The regional characteristics of meteorological drought event and its multidimensional factors measurement by daily SPEI in Guangxi, China

The frequent occurrence of extreme drought events in Guangxi has caused huge losses to human beings and economy in the region for many years. For fine identification of drought evolution characteristics, this study adopted the objective identification method of regional extreme events (OITREE) to carry out the comprehensive feature identification involving multidimensional elements such as intensity, duration and area of meteorological drought events based on the daily standardized precipitation evapotranspiration index (SPEI) data of Guangxi from 1979 to 2018a. By comparing the evolution characteristics of drought elements identified by grid SPEI statistical analysis and OITREE, a comprehensive analysis framework for drought characteristics of multidimensional factor's measurement is formed in this study. Specifically, the grid analysis is more convenient to identify single point drought characteristics, and the OITREE method is better at describing the overall spatiotemporal evolution of drought events. The study found that flash droughts and seasonal droughts occurred alternately and were superimposed concurrently in Guangxi, and the multidimensional spatial and temporal characteristics of these two types of droughts were significantly different. In concrete terms, the average annual frequency of flash drought events in Guangxi was 2.0-3.8, the average annual duration varied from 20 to 60 d, and the concentration point of drought events had a region-wide dispersion; while the average annual frequency of seasonal drought events in Guangxi was 0.82-1.65, the average annual duration varied from 40 to 105 d, and the concentration point of drought events had a local concentration. Furthermore, for the flash drought, seasonal drought and total drought in Guangxi, the three-dimension clustering method was introduced to realize the comprehensive intensity spatial heterogeneity clustering partition and temporal heterogeneity clustering mapping of meteorological drought in Guangxi. The research results can provide important scientific support for promoting the operational risk assessment and regulation of regional drought disasters and forecasting and warning.