| 我国西南地区秋季干湿分类及主要类型
异常年环流特征分析 |
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| 引用本文： | 徐栋夫,李栋梁,王慧.我国西南地区秋季干湿分类及主要类型
异常年环流特征分析[J].大气科学,2014,38(2):373-385. |
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| 作者姓名： | 徐栋夫 李栋梁 王慧 |
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| 作者单位： | 1.南京信息工程大学气象灾害预报预警与协同创新中心, 气象灾害教育部重点实验室, 南京210044 |
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| 基金项目： | 国家重点基础研究发展计划（973）项目2013CB430202，国家自然科学基金项目41305080，高原气象开放实验室基金课题“西南地区2009/2010年干旱成因研究”，高等学校博士学科点专项科研基金资助课题（博导类）20113228110003，江苏高校优势学科建设工程资助项目（PAPD） |
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| 摘 要： | 本文使用我国西南地区97站1960～2009年逐日资料，计算了考虑降水和气温的干湿指数，分析了西南地区秋季及9、10、11月干湿指数的时空变化特征。采用相似方法，构造了综合相似指数，对历年干湿分布进行分类，并给出了秋季各月各类干湿出现的概率。此外还使用再分析资料分月探讨了干湿分布主要类型异常年的大气环流特征。分析结果表明:西南地区秋季存在显著的干旱化趋势，且该地区干湿变化存在全区一致、东西相反和南北相反的特征。根据干湿变化主要模态的空间型，利用综合相似指数可以将历年秋季干湿分为全区一致偏干型、全区一致偏湿型、东湿西干型、东干西湿型、南湿北干型、南干北湿型和非典型型，共7类。全区干湿一致型出现的次数最多（不低于50%），东西相反型次之（约25%），南北相反型较少（约15%），而出现非典型型次数极少（不足10%）。从季节内尺度来看，全区偏干（湿）的持续性较差，但10月份的东部偏湿区域则有较大几率（不低于50%）在下个月扩展到整个区域。全区偏干型异常年，东亚大槽偏弱或偏东，冷空气南侵困难；南海上空低层维持一个异常的气旋环流，西南地区暖湿气流输送偏弱；西太平洋副高偏强、西伸，南亚高压面积偏大，与西太副高重叠，西南地区长期受高压控制。这种异常环流形势的维持，使得该地区天气晴朗少雨，气温偏高，持续干旱。偏湿型异常年则基本呈相反的环流特征。而西南地区东、西部上空异常的垂直运动和东部低层的南、北风异常是造成东湿（干）西干（湿）型异常的重要原因。
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| 关 键 词： | 干湿指数 相似方法 综合相似指数 干湿分布分类 环流特征 |
| 收稿时间： | 2012/12/12 0:00:00 |
| 修稿时间： | 2013/5/23 0:00:00 |
Autumn Dry-Wet Conditions and Main Types of Atmospheric Circulationin Anomalous Years in Southwest China |
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| XU Dongfu,LI Dongliang and Wang Hui.Autumn Dry-Wet Conditions and Main Types of Atmospheric Circulationin Anomalous Years in Southwest China[J].Chinese Journal of Atmospheric Sciences,2014,38(2):373-385. |
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| Authors: | XU Dongfu LI Dongliang and Wang Hui |
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| Institution: | Collaborative Innovation Center on forecast and Evalution of Meteorological disasters, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044;Collaborative Innovation Center on forecast and Evalution of Meteorological disasters, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044;Institute of Plateau Meteorology, China Meteorological Administration, Chengdu 610071;Collaborative Innovation Center on forecast and Evalution of Meteorological disasters, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044 |
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| Abstract: | Based on daily data from 97 stations in Southwest China (SWC) from 1960 to 2009, we calculated the dry-wet index, which considers precipitation and temperature, and studied the spatiotemporal variations of the autumn dry-wet index. Using the similarity method, a composite similar index was introduced and the distribution of dry-wet conditions was classified according to this index. The main types of atmospheric circulation characteristics in anomalous years are discussed using the NCEP/NCAR reanalysis data. The results suggest that the drying trend is significant in SWC. There are three main modes of autumn dry-wet variations in SWC: consistent across the whole region, a dipole in the latitudinal direction, and a dipole in the longitudinal direction. The distribution of dry-wet conditions can be divided into seven types: the consistent dry (A-), the consistent wet (A+), eastern wet-western dry (B-), eastern dry-western wet (B+), southern wet-northern dry (C-), southern dry-northern wet (C+), and atypical (D). The A (including A- and A+) type is the most frequent (no less than 50%); the B (including B- and B+) type is second (about 25%); the C (including C- and C+) type is less frequent (about 15%); and the D type occurs few times (less than 10%). From October to November, the eastern wet areas have a good chance to expand and cover the whole area in the next month (no less than 50%). The A type is mainly affected by anomalies of the East Asia major trough, the circulation over the South China Sea, and the configuration between the western Pacific subtropical high and South Asia high. The B type anomaly correlates with the vertical movement anomalies in the western-eastern SWC and the wind anomalies in eastern SWC. |
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| Keywords: | Dry-wet index Similarity method Composite similar index Classification of dry-wet distribution Atmospheric circulation characteristics |
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