1981-2014年南四湖流域极端降水阈值及极端降水日数变化特征*

为研究南四湖流域的极端降水特征,本研究利用1981—2014年南四湖流域9个气象站的逐日降水资料,研究分析了该流域降水阈值、极端降水日数等变化特征.结果表明:(1)对于第90、95和99百分位的极端降水事件,平均降水阈值分别为24.7、40.0、80.2 mm;(2)南四湖地区北部降水阈值较南部偏大,东部较西部偏大,极端强降水阈值的空间分布与年降水量的分布相似;(3)南四湖地区年平均极端降水量东北部以及北部较强,南部和西南部较小,这种分布和南四湖流域的降水气候平均态分布较为类似,反映了极端降水对于降水的贡献非常大;(4)南四湖地区极端降水日数平均为每年3.08~3.56天,表现出极端降水阀值大的站点,其极端降水日数较少,其相关系数达-0.893;(5)南四湖地区极端降水量对总降水量的贡献为34.2%~37.7%,且多年平均年极端降水强度分布与极端降水阈值分布相似,说明阈值大的地方,其降水强度也大,形成灾害的风险也大;(6)南四湖地区极端降水多年平均日数为23.5天,且以4.5 d/10 a的速率上升;(7)南四湖地区20世纪80年代中后期年总极端降水日数发生突变,且存在2年和16年左右的振荡周期.

Variation Characteristics of the Extreme Precipitation Threshold and the Extreme Precipitation Days in Nansi Lake Area During 1981-2014

The paper aims to study characteristics of the extreme precipitation in Nansi Lake. Using the daily precipitation data of 9 weather stations in Nansi Lake during 1981-2014, the variation characteristics of the extreme precipitation threshold and the extreme precipitation days were analyzed. The results showed that: (1) for extreme precipitation events of the 90th percent, 95th percent and the 99th percent, the average precipitation threshold was 24.7 mm, 40.0 mm and 80.2 mm, respectively; (2) the northern precipitation threshold was larger than the southern one in Nansi Lake area, as the eastern one was larger than the western one; the spatial distribution of the extremely heavy precipitation threshold was similar to the distribution of the amount of annual precipitation; (3) the average annual extreme precipitation of Nansi Lake area was stronger in northeastern and northern Nansi, and was weaker in southern and southwestern Nansi, the distribution was relatively similar to the precipitation climate average distribution of Nansi Lake area, reflecting that the contribution of the extreme precipitation was big to precipitation; (4) the extreme precipitation days in Nansi Lake was 3.08-3.56 days per year, showed that the site with bigger extreme precipitation threshold had less extreme precipitation days, the correlation coefficient reached - 0.893; (5) the contribution of the extreme precipitation to the total precipitation in Nansi Lake was 34.2%-37.7%, and the distribution of average annual extreme precipitation intensity was similar to the distribution of extreme precipitation threshold, showed that places with big threshold had high precipitation intensity and disaster risk; (6) the number of extreme precipitation days on average was 23.5 days, and rose at a rate of 4.5 d/10 a; (7) the total extreme precipitation days in Nansi Lake had mutations in the mid-and late 1980s, and had 2 oscillation periods of 2 years and 16 years.