气候变化领域集成服务门户(CCPortal): The effect of pixel heterogeneity for remote sensing based retrievals of evapotranspiration in a semi-arid tree-grass ecosystem

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DOI	10.1016/j.rse.2021.112440
	The effect of pixel heterogeneity for remote sensing based retrievals of evapotranspiration in a semi-arid tree-grass ecosystem
	Burchard-Levine V.; Nieto H.; Riaño D.; Migliavacca M.; El-Madany T.S.; Guzinski R.; Carrara A.; Martín M.P.
发表日期	2021
ISSN	00344257
卷号	260
英文摘要	Many satellite missions rely on modeling approaches to acquire global or regional evapotranspiration (ET) products. However, a current challenge in ET modeling lies in dealing with sub-pixel heterogeneity, as models often assume homogeneous conditions at the pixel level. This is particularly an issue for heterogeneous landscapes, such as tree-grass ecosystems (TGE). In these areas, while appearing homogeneous at larger spatial scales pertaining to a single land cover type, the separation of the spectral signals of the main landscape features (e.g. trees and grasses) may not be achieved at the conventional satellite sensor resolution (e.g. 10–1000 m). This leads to important heterogeneity within the pixel grid that may not be accounted for in traditional modeling frameworks. This study examined the effect of pixel heterogeneity on ET simulations over a complex TGE in central Spain. High resolution hyperspectral imagery from five airborne campaigns forced the two-source energy balance (TSEB) model at 1.5–1000 m spatial resolutions. Along with this, the sharpened (20 m) and original (1000 m) Sentinels for Evapotranspiration (Sen-ET) products were evaluated over the study site for 2017. Results indicated that TSEB accurately simulated ET (RMSD: ~60 W/m2) when the pixel scale was able to robustly discriminate between grass and tree pixels (<5 m). However, model uncertainty drastically increased at spatial resolution greater than 10 m (RMSD: ~115 W/m2). Model performance remains relatively constant between 30 and 1000 m spatial resolutions, with within pixel heterogeneity being similar at all these scales. For mixed pixels (≥30 m), forcing an effective landscape roughness into TSEB (RMSD: ~80 W/m2) or applying a seasonally changing TSEB (TSEB-2S; RMSD: ~65 W/m2) improved the modeling performance. The Sen-ET products behaved similarly at both scales with RMSD of ET roughly 80 W/m2. The non-linear relationship between input parameters and flux output, along with the poor representation of aerodynamic surface roughness, were the main drivers for the increased uncertainties at coarser scales. These results suggest that care should be taken when using global ET products over TGE and similarly heterogeneous landscapes. The modeling procedure should inherently account for the presence of vastly different vegetation roughness elements within the pixel, to achieve reliable estimates of turbulent fluxes over a TGE. © 2021 Elsevier Inc.
英文关键词	Airborne imagery; Evapotranspiration; Land surface temperature; Latent heat flux; Sensible heat flux; Sentinels for evapotranspiration; Spatial resolution; Surface energy balance; Tree-grass ecosystems
语种	英语
scopus关键词	Ecosystems; Evapotranspiration; Forestry; Heat flux; Image resolution; Interfacial energy; Land surface temperature; Latent heat; Pixels; Remote sensing; Surface measurement; Surface roughness; Uncertainty analysis; Airborne imagery; Grass ecosystem; Land surface temperature; Latent heat flux; Pixel heterogeneity; Sensible heat flux; Sentinel for evapotranspiration; Spatial resolution; Surface energy balance; Tree-grass ecosystem; Energy balance; evapotranspiration; grass; heterogeneity; numerical model; pixel; remote sensing; satellite mission; satellite sensor; semiarid region; spectral resolution; terrestrial ecosystem; Spain; Poaceae
来源期刊	Remote Sensing of Environment
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/178844
作者单位	Environmental Remote Sensing and Spectroscopy Laboratory (SpecLab), Spanish National Research Council (CSIC), Madrid, 28037, Spain; Complutum Tecnologías de la Información Geográfica S.L. (COMPLUTIG), Alcalá de Henares, Madrid, Spain; Center for Spatial Technologies and Remote Sensing (CSTARS), University of California, 139 Veihmeyer Hall, One Shields Avenue, Davis, CA 95616, United States; Max Planck Institute for Biogeochemistry, Department Biogeochemical Integration, Hans-Knöll-Str. 10, Jena, D-07745, Germany; DHI GRAS, Agern Alle 5, Hørsholm, 2970, Denmark; Fundación Centro de Estudios Ambientales del Mediterráneo (CEAM), Paterna, 46980, Spain
推荐引用方式 GB/T 7714	Burchard-Levine V.,Nieto H.,Riaño D.,et al. The effect of pixel heterogeneity for remote sensing based retrievals of evapotranspiration in a semi-arid tree-grass ecosystem[J],2021,260.
APA	Burchard-Levine V..,Nieto H..,Riaño D..,Migliavacca M..,El-Madany T.S..,...&Martín M.P..(2021).The effect of pixel heterogeneity for remote sensing based retrievals of evapotranspiration in a semi-arid tree-grass ecosystem.Remote Sensing of Environment,260.
MLA	Burchard-Levine V.,et al."The effect of pixel heterogeneity for remote sensing based retrievals of evapotranspiration in a semi-arid tree-grass ecosystem".Remote Sensing of Environment 260(2021).