scholarly journals SCoBi Multilayer: A Signals of Opportunity Reflectometry Model for Multilayer Dielectric Reflections

2020 ◽  
Vol 12 (21) ◽  
pp. 3480
Author(s):  
Dylan Boyd ◽  
Mehmet Kurum ◽  
Orhan Eroglu ◽  
Ali Cafer Gurbuz ◽  
James L. Garrison ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Electric Fields ◽  
Moisture Profile ◽  
Moisture Sensitivity ◽  
Bistatic Scattering ◽  
Subsurface Soil ◽  
Moisture Profiles ◽  
The Relationship ◽  
Signals Of Opportunity ◽  
Multilayer Dielectric

A multilayer module is incorporated into the Signals of Opportunity (SoOp) Coherent Bistatic Scattering model (SCoBi) for determining the reflections and propagation of electric fields within a series of multilayer dielectric slabs. This module can be used in conjunction with other SCoBi components to simulate complex, bistatic simulation schemes that include features such as surface roughness, vegetation, antenna effects, and multilayer soil moisture interactions on reflected signals. This paper introduces the physics underlying the multilayer module and utilizes it to perform a simulation study of the response of SoOp-R measurements with respect to subsurface soil moisture parameters. For a frequency range of 100–2400 MHz, it is seen that the SoOp-R response to a single dielectric slab is mostly frequency insensitive; however, the SoOp-R response to multilayer dielectric slabs will vary between frequencies. The relationship between SoOp-R reflectivity and the contributing depth is visualized, and the results show that SoOp-R measurements can display sensitivity to soil moisture below the penetration depth. By simulation of simple soil moisture profiles with different wetting and drying gradients, the dielectric contrast between layers is shown to be the greatest contributing factor to subsurface soil moisture sensitivity. Overall, it is observed that different frequencies can sense different areas of a soil moisture profile, and this behavior can enable subsurface soil moisture data products from SoOp-R observations.

scholarly journals Bistatic scattering simulations of circular and linear polarizations over land surface for signals of opportunity reflectometry

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xuerui Wu ◽  
Yezhi Song ◽  
Jin Xu ◽  
Zheng Duan ◽  
Shuanggen Jin
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Development Stage ◽  
Forward Scattering ◽  
Initial Development ◽  
Surface Parameters ◽  
Vegetation Biomass ◽  
Bistatic Scattering ◽  
Land Surface Parameters ◽  
Signals Of Opportunity

AbstractSignals of Opportunity Reflectometry (SoOp-R) employs the communication system, GNSS (Global Navigation Satellite System) constellation and other potential Signals of Opportunity (SoOp) as the transmitters. In recent years, it has gained increased interests. Several experiments have been carried out, however it is still in the initial development stage. Theoretical predictions of SoOp Reflectometry for land surface parameters detection, such as soil moisture and vegetation biomass, should be carried out simultaneously. Meanwhile, at present less works are paid attention to the polarization study of the polarizations. The first-order radiative transfer equation models are employed here and they are developed according to the wave synthesis technique to get the various polarization combinations. Using the two models as analysis tools, we simulate the bistatic scattering at all potential SoOp Reflectometry bands, i.e., P-, L-, C- and X-band for circular polarizations and linear polarizations. While the original commonly used microwave scattering models are linear polarizations, here we compare the difference. Although the models can simulate bistatic scattering at any incident angles and scattering angles. Four special observation geometry are taken into considerations during the analysis. Using the developed models as tools, the developed models establish the relationship between the land surface parameters (such as soil moisture, soil roughness and vegetation water content, diameters et al.) and bistatic radar cross section. The forward scattering models developed here enables the understanding of the effects of different geophysical parameters and transmitter–receiver observation scenarios on the bisatic scattering at any polarization combinations for any potential SoOP reflectometry bands. Robust retrieval methods for soil moisture and vegetation biomass can benefit from the forward scattering models.

scholarly journals Improving soil moisture profile prediction from ground-penetrating radar data: a maximum likelihood ensemble filter approach

