淠河流域不同强度等级降水变化研究

淠河流域降水时空变率大,深入分析不同强度等级降水的特征和变化,对于全面揭示研究区气候变化、合理有效利用水资源、防治洪旱灾害具有十分重要的意义。基于淠河流域12个气象站1958~2012年逐日降水资料,分析年、季不同级别降水量(频次)的变化特点,以及主汛期(5~9月)连续3d最大降水量的概率分布。结果表明,淠河流域小雨量(频次)四季分布比较均匀,级别越高,降水频次越少,分布越集中,夏季暴雨多发。淠河流域年总降水量增加趋势不显著,总降水频次则显著减少。夏季各级别降水量(频次)均呈增加趋势,其中暴雨增加最显著,冬季总降水频次无明显趋势变化,小雨、中雨量增加显著,春、秋季总降水频次和小雨频次的减少趋势极其显著。淠河流域暴雨量、暴雨频次均在1968年发生增多突变,小雨频次在1975年有极显著减少突变,年总降水量有增多突变,总降水频次则有减少突变。自20世纪70年代后期以来,研究区主汛期连续3d极端强降水出现概率加大,不同重现期极值增大,洪涝灾害风险加剧。

STUDY ON CHANGES OF DIFFERENT-CLASS PRECIPITATION IN INTENSITY IN PI RIVER VALLEY

Pi River located in the west of Anhui Province is the largest tributary of the Huaihe River at its south bank. The spatial and temporal change of precipitation is very obvious in Pi River Valley. Meanwhile, droughts and floods occur frequently in this region. Analysis on the characteristics and changes of different-class precipitation is of great importance for revealing the laws of climate changes fully in the study area, taking precautions against and fighting natural adversities as well as utilizing water resources reasonably. Based on the daily precipitation data from 1958 to 2012 of 12 meteorological stations in Pi River Valley, daily precipitation were classified into four grades according to precipitation intensity, namely, light(0.1-9.9 mm/d), moderate(10.0-24.9 mm/d), heavy(25.0-49.9 mm/d), hard(≥50 mm/d) rain. The regional amount and frequency of different-class precipitation in the year and seasons were established on the basis of corresponding series of each station by using the arithmetical mean method. We analyzed the seasonal distribution as well as changing trend and abrupt changes of regional different-class precipitation, together with probability distribution of the continuous 3 days maximum precipitation in main rainy season (May to September) in Pi River Valley in this paper. The results showed that the mean proportion of light, moderate, heavy, hard rain precipitation to annual total precipitation were 21.2%, 29.7%, 26.4% and 22.7%, respectively, and those of different-class precipitation frequency were 73.4%, 16.9%, 7.0% and 2.7% in turn. Amount and frequency of light rain in seasons was relatively uniform. Precipitation class was higher, the frequency of it in a year was less and time distribution was more concentrated. The increasing trend of annual rainfall was not obvious, but frequency of annual precipitation exhibited a decreasing tendency at the 0.001 significance level, resulting in the increased annual average precipitation intensity. The amount and frequency of all grades both exhibited increasing tendency in summer and the increasing trend of hard rain were more significant than that of other precipitation classes. There wasn't obvious tendency in winter precipitation frequency except moderate rain, at the same time amount of light, moderate rain in winter exhibited increasing trend. The amount and frequency of all grades decreased consistently in spring and autumn and the decreasing tendency of light rain frequency were very significant exceeding 0.001 level. The abrupt changes in amount and frequency of annual hard rain occurred both in 1968. The jump of decreasing at the 0.01 significance level took place in 1975 in annual light rain frequency. There existed an abrupt increasing change in annual total rainfall, while there existed an abrupt reduction change in annual total precipitation frequency. In comparison to 1958-1977, the probabilities of the continuous 3 days extreme precipitation in main rainy season in Pi River Valley were higher in 1978-2012 and the extreme precipitation in different return periods increased obviously. Facing increasing flood frequency and intensity, we should strengthen the flood control and disaster mitigation efficiently.