Abstract
The Essential Climate Variable (ECV) soil moisture (SM) datasets, originated from the European Space Agency, have revealed great potential for application in hydrology and agriculture. Hence, it is essential to continuously enhance the data quality and spatial completeness to satisfy the increasing scientific research requirements. In this study, we explore the potential possibility of Soil Moisture Active Passive (SMAP) datasets in filling the gaps of ECV SM. The comprehensive assessment results show that: (1) The data missing percent of gap-filled ECV decreases 20% on average, which can be one step closer to generate a seamlessly covered global land surface SM product with favorable quality. (2) Compared to the original ECV, the gap-filled ECV products express similar good response to the in-situ measurements, suggesting that the SMAP SM products could be taken to efficiently fill the gaps and consistently maintain favorable accuracy at the same time. (3) Compared to the in-situ measurements, the original ECV SM products demonstrate extremely high probability density peak percentages. Fortunately, this eminent high value could be effectively rectified through gap-filling progress using SMAP. Overall, this study conducts objective and detailed evaluation on the performance of applying SMAP to fill the gaps of ECV, and is expected to act as a valuable reference in ECV SM gap-filling method.
Highlights
Land surface soil moisture (SM), acting as an important vector in underlying surface hydrothermal exchange, is a key element in reflecting root-zone SM conditions and feeding the growth of herbaceous plants [1]–[3]
Soil Moisture Active Passive (SMAP)-derived SM datasets achieve outstanding performance among the assessed products. They even remarkably surpass ECV_C in terms of CC as shown in Figure 2 (c), (f), (g), and (h), and in terms of bias in Figure 3 (a), (b), and (h). It seems that spatial resolution may not be the main factor affecting accuracy, as at both 9 km and 36 km pixel resolution SMAP SM are verified to have high accuracy to in-situ measurements
As a multiple satellite-derived active and passive sensor merged SM product, Essential Climate Variable (ECV) SM has received extensive attention because of its global coverage, and superior data accuracy compared to its constituent components
Summary
Land surface soil moisture (SM), acting as an important vector in underlying surface hydrothermal exchange, is a key element in reflecting root-zone SM conditions and feeding the growth of herbaceous plants [1]–[3]. The associate editor coordinating the review of this manuscript and approving it for publication was Hongjun Su. monitoring, and watershed hydrological process across the globe [4], [5]. It is increasingly vital to acquire high-accuracy SM products with continuous land surface coverage to promote public awareness about the near surface topsoil hydrological situation [6], [7]. Satellite-based remote sensing technology is advancing rapidly and becoming an efficient way to acquire large scale spectral information [8]–[13].
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