DOI: 10.1016/j.jag.2016.11.001
Scopus记录号: 2-s2.0-85014487636
论文题名: Considering combined or separated roughness and vegetation effects in soil moisture retrievals
作者: Parrens M ; , Wigneron J ; -P ; , Richaume P ; , Al Bitar A ; , Mialon A ; , Fernandez-Moran R ; , Al-Yaari A ; , O'Neill P ; , Kerr Y
刊名: International Journal of Applied Earth Observation and Geoinformation
ISSN: 15698432
出版年: 2017
卷: 55 起始页码: 73
结束页码: 86
语种: 英语
英文关键词: L-band
; Optical vegetation depth
; Retrievals
; SMOS
; Soil moisture
; Soil roughness
英文摘要: For more than six years, the Soil Moisture and Ocean Salinity (SMOS) mission has provided multi angular and full-polarization brightness temperature (TB) measurements at L-band. Geophysical products such as soil moisture (SM) and vegetation optical depth at nadir (τnad) are retrieved by an operational algorithm using TB observations at different angles of incidence and polarizations. However, the quality of the retrievals depends on several surface effects, such as vegetation, soil roughness and texture, etc. In the microwave forward emission model used in the retrievals (L-band Microwave Emission Model, L-MEB), soil roughness is modelled with a semi-empirical equation using four main parameters (Qr, Hr, Nrp, with p = H or V polarizations). At present, these parameters are calibrated with data provided by airborne studies and in situ measurements made at a local scale that is not necessarily representative of the large SMOS footprints (43 km on average) at global scale. In this study, we evaluate the impact of the calibrated values of Nrp and Hr on the SM and τnad retrievals based on SMOS TB measurements (SMOS Level 3 product) over the Soil Climate Analysis Network (SCAN) network located in North America over five years (2011–2015). In this study, Qr was set equal to zero and we assumed that NrH = NrV. The retrievals were performed by varying Nrp from −1 to 2 by steps of 1 and Hr from 0 to 0.6 by steps of 0.1. At satellite scale, the results show that combining vegetation and roughness effects in a single parameter provides the best results in terms of soil moisture retrievals, as evaluated against the in situ SM data. Even though our retrieval approach was very simplified, as we did not account for pixel heterogeneity, the accuracy we obtained in the SM retrievals was almost systematically better than those of the Level 3 product. Improved results were also obtained in terms of optical depth retrievals. These new results may have key consequences in terms of calibration of roughness effects within the algorithms of the SMOS (ESA) and the SMAP (NASA) space missions. © 2016 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/79936
Appears in Collections: 气候变化事实与影响
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作者单位: Centre d'Etudes Spatiales de la BIOsphère (CESBIO – Uninversité Fédérale de Toulouse, CNES, CNRS, IRD), UMR5126, BPI 2801, Toulouse Cedex 9, France; Centre INRA Bordeaux, Aquitaine, UR1263 ISPA, F-33140 Villenave d'Ornon, Centre INRA Bordeaux, Aquitaine, France; NASA, Goddard Space Flight Center, Greenbelt, MD, United States
Recommended Citation:
Parrens M,, Wigneron J,-P,et al. Considering combined or separated roughness and vegetation effects in soil moisture retrievals[J]. International Journal of Applied Earth Observation and Geoinformation,2017-01-01,55