西藏高原最高、最低气温的非对称变化

ASYMMETRIC CHANGE OF MAXIMUN AND MINIMUM TEMPERATURE IN TIBETAN PLATEAU FROM 1971 TO 2000

利用中国西藏高原 2 5个台站 1 971～ 2 0 0 0年月平均最高气温 (Tmax)、最低气温 (Tmin)及气温日较差 (ΔT) ,分析了西藏高原最高、最低气温的非对称变化。结果发现 ,西藏高原普遍存在非对称变化现象 ,以Tmax、Tmin显著上升 ,但Tmin上升幅度大于Tmax为主要类型。Tmax上升主要表现在夏季 ,Tmin增暖以秋季最为明显 ,ΔT显著变小主要是由于Tmin明显增暖引起的。Tmin的上升幅度随海拔高度的上升而增加 ,Tmax在 3 0 0 0～ 40 0 0m地区增温最大 ,而ΔT在 40 0 0m以上呈显著的减小趋势。

Monthly mean maximum (T max), minimum temperature (T min) and daily temperature differences (ΔT) at 25 stations over Tibet from 1971 to 2 00 0 are used to analyze the asymmetric change of maximum and minimum temperature i n the Tibetan Plateau. The results show: The asymmetry is detectable in the whol e Tibetand Plateau, and the typical pattern of asymmetry is the increase of T max and T min (T min increase is bigger then that of T max). The increase of T max occurs mainly in summer and that of T min in autumn an d ΔT decrease because of obviously increasing T min. In addition, T min increases with increasing altitude; increase is the strongest in the region of 3000 to 4000 m, and ΔT tends to decrease over 4000 m.