Abstract
Understanding rainfall anomalies and their relationship with floods in the Yangtze River Basin (YRB) is essential for evaluating flood disasters, which have a great impact on the development of agriculture and the economy. On the basis of daily rainfall data from 1961 to 2010 from 178 meteorological stations, the temporal and spatial characteristics of rainfall anomalies in the YRB were studied on an annual scale, seasonal scale, and monthly scale. The annual rainfall of the YRB showed a generally increasing trend from 1961 to 2010 (14.22 mm/10 a). By means of the Bernaola–Galvan abrupt change test and Redfit spectrum analysis, it was found that the annual average rainfall increased abruptly after 1979 and had a cycle of 2–3 years. On the seasonal scale, the rainfall in spring and autumn showed a gradually decreasing trend, especially in September, while it showed a significant increasing trend in summer and winter in the YRB. As for the monthly scale, the rainfall in the rainy season from June to July presented a clear increasing trend during the study period, which greatly enhanced the probability of floods in the YRB. Additionally, through the analysis of the spatial distribution characteristics of rainfall in the entire YRB from 1961 to 2010, it was observed that the annual rainfall amount in the YRB presented an “increase–decrease–increase” tendency from east to west, accompanied by a rain belt that continuously moved from west to east. Moreover, the rainfall characteristics in flood years were summarized, and the results revealed that the years with rainfall anomalies were more likely to have flood disasters. However, anomalies alone would not result in big floods; the spatially and temporally inhomogeneous rainfall distribution might be the primary reason for flood disasters in the entire YRB.
Highlights
Global warming intensifies the interaction between the energy and water cycles in the climate system, leading to a significant increase in flood disasters associated with extreme rainfall in recent decades [1]
The annual distribution of rainfall extremes in the upper, middle, and lower basin of the Yangtze River Basin (YRB) tends to converge in June; as a result, flood disasters have frequently occurred in the YRB since the 1990s [13]
Zhang and Qian (2004) suggested that the temporal and spatial distribution patterns of rainfall in the flood season in different sections of the YRB are quantified by the precipitation concentration degree (PCD) and precipitation concentration period (PCP)
Summary
Global warming intensifies the interaction between the energy and water cycles in the climate system, leading to a significant increase in flood disasters associated with extreme rainfall in recent decades [1]. The annual distribution of rainfall extremes in the upper, middle, and lower basin of the YRB tends to converge in June; as a result, flood disasters have frequently occurred in the YRB since the 1990s [13]. Zhang and Zhao (2006) analyzed the relationship between rainfall patterns and floods in the Weihe River Basin from 1954 to 2003, and suggested that the increased rainfall combined with the great changes in annual and interannual runoff is the primary cause for the frequent floods in the Weihe River [14]. Zhang and Qian (2004) suggested that the temporal and spatial distribution patterns of rainfall in the flood season in different sections of the YRB are quantified by the precipitation concentration degree (PCD) and precipitation concentration period (PCP). It was demonstrated that different areas of the world showed different patterns, but the variance of rainfall increased in all the studied regions [17]
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