Characteristics and Attribution of Winter Extreme Cold Indices in China

This study analyzes the characteristics and driving factors of winter extreme cold indices in China from 1961 to 2023, utilising observational data, CMIP6 climate model simulations, and atmospheric circulation indices. Three indices are examined, including the intensity of cold extremes (TNn), frost days (FD), and ice days (ID). Trend analysis since 1961 reveals a general weakening of winter cold extremes across China. However, 30‐year sliding trend analysis highlights notable regional and interdecadal fluctuation differences. In eastern China, the declining trends in the intensity of cold extremes, frost days, and ice days have decelerated in recent decades. Northeastern China has experienced an intensification of cold extremes since the 1990s, while western China continues to show a weakening of cold extremes; though the weakening trends in cold extremes have also slowed. Attribution analysis using CMIP6 simulations focusing on eastern China indicates that anthropogenic forcing has significantly weakened winter cold extremes. Further analysis reveals that the Arctic Oscillation (AO) plays an important role in modulating extreme cold events over eastern China. The negative AO phase and strengthened Siberian High correspond to increased cold extremes intensity, more frost and ice days. Future projections suggest a continued weakening of extreme cold intensity and a persistent decline in frost and ice days. Nonetheless, the interplay between long‐term trends and short‐term interdecadal fluctuations warrants ongoing attention, especially with intensifying Arctic warming, as eastern China remains at risk for extreme cold events. Enhancing regional climate adaptation strategies and improving early warning systems are recommended.