1978—2012年长江三角洲城市群极端小时降水时空变化特征

Spatio-temporal changes of extreme hourly precipitation in the Yangtze River Deltaurban agglomeration during 1978—2012

【目的】全球气候变暖和快速城镇化背景下极端降水事件频发,严重影响社会经济可持续发展,特别是城市群或都市圈面临更大挑战。为准确评估长江三角洲城市群极端降水演变规律,【方法】利用135个气象站点1978—2012年小时降水资料,选取最大1小时降水量(Rx1hr)、超过95%和99%阈值小时降水量(R95pw1hr和R99pw1hr)、超过10 mm和20 mm小时降水频次(R1hr10 mm和R1hr20 mm)五个极端小时降水指标,采用滑动平均法、EOF分解法分析极端小时降水时空变化特征。【结果】结果表明:(1)除R1hr10 mm外,极端小时降水指标总体呈显著上升趋势;(2)空间上主要表现为东南多,西北少,且显著增加站点主要在江苏南部;(3)极端小时降水峰值主要集中在12—18时,占比68.1%~79.3%;(4)极端小时降水主要表现为区域一致型、正负反向型和中心型,其中第一模态以区域一致型为主,且表现出明显增长趋势。【结论】结果证实1978—2012年长江三角洲城市群极端小时降水呈现明显增加趋势,其空间格局受地形特征、城市化发展影响明显,且城市化对极端小时降水有一定促进作用。该研究有助于科学认识城市群极端降水演变,为城市群防灾减灾与合理规划提供参考。

[Objective]In the context of global warming and rapid urbanization,extreme precipitation events occur frequently,posing great challenges to sustainable economic and social development,especially for these urban agglomerations or metropolitan areas.In order to further evaluate the spatiotemporal variations of extreme hourly precipitation in Yangtze River Delta urban agglomeration,[Methods]using hourly precipitation data from 135 meteorological stations during 1978—2012,five extreme hourly precipitation indicators were selected,including maximum 1-hour precipitation(Rx1hr),hourly precipitation exceeding 95%and 99%thresholds(R95pw1hr and R99pw1hr),and hourly precipitation frequency exceeding 10 mm and 20 mm(R1hr10 mm and R1hr20 mm).The moving average method and EOF decomposition method were used to analyze the changes in hourly precipitation in the Yangtze River Delta urban agglomeration.[Results]The result show that:(1)All extreme hourly precipitation indicators except for R1hr10 mm show a significantly upward trend at a 95%significance level.(2)Spatially,there are more extreme hourly precipitation in the southeast and less in the northwest.The stations with significant increase in extreme hourly precipitation are mainly in southern Jiangsu;(3)The peak-value of extreme hourly precipitation is mainly concentrated in Beijing Standard Time 12:00~18:00,accounting for 68.1%~79.3%;(4)Extreme hourly precipitation is mainly divided into three expressions:regional consistent,positive negative reverse and central.The first mode of Rx1hr,R95pw1hr,R1hr10 mm and R1hr20 mm has high consistency,which belongs to regional consistent mode,while the other modes belong to positive negative reverse and central modes.[Conclusion]Overall,the extreme precipitation events in Yangtze River Delta urban agglomeration have a significantly increasing trend during 1978—2012.The spatial pattern of extreme hourly precipitation is correlated with the topography and urbanization.Urbanization has a certain promoting effect on extreme hourly precipitation,and its impact on urban stations is slightly greater than that on rural stations.This research is helpful to scientifically understand the evolution of extreme precipitation in Yangtze River Delta urban agglomerations,and provides reference for disaster prevention and mitigation,urban planning,and water resources management.