CTE-CRAE - Grup de Recerca en Ciències i Tecnologies de l'Espai
http://hdl.handle.net/2117/22219
2024-03-28T16:51:14Z
2024-03-28T16:51:14Z
Retrieving forest vegetation moisture content from a multi-sensor approach in the Western United States
Chaparro Danon, David
Jagdhuber, Thomas
Piles Guillem, María
Flührer, Anke
Jonard, François
Vall-llossera, M.
Camps Carmona, Adriano José
López-Martínez, Carlos
Feldman, Andrew F.
Entekhabi, Dara
http://hdl.handle.net/2117/387387
2023-05-12T10:30:34Z
2023-05-12T10:27:51Z
Retrieving forest vegetation moisture content from a multi-sensor approach in the Western United States
Chaparro Danon, David; Jagdhuber, Thomas; Piles Guillem, María; Flührer, Anke; Jonard, François; Vall-llossera, M.; Camps Carmona, Adriano José; López-Martínez, Carlos; Feldman, Andrew F.; Entekhabi, Dara
2023-05-12T10:27:51Z
Chaparro Danon, David
Jagdhuber, Thomas
Piles Guillem, María
Flührer, Anke
Jonard, François
Vall-llossera, M.
Camps Carmona, Adriano José
López-Martínez, Carlos
Feldman, Andrew F.
Entekhabi, Dara
Toward estimation of seasonal water dynamics of winter wheat from ground-based L-band radiometry: a concept study
Jagdhuber, Thomas
Jonard, François
Fluhrer, Anke
Chaparro Danon, David
Baur, Martin J.
Meyer, Thomas
Piles Guillem, María
http://hdl.handle.net/2117/368199
2022-06-12T15:42:49Z
2022-06-09T09:04:34Z
Toward estimation of seasonal water dynamics of winter wheat from ground-based L-band radiometry: a concept study
Jagdhuber, Thomas; Jonard, François; Fluhrer, Anke; Chaparro Danon, David; Baur, Martin J.; Meyer, Thomas; Piles Guillem, María
The vegetation optical depth (VOD) variable contains information on plant water content and biomass. It can be estimated alongside soil moisture from currently operating satellite radiometer missions, such as SMOS (ESA) and SMAP (NASA). The estimation of water fluxes, such as plant water uptake (PWU) and transpiration rate (TR), from these earth system parameters (VOD, soil moisture) requires assessing water potential gradients and flow resistances in the soil, the vegetation and the atmosphere. Yet water flux estimation remains an elusive challenge especially on a global scale. In this concept study, we conduct a field-scale experiment to test mechanistic models for the estimation of seasonal water fluxes (PWU and TR) of a winter wheat stand using measurements of soil moisture, VOD, and relative air humidity (RH) in a controlled environment. We utilize microwave L-band observations from a tower-based radiometer to estimate VOD of a wheat stand during the 2017 growing season at the Selhausen test site in Germany. From VOD, we first extract the gravimetric moisture of vegetation and then determine the relative water content (RWC) and vegetation water potential (VWP) of the wheat field. Although the relative water content could be directly estimated from VOD, our results indicate this may be challenging for the phenological phases, when rapid biomass and plant structure development take place within the wheat canopy. We estimate water uptake from the soil to the wheat plants from the difference between the soil and vegetation potentials divided by the flow resistance from soil into wheat plants. The TR from the wheat plants into the atmosphere was obtained from the difference between the vegetation and atmosphere water potentials divided by the flow resistances from plants to the atmosphere. For this, the required soil matric potential (SMP), the vapor pressure deficit (VPD), and the flow resistances were obtained from on-site observations of soil, plant, and atmosphere together with simple mechanistic models. This pathfinder study shows that the L-band microwave radiation contains valuable information on vegetation water status that enables the estimation of water dynamics (up to fluxes) from the soil via wheat plants into the atmosphere, when combined with additional information of soil and atmosphere water content. Still, assumptions have to be made when estimating the vegetation water potential from relative water content as well as the water flow resistances between soil, wheat plants, and atmosphere. Moreover, direct validation of water flux estimates for the assessment of their absolute accuracy could not be performed due to a lack of in situ PWU and TR measurements. Nonetheless, our estimates of water status, potentials, and fluxes show the expected temporal dynamics, known from the literature, and intercompare reasonably well in absolute terms with independent TR estimates of the NASA ECOSTRESS mission, which relies on a Priestly–Taylor type of retrieval model. Our findings support that passive microwave remote-sensing techniques qualify for the estimation of vegetation water dynamics next to traditionally measured stand-scale or plot-scale techniques. They might shed light on future capabilities of monitoring water dynamics in the soil–plant–atmosphere system including wide-area, remote-sensing-based earth observation data.
