我国极端降水变化趋势及其对城市排水压力的影响

全球气候变化对水循环具有重要影响,其中极端降水的变化,对城市排水系统产生巨大冲击,造成城市内涝、交通瘫痪及生命财产损失等问题。为了揭示我国极端降水变化的趋势和区域特征,及其对城市排水系统的压力程度,使用中国气象数据中心1951—2014年全国917个站点的逐日降水量,计算得到我国极端降水及其变化趋势的空间分布特征。并以我国289个主要地级城市为研究对象,构建了气候变化情景下的城市排水压力评估方法,预测并展望了不同时段和不同代表性浓度路径(RCPs)情景下,未来城市的排水压力情况。结果表明,我国极端降水整体上正随着全球气候变化而增加,全国年最大降水量变化速度的平均值为0.06mm/a,但并不是所有区域都具有一致性,具体表现为南部极端降水增加而北部缓解的规律。我国排水压力大的城市主要分布在南部和东北地区,城市排水基础设施完善的东部和极端降水量比较小的西部地区城市排水压力比较低,华北地区极端降水的随机性大,历史上出现的最大降水显著高于该地区常见大雨,也属于内涝风险比较大的区域。随着气候变化的影响,我国未来城市排水压力整体上升,城市未来短期排水压力相对于现有水平总体上升2.9%,具体75个城市的排水压力有所增加明显。且低应对的RCP8.5情景显著高于高应对的RCP2.6情景,这说明减缓气候变化的工作对降低我国城市内涝风险有比较大的积极意义。我国城市排水压力的变化也具有区域性,华北地区极端降水呈现减少的趋势,南部地区极端降水呈现增加趋势,加重了该地区原本就很高的城市内涝风险,需要政府采取积极措施提出有针对性的方案和考虑了气候变化的前瞻性城市排水规划,以降低城市排水压力,尽量减少城市内涝造成的经济损失。

Trends of extreme precipitation in China and their influence on urban drainage pressure

Extreme precipitation, which can cause waterlogging, block traffic and harm residents'' health in urban areas, has increased with ongoing global climate change. We used precipitation data of 917 meteorological stations during 1951-2014 to estimate changes in extreme precipitation in China, and created a system to evaluate 289 primary local cities'' pressures of different time and different RCPs on urban drainage systems under heavy rainfall in China. The results show that extreme precipitation is increasing in China with global warming, and the annual maximum precipitation is increasing by 0.06mm/a. However, these increases are not uniform across China. In some areas of North China, extreme precipitation has even declined while south areas are becoming serious. Pressures on the drainage systems of cities are greater in the south and northeast than in the north and west because of patterns of precipitation in China. In North China, pecuniary losses caused by waterlogging and flooding in cities are greater where precipitation is more random. Urbanization construction also impacts drainage pressure; cities in the east and along the coasts, which have better infrastructure to manage waterlogging, have less pressure on their drainage systems. These pressures will increase about 2.9% after 20 years later relatively to present situations of climate change, and concretely there are 75 local cities in China whose pressures are increased absolutely. Pressures on drainage systems in China are projected to increase in the future under both RCP2.6 and RCP8.5, although RCP8.5 is associated with greater pressure, which indicates that mitigation of climate change may decrease waterlogging and flooding in China. Cities in North China will benefit from climate change in terms of reduced pressure on drainage systems, and will have lower risks of waterlogging in the future. The risks of waterlogging are highest in southern cities, and are projected to increase in the future with climate change. The government should focus on such cities with greater pressures on their drainage system to protect economic development from the risks of waterlogging.