Space–time evolution of historical drought hazards in eastern China

Drought is one of the important topics of interest in meteorology, geography and history. In this study, drought index data of 531 years (1470–2000) from historical records are collected and organized. Eastern China which has been densely populated and prosperous throughout Chinese history is chosen as the study area. Geostatistical methods are used to represent the spatio-temporal distribution of drought hazards. The results show that the northern part of the study area has a higher frequency of droughts and the temporal variations of the distribution have characteristics of a climatic cycle. In order to consider both space and time dimensions, space–time permutation scan statistic method is introduced for drought hazard analysis in this study. With the method, 14 spatio-temporal clusters are detected in the data set. These clusters are grouped into five stages using the Space–Time–Cube model for visualization. An evolution trace of the high-frequency drought areas is depicted in the long temporal scale on the basis of the results. The trajectory rises spirally in the Space–Time–Cube and vacillates in both the north-west–south-east and north-east–south-west directions. The features of the trajectory are related to the variations in the East Asian summer monsoon and other climatic elements. The south-west region is still the high drought hazards incidence area in the current stage.