藏北高原D110点不同季节土壤温度的日变化特征

The Daily Variation of the Soil Temperature in Different Seasons at Site D110 in the Northern Part of Xizang Plateau

利用１９９８ 年ＧＡＭＥＴｉｂｅｔ 加强观测期间取得的一个年周期的土壤温度资料，对藏北高原Ｄ１１０ 点土壤温度日变化特征的月际变化进行了分析。结果表明，在夏半年（５ ～９ 月） 土壤温度存在明显的日变化（ 可达４０ｃｍ 深处） ，且基本上按正弦曲线变化，但相位随深度的增加而滞后；冬半年（１０ ～４ 月） 土壤温度尽管也存在日变化，但变幅较小。就所研究的时段而言，６ 月地表土壤温度的日变化最大。一年中最低温度的变化较小且平稳；而最高温度的变化较大，尤其是９ 月到１０ 月的降温过程和４ 月到５ 月的升温过程都相当剧烈。

Based on the soil temperature data obtained in IOP period of GAME Tibet, 1998, the monthly changes of daily variation features of the soil temperature in D110 site, the northern part of the Xizang Plateau, have been analyzed. The results show that the soil temperature existed evident daily variation in summer season (May-September). It is a sine curve and consistent with solar radiation. However, the phase lagged as the depth increase. In winter season (October-April), there was also daily variation, but the amplitude was relatively small. As to the study period, the maximum daily variation appeared in August 1997. Then it decreased. In May 1998, the daily variation increased suddenly and reached to the highest point in June 1998. Meanwhile, the variation of the minimum temperature was small and gentle, but the maximum was large. In summer, the daily variation of the soil temperature at 40?cm depth is also evident. Its variation is fundamentally a sine curve and consistent with solar radiation. However, its phase is lagged as the depth increase. The transport direction of energy between surface and its below layer could change two times in summer. In winter, although the soil temperature showed relatively evident daily variation and played as sine curve, the temperature on surface was always below that of under layer. Even the surface could absorb the solar energy, but it was too little. The energy was transported from lower layer to upper layer all the day in winter.