2022-06-09T09:04:34Z
Jagdhuber, Thomas
Jonard, François
Fluhrer, Anke
Chaparro Danon, David
Baur, Martin J.
Meyer, Thomas
Piles Guillem, María
The vegetation optical depth (VOD) variable contains information on plant water content and biomass. It can be estimated alongside soil moisture from currently operating satellite radiometer missions, such as SMOS (ESA) and SMAP (NASA). The estimation of water fluxes, such as plant water uptake (PWU) and transpiration rate (TR), from these earth system parameters (VOD, soil moisture) requires assessing water potential gradients and flow resistances in the soil, the vegetation and the atmosphere. Yet water flux estimation remains an elusive challenge especially on a global scale. In this concept study, we conduct a field-scale experiment to test mechanistic models for the estimation of seasonal water fluxes (PWU and TR) of a winter wheat stand using measurements of soil moisture, VOD, and relative air humidity (RH) in a controlled environment. We utilize microwave L-band observations from a tower-based radiometer to estimate VOD of a wheat stand during the 2017 growing season at the Selhausen test site in Germany. From VOD, we first extract the gravimetric moisture of vegetation and then determine the relative water content (RWC) and vegetation water potential (VWP) of the wheat field. Although the relative water content could be directly estimated from VOD, our results indicate this may be challenging for the phenological phases, when rapid biomass and plant structure development take place within the wheat canopy. We estimate water uptake from the soil to the wheat plants from the difference between the soil and vegetation potentials divided by the flow resistance from soil into wheat plants. The TR from the wheat plants into the atmosphere was obtained from the difference between the vegetation and atmosphere water potentials divided by the flow resistances from plants to the atmosphere. For this, the required soil matric potential (SMP), the vapor pressure deficit (VPD), and the flow resistances were obtained from on-site observations of soil, plant, and atmosphere together with simple mechanistic models. This pathfinder study shows that the L-band microwave radiation contains valuable information on vegetation water status that enables the estimation of water dynamics (up to fluxes) from the soil via wheat plants into the atmosphere, when combined with additional information of soil and atmosphere water content. Still, assumptions have to be made when estimating the vegetation water potential from relative water content as well as the water flow resistances between soil, wheat plants, and atmosphere. Moreover, direct validation of water flux estimates for the assessment of their absolute accuracy could not be performed due to a lack of in situ PWU and TR measurements. Nonetheless, our estimates of water status, potentials, and fluxes show the expected temporal dynamics, known from the literature, and intercompare reasonably well in absolute terms with independent TR estimates of the NASA ECOSTRESS mission, which relies on a Priestly–Taylor type of retrieval model. Our findings support that passive microwave remote-sensing techniques qualify for the estimation of vegetation water dynamics next to traditionally measured stand-scale or plot-scale techniques. They might shed light on future capabilities of monitoring water dynamics in the soil–plant–atmosphere system including wide-area, remote-sensing-based earth observation data.
