Evaluation of Satellite-Derived Surface Soil Moisture Products over Agricultural Regions of Canada
Evaluation of Satellite-Derived Surface Soil Moisture Products over Agricultural Regions of Canada
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DOI：
10.3390/rs12091455
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发表时间：
2020-05
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通讯作者：
Yaasiin Oozeer;C. Fletcher;C. Champagne
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作者：
Yaasiin Oozeer;C. Fletcher;C. Champagne
土壤湿度是气候变化和农业干旱的一个关键指标，但由于土地覆盖、土壤类型、时间、空间和深度的变化很大，其测量具有挑战性。对土壤湿度的卫星估计是非常可取的，在过去十年中已变得更加广泛。本研究调查并比较了加拿大四个表层土壤水分卫星数据集的性能，即土壤水分和海洋盐度3级（SMOS L3），欧洲航天局气候变化倡议（ESA CCI）土壤湿度产品的3.3和4.2版本以及最近的产品SMOS-INRA-CESBIO（SMOS-IC）它包含旨在减少SMOS L3中几个已知不确定性来源的校正。这些数据集是根据2012年至2014年期间位于加拿大主要农业地区的现场网络进行评估的。两种统计比较方法，即平均土壤水分和中位数的指标。结果表明，虽然这两种方法对区域网络的比较结果相似，但在大型网络中，指标中值方法更能代表总体相关性和可变性，因此是评价卫星产品性能的更适当方法。总体而言，SMOS产品有较高的每日时间相关性，但较大的偏差，对原位土壤水分比欧空局CCI产品，与SMOS-IC具有较高的相关性和较小的变异性比SMOS L3。SMOS产品比ESA CCI产品更好地捕获日常润湿和干燥事件，SMOS产品捕获至少75%的观测干燥，而ESA CCI产品为55%。总的来说，在有足够观测的时期，这两种SMOS产品都比欧空局CCI产品更适合加拿大的农业应用，尽管SMOS-IC能够比SMOS L3更准确地捕捉土壤水分变化。
Soil moisture is a critical indicator for climate change and agricultural drought, but its measurement is challenging due to large variability with land cover, soil type, time, space and depth. Satellite estimates of soil moisture are highly desirable and have become more widely available over the past decade. This study investigates and compares the performance of four surface soil moisture satellite datasets over Canada, namely, Soil Moisture and Ocean Salinity Level 3 (SMOS L3), versions 3.3 and 4.2 of European Space Agency Climate Change Initiative (ESA CCI) soil moisture product and a recent product called SMOS-INRA-CESBIO (SMOS-IC) that contains corrections designed to reduce several known sources of uncertainty in SMOS L3. These datasets were evaluated against in situ networks located in mostly agricultural regions of Canada for the period 2012 to 2014. Two statistical comparison methods were used, namely, metrics for mean soil moisture and median of metrics. The results suggest that, while both methods show similar comparisons for regional networks, over large networks, the median of metrics method is more representative of the overall correlation and variability and is therefore a more appropriate method for evaluating the performance of satellite products. Overall, the SMOS products have higher daily temporal correlations, but larger biases, against in situ soil moisture than the ESA CCI products, with SMOS-IC having higher correlations and smaller variability than SMOS L3. The SMOS products capture daily wetting and drying events better than the ESA CCI products, with the SMOS products capturing at least 75% of observed drying as compared to 55% for the ESA CCI products. Overall, for periods during which there are sufficient observations, both SMOS products are more suitable for agricultural applications over Canada than the ESA CCI products, even though SMOS-IC is able to capture soil moisture variability more accurately than SMOS L3.