{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T08:34:02Z","timestamp":1772181242497,"version":"3.50.1"},"reference-count":92,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2022,6,25]],"date-time":"2022-06-25T00:00:00Z","timestamp":1656115200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"The Strategic Priority Research Program of the Chinese Academy of Sciences","award":["XDA20100101"],"award-info":[{"award-number":["XDA20100101"]}]},{"name":"The Strategic Priority Research Program of the Chinese Academy of Sciences","award":["42171319"],"award-info":[{"award-number":["42171319"]}]},{"name":"The Strategic Priority Research Program of the Chinese Academy of Sciences","award":["41871241"],"award-info":[{"award-number":["41871241"]}]},{"name":"The Strategic Priority Research Program of the Chinese Academy of Sciences","award":["2021-ZD-04"],"award-info":[{"award-number":["2021-ZD-04"]}]},{"name":"The National Natural Science Foundation of China","award":["XDA20100101"],"award-info":[{"award-number":["XDA20100101"]}]},{"name":"The National Natural Science Foundation of China","award":["42171319"],"award-info":[{"award-number":["42171319"]}]},{"name":"The National Natural Science Foundation of China","award":["41871241"],"award-info":[{"award-number":["41871241"]}]},{"name":"The National Natural Science Foundation of China","award":["2021-ZD-04"],"award-info":[{"award-number":["2021-ZD-04"]}]},{"name":"The State Key Laboratory of Earth Surface Processes and Resource Ecology","award":["XDA20100101"],"award-info":[{"award-number":["XDA20100101"]}]},{"name":"The State Key Laboratory of Earth Surface Processes and Resource Ecology","award":["42171319"],"award-info":[{"award-number":["42171319"]}]},{"name":"The State Key Laboratory of Earth Surface Processes and Resource Ecology","award":["41871241"],"award-info":[{"award-number":["41871241"]}]},{"name":"The State Key Laboratory of Earth Surface Processes and Resource Ecology","award":["2021-ZD-04"],"award-info":[{"award-number":["2021-ZD-04"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Soil moisture (SM) is an important land-surface parameter. Although microwave remote sensing is recognized as one of the most appropriate methods for retrieving SM, such retrievals often cannot meet the requirements of specific applications because of their coarse spatial resolution and spatiotemporal data gaps. A range of general models (GMs) for SM analysis topics (e.g., gap-filling, forecasting, and downscaling) have been introduced to address these shortcomings. This work presents a novel strategy (i.e., optimized wavelet-coupled fitting method (OWCM)) to enhance the fitting accuracy of GMs by introducing a wavelet transform (WT) technique. Four separate GMs are selected, i.e., elastic network regression, area-to-area regression kriging, random forest regression, and neural network regression. The fitting procedures are then tested within a downscaling analysis implemented between aggregated Global Land Surface Satellite products (i.e., LAI, FVC, albedo), Thermal and Reanalysis Integrating Medium-resolution Spatial-seamless LST, and Random Forest Soil Moisture (RFSM) datasets in both the WT space and the regular space. Then, eight fine-resolution SM datasets mapped from the trained GMs and OWCMs are analyzed using direct comparisons with in situ SM measurements and indirect intercomparisons between the aggregated OWCM-\/GM-derived SM and RFSM. The results demonstrate that OWCM-derived SM products are generally closer to the in situ SM observations, and better capture in situ SM dynamics during the unfrozen season, compared to the corresponding GM-derived SM product, which shows fewer time changes and more stable trends. Moreover, OWCM-derived SM products represent a significant improvement over corresponding GM-derived SM products in terms of their ability to spatially and temporally match RFSM. Although spatial heterogeneity still substantially impacts the fitting accuracies of both GM and OWCM SM products, the improvements of OWCMs over GMs are significant. This improvement can likely be attributed to the fitting procedure of OWCMs implemented in the WT space, which better captures high- and low-frequency image features than in the regular space.<\/jats:p>","DOI":"10.3390\/rs14133063","type":"journal-article","created":{"date-parts":[[2022,6,26]],"date-time":"2022-06-26T22:50:23Z","timestamp":1656283823000},"page":"3063","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Applying a Wavelet Transform Technique to Optimize General Fitting Models for SM Analysis: A Case Study in Downscaling over the Qinghai\u2013Tibet Plateau"],"prefix":"10.3390","volume":"14","author":[{"given":"Zixuan","family":"Hu","sequence":"first","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8295-8973","authenticated-orcid":false,"given":"Linna","family":"Chai","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wade T.","family":"Crow","sequence":"additional","affiliation":[{"name":"Hydrology and Remote Sensing Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shaomin","family":"Liu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhongli","family":"Zhu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9926-7693","authenticated-orcid":false,"given":"Ji","family":"Zhou","sequence":"additional","affiliation":[{"name":"School of Resources and Environment, Center for Information Geoscience, University of Electronic Science and Technology of China, Chengdu 611731, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuquan","family":"Qu","sequence":"additional","affiliation":[{"name":"Forschungszentrum J\u00fclich, Institute of Bio- and Geosciences: Agrosphere (IBG-3), 52428 J\u00fclich, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jin","family":"Liu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shiqi","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0287-5826","authenticated-orcid":false,"given":"Zheng","family":"Lu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1038\/ngeo2868","article-title":"The global distribution and dynamics of surface soil moisture","volume":"10","author":"McColl","year":"2017","journal-title":"Nat. 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