Changes in seasonal maximum daily precipitation in China over the period 1961–2006

Abstract

ABSTRACTDaily rainfall data from 485 stations in China over the period 1961‐2006 are used to examine changes in seasonal extreme rainfall. We focus on the temporal changes in their distribution, together with examination of the dependence of seasonal extreme rainfall on elevation. The validity of the stationarity assumption is investigated by testing for nonstationarities in the form of abrupt and slowly varying changes. The nonparametric Pettitt test is used to detect change points in the mean and variance of the rainfall distribution, while the presence of monotonic trends and trend magnitude is tested using Mann‐Kendall test and Sen's slope estimator. Violation of the stationarity assumption is mostly associated with abrupt rather than gradual changes, and monotonic trends are generally not statistically significant. Most of the change points occurred in the 1980s, when China underwent a socioeconomic development. Extreme rainfall in autumn (spring and winter) points to a decreasing (increasing) tendency over the majority of the country, while summer extreme rainfall exhibits a ‘dipole‐like’ structure, with an overall tendency towards increasing trends in the south and decreasing in the north. The parameters of the Generalized Extreme Value (GEV) distribution are used to examine the dependence of extreme rainfall on elevation. The location and scale parameters are negatively correlated with elevation, while orography does not appear to be an important control on the shape parameter. The dependence of GEV parameters on elevation is more pronounced in northern rather than southern China. We also investigated the relation between summer extreme rainfall and climate variability, focusing on the East Asia Summer Monsoon (EASM) index. EASM is negatively (positively) correlated with summer extreme rainfall over South (North) China. Considering the weakening trend of EASM in recent years, there is a potential water shortage in the North China Plain and increasing flood risk in the south. Copyright © 2012 Royal Meteorological Society