气候变化领域集成服务门户(CCPortal): Estimating daily evapotranspiration based on a model of evaporative fraction (EF) for mixed pixels

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DOI	10.5194/hess-23-949-2019
	Estimating daily evapotranspiration based on a model of evaporative fraction (EF) for mixed pixels
	Li F.; Xin X.; Peng Z.; Liu Q.
发表日期	2019
ISSN	1027-5606
起始页码	949
结束页码	969
卷号	23 期号:2
英文摘要	Currently, applications of remote sensing evapotranspiration (ET) products are limited by the coarse resolution of satellite remote sensing data caused by land surface heterogeneities and the temporal-scale extrapolation of the instantaneous latent heat flux (LE) based on satellite overpass time. This study proposes a simple but efficient model (EFAF) for estimating the daily ET of remotely sensed mixed pixels using a model of the evaporative fraction (EF) and area fraction (AF) to increase the accuracy of ET estimate over heterogeneous land surfaces. To accomplish this goal, we derive an equation for calculating the EF of mixed pixels based on two key hypotheses. Hypothesis 1 states that the available energy (AE) of each sub-pixel is approximately equal to that of any other sub-pixels in the same mixed pixel within an acceptable margin of error and is equivalent to the AE of the mixed pixel. This approach simplifies the equation, and uncertainties and errors related to the estimated ET values are minor. Hypothesis 2 states that the EF of each sub-pixel is equal to that of the nearest pure pixel(s) of the same land cover type. This equation is designed to correct spatial-scale errors for the EF of mixed pixels; it can be used to calculate daily ET from daily AE data. The model was applied to an artificial oasis located in the midstream area of the Heihe River using HJ-1B satellite data with a 300 m resolution. The results generated before and after making corrections were compared and validated using site data from eddy covariance systems. The results show that the new model can significantly improve the accuracy of daily ET estimates relative to the lumped method; the coefficient of determination (R2) increased to 0.82 from 0.62, the root mean square error (RMSE) decreased to 1.60 from 2.47 MJ mĝ'2(decreased approximately to 0.64 from 0.99 mm) and the mean bias error (MBE) decreased from 1.92 to 1.18 MJ mĝ'2 (decreased from approximately 0.77 to 0.47 mm). It is concluded that EFAF can reproduce daily ET with reasonable accuracy; can be used to produce the ET product; and can be applied to hydrology research, precision agricultural management and monitoring natural ecosystems in the future. © Author(s) 2019.
语种	英语
scopus关键词	Errors; Evapotranspiration; Heat flux; Mean square error; Remote sensing; Satellites; Surface measurement; Uncertainty analysis; Agricultural management; Coefficient of determination; Daily evapotranspirations; Eddy covariance systems; Evaporative fraction; Heterogeneous land surfaces; Root mean square errors; Satellite remote sensing data; Pixels; eddy covariance; evapotranspiration; heterogeneity; land cover; land surface; latent heat flux; oasis; pixel; remote sensing; satellite data; China; Gansu; Hei River
来源期刊	Hydrology and Earth System Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/159756
作者单位	Li, F., State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Beijing, 100101, China, University of Chinese Academy of Sciences, Beijing, 100049, China, Joint Center for Global Change Studies (JCGCS), Beijing, 100875, China; Xin, X., State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Beijing, 100101, China, Joint Center for Global Change Studies (JCGCS), Beijing, 100875, China; Peng, Z., State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Beijing, 100101, China, University of Chinese Academy of Sciences, Beijing, 100049, China, Joint Center for Global Change Studies (JCGCS), Beijing, 100875, China; Liu, Q., State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Beijing, 100101, China, Joint Center for Global Change Studies (JCGCS), Beijing, 100875, China
推荐引用方式 GB/T 7714	Li F.,Xin X.,Peng Z.,et al. Estimating daily evapotranspiration based on a model of evaporative fraction (EF) for mixed pixels[J],2019,23(2).
APA	Li F.,Xin X.,Peng Z.,&Liu Q..(2019).Estimating daily evapotranspiration based on a model of evaporative fraction (EF) for mixed pixels.Hydrology and Earth System Sciences,23(2).
MLA	Li F.,et al."Estimating daily evapotranspiration based on a model of evaporative fraction (EF) for mixed pixels".Hydrology and Earth System Sciences 23.2(2019).