Spatio-temporal characteristics of drought structure across China using an integrated drought index

摘要

Previous studies have focused on drought duration, intensity and frequency without explicitly investigating the timing of droughts, such as the drought onset and demise, as well as their transition periods, which is of importance for agricultural production. Furthermore, large discrepancies exist for those studies using a single variable based drought index. In this study, a nonparametric multivariate standardized drought index (NMSDI) that combines information about precipitation and streamflow was applied to investigate the spatial and temporal features of the drought structure in China. Subsequently, the relationships between El Nino-Southern Oscillation (ENSO) events and NMSDI variations were examined. The results indicate that: the NMSDI exhibited comparable performance when compared to the corresponding Standardized Precipitation Index and Standardized Streamflow Index, and importantly, it is more sensitive to capturing the onset, persistence, and termination of droughts; the preferred season of drought onset is in summer, with drought demise occurring in winter; the average drought duration in China is nearly 6 months, which is longer than the transition periods of drought onset (3 months) and demise (3 months); ENSO events have a strong influence on drought variations, with the effects depending on climate zones across China. Our results on the timing of droughts have important implications for drought mitigation and adaptation in China, which is helpful for agricultural production under the context of climate warming.