Monitoring forest above-ground biomass from multifrequency vegetation optical depth: a preliminary study
Olivares Cabello, Claudia Lily
Chaparro Danon, David
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
http://hdl.handle.net/2117/367024
2024-01-21T10:19:43Z
2022-05-06T13:29:43Z
Monitoring forest above-ground biomass from multifrequency vegetation optical depth: a preliminary study
Olivares Cabello, Claudia Lily; Chaparro Danon, David; Vall-Llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano José
Vegetation Optical Depth (VOD) is highly sensitive to Above-ground Biomass (AGB), particularly at L-band, as this band is more sensitive to the canopy layer and has greater ca pacity to penetrate the vegetation. However, higher frequen cies, such as C- and X-bands are more related to smaller veg etation structures. Then a combination of these three bands is expected to be relevant to accurate AGB retrievals. This study presents a comparison of three VOD products at three bands and evaluates the performance of a multi-frequency VOD combination by applying a Principal Component Re gression (PCR) to Forest biomass. Results show that L-band VOD captures the 84% of the biomass and the PCR is built, mainly, for this band meaning that higher frequencies do not contribute substantially to the AGB retrieval in this study, still they do not affect the retrievals negatively.
2022-05-06T13:29:43Z
Olivares Cabello, Claudia Lily
Chaparro Danon, David
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
Vegetation Optical Depth (VOD) is highly sensitive to Above-ground Biomass (AGB), particularly at L-band, as this band is more sensitive to the canopy layer and has greater ca pacity to penetrate the vegetation. However, higher frequen cies, such as C- and X-bands are more related to smaller veg etation structures. Then a combination of these three bands is expected to be relevant to accurate AGB retrievals. This study presents a comparison of three VOD products at three bands and evaluates the performance of a multi-frequency VOD combination by applying a Principal Component Re gression (PCR) to Forest biomass. Results show that L-band VOD captures the 84% of the biomass and the PCR is built, mainly, for this band meaning that higher frequencies do not contribute substantially to the AGB retrieval in this study, still they do not affect the retrievals negatively.
Parameter considerations for the retrieval of surface soil moisture from spaceborne GNSS-R
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raúl
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
http://hdl.handle.net/2117/366286
2022-05-01T01:19:08Z
2022-04-25T09:24:01Z
Parameter considerations for the retrieval of surface soil moisture from spaceborne GNSS-R
Muñoz Martin, Joan Francesc; Onrubia Ibáñez, Raúl; Pascual Biosca, Daniel; Hyuk, Park; Camps Carmona, Adriano José; Rudiger, Christoph; Walker, Jeffrey; Monerris Belda, Alessandra
The Microwave Interferometric Reflectometer (MIR) is an airborne GNSS-R instrument developed by Universitat Politècnica de Catalunya. In 2018, it was flown twice over the agricultural Yanco area, New South Wales, Australia, once after a very dry period, and a further time the day after a strong rain event. This rain event resulted in many crop fields being entirely flooded, producing a saturation in the GNSS-R reflectivity value. In this work, the received data set is processed to identify the optimum integration time with the goal to minimize pixel blurring. This issue is assessed for airborne conditions, and then extra-polated to the spaceborne case. The presented results show that the blurring of the GNSS waveform is produced even from an airborne sensor with short integration times. Following the determination of an optimal integration time for the platform in use, the surface roughness term in the reflectivity equation can be isolated due to the signal saturation during very wet surface conditions. The final results from the two channels (L1 C/A and L5) are subsequently presented. In this case, it is shown that most reflectivity variations in GNSS-R measurements are linked to surface roughness and Speckle noise fluctuations rather than soil moisture changes.
2022-04-25T09:24:01Z
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raúl
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
The Microwave Interferometric Reflectometer (MIR) is an airborne GNSS-R instrument developed by Universitat Politècnica de Catalunya. In 2018, it was flown twice over the agricultural Yanco area, New South Wales, Australia, once after a very dry period, and a further time the day after a strong rain event. This rain event resulted in many crop fields being entirely flooded, producing a saturation in the GNSS-R reflectivity value. In this work, the received data set is processed to identify the optimum integration time with the goal to minimize pixel blurring. This issue is assessed for airborne conditions, and then extra-polated to the spaceborne case. The presented results show that the blurring of the GNSS waveform is produced even from an airborne sensor with short integration times. Following the determination of an optimal integration time for the platform in use, the surface roughness term in the reflectivity equation can be isolated due to the signal saturation during very wet surface conditions. The final results from the two channels (L1 C/A and L5) are subsequently presented. In this case, it is shown that most reflectivity variations in GNSS-R measurements are linked to surface roughness and Speckle noise fluctuations rather than soil moisture changes.
