基于再分析资料的近百年中国极端冷事件的变化

Changes of extreme cold events in China over the last century based on reanalysis data

全球变暖背景下,中国区域极端冷事件发生明显变化。由于观测资料的限制,近百年极端冷事件变化特征的研究还较少。通过对比观测资料和两套百年尺度的再分析资料计算得到的13个极端冷事件指数,对中国区域极端冷事件变化特征的分析表明:同全球变暖一致,20世纪早期以来,中国极端冷事件的强度、频率、持续时间均呈减小趋势,基于过冷系数定义的寒流次数、持续日数均呈现减少趋势,采暖度日数减小,反映我国供暖能源需求呈减少趋势。1951年以后极端冷事件的特征的变化更为显著,一些指数的变化明显超过百年尺度的变化,说明20世纪中期以后冷事件迅速减弱、减少。两套百年尺度的再分析资料可用来研究中国区域极端冷事件变化,但在资料匮乏的地区不确定性很大,需要谨慎考虑资料分布范围和资料质量等问题。

Significant changes of extreme cold events in China have occurred in the background of global warming.There are few studies focusing on the characteristics of extreme cold event change in the last century due to the limitation of observation data.By comparing the ETCCDI(Expert Team on Climate Change Detection and Indices)and the newly extended ET-SCI(Expert Team on Sector-specific Climate Indices)calculated from observations and two century-scale reanalysis datasets(NOAA-20CRv2 and ERA-20C),we analyzed the characteristics of the changes of extreme cold events in China.Consisting with global warming,the intensity,frequency,and duration of extreme cold events in China showed a decreasing trend since the early 20th century.Meanwhile,the number and duration of cold wave defined based on the ECF(Excess Cold Factor)presented the trend of reduction,and the decrease in Heating Degree Day(HDD)reflected the decreasing trend of heating energy demand in China.Trends of the characteristics of extreme cold event were more pronounced after 1951 in China,with trends of some indices significantly exceeding the century trends.The above showed that cold events had decreased rapidly since the mid-20th century.It’s worth noting that the two sets of centennial scale reanalysis data can be used to study the changes of regional extreme cold events in China,but the uncertainties are large in areas with insufficient spatio-temporal coverage of site observations,and the deficiencies caused by spatial coverage and quality issues need to be carefully considered.