中文摘要：

利用涡度相关系统（EC）和波文比系统（BREB）监测干旱区农田蒸散发变化，从时间步长、天气条件、生育期以及灌溉的影响四方面人手，对比研究了两种方法在测定农田蒸散发方面的差异，并从仪器测量精度以及大气湍流稳定状况两个方面着重分析了引起这两种观测方法产生差异的原因。结果表明：R0-G测定的不确定性及温湿度探头精度是引起两种方法测定差异的主要原因。受BREB传感器精度的限制，灌水后该法测定农田蒸散发偏低。受大气湍流稳定度的影响，晴天条件下两种方法测定蒸散发差异较小，阴天条件下差异较大。相对于EC而言，全生育期BREB高估总蒸散发约6．1％；在生育前期BREB测定蒸散发偏高，生育后期测定蒸散发偏低。

英文摘要：

Measuring field evapotranspiration （ET） accurately is of great importance in investigating the hydrologic process, developing hydrological models and improving the water use efficiency. Bowen ratio-energy balance method （BREB） and Eddy covariance method （EC） were used to monitor the process of field evapotranspiration in the oasis of Northwest China. Probably there is discrepancy between ET value evaluated by these two methods when time scale, weather condition and growth stages are different. This paper examined the effects of equipment resolution and atmospheric stability on the discrepancy. The results show that the uncertainty of Rn-G and the resolution of sensors have a strong effect on the discrepancy. Due to the limited resolution, BREB underestimated ET after irrigation. The discrepancy is higher during the cloudy days under stable atmospheric conditions than that during the sunny days under unstable atmospheric conditions. Compared with EC, the total ET estimated by BREB was 6.1% higher. BREB overestimated daily ET during the early growth stage, while underestimated it during the late growth stage.