Vegetation canopy height retrieval using L1 and L5 airborne GNSS-R
Muñoz Martínez, Francisco José
Pascual Biosca, Daniel
Onrubia Ibáñez, Raúl
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
http://hdl.handle.net/2117/366262
2022-04-24T13:49:47Z
2022-04-22T11:44:12Z
Vegetation canopy height retrieval using L1 and L5 airborne GNSS-R
Muñoz Martínez, Francisco José; Pascual Biosca, Daniel; Onrubia Ibáñez, Raúl; Hyuk, Park; Camps Carmona, Adriano José; Rudiger, Christoph; Walker, Jeffrey; Monerris Belda, Alessandra
Vegetation canopy height (CH) is one of the important remote-sensing parameters related to forests’ structure, and it can be related to the biomass and the carbon stock. Global navigation satellite system-reflectometry (GNSS-R) has proved capable to retrieve vegetation information at a moderate resolution from space (20–65 km) using L1 C/A signals. In this study, data retrieved by the airborne microwave interferometric reflectometer (MIR) GNSS-R instrument at L1 and L5 are compared to the Global Forest CH product, with a spatial resolution of 30 m. This work analyzes the waveforms (WFs) measured at both bands, and the correlation of the waveform width and the reflectivity values to the CH product. A neural network algorithm is used for the retrieval, showing that the combination of the reflectivity and the waveform width allows to estimate the CH information at a very high resolution, with a root-mean-square error (RMSE) of 4.25 and 4.07 m at L1 and L5, respectively, which is an error about 14% of the actual CH.
2022-04-22T11:44:12Z
Muñoz Martínez, Francisco José
Pascual Biosca, Daniel
Onrubia Ibáñez, Raúl
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
Vegetation canopy height (CH) is one of the important remote-sensing parameters related to forests’ structure, and it can be related to the biomass and the carbon stock. Global navigation satellite system-reflectometry (GNSS-R) has proved capable to retrieve vegetation information at a moderate resolution from space (20–65 km) using L1 C/A signals. In this study, data retrieved by the airborne microwave interferometric reflectometer (MIR) GNSS-R instrument at L1 and L5 are compared to the Global Forest CH product, with a spatial resolution of 30 m. This work analyzes the waveforms (WFs) measured at both bands, and the correlation of the waveform width and the reflectivity values to the CH product. A neural network algorithm is used for the retrieval, showing that the combination of the reflectivity and the waveform width allows to estimate the CH information at a very high resolution, with a root-mean-square error (RMSE) of 4.25 and 4.07 m at L1 and L5, respectively, which is an error about 14% of the actual CH.
Untangling the GNSS-R coherent and incoherent components: Experimental evidences over the ocean
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raul
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
http://hdl.handle.net/2117/366047
2022-04-24T03:47:44Z
2022-04-19T11:34:30Z
Untangling the GNSS-R coherent and incoherent components: Experimental evidences over the ocean
Muñoz Martin, Joan Francesc; Onrubia Ibáñez, Raul; Pascual Biosca, Daniel; Hyuk, Park; Camps Carmona, Adriano José; Rudiger, Christoph; Walker, Jeffrey; Monerris Belda, Alessandra
Global Navigation Satellite Systems Reflected (GNSS-R) signals exhibit an incoherent and a coherent components [1], [2]. Current models assume that one or the other are dominant, and the calibration, and geophysical parameter retrieval (eg. wind speed, soil moisture ...) are developed accordingly. Even the presence itself of the coherent component of a GNSS reflected signal has been a matter of discussion in the last years. In this work, the method used in [3] to separate the leakage of the direct signal from the reflected one is applied to a set of GNSS signals reflected collected over the ocean by the MIR [4], [5], an airborne dual-band (L1/E1 and L5/E5a), multi-constellation (GPS and Galileo) GNSS-R instrument with two 19-elements array with 4 beam-steered each. The results presented demonstrate the feasibility of the proposed technique to untangle the coherent and incoherent components in GNSS reflected signals. This technique allows the processing of these components separately, which will increase the calibration accuracy (as today both are mixed together), and allows high resolution applications since the spatial resolution of the coherent component is determined by the size of the first Fresnel zone [6] (300-500 meters from a LEO satellite), and not by the size of the glistening zone (~25 km from a LEO satellite).
© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
2022-04-19T11:34:30Z
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raul
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
Global Navigation Satellite Systems Reflected (GNSS-R) signals exhibit an incoherent and a coherent components [1], [2]. Current models assume that one or the other are dominant, and the calibration, and geophysical parameter retrieval (eg. wind speed, soil moisture ...) are developed accordingly. Even the presence itself of the coherent component of a GNSS reflected signal has been a matter of discussion in the last years. In this work, the method used in [3] to separate the leakage of the direct signal from the reflected one is applied to a set of GNSS signals reflected collected over the ocean by the MIR [4], [5], an airborne dual-band (L1/E1 and L5/E5a), multi-constellation (GPS and Galileo) GNSS-R instrument with two 19-elements array with 4 beam-steered each. The results presented demonstrate the feasibility of the proposed technique to untangle the coherent and incoherent components in GNSS reflected signals. This technique allows the processing of these components separately, which will increase the calibration accuracy (as today both are mixed together), and allows high resolution applications since the spatial resolution of the coherent component is determined by the size of the first Fresnel zone [6] (300-500 meters from a LEO satellite), and not by the size of the glistening zone (~25 km from a LEO satellite).
First experimental evidence of wind and swell signatures in L5 GPS and E5A Galileo GNSS-R waveforms
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raúl
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
http://hdl.handle.net/2117/366044
2022-04-24T07:23:44Z
2022-04-19T11:02:54Z
First experimental evidence of wind and swell signatures in L5 GPS and E5A Galileo GNSS-R waveforms
Muñoz Martin, Joan Francesc; Onrubia Ibáñez, Raúl; Pascual Biosca, Daniel; Hyuk, Park; Camps Carmona, Adriano José; Rudiger, Christoph; Walker, Jeffrey; Monerris Belda, Alessandra
As compared to the using L1C/A signals, L5/E5a Global Navigation Satellite System - Reflectometry (GNSS-R), gives improved resolution over the Earth's surface due to the sharper auto-correlation function. Furthermore, the larger transmitted power (+3dB with respect to L1 C/A), and correlation gain (+40dB) allows the reception of weaker reflected signals. If high directivity antennas are used, very short incoherent integration times are needed to have enough signal-to-noise (SNR) ratios, allowing the reception of multiple specular reflection points such as crest of consecutive waves without the blurring induced by long incoherent integration times. This study presents for the first time experimental evidence of the wind and swell waves signatures in the GNSS-R waveforms, and compares them with models.
© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
2022-04-19T11:02:54Z
Muñoz Martin, Joan Francesc
Onrubia Ibáñez, Raúl
Pascual Biosca, Daniel
Hyuk, Park
Camps Carmona, Adriano José
Rudiger, Christoph
Walker, Jeffrey
Monerris Belda, Alessandra
As compared to the using L1C/A signals, L5/E5a Global Navigation Satellite System - Reflectometry (GNSS-R), gives improved resolution over the Earth's surface due to the sharper auto-correlation function. Furthermore, the larger transmitted power (+3dB with respect to L1 C/A), and correlation gain (+40dB) allows the reception of weaker reflected signals. If high directivity antennas are used, very short incoherent integration times are needed to have enough signal-to-noise (SNR) ratios, allowing the reception of multiple specular reflection points such as crest of consecutive waves without the blurring induced by long incoherent integration times. This study presents for the first time experimental evidence of the wind and swell waves signatures in the GNSS-R waveforms, and compares them with models.
Error propagation in microwave soil moisture and vegetation optical depth retrievals
Feldman, Andrew F.
