Evaluation of WaPOR V2 evapotranspiration products across Africa,Hydrological Processes

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Evaluation of WaPOR V2 evapotranspiration products across Africa
Hydrological Processes ( IF 2.8 ) Pub Date : 2020-06-02 , DOI: 10.1002/hyp.13791
Megan L. Blatchford ₁ , Chris M. Mannaerts ₁ , Sammy M. Njuki ₁ , Hamideh Nouri ₂ , Yijian Zeng ₁ , Henk Pelgrum ₃ , Steven Wonink ₃ , Poolad Karimi ₄

Affiliation

The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open‐access of remotely sensed derived data (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 (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) 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 correlation of 0.71, and a root mean square error of 1.2 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 relative soil moisture content (SMC), 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‐WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.

中文翻译：

评估整个非洲的 WaPOR V2 蒸发蒸腾产物

联合国粮食及农业组织 (FAO) 门户通过开放获取遥感衍生数据 (WaPOR) 来监测水资源生产力，提供非洲和非洲每 10 天的连续实际蒸散和截留 (ETIA-WPR) 数据中东从 2009 年起以三种空间分辨率。大陆水平 (250 m) 覆盖非洲和中东 (L1)。国家级（100 m）覆盖 21 个国家和 4 个流域（L2）。第三层（30 m）覆盖八个灌溉区（L3）。为了量化非洲 WaPOR 版本 2 (V2.0) ETIa-WPR 的不确定性，我们使用了多种验证方法。我们根据可用水量和长期水平衡检查物理一致性，然后验证非洲主要气候的大陆时空趋势。我们根据 14 个涡旋协方差站 (EC) 的原位数据直接验证了 ETIa-WPR。最后，我们检查了不同空间分辨率之间的级别一致性。我们的研究结果表明 ETIa-WPR 表现良好，但有一些明显的高估。ETIa-WPR 在气候类别方面显示出预期的空间和时间一致性。与 EC 通量塔相比，ETIA-WPR 在点尺度上显示出混合结果，总体相关性为 0.71，均方根误差为 1.2 毫米/天。L1 和 L2 之间的级别一致性非常高。然而，L1 和 L3 之间的一致性在灌溉区域之间差异很大。在雨养地区，ETIA-WPR 在 ETIa-WPR 低时高估，而在 ETIa 高时低估。在灌溉地区，ETIA-WPR 值似乎一直高估 ETa。相对土壤水分含量 (SMC)、质量层的输入和局部平流效应是一些已确定的原因。ETIa-WPR 产品的质量评估通过结合多种评估方法得到加强。根据结果，ETIA-WPR 数据集的质量足以为了解和监测当地和大陆水过程和水管理做出贡献。

更新日期：2020-06-02

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