半干旱地区土壤湿度变化特征

利用兰州大学半干旱气候与环境观测站(SACOL)站2006年5月至2009年12月5～80 cm的土壤体积含水量间隔半小时的数据,分析了半干旱地区土壤湿度变化特征.结果表明:5～40 cm土壤湿度有明显的季节变化,呈现出三高三低的变化特征,80 cm土壤湿度季节变化不明显；土壤湿度浅层比深层波动大,5～80 cm各层土壤体积含水量平均日较差依次为1.08％,0.57％,0.25％,0.11％,0.04％,相比于10 cm土壤体积含水量5.71％的方差,80 cm的方差只有2.69％；土壤湿度大小因土壤深度、季节和天气背景不同而有所差异,春、夏、秋季土壤湿度随深度加深呈降低型,冬季呈现增长型；随着深度的加深,上下层土壤湿度的相关性逐渐减弱,滞后时间在增加,滞后时间最短为3.5h,最长为35 h.

Changes characteristics of the soil moisture in semi-arid areas

Analysised the change characteristic of soil moisture in semi-arid area by using the soil moisture data 5～80 cm soil layer observed every half hour in SACOL station from May 2006 to December 2009.The results show that the seasonal changes in soil moisture in 5～40 cm soil layers are obvious,which manifest characteristic of three high and three low trend;in the 80 cm soil layer the seasonal changes are not obvious.The fluctuation of soil moisture in shallow layer is larger than that in deep layer,the average daily range of the soil moisture content of each layer 5～80 cm is 1.08%,0.57%,0.25%,0.11%and 0.04%respectively.The variance of the 10 cm layer is 5.71%,while the 80 cm layer’s is only 2.69%.Soil moisture changes with the depth of the soil layer, season and weather background.With the deepening of soil layer,the soil moisture is increasing in winter, however the situation is opposite in other seasons.The time lag of soil moisture between the upper and lower soil layer is increasing when the soil layer deepens,the shortest is 3.5 hours and the longest is 35 hours;but the correlation of soil moisture between the upper and lower soil layer decreases.