夏季不同土壤湿度和天气背景条件下绿洲土壤温湿特征的个例分析

 利用在甘肃省酒泉金塔地区开展的“绿洲沙漠能量和水分循环观测试验(JTEX)”获得的2005年5—7月的补充观测资料,分析了在不同土壤湿度和天气背景条件下的夏季绿洲农田土壤温、湿场特征。结果表明：一般来说,对于5—40 cm深度的土壤,随着深度的增加其湿度也随之增加。5 cm、10 cm的土壤湿度具有明显的日变化,且在中午时最为湿润;20 cm土壤湿度的日变化幅度小于上两层,变化趋势却与5 cm的相反;40 cm土壤湿度的日变化不明显。晴天浅层的土壤湿度日变化大于阴天。晴天个例中,土壤湿度较大时,5 cm土壤在白天比10 cm的湿润;当土壤较为干燥时,全天浅层土壤湿度都小于较深层的。各层土壤温度在一个中心值周围分布, 40 cm深度以上土壤温度均具有明显的日变化;土壤温度的极值出现时间滞后于地表温度,离地面的距离越大,峰值出现的时间比地表温度滞后的越长,且变化幅度越小。晴天的土壤湿度越小,浅层土壤湿度日变化幅度就越大,各层土壤温度也就越高。土壤深层基本不受天气情况的影响,但受灌溉的影响较大。

Characteristics of Temperature and Moisture of Jinta Oasis in Summer under Different Soil Moisture and Weather Conditions

Based on the data got from "The Energy and Water Cycle Field Experiment"(JTEX) held from May to July 2005 in Jinta Oasis of Jiuquan district in Gansu Province,the characteristics of temperature and moisture fields of farmland in Jinta oasis were analyzed.The results showed that the soil moisture content increased along with the soil depth deepening from 5cm to 40 cm under the surface layer.The diurnal changes of soil moisture at 5cm and 10cm were obvious,and were biggest at noon;the diurnal change at 20 cm was not obvious as that at the above two depths and the changing trend was opposite to that at 5 cm;the diurnal change at 40 cm was nearly even.The change amplitude of shallow soil moisture in a sunny day was smaller than that in a cloudy day.In sunny day case,when the soil was relatively moist,5 cm soil was moister than 10 cm soil;when the soil was relatively dry,the shallower soil was drier than the deeper in all the day.The temperature of 5-40 cm soil varied surrounding a center value and had obvious diurnal variation except the 40 cm soil temperature.The maximum of soil temperature appeared later than that of surface temperature,and further from surface,later the maximum appeared and smaller the range of diurnal variation.In a sunny day,smaller the soil moisture,bigger its daily variation range,and also the higher temperature of 5-20 cm soil.The soil far from the surface was almost not affected by the weather condition but could be affected by the irrigation.