Changing structure of precipitation evolution during 1957-2013 in Yangtze River Delta, China

Based on the daily precipitation of 16 rain gauges in Yangtze River Delta (YRD), the spatial and temporal changing properties of precipitation structure during 1957-2013 are investigated in the view of consecutive rainy duration. The results show that: (1) increasing precipitation amount can be detected in YRD while rainy days exhibit decreasing tendency over the basin. So precipitation intensity has been increasing in the past 57 years. (2) During the past 57 years, the mean wet periods become shorter over most of YRD. Wet periods with short duration show upward occurrence and fractional contribution to annual precipitation. Being shorter, wet periods in Yangtze River Delta are characterized by intensified precipitation, which may result in high risk of flash flood. (3) Extreme precipitation events during 1957-2013 are more evidently associated with short wet periods and peak for 2-day duration both in occurrence and fractional contribution. (4) An combination of climate change and urbanization intensifies the change in the distribution of temporal evolution of precipitation structure towards the precipitation events with shorter duration and higher intensity. Therefore, these changing properties are of significance to understanding the impact of climate change and human interference on hydrological processes and the flood prevention in the future in Yantze River Delta.