河西走廊中部干旱区陆面水分和辐射特征研究

Characteristics of Land Surface Moisture and Radiation in Arid Region in the Middle of Hexi Corridor

利用河西张掖试验站2005年11月—2006年10月的陆面过程观测资料,研究了河西中部干旱区土壤温度、土壤湿度、降水量、地表反照率、地表辐射分量和土壤热通量等物理量的年变化和日变化特征及其影响机制,分析了土壤湿度与降水量的相关关系、地表反照率与降水量及土壤湿度的相关关系。结果表明：干旱荒漠地区土壤温度对太阳加热的响应比较迅速,而且年较差和日较差也比较大。地表层土壤主要受蒸发和降水的影响,土壤湿度变化响应得较快,而深层土壤湿度基本不受地表影响,在冬季土壤湿度变化对降水的响应要滞后1~2个月。降水量与5 cm土壤湿度的相关最好,与深层50cm的土壤湿度相关最差。地表反照率的起伏变化与降水过程对应的比较好,反照率的谷值正好对应降水过程比较集中的时段。地表反照率随土壤湿度的增大是减小的,两者的相关系数达到了0.7346。干旱荒漠区辐射分量年变化幅度普遍比较大,年平均日变化特征表现为非常典型而平滑的日循环形态。土壤冬季向大气输出热量而夏季转变为大气向土壤输入热量,且输入的热量要大于输出。随着季节变化,土壤热通量的日最大值冬季出现最晚、夏季最早,与20 cm土壤温度的变化趋势基本一致。

Utilizing the data of land-surface process obtained in the middle of Zhangye of arid region in Hexi Corridor during about one year from November 2005 to October 2006,the annual and diurnal variation characteristics and influence mechanism of the soil temperature,soil moisture,amount of precipitation,surface albedo,surface radiation and soil heat flux are studied.The relationship of soil moisture with amount of precipitation,surface albedo with amount of precipitation and soil moisture are also analyzed.The results show that in the arid desert region the soil temperature responses to the solar heating rapidly,and annual and diurnal ranges are large.The soil moisture of surface soil affected by evaporation and precipitation changes quickly,while the deep soil moisture is always unaffected.The response of soil moisture to the precipitation in winter delays 1 or 2 months.The relationship of precipitation with 5 cm soil moisture is the best,but is the worst with 50 cm soil moisture.The fluctuations of surface albedo well relate to the precipitation well and the extreme values are just corresponded to the concentrated precipitation periods.Surface albedo increases with the soil moisture decreasing,and their correlation coefficient gets up 0.7346.The annual variations of surface radiation in the arid desert region are generally large.The characteristics of diurnal variation through a year show a typical smooth daily cycle curve.The heat is exported from soil to atmosphere in winter while imported from atmosphere to soil in summer.The import is lager than export.The diurnal maximum value of soil heat flux is the latest in winter and earliest in summer,which change tendency is generally consistent with 20 cm soil temperature.