Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome
Climate change greatly impacts forest carbon and water dynamics in the boreal biome. To understand the vulnerability of the North American boreal biome to climate change disturbances, including droughts and temperature extremes, a biome-wide characterization of near-surface soil moisture (SM) is ess...
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IEEE
2025-01-01
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| Series: | IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing |
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| Online Access: | https://ieeexplore.ieee.org/document/10999089/ |
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| author | Azza Gorrab Oliver Sonnentag Arnaud Mialon Chelene C. Hanes Juliette Ortet Aaron A. Berg Muhammad Umair Alexandre Roy |
| author_facet | Azza Gorrab Oliver Sonnentag Arnaud Mialon Chelene C. Hanes Juliette Ortet Aaron A. Berg Muhammad Umair Alexandre Roy |
| author_sort | Azza Gorrab |
| collection | DOAJ |
| description | Climate change greatly impacts forest carbon and water dynamics in the boreal biome. To understand the vulnerability of the North American boreal biome to climate change disturbances, including droughts and temperature extremes, a biome-wide characterization of near-surface soil moisture (SM) is essential. SM is an important control on photosynthetic carbon dioxide uptake and the associated evaporative loss of water through transpiration. Two missions with passive microwave radiometers operating at <italic>L</italic>-band (1–2 GHz) were launched to estimate SM at a global scale: soil moisture and ocean salinity (SMOS) launched in 2009 and soil moisture active passive (SMAP) launched in 2015. In this study, we analyzed the relationships between various microwave observations [brightness temperature (TB), soil reflectivity (<italic>r</italic>), and soil moisture (SM)] derived from SMOS and SMAP with in situ SM measurements (2016–2021) over 16 sites across the boreal biome of North America. Our results show good agreement between SMAP and SMOS in terms of relationships between TB and in situ SM measurements (with a coefficient of determination <italic>R</italic> <sup>2</sup> > 0.7). Analysis comparing microwave variables (TB, <italic>r,</italic> and SM) and in situ SM data demonstrated considerable differences across sites and years. We observed moderate to strong correlation coefficients (R_TB > 0.5) between the TB and in situ SM data, generally when a seasonal soil drying trend emerges over the summer. However, soils with high water content and frequent precipitation input showed weaker correlations between TB and in situ SM. By analyzing the correlations between <italic>r</italic> and in situ SM data, we demonstrated that the soil effective temperature partly affects performances in terms of R_TB. Comparisons with other SMAP SM retrievals (multitemporal dual-channel algorithm and multichannel collaborative algorithm) revealed similar results in correlations and showed high spatiotemporal differences across all SM retrievals and study sites. Our findings highlight the complexity of the interactions between microwave observations and SM dynamics across the boreal biome, thus challenging the <italic>L</italic>-band passive microwave SM retrievals. |
| format | Article |
| id | doaj-art-af3e8a51f603430eb0f8e4f09f15845c |
| institution | Kabale University |
| issn | 1939-1404 2151-1535 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IEEE |
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| series | IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing |
| spelling | doaj-art-af3e8a51f603430eb0f8e4f09f15845c2025-08-20T03:24:35ZengIEEEIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing1939-14042151-15352025-01-0118127131272710.1109/JSTARS.2025.356906310999089Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal BiomeAzza Gorrab0https://orcid.org/0000-0002-6870-6435Oliver Sonnentag1https://orcid.org/0000-0001-9333-9721Arnaud Mialon2https://orcid.org/0000-0001-7970-0701Chelene C. Hanes3https://orcid.org/0000-0002-7742-7120Juliette Ortet4https://orcid.org/0009-0002-8294-1076Aaron A. Berg5https://orcid.org/0000-0001-8438-5662Muhammad Umair6https://orcid.org/0000-0002-7651-9015Alexandre Roy7https://orcid.org/0000-0002-1472-3619Département Des Sciences de L'Environnement, Université du