中文摘要：

在陆一气相互作用中，土壤热状况（土壤温度、土壤导热率等）和土壤湿度等陆面状况对大气环流和气候变化都有着重要影响。黄土高原横跨干旱、半干旱及半湿润地区，为我国第二大高原，幅员辽阔。该复杂下垫面上的陆一气相互作用不仅直接影响到黄土高原地区的气候和环境变化，而且对东亚、乃至全球的气候和环境变化都可能产生重要影响。而对黄土高原区域的土壤热状况及土壤温度的研究是黄土高原陆一气相互作用研究的重要组成部分。分析了黄土高原典型塬区不同下垫面的土壤温度状况，分析了造成各种下垫面温度分布和变化不同的原因，得到如下结论：在近地层，随着土壤深度的增加，土壤温度振幅逐渐减小，40cm土壤温度相对以上各层变化不明显。就季节变化而言，土壤温度在1a中有两次稳定状态。第一次出现在4月上旬，其值约为6oC左右；第二次出现在11月中旬，温度值为14℃。相对于全年土壤温度而言，在12月到次年2月有一个低温中心，温度低于零度；7—8月间有一个暖中心。各层土壤温度在1月份是最低的，其后一路上升，4、5月份是土壤温度快速上升期，至8月上旬土壤温度达到最大值，为土壤升温期；其后温度开始下降。土壤温度梯度具有明显的日变化特征，夜间，土壤的热量是从深层传向地表的，而随着太阳高度角的加大，土壤温度梯度转为负值，深层土壤从地表获得能量，到了傍晚19时左右，温度梯度又转为正值；土壤温度梯度的变幅在有植被时要明显小于无植被时。各站的日平均土壤导热率，柴寺、塬下和中心站分别是1．43，1．24，1．17W·m-1·k-1，土壤物理性质和土壤质地的不同是各站土壤温度分布和土壤热传导率存在差异的原因之一。

英文摘要：

In perature, soil and climate c the land- atmosphere interaction, land surface conditions such as soil thermal condition （ soil tem- thermal conductivity etc. ） and soil moisture etc. , have significant impact on atmospheric circulation hange. The Loess Plateau is the second biggest plateau in China with a vast territory, which lies a- thwart semi-arid, arid and semi-wet area. The land -atmosphere interaction on the complex underlying surface not only directly affect climate and environment changes of the Loess Plateau, but may also have an impact on those of East Asia, or even global. The study regarding soil heat condition and soil temperature of the Loess Plateau region is one of the most important components in the land - atmosphere interaction research on the Loess Plateau. The da- ta used in this paper were quoted from the observed data at Pingliang thunder and hail test station by Chinese Acad- emy of Sciences, cold and Arid Regions Environmental and Engineering Research Institute, as well as the soil tem- perature data from Baimiao plateau Central Meteorological Tower from October 2005 to November 2006. The field observation data during three consecutive years from 2004 to 2006 in Pingliang Baimiao Plateau on the＂ Loess Plat- eau of land - atmosphere interaction observation experiment study of （ Loess Plateau land surface＂ process field EX- periments, LOPEX ） in 2005 have also been analyzed. In this paper, we analyzed on soil temperature conditions of different underlying surfaces, as well as the causes of the diversity in underlying surface temperature distribution and variation from soil physical angle. The results have been shown as below： over the near surface layer, the soil temperature amplitude decreases gradually with the increase of soil depth, but do not change significantly at the depth lower than 40cm. As the seasons change, the soil temperature has two steady states during the whole year. The first one appears in early April, with the value of around 6 ~C ; the second one appea