青藏铁路沿线1966-2004年冻结与融化指数的变化趋势

Variation Trends of the Freezing and Thawing Index along the Qinghai-Xizang Railway for the Period 1966-2004

利用日气温观测值计算了青藏铁路沿线7个主要气象站1966-2004年的年冻结与融化指数,分析了这些指数的统计与分布特征,并应用两种趋势检验方法:非参数Mann-Kendall检验法和简单线性回归法分析了这些台站年冻结与融化指数的变化趋势。结果表明,青藏铁路沿线多年平均冻结指数大致分布在95～2300oC·日之间,多年平均融化指数大致在630～3250oC·日之间。7个站点的冻结指数均呈减少趋势,其线性倾向率分布在-16.6～-59.1oC·日/10a之间;融化指数均呈增加趋势,其线性倾向率分布在19.8～45.6oC·日/10a之间。MK趋势检验的结果显示,除格尔木表现出微弱的减少趋势外,其他站点都呈现了0.05水平下的显著减少趋势;年融化指数除格尔木和沱沱河表现出弱增加趋势外,其他5个台站都显示出了0.05水平下的显著增加趋势。简单线性回归方法得到的趋势结果与MK趋势检验结果相一致。

Yearly freezing and thawing index for seven main stations along the Qinghai-Xizang Railway were calculated based on daily maximum and minimum temperature records for the period 1966-2004. Statistical characteristics and variations of the annual freezing and thawing index for these stations were outlined. Trends in annual freezing and thawing index for these stations were analyzed using two methods, namely a non-parametric trend test method, i.e. the Mann-Kendall test and a simple linear regression method. The results show that the mean annual freezing index for these stations ranges from 95 to 2300 ℃, and the mean annual thawing index ranges from 630 to 3250℃. The mean annual freezing index of the seven stationsexhibited decreasing trends with linear tendencies ranging from -16.6 to -59.1 ℃/10a, and the mean annual thawing index of the seven stations showed increasing trends with linear tendencies ranging from 19.83 to 45.6 ℃/10a. The results of the MK trend test show that the significant decreasing trends in the annual freezing index for most stations except for Golmud were detected at the 0.05 significant level. The increasing trends in the annual thawing index for four stations except Golmud and Tuotuohe were determined by the MK method at the 0.05 significant level. Golmud was the only station where no significant trends in both the annual freezing and thawing index were found. Results from the simply linear regression method are similar with that from the MK test.