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青藏高原土壤湿度的时空变化在高原能水循环中起着重要作用。利用GAME-Tibet期间观测的青藏高原中部BJ站2001年1月1日~2005年12月31日00:00~230:0逐时高分辨率土壤湿度资料,分析了4~210 cm深度土壤湿度的日、季节和年际等不同时间尺度的变化特征。结果表明:(1)4 cm深度土壤湿度日变化显著2,0~210 cm深度土壤湿度日变化微弱;土壤湿度日振幅随土壤深度的增加逐渐衰减,但在210 cm深度又出现增加的趋势;4 cm、20 cm、60 cm、100 cm1、60 cm和210cm深度土壤湿度的平均日振幅分别为0.97%、0.22%、0.03%、0.01%、0.01%和0.03%。(2)根据土壤湿度在时间尺度和垂直剖面上的变化特征,将土壤湿度年内的变化过程划分为积累期(3~8月)、衰减期(8~12月)和相对稳定期(12~3月)3个阶段。(3)2001~2005年,BJ站4 cm、20 cm、60 cm、100 cm和160 cm深度土壤湿度8月的平均值表现为线性增加的趋势,210 cm深度土壤湿度8月的平均值则呈现出线性减小的趋势;湿季,土壤湿度显著地受到降水的影响,干季,土壤湿度主要受土壤温度的影响。
The temporal and spatial variations of soil moisture in the Tibetan Plateau play an important role in the cycling of plateau water. Based on the hourly high resolution soil moisture data from January 1, 2001 to December 31, 2005 at the central Tibetan Plateau observed during the GAME-Tibet period, the soil moisture at 4 ~ 210 cm depth was analyzed The daily, seasonal and interannual changes in different time scales. The results showed that: (1) The diurnal variation of soil moisture at 4 cm depth was significant. The diurnal variation of soil moisture at 2,0 ~ 210 cm depth was weak. The daily amplitude of soil moisture decreased gradually with the increase of soil depth, but increased at the depth of 210 cm. The average daily amplitudes of soil moisture at depths of 4 cm, 20 cm, 60 cm, 100 cm1, 60 cm and 210 cm were 0.97%, 0.22%, 0.03%, 0.01%, 0.01% and 0.03%, respectively. (2) According to the variation characteristics of soil moisture in time scale and vertical section, the change process of soil moisture in the year was divided into accumulation period (March to August), decay period (August to December) and relative stable period (12 ~ March) 3 stages. (3) From 2001 to 2005, the mean values of soil moisture in August at 4 cm, 20 cm, 60 cm, 100 cm and 160 cm depths at BJ stations showed a linear increase trend, and the mean of 210 cm soil moisture at August was at August Showing a trend of decreasing linearly. In wet season, soil moisture was significantly affected by precipitation. In dry season, soil moisture was mainly affected by soil temperature.