| 近40年长江中游地区旱涝特点分析 |
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| 引用本文： | 吴贤云,丁一汇,王琪,叶成志.近40年长江中游地区旱涝特点分析[J].应用气象学报,2006,17(1):19-28. |
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| 作者姓名： | 吴贤云 丁一汇 王琪 叶成志 |
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| 作者单位： | 1.湖南省气象台, 长沙 410007 |
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| 摘 要： | 对Z指数确定的旱涝等级及各站月降水距平百分率的标准差分析表明:长江中游地区大范围的旱涝主要集中在盛夏和秋季。不同季节, 旱涝的主要分布区域不同, 但洞庭湖区始终是一个旱涝多发地。对1960年1月—2001年12月各月长江中游地区50个代表站的旱涝等级进行经验正交函数分析, 并在此基础上进行多通道奇异谱分析, 得到长江中游地区的旱涝分布主要存在4种空间型, 且具有明显的年代际和年际尺度变化, 在20世纪80年代以前, 长江中游地区以偏旱型为主, 而到80年代以后则转变以偏涝型为主; 另外, 长江中游地区的旱涝具有准8年、准5年、准2年和准4年的周期振荡性质, 但从80年代初开始, 旱涝的准2年周期特征在长江中游地区表现不再明显。
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| 关 键 词： | Z指数 旱涝等级 经验正交函数 (EOF) 多通道奇异谱分析 (MSSA) |
| 收稿时间： | 2005-04-18 |
| 修稿时间： | 2005-11-04 |
Characteristics of the Recent 40-year Flood/Duought over the Middle Reaches of the Yangtze |
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| Wu Xianyun,Ding Yihui,Wang Qi,Ye Chengzhi.Characteristics of the Recent 40-year Flood/Duought over the Middle Reaches of the Yangtze[J].Quarterly Journal of Applied Meteorology,2006,17(1):19-28. |
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| Authors: | Wu Xianyun Ding Yihui Wang Qi Ye Chengzhi |
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| Affiliation: | 1.Hunan Provincial Meteorological Observatory, Changsha 4100072.National Climate Center, Beijing 1000813.Hunan Provincial Meteorological Service & Development Center, Changsha 410007 |
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| Abstract: | Using the Z-index method and the 50-station monthly mean rainfall data over the middle reaches of the Yangtze from Jan 1960 to Dec 2001,the monthly flood/drought grades of each station and the whole region are calculated.Through analyzing the monthly regional flood/drought grades combined with the monthly standard deviation of precipitation,results show that both flood and drought events occur frequently over the middle reaches of the Yangtze during the recent 40 years with average about 1.3 drought months and 1.6 flood months per year,but the frequency and location of flood and drought are quite different from season to season.They mainly happen in midsummer and autumn with a large scale and the Dongting Lake is always among those flood or drought area likely owing to its special landform.Using the EOF(empirical orthogonal function) method,the monthly flood/drought grades of 50 stations from Jan 1960 to Dec 2001 are studied.Based on the first four S-EOFs,the floods/droughts over the middle reaches of the Yangtze are mainly divided into the following four patterns: large scale flood in the whole region,flood in the northwest while drought in the southeast,flood in the southwest while drought in the northeast and drought in the center but flood all around,among which the first pattern is the dominating one whose deviation is much greater than those of the other three.That is to say flood over the middle reaches of the Yangtze is the major one in climate events.The MSSA(multi-channel singular spectrum analysis) method is used to analyze the first 10 S-PCs(spatial-principal components) generated by the above EOF.It shows that the inter-decadal and inter-annual variations of flood/drought over the middle reaches of the Yangtze are very clear.There is a sharp turning point in the early of 1980s,there are more droughts before and more floods after that period.So,since 1980s,floods occur frequently and become one of the biggest weather disasters over the middle reaches of the Yangtze.At the same time,the flood and drought in the middle reaches of the Yangtze have periodic characteristics of quasi-eight-year,quasi-five-year,quasi-biennial and quasi-quadrennial oscillations.Focusing on the details of the quasi-biennial oscillation of the flood/drought,it is found that it is different from other researches.The flood/drought's quasi-biennial oscillation in the target region is quite regular though its magnitude decreases gradually before the 1980s,but it is not clear after the 1980s. |
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| Keywords: | Z-index flood/drought grades EOF MSSA |
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