Abstract:

Annual freezing and thawing index of 7 meteorological stations along the Qing-hai-Xizang Railway were calculated based on daily maximum and minimum temperature records for 1966?2004. Trends of annual freezing and thawing index were analyzed using the Mann-Kendall test and a simple linear regression method. The results show that: 1) The mean annual freezing indices range from 95 to 2300℃·d and the mean annual thawing indi-ces range from 630 to 3250℃·d. The mean annual freezing index of the 7 stations exhibited decreasing trends with decreasing rate of ?16.6– ?59.1℃·d /10a. The mean annual thawing index of these 7 stations showed increasing trends with the related decreasing rate is 19.83–45.6℃·d /10a. 2) The MK trend test indicated the significant decreasing trends (sig-nificant at < 0.05 significant level) in the annual freezing index for most stations except for Golmud. The significant increasing trends can be observed in the annual thawing index for 4 stations except Golmud and Tuotuohe. Golmud was the only station with no trends in both annual freezing and annual thawing index.

Key words: freezing and thawing index, global warming, trends, Qinghai-Xizang Railway