The impacts and its contribution rate of urbanization on extreme precipitation, 1976-2015: A case study in the Lake Taihu Plain region

Abstract

城镇化背景下极端降水事件频发，洪涝灾害问题日益突出，探讨城镇化对极端降水的影响已成为热点与难点问题.本文以长江下游太湖平原地区为例，基于区内40个雨量站长序列的逐日资料（1976-2015年），结合城镇化下土地利用/覆被和社会经济等数据，对比分析了不同城镇化阶段极端降水相关指标的时空变化规律，并定量评估不同城镇化水平对极端降水影响的贡献率.结果表明：（1）从极端降水时空变化特征来看，极端降水频率和极端降水强度总体呈上升趋势，且高城镇化水平地区的极端降水量级指标多呈现显著上升趋势.（2）整体上，城市地区城镇化对表征极端降水量级和日数的指标有显著强化作用，对大部分指标的贡献率都在11%以上，最高可达53%；而城郊地区城镇化对极端降水日数指标产生一定抑制作用.城镇化使得城市地区极端降水变化较农村地区更加剧烈，城郊地区降水更加集中，洪涝风险增大.;The rapid development of urbanization and other human activities are closely related to the frequency and intensity of extreme precipitation. It is of great significance to explore the impact of urbanization on extreme precipitation. Taking the Lake Taihu Plain region as an instance, based on the daily rainfall data of 40 stations during 1976-2015 as well as land utility and cover change and socio-economic data in the region, this paper revealed the temporal and spatial variations of extreme precipitation indices in different urbanization stages, and quantitatively assessed the contribution rate of urbanization. The results indicated that:(1) Except for consecutive dry days and consecutive wet days, the extreme precipitation indices exhibited upward trends. Moreover, most stations with significant increase in magnitude indices were located in highly urbanized areas. (2) On the whole, the urbanization effect in urban stations promoted the intensity and frequency of precipitation with the contribution rate above 11% positively; while the urbanization effect in urban and suburban stations showed different effects on the frequency and duration of extreme precipitation. In summary, the variations of extreme precipitation in urban areas are much more intense than in rural areas, resulting in more concentrated precipitation in suburban areas and increased flood risk.