A remote sensing surface energy balance algorithm for land (SEBAL) - 2. Validation
A remote sensing surface energy balance algorithm for land (SEBAL) - 2. Validation
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DOI：
10.1016/s0022-1694(98)00253-4
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发表时间：
1998-12-01
影响因子：
6.4
通讯作者：
van der Wal, T
中科院分区：
文献类型：
--
作者：
Bastiaanssen, WGM;Pelgrum, H;van der Wal, T
简要总结了利用遥感数据估算复合地形地表能量平衡空间分布的现有算法的主要瓶颈。具有足够大的水文对比度（旱地和湿地地表类型，植被覆盖并不重要）的地区的可见光和热红外光谱辐射之间的关系构成了制定新的陆地地表能量平衡算法的基础。新的算法（一）估计的空间变化的最重要的水文气象参数的经验，（二）只需要现场信息的短波大气透射率，地表温度和植被高度，（三）不涉及数值模拟模型，（四）计算通量独立于土地覆盖和（五）可以处理热红外图像之间的分辨率为几米到几公里。根据不同的地理区域和图像采集时间调整经验关系。在回归系数的推导中插入实际卫星数据。第2部分涉及SEBAL的验证。(C)1998年，Elsevier Science BV。利用遥感信息和有限的实地输入数据，通过陆地表面能量平衡算法（SEBAL）获得的地表通量，用大规模实地实验EFEDA（西班牙）、HAPEX-Sahel（尼日尔）和HEIFE（中国）的数据进行了验证。在85%的情况下，举行规模的表面通量比与SEBAL-based表面通量比相比，差异的仪器不准确的范围内。在没有任何校准程序的情况下，几百米足迹的蒸发分数\DeIta（潜热通量/净可用辐射）的均方根误差从Lambda（RMSE）= 0.10到0.20不等，几个足迹聚集到几公里的长度尺度将总误差降低到5%。在EFEDA期间由飞机测量的通量被用来研究遥感流域通量的正确性（1，000，000公顷）：蒸发分数的总体差异可以忽略不计。对于尼日尔的萨赫勒景观，观察到的差异较大（15%），这可能是由于图像获取时刻（1992年9月1日）和原位通量分析时刻（1992年9月17日）之间粗质地土壤的水分迅速耗尽。对于HEIFE，SEBAL估计的和地面验证的地表通量的平均差异为23 W m（-2），考虑到地表通量未用于校准，这是令人鼓舞的。SEBAl对埃及Qattara洼地（2，000，000公顷）海平面以下蒸发量的估计与地下水系统的数值预测排放量一致。在埃及尼罗河三角洲，从一个分布式的水平衡模型在70万公顷的灌溉农业区的蒸发导致5%的差异，每天从SEBAL获得的蒸发通量。它的结论是，在干旱区的所有研究领域，如果被认为是一个较大数量的像素的误差平均。本章第一部分涉及《保护环境法》的制定。(C)1998 Elsevier Science B.V.保留所有权利。
The major bottlenecks of existing algorithms to estimate the spatially distributed surface energy balance in composite terrain by means of remote sensing data are briefly summarised. The relationship between visible and thermal infrared spectral radiances of areas with a sufficiently large hydrological contrast (dry and wet land surface types, vegetative cover is not essential) constitute the basis for the formulation of the new Surface Energy Balance Algorithm for Land (SEBAL). The new algorithm (i) estimates the spatial variation of most essential hydro-meteorological parameters empirically, (ii) requires only field information on short wave atmospheric transmittance, surface temperature and vegetation height, (iii) does not involve numerical simulation models, (iv) calculates the fluxes independently from land cover and (v) can handle thermal infrared images at resolutions between a few meters to a few kilometers. The empirical relationships are adjusted to different geographical regions and time of image acquisition. Actual satellite data is inserted in the derivation of the regression coefficients. Part 2 deals with the validation of SEBAL. (C) 1998 Elsevier Science BV. All rights reserved.The surface fluxes obtained with the Surface Energy balance Algorithm for Land (SEBAL), using remote sensing information and limited input data form the field were validated with data available from the large-scale field experiments EFEDA (Spain), HAPEX-Sahel (Niger) and HEIFE (China). In 85% of the cases where held scale surface flux ratios were compared with SEBAL-based surface flux ratios, the differences were within the range of instrumental inaccuracies. Without any calibration procedure, the root mean square error of the evaporative fraction \DeIta (latent heat flux/net available radiation) for footprints of a few hundred metres varied from Lambda(RMSE) = 0.10 to 0.20 Aggregation of several footprints to a length scale of a few kilometres reduced the overall error to five percent. Fluxes measured by aircraft during EFEDA were used to study the correctness of remote sensed watershed fluxes (1,000,000 ha):The overall difference in evaporative fraction was negligible. For the Sahelian landscape in Niger, observed differences were larger (15%), which could be attributed to the rapid moisture depletion of the coarse textured soils between the moment of image acquisition (Is September 1992) and the moment of in situ flux analysis (17 September 1992). For HEIFE, the average difference in SEBAL estimated and ground verified surface fluxes was 23 W m(-2), which, considering that surface fluxes were not used for calibration, is encouraging. SEBAl estimates of evaporation from the subsealevel Qattara Depression in Egypt (2,000,000 ha) were consistent with the numerically predicted discharge from the groundwater system. Tn Egypt's Nile Delta, the evaporation from a distributed held scale water balance model at a 700,000 ha irrigated agricultural region led to a difference of 5% with daily evaporative fluxes obtained from SEBAL. It is concluded that, for all study areas in arid zones, the errors average out if a larger number of pixels is considered. Part 1 of this chapter deals with the formulation of SEPAL. (C) 1998 Elsevier Science B.V. All rights reserved.