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Open AccessArticle

Evaluation of Two SMAP Soil Moisture Retrievals Using Modeled- and Ground-Based Measurements

by Li Bai 1, Xin Lv 1,* and Xiaojun Li 2
1
Agricultural College of Shihezi University, Shihezi 832003, China
2
INRA, UMR1391 ISPA, F-33140 Villenave d’Ornon, France
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(24), 2891; https://doi.org/10.3390/rs11242891
Received: 10 November 2019 / Revised: 1 December 2019 / Accepted: 2 December 2019 / Published: 4 December 2019
(This article belongs to the Special Issue Satellite Soil Moisture Validation and Applications)
A comprehensive evaluation of the performance of satellite-based soil moisture (SM) retrievals is undoubtedly very important to improve its quality and evaluate its potential application in hydrology, climate, and natural disasters (drought, flood, etc.). Since the release of the SMAP (Soil Moisture Active Passive) mission data in April 2015, the associated SM retrieval algorithms have developed rapidly, and their improvement work is still in progress. However, some newly developed SM retrievals have not been fully assessed and inter-compared. One such product is the new multi-temporal dual-channel retrieval algorithm (MT-DCA) SM retrievals, which was recently retrieved using the so-called MT-DCA algorithm. To solve this, we aim to assess the MT-DCA SM retrievals along with the SMAP-enhanced level three SM products (SPL3SMP_E, version 2). More specifically, in this paper we evaluated and inter-compared the two SMAP SM retrievals with the ECMWF (European Centre for Medium-Range Weather Forecasts) modeled SM and ISMN (International Soil Moisture Network) in situ observations by applying four statistical scores: Pearson correlation coefficient (R), root mean square difference (RMSD), bias, and unbiased RMSD (ubRMSD). It was found that both SMAP SM retrievals can better capture the seasonal variations of ECMWF-modeled SM and ground-based measurements according to correlations, and MT-DCA SM was drier than SPL3SMP_E SM by ~0.018 m3/m3 on average on a global scale. With respect to the ISMN ground-based measurements, the performance of SPL3SMP_E SM compared better than the MT-DCA SM. The median ubRMSD of SPL3SMP_E SM and MT-DCA SM with ground measurements computed over all selected ISMN sites were 0.058 m3/m3 and 0.070 m3/m3, respectively. View Full-Text
Keywords: soil moisture; SMAP; MT-DCA; inter-comparison; in situ measurements; LAI; IGBP soil moisture; SMAP; MT-DCA; inter-comparison; in situ measurements; LAI; IGBP
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MDPI and ACS Style

Bai, L.; Lv, X.; Li, X. Evaluation of Two SMAP Soil Moisture Retrievals Using Modeled- and Ground-Based Measurements. Remote Sens. 2019, 11, 2891.

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