大孔径闪烁仪与涡度相关系统对灌溉农田蒸散量的对比观测

蒸散是地表能量平衡的重要组成部分, 在土壤-植物-大气连续体的能量、质量、动量交换过程中起着重要作用。大孔径闪烁仪(LAS)是近时期兴起的观测跨像元尺度地表通量的地面仪器, 为验证其观测数据的可靠性, 本文把专家认可且在中国生态系统研究网络(CERN)中广泛应用的涡度相关仪(EC)的观测数据作为参考依据, 于2010 年8 月在中国科学院栾城农业生态系统试验站夏玉米田对大孔径闪烁仪计算结果进行验证。验证结果表明, 两种仪器测定的地表感热通量日变化和月变化观测结果基本一致。由于下垫面属性、环境因子及观测范围等因素的影响, 大孔径闪烁仪与涡度相关仪观测的蒸散量日变化之间有一定的差异，但日蒸散总量的测定基本一致。试验证明了大孔径闪烁仪观测数据的准确性。将大孔径闪烁仪计算的蒸散量与涡度相关仪观测值进行线性回归分析, 二者的吻合度较高(R²=0.800 4)。研究结果显示, 大孔径闪烁仪在地表水热通量的数据监测中具有很大的使用价值, 为日后用大孔径闪烁仪验证遥感估算蒸散值奠定了基础。

Comparative advantages of Large Aperture Scintillometer and Eddy Covariance instrument for measuring evapotranspiration in irrigated farmlands

Evapotranspiration (ET), a critical element of surface energy balance, plays an important role in the exchange of energy, mass and momentum in the soil-plant-atmosphere continuum. Large Aperture Scintillometer (LAS) is recent emerging instrument put on the ground to observe surface fluxes across pixel dimensions. This study validated the reliability of LAS observations with observation data from Eddy Covariance (EC) instruments. EC is the officially recognized and commonly used ET equipment in the Chinese Ecosystem Research Network (CERN). Heat flux was measured in summer maize fields via both LAS and EC at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in August 2010 and compared. The results showed a significant consistency in both daily and monthly changes in heat flux measurements by LAS and EC. ET obtained from LAS was almost consistent with that from EC (R²=0.800 4) at the monthly scale. However, some differences existed in the daily change probably due to the effects of underlying principles, environment conditions and measurement scale. The study suggested that surface water and heat flux data collected via LAS was reliable and applicable in verifying estimated ET via remote sensing.