近45年拉萨浅层地温对气候变化的响应

Responses of Climatic Change on Soil Temperature at Shallow Layers in Lhasa from 1961 to 2005

利用1961-2005年拉萨0～40cm各层逐月平均地温,采用气候倾向率、累积距平、信噪比等气候统计方法,研究了近45年拉萨浅层平均地温的变化趋势、气候突变和异常年份等。结果表明:浅层各季节平均地温均呈现极显著的升高趋势,升温率为0.43～0.60℃/10a,春季最大,夏季最小。各层年平均地温以0.45～0.66℃/10a的升温率显著上升,40cm深度的升温率最大,与同时期平均气温的升温率比较,地温比气温对气候变暖的响应更强。20世纪60年代至90年代浅层年、季平均地温呈明显的逐年代升高趋势,以冬、春季最为明显。20世纪60年代到80年代中期为偏冷阶段,80年代后期至90年代地温为偏暖阶段。各浅层平均地温在1986年秋季均发生了突变,冬季突变时间都出现在1984年。年平均地温除在40cm处1999年异常偏高外,其它各层为异常偏低年份,且发生在20世纪60年代。气温升高是影响地温上升的主要原因。

The variation trend, abrupt change and anomalous years of annual and seasonal mean soil temperature at shallow layers during the period of 1961 - 2005 in Lhasa were investigated by using modern statistical diagnostic methods such as linear trend analysis, accumulated variance and signal noise ratio methods. The main results are as follows： （1）In terms of linear trend, theseasonal mean soil temperature at shallow layers displayed a significant increasing trend in Lhasa in past 45 years, and it indicated an increase of （0.43-0.60℃）/10a which was maximum in spring, minimum in summer. Also, the annual mean soil temperature at shallow layers had a significant increasing trend, and the rising rates were （0.45-0.66℃） /10a, specifically at the depth of 40cm. Compared to the air temperature, the rising range of soil temperature at 40cm was larger in the same period. （2） The inter-decadal variations of the annual and seasonal mean soil temperature in the shallow layers had an obvious increasing tendency from 1960s to 1990s, especially in winter and spring. The mean soil temperature was colder trom 1960s to the middle of 1980s, but it was warmer from the end of 1980s to 1990s. （3） The abrupt change of mean soil temperature at different shallow layers occurred in autumn of 1986, and all the abrupt change of winter appeared in 1984. （4） Except for the annual mean soil temperature at 40cm was anomalously high in 1999, anomalous lower years occurred in the 1960s at the other shallow layers. Therefore, the increase of the soil temperature was mainly caused by the significant increase of air temperature.