中国近45年低温指数时空持续变化分析

Spatiotemporal change of consecutive cold day index in China in recent 45years

选取全国621个气象台站的逐日最低气温资料,分析了中国近45 a来持续低温指数(consec-utive cold day index,CCDI)的时空变化规律,得到如下几点结论:(1)近45a来,我国大部分地区CCDI呈下降趋势,仅在西南和华中地区的个别站点存在小幅的升高趋势;(2)以每10a为一个年代,在各个年代,我国北方地区CCDI值均高于南方地区。从20世纪60年代到90年代CCDI呈下降趋势,但进入21世纪,长城一线以北,特别是我国东北地区CCDI表现出明显的增大趋势;(3)REOF分析表明:以东北、华北、新疆北部和华中的部分地区CCDI的降低为特征的模态是近45a来CCDI变化的第一主要模态,但该典型模态自80年代以来表现趋弱,上述地区CCDI的降低趋势变缓,个别地区甚至出现增加的趋势。以成渝地区为中心的CCDI增大是近45a来CCDI变化的第二主要模态,且该模态在近45a表现稳定。

The spatiotemporal variation of consecutive cold day index （CCDI） was analyzed based on daily extreme low temperature data of 621 meteorological stations in China during recent 45 years. Results are as follows ： （ 1 ） The CCDI decreases in most regions of China, with some exceptions in southwest and central China in recent 45 years. （2） The CCDI in the northern part of China is higher than that in the South based on the data of every 10 year periods. From 1960s to 1990s, the CCDI had a decrease trend, however, it has increased since 2000s in the northern part of China （to the north of the Great Wall） , especially in northeast China. （3） The rotated empirical orthogonal function （REOF） analysis shows that the first mode of CCDI change is characterized by the CCDI decrease in northeast and north China, some regions of central China and northern part of Xinjiang Province in recent 45 years, however, this typical mode became weak since 1980s, with the CCDI decreasing in overall slower rate and a few occasional increasing in some stations. The second mode has high rotated eigenveetor loading value （negative value）, indicating the rising CCDI tendency around Chengdu and Chongqing, and behaves stably in recent 45 years.