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。
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 hut 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 （spatialprincipal components） generated by the above EOF. It shows that the inter-decadal and inter-annual variations ly 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
出处
《应用气象学报》
CSCD
北大核心
2006年第1期19-28,共10页
Journal of Applied Meteorological Science
基金
国家"十五"科技攻关项目"全球与中国气候变化的检测和预估"(2001BA611B-01)资助
