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Evaluation of WaPOR V2.0 evapotranspiration products across Africa
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  • Megan Blatchford,
  • Chris Mannaerts,
  • Sammy Njuki,
  • Hamideh Nouri,
  • Yijian Zeng,
  • Henk Pelgrum,
  • Steven Wonink,
  • Poolad Karimi
Megan Blatchford
University of Twente
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Chris Mannaerts
University of Twente
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Sammy Njuki
University of Twente
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Hamideh Nouri
University of Gottingen
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Yijian Zeng
University of Twente
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Henk Pelgrum
eleaf
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Steven Wonink
eleaf
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Poolad Karimi
IHE Delft Institute for Water Education
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Abstract

The FAO Water Productivity Open Access Portal (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250m) covers Africa and the Middle East (L1). The national level (100m) covers 21 countries and four river basins (L2). The third level (30m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in-situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall R2 of 0.61, and a root mean square error of 1.04 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The soil moisture content, the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WaPOR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.

Peer review status:ACCEPTED

30 Nov 2019Submitted to Hydrological Processes
03 Dec 2019Submission Checks Completed
03 Dec 2019Assigned to Editor
03 Dec 2019Reviewer(s) Assigned
21 Feb 2020Review(s) Completed, Editorial Evaluation Pending
25 Feb 2020Editorial Decision: Revise Major
10 Apr 20201st Revision Received
13 Apr 2020Submission Checks Completed
13 Apr 2020Assigned to Editor
13 Apr 2020Reviewer(s) Assigned
14 Apr 2020Review(s) Completed, Editorial Evaluation Pending
24 Apr 2020Editorial Decision: Accept