近51年我国对流层顶高度的变化特征

Characteristic of Tropopause Height over China in Recent 51 Years

利用NCEP/NCAR的对流层顶气压多年月平均和逐月平均再分析资料,运用EOF和REOF方法对近51年中国对流层顶高度的空间分布和时间演变特征进行了详细分析。结果表明,中国地区热带对流层顶(第二对流层顶)和极地对流层顶(第一对流层顶)的边界线,2月最南,8月最北,较高的热带对流层顶从2月开始,逐渐北进,8月到达最北界(44°N附近),然后开始南退,2月其北界处于最南端,在29°～30°N附近;我国29°～44°N之间的中纬度地区,对流层顶高度的年变化幅度较大;对流层顶高度场有三种主要的模态:第一种为全区一致的偏高(偏低)型;第二种为南高(低)北低(高)的南北相反分布型;第三种为南北地区-中部地区相反分布型。对对流层顶高度场进行REOF分解可将中国地区分为6个气候分区,即华南区、新疆区、东北区、华北区、长江流域区和青藏高原区,各区对流层顶高度最大值一般都出现在夏季,最小值出现在冬季,只有华南区的最大值出现在春季,最小值出现在夏季。中国地区对流层顶高度的年际变化和长期趋势具有十分明显的区域性。

Using the long term monthly mean pressure and monthly mean pressure data on tropopause of NCEP/NCAR reanalysis data,the spatial distributional and temporal evolution of tropopause height over China in recent 51 years are studied by Empirical Orthogonal Function（EOF） and Rotated Empirical Orthogonal Function（REOF） methods.The results show that the boundary line between the tropical tropopause（the second tropopause） and the polar tropopause（the first tropopause） is on the most southern side of China in February and on the most northern side of China in August.The higher tropical tropopause gradually moves too north since February and reaches the north-edge about 44°N in August,and then withdraws southward and reaches the south-edge about 29°~30°N in February.Annual variation amplitude of the tropopause height is greater in the region of 29°~44°N in China.There are three main EOF modes of tropopause height field： The first EOF mode is consistently higher（lower） than normal;the second EOF mode is a opposite pattern between southern（northern） region and northern（southern） region;the third EOF mode is a opposite pattern between northern-southern（central） region and central（northern-southern） region.Furthermore,based on the data of tropopause height field,the studied region can be divided into 6 sub-regions by REOF.They are South China,Xinjiang region,Northeast China,North China,the Yangtze River valley and Tibet Plateau area.The maximum tropopause height generally occurs in summer and the minimum occurs in winter in each region except for South China.In South China,the maximum tropopause height occurs in spring and the minimum occurs in summer.The interannual change and secular trend of the tropopause height show obvious regional differences.