Vertical variation and temporal trends of extreme precipitation indices in a complex topographical watershed in the Hengduan Mountain Region, China

Abstract

AbstractSpatial–temporal trends of extreme precipitation have great impacts on disaster risks, and relevant studies usually receive much attention. In China, spatial–temporal trends have been analysed in numerous studies based on daily rainfall data; however, the densities of rain gauges in many studies were relatively low, and the effects of complex topography on extreme precipitation were usually not considered, which have lowered the reliability and accuracy of the reported results. In this study, several widely used extreme precipitation indices were chosen, and the spatial–temporal trends of a typical watershed in the Hengduan Mountain Region in Southwest China, the Longchuanjiang watershed, were analysed using the Mann–Kendall trend analysis based on daily rainfall data. The effect of elevation on the extreme precipitation indices based on the high‐intensity rain gauges and the effect of elevation on the temporal trends of extreme precipitation indices were analysed, which have rarely been reported. The results indicated that: (a) significant positive correlations with elevation were reported for annual precipitation and most of the extreme precipitation indices, including PRCPTOT, Rx5day, R95P, R99P, RD, SDII, and CWD, while significant negative correlations were reported for CDD; the relationships between SDII and Rx1day were not significant with elevation; (b) the density of rain gauges in the regions with complex topography can have great impacts on the results; and (c) no significant correlation between the elevation and the temporal trends of extreme precipitation indices were reported. This study highlights the effects of the density of rain gauges and elevation, or topographical factors on the spatial distribution and temporal trends of extreme precipitation indices, which has rarely been reported in previous studies, implying that such effects should be fully taken into consideration in the relevant studies in the future.