Variability of extreme summer precipitation over Circum-Bohai-Sea region during 1961-2008

The variability of extreme summer precipitation over Circum-Bohai-Sea region during 1961-2008 was investigated based on the daily precipitation data of 63 meteorological stations using the linear regression method, the non-parametric Mann-Kendall test, and the continuous wavelet transform method. The results showed that there were large spatial differences in the trends of extreme summer precipitation indices. Decreasing trends were found in summer total precipitation, extreme precipitation frequency, intensity and proportion, the maximum consecutive wet days (CWD), and the maximum 1- and 5-day precipitation, and the largest decrease was observed in the central coast area (except CWD), although the trends were not statistically significant at the 5% level at most places. Inversely, the maximum consecutive dry days exhibited non-significant increasing trends. Additionally, the significant 2-4-year periods were detected for eight indices, showing the significant interannual variability of extreme summer precipitation. Overall, the results of this study indicated that in the last 48 years, there was severe water stress over Circum-Bohai-Sea region, especially in the central coast area, which exerted negative effects on economic development and natural ecosystems.