Chaparro Danon, David
Entekhabi, Dara
http://hdl.handle.net/2117/365811
2022-04-17T17:35:07Z
2022-04-13T08:04:55Z
Error propagation in microwave soil moisture and vegetation optical depth retrievals
Feldman, Andrew F.; Chaparro Danon, David; Entekhabi, Dara
Satellite soil moisture and vegetation optical depth [(VOD); related to the total vegetation water mass per unit area] are increasingly being used to study water relations in the soil-plant continuum across the globe. However, soil moisture and VOD are typically jointly estimated, where errors in the optimization approach can cause compensation between both variables and confound such studies. It is thus critical to quantify how satellite microwave measurement errors propagate into soil moisture and VOD. Such a study is especially important for VOD given limited investigations of whether VOD reflects in situ plant physiology. Furthermore, despite new approaches that constrain (or regularize) VOD dynamics to reduce soil moisture errors, there is limited study of whether regularization reduces VOD errors without obscuring true vegetation temporal dynamics. Here, we find that, across the globe, VOD is less robust to measurement error (more difficult for optimization methods to find the true solution) than soil moisture in their joint estimation. However, a moderate degree of regularization (via time-constrained VOD) reduces errors in VOD to a greater degree than soil moisture and reduces spurious soil moisture-VOD coupling. Furthermore, despite constraining VOD time dynamics, regularized VOD variations on subweekly scales are both closer to simulated true VOD time series and have global VOD post-rainfall responses with reduced error signatures compared to VOD retrievals without regularization. Ultimately, we recommend moderately regularized VOD for use in large scale studies of soil-plant water relations because it suppresses noise and spurious soil moisture-VOD coupling without removing the physical signal.
The MTDCA soil moisture and VOD datasets are freely available at https://doi.org/10.5281/zenodo.5579549. The DCA retrievals generated for this study are freely available from the authors upon request.
2022-04-13T08:04:55Z
Feldman, Andrew F.
Chaparro Danon, David
Entekhabi, Dara
Satellite soil moisture and vegetation optical depth [(VOD); related to the total vegetation water mass per unit area] are increasingly being used to study water relations in the soil-plant continuum across the globe. However, soil moisture and VOD are typically jointly estimated, where errors in the optimization approach can cause compensation between both variables and confound such studies. It is thus critical to quantify how satellite microwave measurement errors propagate into soil moisture and VOD. Such a study is especially important for VOD given limited investigations of whether VOD reflects in situ plant physiology. Furthermore, despite new approaches that constrain (or regularize) VOD dynamics to reduce soil moisture errors, there is limited study of whether regularization reduces VOD errors without obscuring true vegetation temporal dynamics. Here, we find that, across the globe, VOD is less robust to measurement error (more difficult for optimization methods to find the true solution) than soil moisture in their joint estimation. However, a moderate degree of regularization (via time-constrained VOD) reduces errors in VOD to a greater degree than soil moisture and reduces spurious soil moisture-VOD coupling. Furthermore, despite constraining VOD time dynamics, regularized VOD variations on subweekly scales are both closer to simulated true VOD time series and have global VOD post-rainfall responses with reduced error signatures compared to VOD retrievals without regularization. Ultimately, we recommend moderately regularized VOD for use in large scale studies of soil-plant water relations because it suppresses noise and spurious soil moisture-VOD coupling without removing the physical signal.
Global L-band vegetation volume fraction estimates for modeling vegetation optical depth
Chaparro Danon, David
Jagdhuber, Thomas
Piles Guillem, María
Entekhabi, Dara
Jonard, François
Fluhrer, Anke
Feldman, Andrew F.
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
http://hdl.handle.net/2117/365791
2022-04-12T16:40:22Z
2022-04-12T16:32:51Z
Global L-band vegetation volume fraction estimates for modeling vegetation optical depth
Chaparro Danon, David; Jagdhuber, Thomas; Piles Guillem, María; Entekhabi, Dara; Jonard, François; Fluhrer, Anke; Feldman, Andrew F.; Vall-Llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano José
The attenuation of microwave emissions through the canopy is quantified by the vegetation optical depth (VOD), which is related to the amount of water, the biomass and the structure of vegetation. To provide microwave-derived plant water estimates, one must account for biomass/structure contributions in order to extract the water component from the VOD. This study uses Aquarius scatterometer data to build an L-band global seasonality of vegetation volume fraction (d), representative of biomass/structure dynamics. The dynamic range of d is adapted for its application in a gravimetric moisture (Mg) retrieval model. Results show that d ranging from 0 to 3.35.10- 4 is needed for modelling physically reasonable Mg values. The global average of d shows consistent spatial patterns across vegetation distributions, and d seasonality is coherent with the phenology of the studied vegetation types. These findings enable the separation of information on vegetation water and biomass/structure inherent within VOD.
2022-04-12T16:32:51Z
Chaparro Danon, David
Jagdhuber, Thomas
Piles Guillem, María
Entekhabi, Dara
Jonard, François
Fluhrer, Anke
Feldman, Andrew F.
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
The attenuation of microwave emissions through the canopy is quantified by the vegetation optical depth (VOD), which is related to the amount of water, the biomass and the structure of vegetation. To provide microwave-derived plant water estimates, one must account for biomass/structure contributions in order to extract the water component from the VOD. This study uses Aquarius scatterometer data to build an L-band global seasonality of vegetation volume fraction (d), representative of biomass/structure dynamics. The dynamic range of d is adapted for its application in a gravimetric moisture (Mg) retrieval model. Results show that d ranging from 0 to 3.35.10- 4 is needed for modelling physically reasonable Mg values. The global average of d shows consistent spatial patterns across vegetation distributions, and d seasonality is coherent with the phenology of the studied vegetation types. These findings enable the separation of information on vegetation water and biomass/structure inherent within VOD.
Validation of SMOS L3 and L4 soil moisture products in the REMEDHUS (Spain) and CEMADEN (brazil) networks
Rossato, Luciana
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
Chaparro Danon, David
Alvalá, Regina Célia dos Santos
Barbosa Alves, Humberto
http://hdl.handle.net/2117/339608
2022-05-17T10:45:04Z
2021-02-15T11:13:54Z
Validation of SMOS L3 and L4 soil moisture products in the REMEDHUS (Spain) and CEMADEN (brazil) networks
Rossato, Luciana; Vall-Llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano José; Chaparro Danon, David; Alvalá, Regina Célia dos Santos; Barbosa Alves, Humberto
This work analyzes the quality of the soil moisture L3 (25 km) and L4 (1 km) products generated at the Barcelona Expert Center (BEC) in two sites located in distinct semi-arid regions, where measurement networks are installed: “Red de Estaciones de Medición de la Humedad del Suelo” (REMEDHUS), which is located in the central part of the Duero basin (Spain), and National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN), at Northeast of the Brazil. REMEDHUS has been used as a calibration/validation site for SMOS and SMAP missions. It is a dense network covering 35 x 35 km2 and it has 22 stations. The CEMADEN network provides a database for the development of early warnings for natural disasters that occurs in Brazil, such as droughts and floods. It is a sparse network covering 1000 x 1000 km2 with more than 500 station. Results show good correspondence between SMOS L4 data and the in situ soil moisture data for REMEDHUS and CEMADEN networks. Correlations mean range from 0.3 to 0.8, and depend mainly on the station situation, soil type, and land cover on both Spain and Brazil networks. For the average data of both series, the correlation coefficient is higher than 0.6. Results show that the L4 product are better correlated than the L3 product, although L4 and L3 products are quite similar. This indicates that both products are ready for its operational use, with L4 providing a better representation of the soil moisture status at finer scales.; Este trabalho analisa a qualidade dos produtos L3 (25 km) e L4 (1 km) de umidade do solo gerados no Barcelona Expert Center (BEC) em dois locais localizados em regiões semi-áridas distintas, onde estão instaladas redes de medição: Estações de Medição de Umidade do Solo” (REMEDHUS), localizado na parte central da bacia do Douro (Espanha), e Centro Nacional de Monitoramento e Aviso Prévio de Desastres Naturais (CEMADEN), no nordeste do Brasil. O REMEDHUS foi usado como um local de calibração / validação para missões SMOS e SMAP. É uma rede densa cobrindo 35 x 35 km2 e possui 22 estações. A rede CEMADEN fornece um banco de dados para o desenvolvimento de alertas precoces de