西藏浅层地温气候特征分析及与降水的关系

FEATURES OF TIBET SOIL TEMPERATURE AND ITS RELATION WITH RAINFALL

选择了西藏地区建站早、有代表性的１５个站１９６１～１９９６年逐月１０ｃｍ、２０ｃｍ、４０ｃｍ三个层次的地温资料以及月降水量资料。运用ＥＯＦ方法分析了各层地温的时空特征，并对不同时段的地温场和降水场进行ＳＶＤ分解，并讨论了前期地温变化，尤其是１０ｃｍ地温变化与我区降水之间的关系。分析表明，浅层地温最高值雅鲁藏布江中游地区出现在６月，其它各地一般出现在７月，最低值全区均出现在１月。地温年较差雅鲁藏布江中游地区最小，林芝、昌都次之，阿里地区最大。雅鲁藏布江中游大部分地区近３６年浅层地温呈现上升趋势，且冬春季升温幅度较汛期要高。阿里、昌都及林芝变化则不明显。地温阿里地区最低，低值中心靠近改则，昌都的西北部和南部为两个次低值区；雅江一线、东南部地温较高，最高值中心在察隅，次高值在泽当～林芝的沿江地区。１０、２０、４０ｃｍ地温年变化和冬春季、汛期变化存在准３年或准６年的周期性规律。前期地温场变化，特别是１０ｃｍ地温变化与降水有着密切的联系。大部分地区，特别是雅江中游地区和阿里地区、冬春季地温偏高（低），汛期降水偏少（多）。

The monthly mean soil temperature data(10cm,20cm and 40cm) and the monthly railfall data of 15 station(between 1961 and 1996) are used.Based on the empirical orthogonal function(EOF) and singular value decomposition(SVD) method the spatial distribution and time variation of soil temperatures in the plateau are analysed.The relation between the rainfall and the previous seasonal soil temperature condition is discussed. 1.The highest soil temperature occur in June and July and the lowest in January.The soil temperature difference along the Yarlung Zangbo River is the smallest,the biggest one is located at Ngari. 2.The time series of soil temperatures along the Yarlung Zangbo Rive show that it has an increase,which is bigger in winter than that in summer. 3.The spatial distribution of soil temperatures shows that the lowest center is in the northwest region and the highest in the southeast region. 4.The EOF analysis shows there exist quasi triennial and quasi six years oscillations of the annual and seasonal variation of soil temperatures. 5.The SVD analysis indicates there is a close ties between the rainfall and pre seasonal variation of soil temperature(expecially for the 10cm ST).In most regions of the plateau,if the pre seasonal soil temperature is above(below) normal,the rainfall goes below(above) normal.