关键词: 连阴雨, 长江中下游, 变化特征

Abstract: 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.

Key words: Consecutive Rainfall, the middle and lower reaches of the Yangtze River, Variation characteristics