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Article

Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products

1
Department of Hydrology, Geological Survey of Denmark and Greenland, 1350 Copenhagen, Denmark
2
Natural Water Production Theme, European Centre of Excellence for Sustainable Water Technology (Wetsus), 8911 Leeuwarden, The Netherlands
*
Author to whom correspondence should be addressed.
Academic Editor: Sayed M. Bateni
Remote Sens. 2021, 13(5), 853; https://doi.org/10.3390/rs13050853
Received: 3 February 2021 / Revised: 18 February 2021 / Accepted: 22 February 2021 / Published: 25 February 2021
This study aims to improve the standard water balance evapotranspiration (WB ET) estimate, which is typically used as benchmark data for catchment-scale ET estimation, by accounting for net intercatchment groundwater flow in the ET calculation. Using the modified WB ET approach, we examine errors and shortcomings associated with the long-term annual mean (2002–2014) spatial patterns of three remote-sensing (RS) MODIS-based ET products from MODIS16, PML_V2, and TSEB algorithms at 1 km spatial resolution over Denmark, as a test case for small-scale, energy-limited regions. Our results indicate that the novel approach of adding groundwater net in water balance ET calculation results in a more trustworthy ET spatial pattern. This is especially relevant for smaller catchments where groundwater net can be a significant component of the catchment water balance. Nevertheless, large discrepancies are observed both amongst RS ET datasets and compared to modified water balance ET spatial pattern at the national scale; however, catchment-scale analysis highlights that difference in RS ET and WB ET decreases with increasing catchment size and that 90%, 87%, and 93% of all catchments have ∆ET < ±150 mm/year for MODIS16, PML_V2, and TSEB, respectively. In addition, Copula approach captures a nonlinear structure of the joint relationship with multiple densities amongst the RS/WB ET products, showing a complex dependence structure (correlation); however, among the three RS ET datasets, MODIS16 ET shows a closer spatial pattern to the modified WB ET, as identified by a principal component analysis also. This study will help improve the water balance approach by the addition of groundwater net in the ET estimation and contribute to better understand the true correlations amongst RS/WB ET products especially over energy-limited environments. View Full-Text
Keywords: evapotranspiration; water balance approach; remote-sensing products; spatial pattern evaluation; bivariate density estimation and similarity assessment; energy-limited environment evapotranspiration; water balance approach; remote-sensing products; spatial pattern evaluation; bivariate density estimation and similarity assessment; energy-limited environment
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MDPI and ACS Style

Soltani, M.; Koch, J.; Stisen, S. Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products. Remote Sens. 2021, 13, 853. https://doi.org/10.3390/rs13050853

AMA Style

Soltani M, Koch J, Stisen S. Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products. Remote Sensing. 2021; 13(5):853. https://doi.org/10.3390/rs13050853

Chicago/Turabian Style

Soltani, Mohsen, Julian Koch, and Simon Stisen. 2021. "Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products" Remote Sensing 13, no. 5: 853. https://doi.org/10.3390/rs13050853

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