Evaluation of compound precipitation and temperature extremes in a changing climate

Past studies on weather and climate extremes have focused on individual extremes. These studies cannot effectively track/model compound extreme events. The major objective of this study is to evaluate the changing risk of compound precipitation and temperature extreme events based on historical observed period (1964–2014) and the future period (2045-2054 and 2085-2094). We explored four different compound extreme event impacts of temperature and precipitation (dry-warm, dry-cold, wet-cold, and wet-warm) at the United States Department of Energy Office of Environmental Management (DOE-EM) sites. 25% and 75% quantile thresholds were used to define extreme climate conditions. The empirical approach for the analysis of compound extremes was conducted by counting the number of concurrent occurrences of multiple extremes during the same month (year). The empirical probability density function of compound events was constructed using nonparametric kernel density estimators to compare the seasonal distribution of four different compound event modes. Our results show slightly increasing trends in both Wet-Cold Mode and Wet-Warm Mode, and slightly decreasing trends in Dry-Cold Mode. Results from our study provide better understanding of the impact of climate extremes on mission-critical assets at EM cleanup sites.