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Can we use satellite-based soil-moisture products at high resolution to investigate land-use differences and land-atmosphere interactions? a case study in the savanna

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Yagüe Anguis, Carlos (2020) Can we use satellite-based soil-moisture products at high resolution to investigate land-use differences and land-atmosphere interactions? a case study in the savanna. Remote sensing, 12 (11). ISSN 2072-4292

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Official URL: http://dx.doi.org/10.3390/rs12111701




Abstract

The use of soil moisture (SM) measurements from satellites has grown in recent years, fostering the development of new products at high resolution. This opens the possibility of using them for certain applications that were normally carried out using in situ data. We investigated this hypothesis through two main analyses using two high-resolution satellite-based soil moisture (SBSM) products that combined microwave with thermal and optical data: (1) The Disaggregation based on Physical And Theoretical scale Change (DISPATCH) and, (2) The Soil Moisture Ocean Salinity-Barcelona Expert Center (SMOS-BEC Level 4). We used these products to analyse the SM differences among pixels with contrasting vegetation. This was done through the comparison of the SM measurements from satellites and the measurements simulated with a simple antecedent precipitation index (API) model, which did not account for the surface characteristics. Subsequently, the deviation of the SM from satellite with respect to the API model (bias) was analysed and compared for contrasting land use categories. We hypothesised that the differences in the biases of the varied categories could provide information regarding the water retention capacity associated with each type of vegetation. From the satellite measurements, we determined how the SM depended on the tree cover, i.e., the denser the tree cover, the higher the SM. However, in winter periods with light rain events, the tree canopy could dampen the moistening of the soil through interception and conducted higher SM in the open areas. This evolution of the SM differences that depended on the characteristics of each season was observed both from satellite and from in situ measurements taken beneath a tree and in grass on the savanna landscape. The agreement between both types of measurements highlighted the potential of the SBSM products to investigate the SM of each type of vegetation. We found that the results were clearer for DISPATCH, whose data was not smoothed spatially as it was in SMOS-BEC. We also tested whether the relationships between SM and evapotranspiration could be investigated using satellite data. The answer to this question was also positive but required removing the unrealistic high-frequency SM oscillations from the satellite data using a low pass filter. This improved the performance scores of the products and the agreement with the results from the in situ data. These results demonstrated the possibility of using SM data from satellites to substitute ground measurements for the study of land–atmosphere interactions, which encourages efforts to improve the quality and resolution of these measurements.


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© 2020 by the authors. Artículo firmado por 14 autores. The authors thank AEMET and UC for the Spain02 v5 dataset, available at http://www. meteo.unican.es/datasets/spain02. We also acknowledge the ICTS-EBD technical resources. SMOS-BEC data were produced by the Barcelona Expert Center (bec.icm.csic.es), a joint initiative of the Spanish Research Council (CSIC) and the Technical University of Catalonia (UPC), mainly funded by the Spanish National Program on Space. The authors would like to thank the SMOS CATDS L3SM product (http://www.cesbio.ups-tlse.fr/SMOS_blog/), IFAPA for the Sta Clotilde data, SYPNA land use information data, and the soil-type data available in the WRF model from USDA. Carlos Román-Cascón work was funded through a Postdoctoral Grant funded by the Centre National d’Études Spatiales (CNES). The European Commission Horizon 2020 Programme for Research and Innovation (H2020) in the context of the Marie Sklodowska-Curie Research and Innovation Staff Exchange (RISE) action (ACCWA project, grant agreement No 823965) has funded the PhD of Nitu Ojha. Dr. Andreu’s work was funded by the European Union’s Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie grant agreement No 703978. The Spanish government project CGL2015-65627-C3-3-R (MINECO/FEDER) has also partially funded part of this work.

Uncontrolled Keywords:Variability; Grasses; Scales; Trees; Water
Subjects:Sciences > Physics > Atmospheric physics
ID Code:62119
Deposited On:23 Sep 2020 09:49
Last Modified:23 Sep 2020 10:48

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