Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records
Reliable soil moisture retrievals from passive microwave satellite sensors are limited during certain conditions, e.g., snow coverage, radio-frequency interference, and dense vegetation. In these cases, the retrievals can be masked using flagging algorithms. Currently available single- and multi-sen...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-10-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/12/20/3439 |
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| author | Mendy van der Vliet Robin van der Schalie Nemesio Rodriguez-Fernandez Andreas Colliander Richard de Jeu Wolfgang Preimesberger Tracy Scanlon Wouter Dorigo |
| author_facet | Mendy van der Vliet Robin van der Schalie Nemesio Rodriguez-Fernandez Andreas Colliander Richard de Jeu Wolfgang Preimesberger Tracy Scanlon Wouter Dorigo |
| author_sort | Mendy van der Vliet |
| collection | DOAJ |
| description | Reliable soil moisture retrievals from passive microwave satellite sensors are limited during certain conditions, e.g., snow coverage, radio-frequency interference, and dense vegetation. In these cases, the retrievals can be masked using flagging algorithms. Currently available single- and multi-sensor soil moisture products utilize different flagging approaches. However, a clear overview and comparison of these approaches and their impact on soil moisture data are still lacking. For long-term climate records such as the soil moisture products of the European Space Agency (ESA) Climate Change Initiative (CCI), the effect of any flagging inconsistency resulting from combining multiple sensor datasets is not yet understood. Therefore, the first objective of this study is to review the data flagging system that is used within multi-sensor ESA CCI soil moisture products as well as the flagging systems of two other soil moisture datasets from sensors that are also used for the ESA CCI soil moisture products: The level 3 Soil Moisture and Ocean Salinity (SMOS) and the Soil Moisture Active/Passive (SMAP). The SMOS and SMAP soil moisture flagging systems differ substantially in number and type of conditions considered, critical flags, and data source dependencies. The impact on the data availability of the different flagging systems were compared for the SMOS and SMAP soil moisture datasets. Major differences in data availability were observed globally, especially for northern high latitudes, mountainous regions, and equatorial latitudes (up to 37%, 33%, and 32% respectively) with large seasonal variability. These results highlight the importance of a consistent and well-performing approach that is applicable to all individual products used in long-term soil moisture data records. Consequently, the second objective of the present study is to design a consistent and model-independent flagging strategy to improve soil moisture climate records such as the ESA CCI products. As snow cover, ice, and frozen conditions were demonstrated to have the biggest impact on data availability, a uniform satellite driven flagging strategy was designed for these conditions and evaluated against two ground observation networks. The new flagging strategy demonstrated to be a robust flagging alternative when compared to the individual flagging strategies adopted by the SMOS and SMAP soil moisture datasets with a similar performance, but with the applicability to the entire ESA CCI time record without the use of modelled approximations. |
| first_indexed | 2024-03-10T15:29:20Z |
| format | Article |
| id | doaj.art-2c735c36f541419c993763a9deb08565 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T15:29:20Z |
| publishDate | 2020-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-2c735c36f541419c993763a9deb085652023-11-20T17:46:20ZengMDPI AGRemote Sensing2072-42922020-10-011220343910.3390/rs12203439Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data RecordsMendy van der Vliet0Robin van der Schalie1Nemesio Rodriguez-Fernandez2Andreas Colliander3Richard de Jeu4Wolfgang Preimesberger5Tracy Scanlon6Wouter Dorigo7VanderSat B.V., 2011VK Haarlem, The NetherlandsVanderSat B.V., 2011VK Haarlem, The NetherlandsCentre d’Etudes Spatiales de la Biosphère (CESBIO), Centre National de la Recherche Scientifique, Université de Toulouse, Université Toulouse 3 - Paul Sabatier, Centre National d’Etudes Spatiales, Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement, Institut de Recherche pour le Développement, 18 av. Edouard Belin, bpi 2801, 31401 Toulouse, FranceJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USAVanderSat B.V., 2011VK Haarlem, The NetherlandsDepartment of Geodesy and Geoinformation, Vienna University of Technology (TU Wien), Vienna 1040, AustriaDepartment of Geodesy and Geoinformation, Vienna University of Technology (TU Wien), Vienna 1040, AustriaDepartment of Geodesy and Geoinformation, Vienna University of Technology (TU Wien), Vienna 1040, AustriaReliable soil moisture retrievals from passive microwave satellite sensors are limited during certain conditions, e.g., snow coverage, radio-frequency interference, and dense vegetation. In these cases, the retrievals can be masked using flagging algorithms. Currently available single- and multi-sensor soil moisture products utilize different flagging approaches. However, a clear overview and comparison of these approaches and their impact on soil moisture data are still lacking. For long-term climate records such as the soil moisture products of the European Space Agency (ESA) Climate Change Initiative (CCI), the effect of any flagging inconsistency resulting from combining multiple sensor datasets is not yet understood. Therefore, the first objective of this study is to review the data flagging system that is used within multi-sensor ESA CCI soil moisture products as well as the flagging systems of two other soil moisture datasets from sensors that are also used for the ESA CCI soil moisture products: The level 3 Soil Moisture and Ocean Salinity (SMOS) and the Soil Moisture Active/Passive (SMAP). The SMOS and SMAP soil moisture flagging systems differ substantially in number and type of conditions considered, critical flags, and data source dependencies. The impact on the data availability of the different flagging systems were compared for the SMOS and SMAP soil moisture datasets. Major differences in data availability were observed globally, especially for northern high latitudes, mountainous regions, and equatorial latitudes (up to 37%, 33%, and 32% respectively) with large seasonal variability. These results highlight the importance of a consistent and well-performing approach that is applicable to all individual products used in long-term soil moisture data records. Consequently, the second objective of the present study is to design a consistent and model-independent flagging strategy to improve soil moisture climate records such as the ESA CCI products. As snow cover, ice, and frozen conditions were demonstrated to have the biggest impact on data availability, a uniform satellite driven flagging strategy was designed for these conditions and evaluated against two ground observation networks. The new flagging strategy demonstrated to be a robust flagging alternative when compared to the individual flagging strategies adopted by the SMOS and SMAP soil moisture datasets with a similar performance, but with the applicability to the entire ESA CCI time record without the use of modelled approximations.https://www.mdpi.com/2072-4292/12/20/3439passive microwave radiometrydata flaggingsoil moisture |
| spellingShingle | Mendy van der Vliet Robin van der Schalie Nemesio Rodriguez-Fernandez Andreas Colliander Richard de Jeu Wolfgang Preimesberger Tracy Scanlon Wouter Dorigo Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records Remote Sensing passive microwave radiometry data flagging soil moisture |
| title | Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records |
| title_full | Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records |
| title_fullStr | Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records |
| title_full_unstemmed | Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records |
| title_short | Reconciling Flagging Strategies for Multi-Sensor Satellite Soil Moisture Climate Data Records |
| title_sort | reconciling flagging strategies for multi sensor satellite soil moisture climate data records |
| topic | passive microwave radiometry data flagging soil moisture |
| url | https://www.mdpi.com/2072-4292/12/20/3439 |
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