摘要
With rapid urbanization occurring across developing countries since the late last century,many recent observational studies show statistically significant increases in the intensity and frequency of short-duration(i.e.,less than 6 h)urban extreme rainfall(UER)events over and downwind of major megacities during the warm season,but decreasing trends in light rainfall and rainy day over surrounding areas and also in total regional rainfall[1–4](An UER event is typically defined as a rainfall rate of greater than 95th percentile or higher over an urban region of concern).Moreover,the number of short-duration UER events tends to increase faster than that of long-duration ones,and the increasing UER trend appears to be more pronounced over some of China’s major megacities due to more rapid urbanization during the past three decades[1–3].As an example,a near-century climatology of hourly UER rates at a downwind maximum-accumulated rainfall station from the megacity of Shanghai is given in Fig.1[1],showing an increasing hourly rainfall trend since the rapid urbanization beginning from 1981 that is much greater than a longer-term hourly rainfall trend(Fig.1a).The large increases in the megacity-averaged hourly rainfall trend during Shanghai’s rapid urbanization period are also evident(Fig.1b).
With rapid urbanization occurring across developing countries since the late last century,many recent observational studies show statistically significant increases in the intensity and frequency of short-duration(i.e.,less than 6 h)urban extreme rainfall(UER)events over and downwind of major megacities during the warm season,but decreasing trends in light rainfall and rainy day over surrounding areas and also in total regional rainfall[1–4](An UER event is typically defined as a rainfall rate of greater than 95th percentile or higher over an urban region of concern).Moreover,the number of short-duration UER events tends to increase faster than that of long-duration ones,and the increasing UER trend appears to be more pronounced over some of China’s major megacities due to more rapid urbanization during the past three decades[1–3].As an example,a near-century climatology of hourly UER rates at a downwind maximum-accumulated rainfall station from the megacity of Shanghai is given in Fig.1[1],showing an increasing hourly rainfall trend since the rapid urbanization beginning from 1981 that is much greater than a longer-term hourly rainfall trend(Fig.1a).The large increases in the megacity-averaged hourly rainfall trend during Shanghai’s rapid urbanization period are also evident(Fig.1b).
作者
Da-Lin Zhang
张大林(Department of Atmospheric and Oceanic Science,University of Maryland,College Park,MD 20742,USA;State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,China)
基金
This work was jointly supported by the National Key Basic Research and Development Program of China(2018YFC1507400)
the Development Foundation of Chinese Academy of Meteorological Sciences(2017Z006)
the US Office of Naval Research Grant(N000141712210).
