准确获取地表蒸散发量对农业、生态、气候、水文等多个学科领域的研究和实际应用都具有非常重要的意义和参考价值。地面观测被认为是获取蒸散量最为准确的方法，研究地面多尺度蒸散发观测方法，分析不同方法观测结果的异同及产生差异的原因，为获取准确可靠的地面蒸散发观测数据提供理论依据。本文利用怀来站蒸渗仪、涡动相关仪、大孔径闪烁仪观测资料，结合自动气象站、无线传感器网络土壤水分数据和遥感卫星数据，比较了蒸渗仪观测的土壤蒸发、玉米农田蒸散日、季节变化，分析了米-百米-公里多尺度蒸散发观测仪器在水浇地和旱地农田观测结果的差异及差异产生的原因，主要得出以下结论：（1）玉米农田蒸散和土壤蒸发具有明显的季节性差异，生长初期，蒸散以土壤蒸发为主，二者差异较小，生长旺盛期，蒸散以玉米蒸腾为主，二者差异较为明显，生长末期，蒸腾作用减弱，二者变化逐步趋于一致。（2）农田土壤蒸发与农田玉米蒸散比值年际间变化差异明显，但2012年和 2013都在7月抽穗-灌浆时期比值最小，降水量大小和是否灌溉是造成2012和2013年玉米蒸散量差异的主要原因，辐射能量和土壤水分是影响怀来地区蒸散强度主要因子。（3）蒸渗仪观测尺度较小，其农田代表性主要由其观测范围内作物长势决定。相对于斑块尺度的涡动相关仪的观测，蒸渗仪观测值偏高，蒸渗仪与周围农田水热隔绝，是造成其蒸散量高估的主要原因。（4）涡动相关仪和大孔径闪烁仪在相对均一的农田下垫面观测结果较一致，观测源区内的灌溉情况、作物长势和下垫面的水热状况是造成涡动相关仪和大孔径闪烁观测差异的主要原因。（5）考虑下垫面类型不同，对两台蒸渗仪（裸土、玉米）和两台涡动相关仪（旱地、水浇地）观测值，分别按照大孔径闪烁仪观测源内裸土、农田面积比和旱地水、浇地面积比加权计算后，不同尺度蒸散发观测结果差异不明显。

Accurately obtaining surface evapotranspiration is of great values and can be referenced in the research and application among several subjects, like climate, hydrology, agriculture and ecology. Ground observation is considered the most accurate method of Obtaining evapotranspiration. Researching multi-scale evapotranspiration observation methods and analysis of the results of different methods of observation and the reasons casuing the differents provide a theoretical basis for obtaining accurate and reliable ground evapotranspiration observation data. Base on the measurements of lysimeter, Eddy covariance system(EC) and Large Aperture Scintillometer (LAS) combine with automatic weather station data, Wireless Sensor Network(WSN) observation data and satellite remote sensing data compare the daily and seasonal variation of soil evaporation and maize field evapotranspiration observated by lysimeters. The differences of multi-scale evapotranspiration（meters-hundred meters-Kilometers） observation and the reasons causing the differences are analyzed.The main conclusions are as follow: (1)By comparing the soil evaporation with maize field evapotranspiration, the daily variation curves are quite consistent, while seasonal differences were obvious,which chang with the growth of maize. (2)Soil evaporation and evapotranspiration ratio variation is not consistent, but in Heading - filling period the ration is the small in both years July. Precipitation size and whether irrigation is the mainly reasons caused the differernt of evapotranspiration between 2012 and 2013. Evapotranspiration is mainly affected by net radiation and soil moisture in huailai. (3) Lysimeter observations smaller scale and its farmland representative is main decisied by crops situation. Compared to EC Lysimeter overestimate evapotranspiration. As heat can not exchange between the soil in lysimeter and outside, which result in the evapotranspiration of lysimeter is relatively higher and the soil moisture is relatively lower than field. (4) The observations are quite consistent between EC and LAS in uniform underlying surface. Irrigation ,hydrothermal conditions and crop conditions is the main factors which cause the different between EC and LAS. (5) Consider the underlying surface types, according to the source of LAS, for both lysimeter (bare,maize) and EC (dryland, irrigated) observations weighted by the area ratio. Evapotranspiration observations at different scales are no significant differences.