旱作春小麦蒸散量测算方法的比较

采用波文比—能量平衡法和蒸渗计对农田蒸散量进行了为期3a的对比观测试验。结果表明，在半干旱雨养农业区，两者测算的农田蒸散量平均偏差为20％，波文比—能量平衡法计算值大于蒸渗计实测值，基本满足精度要求；无感热平流时两种方法所得蒸散量相关性较有感热平流时的好；在平流逆温状态下采用波文比—能量平衡法的计算误差大于非平流状态下的计算误差；由于蒸渗计隔断了与周围农田的水热交换，导致了蒸渗计测量的蒸散量较采用波文比—能量平衡法的计算值偏低，其偏差大小需要进一步试验确定。

Comparison of Methods for Estimating Evapotranspiration in Rainfed Spring Wheat Field

Observation and experiment on the evapotranspiration rates (ET) of farmland were conducted in Dingxi Arid Meteorology and Ecological Environment Experimental Station, Institute of Arid Meteorology, CMA in 1993,1994 and 1996 by using Lysimeter technique and Bowen ratio-energy balance method (BREB). The results show that the BREB overestimated ET by about 20%, which can satisfy the accuracy demands in the semi-arid rainfed agricultural region. Moreover, the error in the BREB calculations of ET is smaller during non-advective periods than in advective periods. The agreement between the BREB method and Lysimeter technique on ET is better, but the Lysimeter technique underestimated ET because water and energy exchange is separated between Lysimeter and around field, and the exact error need to be confirmed by more observation study.