波文比仪与蒸渗仪测定作物蒸发蒸腾量对比

为了更准确地估算作物蒸发蒸腾量，该文结合波文比仪和大型称重式蒸渗仪，对波文比-能量平衡法估算的冬小麦蒸发蒸腾量（ET_b）和蒸渗仪实测的冬小麦蒸发蒸腾量（ET_l）进行了分析研究。结果表明，波文比计算值（ET_b）和蒸渗仪实测值（ET_l）的变化趋势基本一致，相关性比较好。波文比计算值（ET_b）和蒸渗仪实测值（ET_l）的日变化曲线都呈单峰型，早晚小，中午大，夜间多为负值，波文比计算值的日变化比较稳定，蒸渗仪实测值的日变化比较敏感。风速较大时，蒸渗仪实测值日变化随风速的增大而减小的趋势比较明显，波文比计算值日变化受大的风速影响较小；风速较小时，波文比计算值和蒸渗仪实测值的日变化与风速呈很弱的负相关关系。波文比计算值日变化和太阳净辐射日变化的关系比较密切，蒸渗仪实测值日变化和太阳净辐射日变化的关系不是很明显。波文比计算值更能稳定地反映出冬小麦蒸发蒸腾量的日变化规律。

Comparative study of crop evapotranspiration measured by Bowen ratio and lysimeter

Crop evapotranspiration provides scientific basis for rational irrigation and water resources allocation. In order to estimate the crop evapotranspiration accurately, two evapotranspiration variables of winter wheat were analyzed. One was estimated by Bowen ratio-energy balance equation (ET_b), the other was measured by lysimeter (ET_l). The results indicated that the variations of ET_b were almost the same as those of ET_l. Variations of ET_b and ET_l were single peak curves. Their values were bigger at noon, and smaller in the morning and evening, and negative at night. The diurnal variation of ET_b was smaller than that of ET_l. Their diurnal variations were weakly negatively correlated with wind speed if the wind speed was small, but if the wind speed was big, the trend that ET_l decreases with the increase of wind speed was obvious. The ET_b was highly related to net solar radiation, while ET_l was not obviously related to net solar radiation. Crop evapotranspiration estimated by Bowen ratio represents the diurnal variation more steadily.