results show that the drought takes place in Guangxi Province as a sign of the heavy drought in August, later it spreads eastward and northward in September, and in October the drought area enlarges and is over the whole Yangtze River valley. With time, the ravage of the drought is aggravative. The drought occurring in the area to the south of the Yangtze River from August to October 2004 is the most severe drought disaster of all from 1951. The interannual change of the precipitation to the south of the Yangtze River is periodic. Besides this, the occurrence and continuance of the drought connect remarkably with the anomalies of the atmospheric circulation over East Asia. The negative anomaly of the meridional water vapor transport appears. The phenomena indicate the meridional transport is weaker from south to north but stronger from north to south than normal. At 850 hPa, the water vapor transport anomaly is strengthened and this kind of situation also urges the development of drought. The analysis of stream field at 850 hPa indicates that a cyclone anomaly lies over the Taiwan Strait. The cyclone anomaly results in a change of the direction of the mixed flow which is made up of three flows (the southeast flow, the cross-equatorial flow and the southeast flow), and the mixed flow that lies over the mainland strengthens the transport of dry cold flow from north to south, which speeds the development of drought. The analysis of vertical velocity at 850 hPa indicates the anomaly of the sinking flow during the drought which is not in favor of rain. The subtropical anticyclone controlling the area to south of the Yangtze River in autumn 2004 influences the development of drought. Especially, there is a closed isoline of 588 dagpm controlling the area to the south of the Yangtze River in September and October 2004, it is not inclined to raining. And in the middle and high latitude area, the positions of the trough and the ridge is favorable for the southward motion of the cold air, which will be propitious to the development of the drought. |
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| Keywords: | drought south of Yangtze River atmospheric circulation anomaly |
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