University of Leicester
Browse

File(s) under embargo

3

month(s)

26

day(s)

until file(s) become available

Evaluation of spatial downscaling forsatellite retrieval of evapotranspiration from the nonparametric approach in an arid area

journal contribution
posted on 2024-02-09, 17:15 authored by Zi Yang, Xin Pan, Yuanbo Liu, Kevin Tansey, Jie Yuan, Zhanchuan Wang, Suyi Liu, Yingbao Yang
Evapotranspiration (ET) data is critical for monitoring the limited hydrological resources in arid areas. At present, the spatial resolution of ET derived by the thermal infrared images from satellite data is coarse (always more than 500 m). The low-resolution data cannot meet the needs of the high-precision mapping of ET. Therefore, it is important to undertake a downscaling procedure to improve the spatial resolution of ET. This paper selects the oasis region and surrounding deserts of Zhangye City of China as study area and compares with two downscaling procedures that include input and output downscaling procedure. The ET is estimated with the Remote Sensing-Non Parametric (RS-NP) model. The two downscaling procedures use Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM) to improve the spatial resolution of ET from 1-km to 100 m. Compared with the result derived from the output downscaling procedure, the high-resolution ET derived from the input downscaling procedure has a slightly better performance with R2 of 0.92 and RMSE of 41.8 W/m2, respectively. Neglecting the downscaling of land surface temperature and broadband reflectance (BBR) result in larger errors of ET estimation with bias values of 73.0 W/m2 and 23.7 W/m2, respectively. Those values account for almost 1/3 and 1/10 of ET values, respectively. In non-vegetated areas, those proportions increase further around 90.6 % and 21.3 %, respectively. Furthermore, the influence of the neglect of the downscaling of the near-infrared reflectance on the ET estimation dominates that of BBR with a proportion of 42 %. The input downscaling procedure is suitable for generating the high-precision map of ET, especially in vegetated areas and during northern hemisphere summer months. Our study is helpful to obtain ET maps in fine spatial resolutions and contribute to the comprehensive understanding of the importance of the downscaling of each kind of input for reliable ET estimations.

Funding

National Nature Science Foundation of China [41701487, 42230112, 42071346 and 42371397]

The State Scholarship Funds of China

Royal Society IEC\NSFC\223292 - International Exchanges 2022 Cost Share (NSFC) grant of the UK

History

Author affiliation

School of Geography, Geology and the Environment, University of Leicester

Version

  • AM (Accepted Manuscript)

Published in

Journal of Hydrology

Volume

628

Pagination

130538

Publisher

Elsevier BV

issn

0022-1694

Copyright date

2024

Available date

2024-11-20

Language

en

Deposited by

Professor Kevin Tansey

Deposit date

2024-02-04

Rights Retention Statement

  • No

Usage metrics

    University of Leicester Publications

    Categories

    No categories selected

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC