1967-2006年中国东南沿海盛夏降水强度变化特征分析

Analysis of Changes in Precipitation Intensity in Later-Summer over Southeast Coast of China in 1967-2006

利用中国地面台站逐日和逐时降水资料,对中国东南沿海地区近40年(1967—2006年)盛夏(7—8月)降水强度变化特征进行了分析。逐日降水资料的分析结果表明我国东南沿海盛夏的降水量呈显著增加趋势,且主要是由日降水强度增强所致,日降水频次的贡献不显著。结合逐时降水资料的分析结果发现,东南沿海地区虽然降水日的平均降水时数显著增加,平均逐时降水强度也显著增强。通过按降水持续时数确定的降水事件分类分析发现,短持续降水(≤4 h)平均小时强度显著增强,具体表现为弱小时强度降水减少和强降水增多。长持续性降水(≥15 h)平均小时强度减弱,但降水频次增加。由于长持续性降水的平均小时降水强度远大于短时降水平均小时强度,对整体小时强度增强是正贡献。总之,我国东南沿海盛夏平均降水强度增强主要来自长持续性降水频次的增多、短时强降水频次的增多和短时弱降水频次的减少。

Using daily and hourly station rain gauge data during 1967-2006,the changes in the characteristics of the later-summer（July-August） rainfall intensity over southeast coastal China were analyzed.The results depending on the daily rainfall data confirm that the amount of precipitation in southeastern China has significantly increased,which mainly results from the significant increase of daily precipitation intensity while the frequency does not increase significantly.Based on the hourly rainfall data,it is found the hourly intensity of precipitation and duration time are significantly increased simultaneously in this region.Comparing the average precipitation indices during 1967-1986 with that during 1987-2006.It is found the intensity of short duration（≤ 4 h） precipitation increases while that of long duration（≥ 15 h） precipitation decreases and the frequency of long duration precipitation increases.Even so,the average intensity of long duration precipitation is much higher than that of short duration precipitation.In short,the significant increase of the hourly precipitation intensity is resulted from the frequency increase of long duration-and short duration-heavy precipitation and the frequency decrease of short durationslight precipitation in the past 40 years over the southeastern coast of China.