{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T16:59:45Z","timestamp":1775581185325,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2018,3,26]],"date-time":"2018-03-26T00:00:00Z","timestamp":1522022400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Soil moisture is an essential variable in Earth surface modeling. Two dedicated satellite missions, the Soil Moisture and Ocean Salinity (SMOS) and the Soil Moisture Active Passive (SMAP), are currently in operation to map the global distribution of soil moisture. However, at the longer L-band wavelength of these satellites, the emitting behavior of the land becomes very complex due to the unknown deeper penetration depth. This complexity leads to more uncertainty in calibration and validation of satellite soil moisture product and their applications. In the framework of zeroth-order incoherent microwave radiative transfer model, the soil effective temperature is the only component that contains depth information and thus provides the necessary link to quantify the penetration depth. By means of the multi-layer soil effective temperature (Lv\u2019s T e f f ) scheme, we have determined the relationship between the penetration depth and soil effective temperature and verified it against field observations at the Maqu Network. The key findings are that the penetration depth can be estimated according to Lv\u2019s T e f f scheme with the assumption of linear soil temperature gradient along the optical depth; and conversely, the soil temperature at the penetration depth should be equal to the soil effective temperature with the same linear assumption. The accuracy of this inference depends on to what extent the assumption of linear soil temperature gradient is satisfied. The result of this study is expected to advance understanding of the soil moisture products retrieved by SMOS and SMAP and improve the techniques in data assimilation and climate research.<\/jats:p>","DOI":"10.3390\/rs10040519","type":"journal-article","created":{"date-parts":[[2018,3,26]],"date-time":"2018-03-26T12:08:25Z","timestamp":1522066105000},"page":"519","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":52,"title":["Estimation of Penetration Depth from Soil Effective Temperature in Microwave Radiometry"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8957-6636","authenticated-orcid":false,"given":"Shaoning","family":"Lv","sequence":"first","affiliation":[{"name":"Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands"},{"name":"Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Region, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2166-5314","authenticated-orcid":false,"given":"Yijian","family":"Zeng","sequence":"additional","affiliation":[{"name":"Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands"}]},{"given":"Jun","family":"Wen","sequence":"additional","affiliation":[{"name":"College of Atmospheric Sciences, the Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, Chengdu University of Information Technology, Chengdu 610225, China"}]},{"given":"Hong","family":"Zhao","sequence":"additional","affiliation":[{"name":"Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands"}]},{"given":"Zhongbo","family":"Su","sequence":"additional","affiliation":[{"name":"Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands"}]}],"member":"1968","published-online":{"date-parts":[[2018,3,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1002\/asl.367","article-title":"The onset of the West African monsoon simulated in a high-resolution atmospheric general circulation model with reanalyzed soil moisture fields","volume":"13","author":"Yamada","year":"2012","journal-title":"Atmos. Sci. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2381","DOI":"10.1175\/1520-0442(2001)014<2381:IOSMOT>2.0.CO;2","article-title":"Influence of soil moisture on the Asian and African monsoons. Part I: Mean monsoon and daily precipitation","volume":"14","author":"Douville","year":"2001","journal-title":"J. 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