A Regional Approach of Decadal Assessment of Extreme Precipitation Estimates: A Case Study in the Yangtze River Basin, China

Changes in overall observed precipitation have been recognized in many parts of the world in recent decades, leading to the argument on climate change and its impact on extreme precipitation. However, the concept of natural variations and the complex physical mechanisms hidden in the observed data sets must also be taken into consideration. This study aims to examine the matter further with reference to inter-decadal variability in extreme precipitation quantiles appropriate for risk analysis. Temporal changes in extreme precipitation are assessed using a parametric approach incorporating a regional method in region-of-influence form. The index-flood method with the application of generalized extreme value distribution is used to estimate the decadal extreme precipitation. The study also performs a significance test to determine whether the decadal extremes are significant. A case study is performed on the Yangtze River Basin, where annual maximum 1-day precipitation data for 180 stations were analyzed over a 50-year period from 1961 to 2010. Extreme quantiles estimated from the 1990s data emerged as the significant values on several occasions. The immediate drop in the quantile values in the following decade, however, suggested that it is not practical to assign more weight to recent data for the quantile estimation process. The temporal patterns identified are in line with the previous studies conducted in the region and thus make it an alternative way to perform decadal analysis with an advantage that the scheme can be transferred to ungauged conditions.