Spatio-temporal characteristics of precipitation and dryness/wetness in Yangtze River Delta, eastern China, during 1960-2012

Changes in precipitation have a large effect on human society and are a key factor in the study of the patterns of hydrological and meteorological variables. Based on daily precipitation records during 1960-2012 at 24 meteorological stations in the Yangtze River Delta (YRD), the spatial and temporal variations of six extreme precipitation indices were detected by the modified Mann-Kendall test. Then, the characteristics of dryness/wetness patterns were assessed by Standardized Precipitation Index (SPI) and principal component analysis (PCA) on a 24-month time scale. For precipitation extremes, most of the precipitation indices had increasing trends, especially the annual total precipitation in wet day (PRCPTOT), which showed a significant positive trend distributed mainly in the southern part of the YRD. In contrast, decreasing trends in consecutive dry days (CDD) weredetected at most stations of the YRD, with more than 20% of the stations having negative trends that were statistically significant. Additionally, three dominant geographic sub-regions of dryness/wetness pattern were identified in YRD: the central and southern, northeastern, and northwestern areas of the YRD. With respect to temporal variations of dryness/wetness conditions in each sub-region, a long-term wet tendency in the central and southern area was characterized as being stronger than the tendency in other parts of the YRD over the past 53 years, which indicates that flood disaster may become increasingly serious in the area. Furthermore, a 4 to 8-year period of variation was observed for each sub-region. The results of this study suggest that adaptive water resource measures for future water resource management and water-related disaster reduction mitigation should be considered separately for these regions in the YRD. (C) 2016 Elsevier B.V. All rights reserved.