中国降水集中期之特征

使用中国国家气象信息中心整编的全中国2474个观测站1961—2013年逐日降水观测资料、美国国家环境预报中心(NCEP)和美国国家大气研究中心(NCAR)制作的1979—2013年逐日850 hPa风、温度、相对湿度场和500 hPa高度场。定义每站5—8月总降水量的45%(河套地区和四川盆地中部为5—9月总降水量的40%)出现的最短时段为该站降水集中期,采用气候统计、气候分析方法和清晰的站点绘图方式研究了中国降水集中期雨量、起止日等时空特点和变化特征。结果表明,中国降水集中期起止时间并非简单的南北、东西向推进,而是最早始于江南华南交界,最晚始于河套地区和四川盆地;最早结束于华南北部和江南大部分地区,最晚结束于河套地区、四川盆地、西藏南部。东北、西北大部分地区的降水集中期早于华北和河套地区。降水集中期以西部沙漠戈壁地区的7—10 d最短,西南地区的30—40 d最长。来自索马里急流的西南水汽支和西太平洋副热带高压西侧的东南水汽支是集中期降水的主要水汽源,中国中东部降水峰值随两支气流的推进而推进。集中期雨量的主要区域特点为:四川盆地雨量在20世纪80年代以后趋势性减少,近年开始回升;云南自2003年起,除2008年以外降水持续偏少。华南北部和江南20世纪80年代的持续少雨和90年代的持续多雨最显著,多雨期降水集中期起止时间推迟,导致长江中下游降水峰值易与上游来水的峰值相遇,这是长江中下游20世纪90年代至21世纪初洪涝频发的主要原因之一。

Characteristics of the precipitation concentration period in China

Using the diurnal precipitation data sets of 2474 stations from 1961 to 2013 and the relevant NCEP/NCAR reanalises data, the precipitation concentration period (PCP) is firstly defined as the shortest time, during which the precipitation accounts for 45% of the total amounts from May to August, with 40% from May to September for the Hetao region and the central Sichuan basin.The precipitation concentration period's climatic state and variation characteristics were discussed. It is found that: (1) PCP occurs earliest to the north of South China but latest in the Hetao region and the Sichuan Basin. (2) PCP ends earliest in South China and a larger part the area south of the Yangtze River, but latest in the Hetao region, the Sichuan basin and southern Tibet. (3) PCP can last 7 to 40 d, the shortest with 7 to 10 d is in desert of West China and the longest with 30 to 40 d in Southwest China. (4) PCP of China occurs with the Somali jet bursting out, and expands with the western Pacific subtropical high developing.And,(5) every regional precipitation during PCP has distinct regional characteristics, and it is prominent that the precipitation is lesser in 1980s, but more in 1990s in the areas north of South China and south of the Yangtze River.