Variability of precipitation extremes over the Yangtze River Delta, eastern China, during 1960–2016

Abstract

Understanding the changing characteristics and related mechanisms behind precipitation extremes is crucial for developing adaptive measures of water resource management as well as flood risk management. Based on daily precipitation measurement taken at 57 meteorological stations from 1960 to 2016, the variability of precipitation extremes over the Yangtze River Delta (YRD) is analyzed utilizing a Mann-Kendall trend test as well as a Hurst exponent analysis. Moreover, the climatic teleconnection that occurs from large-scale atmospheric circulation and such precipitation extremes is also investigated with the help of a wavelet coherence analysis. Results indicate that most extreme precipitation indices predominantly exhibit significant positive trends, indicating a wetting trend in the YRD over the past 61 years. Meanwhile, the contribution of precipitation of very wet days to annual total wet-day precipitation increased significantly. Furthermore, the increasing trend of precipitation extremes in the YRD is found to be attributable to the frequency and intensity, rather than to the duration of extreme precipitation events. The patterns of variation in these precipitation extremes reveal dramatic spatial heterogeneity, with extreme events concentrated primarily along the coastal plains. Overall, the YRD will likely face more severe flood risks in the foreseeable future. This is especially the case for the southern and central-western regions of the YRD. In contrast, the northern region of the YRD is forecast to become drier over time. The increasing trends in precipitation extremes for the YRD observed in this study are found to be linked closely with the positive anomalies of the El Nino-Southern Oscillation as well as the negative anomalies of the East Asian summer monsoon.