Québec à Trois-Rivières, Trois-Rivières, QC, CanadaDépartement de Géographie, Université de Montréal, Montréal, QC, CanadaCentre d'Etudes Spatiales de la BIOsphère, CESBIO (CNES/CNRS/INRAE/IRD/UT3), Toulouse, FranceGreat Lakes Forestry Centre, Canadian Forest Service, Natural Resources Canada, Sault Ste. Marie, ON, CanadaDépartement Des Sciences de L'Environnement, Université du Québec à Trois-Rivières, Trois-Rivières, QC, CanadaDepartment of Geography, Environment and Geomatics, University of Guelph, Guelph, ON, CanadaDépartement de Géographie, Université de Montréal, Montréal, QC, CanadaDépartement Des Sciences de L'Environnement, Université du Québec à Trois-Rivières, Trois-Rivières, QC, CanadaClimate change greatly impacts forest carbon and water dynamics in the boreal biome. To understand the vulnerability of the North American boreal biome to climate change disturbances, including droughts and temperature extremes, a biome-wide characterization of near-surface soil moisture (SM) is essential. SM is an important control on photosynthetic carbon dioxide uptake and the associated evaporative loss of water through transpiration. Two missions with passive microwave radiometers operating at <italic>L</italic>-band (1–2 GHz) were launched to estimate SM at a global scale: soil moisture and ocean salinity (SMOS) launched in 2009 and soil moisture active passive (SMAP) launched in 2015. In this study, we analyzed the relationships between various microwave observations [brightness temperature (TB), soil reflectivity (<italic>r</italic>), and soil moisture (SM)] derived from SMOS and SMAP with in situ SM measurements (2016–2021) over 16 sites across the boreal biome of North America. Our results show good agreement between SMAP and SMOS in terms of relationships between TB and in situ SM measurements (with a coefficient of determination <italic>R</italic> <sup>2</sup> > 0.7). Analysis comparing microwave variables (TB, <italic>r,</italic> and SM) and in situ SM data demonstrated considerable differences across sites and years. We observed moderate to strong correlation coefficients (R_TB > 0.5) between the TB and in situ SM data, generally when a seasonal soil drying trend emerges over the summer. However, soils with high water content and frequent precipitation input showed weaker correlations between TB and in situ SM. By analyzing the correlations between <italic>r</italic> and in situ SM data, we demonstrated that the soil effective temperature partly affects performances in terms of R_TB. Comparisons with other SMAP SM retrievals (multitemporal dual-channel algorithm and multichannel collaborative algorithm) revealed similar results in correlations and showed high spatiotemporal differences across all SM retrievals and study sites. Our findings highlight the complexity of the interactions between microwave observations and SM dynamics across the boreal biome, thus challenging the <italic>L</italic>-band passive microwave SM retrievals.https://ieeexplore.ieee.org/document/10999089/Boreal biomein situ measurementsoil moisture (SM)soil moisture active passive (SMAP) brightness temperaturesoil moisture and ocean salinity (SMOS) |
| spellingShingle | Azza Gorrab Oliver Sonnentag Arnaud Mialon Chelene C. Hanes Juliette Ortet Aaron A. Berg Muhammad Umair Alexandre Roy Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Boreal biome in situ measurement soil moisture (SM) soil moisture active passive (SMAP) brightness temperature soil moisture and ocean salinity (SMOS) |
| title | Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome |
| title_full | Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome |
| title_fullStr | Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome |
| title_full_unstemmed | Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome |
| title_short | Assessment of <italic>L</italic>-Band Passive Microwave Soil Moisture Retrievals Against In Situ Measurements in the North American Boreal Biome |
| title_sort | assessment of italic l italic band passive microwave soil moisture retrievals against in situ measurements in the north american boreal biome |
| topic | Boreal biome in situ measurement soil moisture (SM) soil moisture active passive (SMAP) brightness temperature soil moisture and ocean salinity (SMOS) |
| url | https://ieeexplore.ieee.org/document/10999089/ |
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