A Revised Temporal Scaling Method to Yield Better ET Estimates at a Regional Scale
A Revised Temporal Scaling Method to Yield Better ET Estimates at a Regional Scale
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DOI：
10.3390/rs70506433
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发表时间：
2015-05
期刊：
影响因子：
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通讯作者：
Yi Song;M. Ma;Long Jin;Xufeng Wang
中科院分区：
文献类型：
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作者：
Yi Song;M. Ma;Long Jin;Xufeng Wang
本文提出了一种基于蒸发分数（EF）时间稳定性检测算法的修正时间标度方法，用于估算区域尺度上的总蒸散发（ET）。研究区位于中国第二大内陆河流域黑河流域。本研究使用的遥感数据和野外观测数据来自黑河流域联合遥测实验研究（HiWATER）项目。利用涡动相关（EC）系统和自动气象站（AMS）的气象观测计算得到的半小时EF值（EFEC）代表了研究区内大部分地区的EF日变化。利用先进星载热发射与反射辐射计（ASTER）遥感图像计算正午瞬时辐射量（EFASTER），反映了整个研究区正午辐射量的空间分布。利用一种检测算法检验了EFEC的时间稳定性。EFEC值不一致的区间与EFEC值一致的区间有明显区别；白天总ET（9:00 - 19:00）分别进行综合。利用来自17个EC塔的测量数据，在卫星像元尺度上验证了白天总ET。采用时间尺度法检测EF的时间稳定性和动态平差，修正时间尺度法的均方根误差（RMSE）为0.54 (mm·d - 1)，平均相对误差（MRE）为7.26%，相关系数（Corr.）为0.81；这些值都优于其他两种方法（即恒定EF和可变EF方法）。修正后的方法易于推广到其他地区，并在区域尺度上对平坦和定期灌溉的农田表现出优越的性能。
This study presents a revised temporal scaling method based on a detection algorithm for the temporal stability of the evaporative fraction (EF) to estimate total daytime evapotranspiration (ET) at a regional scale. The study area is located in the Heihe River Basin, which is the second largest inland river basin in China. The remote sensing data and field observations used in this study were obtained from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) project. The half-hourly EF values (EFEC) calculated using meteorological observations from an eddy covariance (EC) system and an automatic meteorological station (AMS) represented the diurnal pattern of the EF across the majority of the study area. The remotely sensed instantaneous midday EF (EFASTER), which indicates the spatial distribution of the midday EF over the entire study area, was calculated from an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image. The temporal stability of EFEC was examined using a detection algorithm. Intervals with inconsistent EFEC values were distinguished from those with consistent EFEC values; the total daytime ET (from 9:00 to 19:00) within these interval types was integrated separately. Validation of the total daytime ET at the satellite pixel scale was conducted using measurements from17 EC towers. Using the detection algorithm for the temporal stability of the EF and dynamic adjustment, the revised temporal scaling method resulted in a root-mean-square error (RMSE) of 0.54 (mm·d−1), a mean relative error (MRE) of 7.26% and a correlation coefficient (Corr.) of 0.81; all of these values were superior to those of the two other methods (i.e., the constant EF and variable EF methods). The revised method easily extends to other areas and exhibits a superior performance in flat and regularly-irrigated farmlands at the regional scale.