Assessment of the hazard of extreme low-temperature events over China in 2021

In January 2021,an impressive extreme low-temperature event(ELTE)occurred in China,bringing record-breaking low temperatures to some regions.The comprehensive hazard and the overall situation of ELTEs in the whole of 2021 are still unclear.Accordingly,the overview of ELTEs over the mainland in 2021 and their hazards were systematically reviewed and comprehensively evaluated by using an improved identification and assessment method,which can objectively determine the hazard levels of ELTEs and distinguish spatial differences in the hazard of a single event.A total of 20 ELTEs occurred in 2021;their intensity was remarkably higher than the climatology,while the impacted area and duration were lower than or near the climatology,indicating a normal hazard.In general,the losses of low-temperature related disasters in 2021 were relatively less than the average loss in the past ten years,which is likely related to the low proportion of higher-than-moderately low events in the whole year.ELTEs in 2021 had large impacts on Northwest,North and Northeast China and small impacts on the southeastern Qinghai-Tibet Plateau and western parts of Southwest China.Winter and autumn had a higher-than-normal hazard index for ELTEs due to two high-hazard events in early-to-mid January and early-to-mid November,respectively.These two high-hazard events showed different spatial impacts.The former mainly affected central and eastern parts of China.However,the latter mostly attacked central and western parts of China,especially resulting in high-hazard in parts of Xinjiang.