desastres naturais que ocorrem no Brasil, como secas e inundações. É uma rede esparsa cobrindo 1000 x 1000 km2 com mais de 500 estações. Os resultados mostram boa correspondência entre os dados SMOS L4 e os dados de umidade do solo in situ para as redes REMEDHUS e CEMADEN. As correlações variam de 0,3 a 0,8 e dependem principalmente da situação da estação, tipo de solo e cobertura do solo nas redes da Espanha e do Brasil. Para os dados médios de ambas as séries, o coeficiente de correlação é superior a 0,6. Os resultados mostram que o produto L4 está melhor correlacionado que o produto L3, embora os produtos L4 e L3 sejam bastante semelhantes. Isso indica que ambos os produtos estão prontos para seu uso operacional, com L4 fornecendo uma melhor representação do status de umidade do solo em escalas mais refinadas
2021-02-15T11:13:54Z
Rossato, Luciana
Vall-Llossera Ferran, Mercedes Magdalena
Camps Carmona, Adriano José
Chaparro Danon, David
Alvalá, Regina Célia dos Santos
Barbosa Alves, Humberto
This work analyzes the quality of the soil moisture L3 (25 km) and L4 (1 km) products generated at the Barcelona Expert Center (BEC) in two sites located in distinct semi-arid regions, where measurement networks are installed: “Red de Estaciones de Medición de la Humedad del Suelo” (REMEDHUS), which is located in the central part of the Duero basin (Spain), and National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN), at Northeast of the Brazil. REMEDHUS has been used as a calibration/validation site for SMOS and SMAP missions. It is a dense network covering 35 x 35 km2 and it has 22 stations. The CEMADEN network provides a database for the development of early warnings for natural disasters that occurs in Brazil, such as droughts and floods. It is a sparse network covering 1000 x 1000 km2 with more than 500 station. Results show good correspondence between SMOS L4 data and the in situ soil moisture data for REMEDHUS and CEMADEN networks. Correlations mean range from 0.3 to 0.8, and depend mainly on the station situation, soil type, and land cover on both Spain and Brazil networks. For the average data of both series, the correlation coefficient is higher than 0.6. Results show that the L4 product are better correlated than the L3 product, although L4 and L3 products are quite similar. This indicates that both products are ready for its operational use, with L4 providing a better representation of the soil moisture status at finer scales.
Este trabalho analisa a qualidade dos produtos L3 (25 km) e L4 (1 km) de umidade do solo gerados no Barcelona Expert Center (BEC) em dois locais localizados em regiões semi-áridas distintas, onde estão instaladas redes de medição: Estações de Medição de Umidade do Solo” (REMEDHUS), localizado na parte central da bacia do Douro (Espanha), e Centro Nacional de Monitoramento e Aviso Prévio de Desastres Naturais (CEMADEN), no nordeste do Brasil. O REMEDHUS foi usado como um local de calibração / validação para missões SMOS e SMAP. É uma rede densa cobrindo 35 x 35 km2 e possui 22 estações. A rede CEMADEN fornece um banco de dados para o desenvolvimento de alertas precoces de desastres naturais que ocorrem no Brasil, como secas e inundações. É uma rede esparsa cobrindo 1000 x 1000 km2 com mais de 500 estações. Os resultados mostram boa correspondência entre os dados SMOS L4 e os dados de umidade do solo in situ para as redes REMEDHUS e CEMADEN. As correlações variam de 0,3 a 0,8 e dependem principalmente da situação da estação, tipo de solo e cobertura do solo nas redes da Espanha e do Brasil. Para os dados médios de ambas as séries, o coeficiente de correlação é superior a 0,6. Os resultados mostram que o produto L4 está melhor correlacionado que o produto L3, embora os produtos L4 e L3 sejam bastante semelhantes. Isso indica que ambos os produtos estão prontos para seu uso operacional, com L4 fornecendo uma melhor representação do status de umidade do solo em escalas mais refinadas