INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. (2017) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.5107 Linking trends in urban extreme rainfall to urban fooding in China Xinyao Zhou, a Zhijie Bai a,b and Yonghui Yang a * a Key Laboratory of Agricultural Water Resources, Hebei Laboratory of Agricultural Water-Saving, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, China b College of Life Sciences, Universtiy of Chinese Academy of Sciences, Beijing, China ABSTRACT: Storm-induced urban fooding is a global issue that causes large damages and fatalities. Characterizing extreme rainfall is critical to urban food risk management. Although China’s cities have been experiencing a rapid increase in urban fooding in recent decades, there is a lack of national-wide analysis of the occurrence of extreme urban rainfall. This study examined the trends in extreme rainfall in 146 cities in China for the period 1960–2014. The trends were also analysed in terms of city size (small, big and mega cities) in two city clusters (Jing-Jin-Jin City Cluster and Yangtze City Cluster). There was a strong spatial variation in the trends of extreme rainfall across the country, with negative trends in North China and positive trends in Southeast China. Both positive and negative trends were noted for the other regions of China. All the cities in Jing-Jin-Ji City Cluster had a decreasing trend in extreme rainfall, with a signifcant decline (p = 0.03) for mega cities. Then all cities in the Yangtze City Cluster had an increasing trend in extreme rainfall, with a signifcant increase (p=0.02) for big cities. The fndings suggested that efforts to alleviate storm-induced urban fash foods should take into account both spatial disparities in climate and future changes in extreme rainfall events. KEY WORDS urban fooding; urban extreme rainfall; sponge city; trend analysis; China Received 28 September 2016; Revised 21 January 2017; Accepted 28 March 2017 1. Introduction There is an increasing report of urban fooding events, which have caused signifcant damages and fatalities over the world (Burke and Sipe, 2014; Bisht et al., 2016; Sandink, 2016; Smith et al., 2016; Zope et al., 2016). These damages can be mitigated through better urban heavy rainfall forecasting and urban storm drainage sys- tem design (Smith et al., 2016). The characterization of urban heavy rainfalls which cause fash fooding is crucial to urban food risk management. Changes in urban extreme precipitation events are driven by both climate change and urbanization (Yang et al., 2013). There is a general consensus that climate change increases the rate of occurrence of extreme precipitation events. Global warming leads to the concentration of mois- ture in warmer atmosphere that in turn increases the inten- sity of extreme precipitation events (Min et al., 2011; Kunkel et al., 2013; Lehmann et al., 2015; Donat et al., 2016), signifcantly increasing extreme rainfall events across the globe (Goswami et al., 2006; Costa and Soares, 2009; Balling and Goodrich, 2011; Sarr et al., 2013; IPCC, 2014; Balling et al., 2016). At the same time, urbanization modifes local boundary layer processes and *Correspondence to: Y. Yang, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang 050021, China. E-mail: yonghui.yang@sjziam.ac.cn the corresponding patterns of precipitation (Changnon, 1979; Shepherd et al., 2002). Urban effects either increase rainfall due to perturbation of urban heat island (UHI) or suppress precipitation due to low humidity and enhanced aerosol load (Rosenfeld, 2000; Shepherd, 2005). There- fore, the combined impact of climate change and urbaniza- tion on the changes in urban extreme precipitation varies from city to city. In a study on the trends in heavy precipitation in both urban and rural areas in India, Kishtawal et al. (2010) noted that increase in trend of extreme precipitation was signifcantly higher in urban than in rural areas. Pin- gale et al. (2014) analysed the trends in extreme annual daily rainfall for 1971–2005 in 33 urban areas in the Rajasthan arid and semi-arid regions of India using the Mann-Kendall test and Sen’s slope estimator and found negative trends in annual rainfall and extreme annual daily rainfall in most of the cities. Using the Mann-Kendall method, Klongvessa and Chotpantarat (2015) observed a signifcant increase in annual rainfall in urban areas in Eastern Bangkok and then a signifcant decline in max- imum 1-day rainfall in the whole of Bangkok for the period 1982–2010. Using extreme rainfall in 217 urban areas across the globe for the period 1973–2012 in a non-parametric Mann-Kendall test, Mishra et al. (2015) found a signifcant increase in precipitation extremes for a smaller fraction (10%) of total urban areas. The above studies and many others suggest that there is no single uni- form trend in extreme rainfall in urban areas. © 2017 Royal Meteorological Society