Variability of precipitation extremes and dryness/wetness over the southeast coastal region of China, 1960-2014

The spatio-temporal variability of precipitation extremes was investigated over the southeast coastal region of China, based on daily precipitation records from 73 meteorological stations for the period of 1960-2014. The standardized precipitation index (SPI), rotatedempirical orthogonal function (REOF), and wavelet analysis methods were used to assess the characteristics of dryness/wetness patterns, as well as their correlations with the El Nino/Southern Oscillation (ENSO). Most of the extreme indices exhibited increasing trends at the regional scale over the past 55 years and generally had larger magnitudes than in other regions, with heavy precipitation that was more concentrated in time. The annual total wet day precipitation (PRCPTOT), total precipitation on very wet days (R95p), and total precipitation on extremely wet days (R99p) displayed sharp increases, with magnitudes of 22.60 (P=0.33), 21.50 (P=0.02) and 7.80 (P=0.06) mmdecade(-1), respectively. In contrast, the regional averaged maximum consecutive wet days (CWD) decreased by -0.10 daysdecade(-1) (P=0.48). The stations with sharp increases in extreme heavy precipitation were mainly located in the north and coastal areas. In addition, three dominant dryness/wetness patterns (REOFs) corresponding to different climatic partitions were identified. With regard to the time coefficients (PCs) of each REOF, no significant trend in PC1 was detected, while an increasing trend (P<0.001) in PC2 and decreasing trend (P < 0.001) in PC3 were found. The evolution of dryness/wetness occurred over a 4- to 12-year period in the first three REOFs, and their PCs all had significant positive correlations with ENSO at a 12-month lag time. This study suggests that the risks of heavy precipitation and flooding are likely to increase in southeast China, particularly in the northern and coastal areas, and extreme events may be strengthened in the southern subtropical zone during certain seasons.