Drought Risk Assessment in Central Asia Using a Probabilistic Copula Function Approach

Abstract

The aim of this research is to adopt the Standardized Precipitation Evapotranspiration Index (SPEI) with three-month timescale (SPEI-3) to analyze drought risk in Central Asia. Based on SPEI-3, a drought event is defined through Run Theory. The multidimensional Copula function based on drought risk is then comprehensively assessed through the multivariable joint probability of drought duration, drought severity, and drought peak. Results indicate as follows: (1) the climate conditions were relatively stable from 1961–1974 and 1979–1995, while they varied from 1974 to 1979 and from 1995 to 2017, during which the study areas experienced recurrent drought. (2) The drought characteristics show noticeable spatial variability, and the severity of drought is larger in the west than in the east in Central Asia; the duration of drought contrasts with the severity of drought spatially. (3) The drought risk in the three-dimensional joint distribution is similar to the analysis using the two-dimensional distributions, and the study area has gone through the process from moderate to slight and then to severe drought risk from 1961 to 2017; the return period studied in this paper was calculated to be 80% probability in about two years.