夏季中国中东部不同历时降水时空分布特征

利用1961~2012年台站逐时降水资料,分析了夏季中国中东部不同历时降水的主要气候分布和长期变化特征,为深入认识其时空变化规律和形成机理奠定基础。分析结果表明,降水事件的平均历时由南向北呈"短—长—短"分布型,华南和北方地区以6 h以下的短历时降水为主;而中部地区(28°N~37°N)6 h以上长历时降水占总降水量60%以上。随着降水历时的增加,小雨事件(0.1~1.0 mm/h)的发生概率降低,中雨事件(1.1~10.0 mm/h)的发生概率升高;大雨、暴雨事件(10.0 mm/h)更易出现在35°N以南历时偏短的降水事件中。1961~2012年,中国中东部总降水量呈"南升北降"的趋势分布,夏季南方大部分地区降水强度、时数和事件数均呈上升趋势;而北方地区降水时数和事件数显著减少,不过降水强度呈增强趋势。中东部降水历时总体呈上升趋势,尤其以我国长江与黄河之间的中部地区变化最为显著。同时,该地区短历时(1~6 h)降水无显著的年代际转折,长历时(6 h)降水的年代际增加是20世纪70年代末至20世纪90年代初降水增多的主要原因。20世纪90年代初期以来,南方地区降水的年代际增多则是长、短降水共同作用的结果,但超过6 h降水的影响范围更广,且影响中心较短历时降水偏北。

Spatiotemporal Characteristics of Summer Precipitation with Different Durations in Central East China

Based on the dataset of hourly rain gauge records in central East China for the period 1961-2012, the spatiotemporal characteristics of summer rainfall events in terms of their durations are analyzed. The results show that the rainfall duration exhibits a short-long-short meridional pattern in central East China, i.e., short-duration rainfall events (1-6 h) prevail in southern and northern China, whereas long-duration rainfall events (>6 h) contribute more than 60% to the total rainfall in the region between about 28°N and 37°N. As the duration increases, the occurrence of light rainfall events with intensity weaker than 1 mm/h decreases, while the occurrence of moderate rainfall events with intensify between 1.1 mm/h and 10.0 mm/h increases. Rainfall events with intensity stronger than 10.0 mm/h tend to be characterized by relatively short duration in the region south of about 35°N. The total summer rainfall amount increases in southern China due to the increasing trends of both intensity and occurrence, and decreases in northern China with decreasing occurrence but increasing intensity. The rainfall duration generally shows an increasing trend in central East China, especially in the region between the Yangtze River and Yellow River. The significant increase of total rainfall amount in this region from the late 1970s to early 1990s is mainly attributed to the increase of long-duration rainfall amount, while no obvious interdecadal abrupt change is detected in the short-duration rainfall amount. The significant increase of total rainfall amount in southern China after the early 1990s is related to both the increase of long-duration and short-duration rainfall amount, but the impact of the former is more wide-ranging and northward.