长江中下游地区连阴雨变化特征分析

利用长江中下游地区86站1961~2011年逐日降水量资料,采用线性倾向估计法和M-K突变检验法,分析该地区年连阴雨日数、过程次数、总降水量及降水强度的时空变化特征。结果显示:长江中下游地区大部连阴雨日数有70~130 d/a、连阴雨过程次数有7~12次/a、连阴雨总雨量为500~1 300 mm/a、年均连阴雨强度为8~10 mm/d,连阴雨过程持续时间多在8~11 d/次左右。其中连阴雨日数和频次总体呈现出南多北少、连阴雨总雨量呈东南多西北少、雨强呈东强西弱的分布态势;近50 a来,长江中下游地区平均年连阴雨日数、连阴雨过程频次、连阴雨总雨量均呈减少趋势,减少速率分别为3.8 d/10 a、0.3次/10 a、18.5 mm/10 a,其中连阴雨日数、频次减少趋势显著;降水强度呈显著增加趋势,增加速率为0.2 mm/(d·10 a)。空间上,西部连阴雨日数、过程次数均呈显著减少趋势,东部呈微弱的减少趋势;大部地区连阴雨总量均呈显著减少趋势,其中西部尤为突出。突变分析发现,长江中下游连阴雨存在突变年份,各统计因子突变主要集中在1991~2011年,连阴雨日数减少突变发生在2003年,2006年起减少趋势超过显著性水平;连阴雨频次突变发生在2004年,2010年起减少趋势超过显著性水平;连阴雨总雨量突变发生在2006年,但这种突变不显著;连阴雨降水强度于1992~1994年发生突变,2010年起增加趋势超过显著性水平。

AN ANALYSIS ON THE CHANGE CHARACTERISTICS OF CONSECUTIVE RAINFALL IN THE MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER

Based on the daily precipitation data from 86 stations in the middle and lower reaches of the Yangtze River during the period of 1961-2011, characteristics of spatial and temporal variation of consecutive rainfall days, frequencies, total amount and intensity were analyzed using the methods of linear trend estimate and M-K test. The results showed that the consecutive rainfall days were 70-130 d/a and the frequency was 7-12 times/a in most of the middle and lower reaches of the Yangtze River. Also, the total amount of rainfall was 500-1 300 mm/a with the annual consecutive rainfall intensity of 8-10 mm/d. The consecutive rainfall process lasted about 8-10 days each time. In the research regions, more days and higher frequency of consecutive rainfall were observed in the south than in the north, greater total amount of consecutive rainfall appeared in the southeast than in the northwest, and stronger rainfall intensity emerged in the east than in the west. Recent 50 years have witnessed the decreasing trends of the days, frequencies and total amount of the consecutive rain over the middle and lower reaches of the Yangtze River, with the decreasing rate of 3.8 d/10 a, 0.3 time/10a and 18.5 mm/10 a, respectively. Although the consecutive rainfall days and frequencies were significantly reduced, the rainfall intensity was significantly increased with an increasing rate of 0.2 mm/(d·10 a). The spatial distribution trend of consecutive rainfall over the middle and lower reaches of the Yangtze River was uneven. The annual days and frequencies of consecutive rainfall significantly decreased in the western regions, but slightly decreased in most eastern regions. In most areas of the middle and lower reaches of the Yangtze River, the total amount of annual consecutive rainfall was significantly reduced, especially in the western regions. The abrupt change analysis supported the existence of years with abrupt changes in the middle and lower reaches of the Yangtze River. The abrupt change of each variable mainly occurred during the period of 1991-2011. The abrupt change of reduced consecutive rainfall days emerged in 2003, and the decreasing trend became statistically significant since 2006. The abrupt change of consecutive rainfall frequencies occurred in 2004, and the decreasing trend became statistically significant since 2010. The abrupt change of total amount of consecutive rainfall intensity was present in 2006, but such change was not statistically significant. The abrupt change of consecutive rainfall was observed in 1992-1994, with a significant increasing trend emerged in 2010.