近49 a中国30°N带不同地形下大城市与其郊区的降水特征

Precipitation characteristics in large cities and their suburbs under different terrains in 30°N zone of China in recent 49 years

基于1969-2017年全国站点逐日降水资料、地形高度资料以及2017年全国常住人口数据,采用概率密度函数PDF法、最小二乘法、Mann-Kendall法和累积距平法等多种统计分析方法,结合中国地形多样性,从降水量的PDF特征、变化趋势和极端降水特征三个方面,分析了近49 a中国30°N带不同地形下大城市与其郊区的降水特征,结果表明:(1)中国30°N带降水的区域性和极端性明显,其中长江入海口代表站的年降水量PDF曲线最接近正态分布;极端降水阈值和极端降水强度基本为自西向东增加,且与地形高度呈反比关系;对于暴雨及以上等级的降水,代表站降水概率小但降水占比大。(2)降水的城市化效应明显,表现为代表站的日、月、季、年降水量PDF曲线普遍存在城郊差异,且日和年尺度的差异较月和季的尺度差异更明显;大城市代表站相对于其郊区代表站,前者年降水量普遍增加得快,且最小值大于后者;前者极端降水阈值、极端降水强度和年最大日降水量最大值普遍大于后者,且发生中雨及以上等级强降水的概率和占比较后者大。(3)代表站降水存在明显的年际变化和季节变化,存在一定的周变化;年降水量的突变时间集中发生在1980s中、后期以及1990s至2000s初;降水量的季节变化特征为夏季最多、冬季最少,其中江汉平原、长江中下游、长江入海口地形下夏季降水的城市化效应明显;大部分地形下工作日降水的城市化效应较休息日明显。

Based on daily precipitation data from 1969 to 2017, topographical data and residential population data in 2017, by using a number of statistical analysis methods such as probability density function(PDF) method, least square method, Mann-Kendall method and cumulative anomaly method, the precipitation characteristics in large cities and their suburbs under different terrains in 30°N latitude zone of China in recent 49 years are analyzed from the PDF characteristics, the trend of precipitation and the characteristics of extreme precipitation combining with the terrain diversity of China. The results show that:(1) The precipitation of 30°N latitude zone of China has obvious regional and extreme characteristics. The annual precipitation PDFs at the Yangtze River estuary stations are the closest to normal distribution. The extreme precipitation threshold and extreme precipitation intensity generally increase from west to east and are inversely related to the terrain height. For extreme precipitation in rainstorm and above, the probability of precipitation is low while the precipitation proportion is high.(2) The urbanization effect of precipitation is obvious, as represented by the facts that the PDFs of the daily, monthly, seasonal and annual precipitation at the representative stations generally have urban and suburban differences, and the difference at daily or annual scales is more obvious than that at monthly or seasonal scales. Annual precipitation at representative stations in large cities generally increases faster than that in their suburbs, and the minimum value is greater. Extreme precipitation threshold, extreme precipitation intensity and the maximum value of annual maximum daily precipitation are generally larger, and the probability and the proportion of moderate and above-class heavy rain of the former is larger than the latter.(3) Precipitation has obvious interannual and seasonal variations, and has certain weekly variation. The annual precipitation mutations occur concentrated in the mid-late 1980 s, the 1990 s and the beginning of 2000 s. The seasonal variation characteristics of precipitation is the most in summer and the least in winter. The urbanization effect of summer precipitation is obvious under the terrains of Jianghan Plain, the middle and lower reaches of the Yangtze River and the Yangtze River estuary. The urbanization effect of precipitation in working days is more obvious than the rest days under most terrains.