Variation of temperature extremes in wintertime over Beijing-Tianjin-Hebei region in the era of sharp decline of Arctic sea ice

The more frequent winter temperature extremes have exerted significant negative impacts on the coordinated development of the Beijing-Tianjin-Hebei(BTH) region of China during the recent decades. To more deeply understand the extreme temperature events(ETEs) in the region, in this study, the temperature intra-seasonal variability(TSV) and ETEs are investigated based on the observation data. Our results suggest that the TSV of wintertime over the BTH region has significantly amplified in the era of sharp decline of Arctic sea ice during 1990/1991-2020/2021, which is reflected by a polarization between warm and cold extremes, particularly increasing cold nights and temperature whiplash events. The amplified TSV is mainly driven by the abnormal atmospheric circulation triggered by rapidly melting autumn Arctic sea ice. The synergistic effects of obviously weakened polar vortex, significantly strengthened Ural Blocking High (UH) and Siberian High (SH), and increased days of extreme negative phase of Arctic Oscillation (AO), which are conducive to the inverted omega type circulation at 500 hPa, may cause more cold extremes and enhance the TSV in the BTH region since 1990/1991 winter. While global warming favors more frequent warm extremes in this region. We hope this study can help reduce the impact of ETEs and provide some scientific support for the coordinated development of the BTH region.