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Evaporative Fluxes and Surface Soil Moisture Retrievals in a Mediterranean Setting from Sentinel-3 and the “Simplified Triangle”. REMOTE SENSING 2020. [DOI: 10.3390/rs12193192] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Earth Observation (EO) makes it possible to obtain information on key parameters characterizing interactions among Earth’s system components, such as evaporative fraction (EF) and surface soil moisture (SSM). Notably, techniques utilizing EO data of land surface temperature (Ts) and vegetation index (VI) have shown promise in this regard. The present study investigates, for the first time, the accuracy of one such technique, known as the “simplified triangle”, using Sentinel-3 EO data, acquired for 44 days in 2018 at three savannah FLUXNET sites in Spain. The technique was found to be able to predict both EF and SSM with reasonable accuracy when compared to collocated ground measurements. Comparisons performed for all days together showed relatively low Root Mean square Difference (RMSD) for both EF (0.191) and SSM (0.012 cm3 cm−3) and good correlation coefficients (R) of 0.721 and 0.577, respectively. Both EF and SSM were also largely in agreement with land cover and seasonal variability. The present study comprises the first detailed assessment of the “simplified triangle”, in this case, using Sentinel-3 data and in a Mediterranean setting. Findings, albeit preliminary, are of significant value regarding the use of the investigated technique as a tool of environmental management, and towards ongoing, worldwide efforts aiming at developing operationally relevant products based on the Ts/VI feature space and EO data based on new satellites such as Sentinel-3.
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Nutini F, Stroppiana D, Busetto L, Bellingeri D, Corbari C, Mancini M, Zini E, Brivio PA, Boschetti M. A Weekly Indicator of Surface Moisture Status from Satellite Data for Operational Monitoring of Crop Conditions. SENSORS 2017; 17:s17061338. [PMID: 28598399 PMCID: PMC5492004 DOI: 10.3390/s17061338] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 06/05/2017] [Accepted: 06/06/2017] [Indexed: 11/16/2022]
Abstract
The triangle method has been applied to derive a weekly indicator of evaporative fraction on vegetated areas in a temperate region in Northern Italy. Daily MODIS Aqua Land Surface Temperature (MYD11A1) data has been combined with air temperature maps and 8-day composite MODIS NDVI (MOD13Q1/MYD13Q1) data to estimate the Evaporative Fraction (EF) at 1 km resolution, on a daily basis. Measurements at two eddy covariance towers located within the study area have been exploited to assess the reliability of satellite based EF estimations as well as the robustness of input data. Weekly syntheses of the daily EF indicator (EFw) were then derived at regional scale for the years 2010, 2011 and 2012 as a proxy of overall surface moisture condition. EFw showed a temporal behavior consistent with growing cycles and agro-practices of the main crops cultivated in the study area (rice, forages and corn). Comparison with official regional corn yield data showed that variations in EFw cumulated over summer are related with crop production shortages induced by water scarcity. These results suggest that weekly-averaged EF estimated from MODIS data is sensible to water stress conditions and can be used as an indicator of crops’ moisture conditions at agronomical district level. Advantages and disadvantages of the proposed approach to provide information useful to issue operational near real time bulletins on crop conditions at regional scale are discussed.
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Affiliation(s)
- Francesco Nutini
- Institute for Electromagnetic Sensing of the Environment, Italian National Research Council, Via Bassini 15, Milano 20133, Italy.
| | - Daniela Stroppiana
- Institute for Electromagnetic Sensing of the Environment, Italian National Research Council, Via Bassini 15, Milano 20133, Italy.
| | - Lorenzo Busetto
- Institute for Electromagnetic Sensing of the Environment, Italian National Research Council, Via Bassini 15, Milano 20133, Italy.
| | - Dario Bellingeri
- ARPA Lombardia, Lombardy Environmental Protection Agency, Via Ippolito Rosellini 17, Milano 20124, Italy.
| | - Chiara Corbari
- Politecnico di Milano, Department of Civil and Environmental Engineering, Piazza Leonardo da Vinci 32, Milano 20133, Italy.
| | - Marco Mancini
- Politecnico di Milano, Department of Civil and Environmental Engineering, Piazza Leonardo da Vinci 32, Milano 20133, Italy.
| | - Enrico Zini
- ARPA Lombardia, Lombardy Environmental Protection Agency, Via Ippolito Rosellini 17, Milano 20124, Italy.
| | - Pietro Alessandro Brivio
- Institute for Electromagnetic Sensing of the Environment, Italian National Research Council, Via Bassini 15, Milano 20133, Italy.
| | - Mirco Boschetti
- Institute for Electromagnetic Sensing of the Environment, Italian National Research Council, Via Bassini 15, Milano 20133, Italy.
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A New Contextual Parameterization of Evaporative Fraction to Reduce the Reliance of the Ts − VI Triangle Method on the Dry Edge. REMOTE SENSING 2017. [DOI: 10.3390/rs9010026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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