2013 ◽  
Vol 10 (2) ◽  
pp. 1581-1615
Author(s):  
A. P. Tran ◽  
M. Vanclooster ◽  
S. Lambot
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Ground Penetrating Radar ◽  
Time Lapse ◽  
Loamy Sand ◽  
Moisture Profile ◽  
Ground Penetrating ◽  
Maximum Likelihood Ensemble Filter ◽  
Moisture Profiles ◽  
Soil Moisture Profile

Abstract. The vertical profile of root zone soil moisture plays a key role in many hydro-meteorological and agricultural applications. We propose a closed-loop data assimilation procedure based on the maximum likelihood ensemble filter algorithm to update the vertical soil moisture profile from time-lapse ground-penetrating radar (GPR) data. A hydrodynamic model is used to propagate the system state in time and a radar electromagnetic model to link the state variable with the observation data, which enables us to directly assimilate the GPR data. Instead of using the surface soil moisture only, the approach allows to use the information of the whole soil moisture profile for the assimilation. We validated our approach by a synthetic study. We constructed a synthetic soil column with a depth of 80 cm and analyzed the effects of the soil type on the data assimilation by considering 3 soil types, namely, loamy sand, silt and clay. The assimilation of GPR data was performed to solve the problem of unknown initial conditions. The numerical soil moisture profiles generated by the Hydrus-1D model were used by the GPR model to produce the "observed" GPR data. The results show that the soil moisture profile obtained by assimilating the GPR data is much better than that of an open-loop forecast. Compared to the loamy sand and silt, the updated soil moisture profile of the clay soil converges to the true state much more slowly. Increasing update interval from 5 to 50 h only slightly improves the effectiveness of the GPR data assimilation for the loamy sand but significantly for the clay soil. The proposed approach appears to be promising to improve real-time prediction of the soil moisture profiles as well as to provide effective estimates of the unsaturated hydraulic properties at the field scale from time-lapse GPR measurements.

Bistatic Scattering Simulations of Circular and Linear Polarizations Over Land Surface for Signals of Opportunity Reflectometry

2020 ◽  
Author(s):  
Xuerui Wu ◽  
Jin Xu ◽  
Zheng Duan ◽  
Shuanggen Jin ◽  
Yezhi Song
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Development Stage ◽  
Forward Scattering ◽  
Initial Development ◽  
Surface Parameters ◽  
Vegetation Biomass ◽  
Bistatic Scattering ◽  
Land Surface Parameters ◽  
Signals Of Opportunity

Abstract Signals of Opportunity (SoOp) Reflectometry employs the communication system,GNSS(Global Navigation Satellite System) constellation and other potential Signals of Opportunity as the transmitters .In recent years, it has gained increased interests. Several experiments have been carried out, however it is still in the initial development stage. Theoretical predictions of SoOp Reflectometry for land surface parameters detection, such as soil moisture and vegetation biomass, should be carried out simultaneously. Meanwhile, at present less works are paid attention to the polarization study of the polarizations. The first-order transfer equation modelmodels are employed here and they are developed according to the wave synthesis technique to get the various polarization combinations. Using the two models as analysis tools, we simulate the bistatic scattering at all potential SoOp Reflectometry bands, i.e P-,L-,C- and X-band for circular polarizations and linear polarizations. While the orginal commonly used microwave scattering models are linear polarizations, here we compare the difference. Although the models can simulate bistatic scattering at any incident angles and scattering angles. Four special observation geometry are taken into considerations during the analysis. By using the developed models as tools, the developed models establish the relationship between the land surface parameters(such as soil moisture, soil roughness and vegetation water content, diameters et al.) and bistatic radar cross section. The forward scattering models developed here enables the understanding of the effects of different geophysical parameters and transmitter-receiver observation scenarios on the bisatic scattering at any polarization combinations for any potential SoOP reflectometry bands. Robust retrieval methods for soil moisture and vegetation biomass can benefit from the forward scattering models.

scholarly journals Assimilation of near-surface cosmic-ray neutrons improves summertime soil moisture profile estimates at three distinct biomes in the USA

2014 ◽  
Vol 11 (5) ◽  
pp. 5515-5558 ◽  
Author(s):  
R. Rosolem ◽  
T. Hoar ◽  
A. Arellano ◽  
J. L. Anderson ◽  
W. J. Shuttleworth ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Mixed Forest ◽  
Land Surface Model ◽  
Cosmic Ray ◽  
Surface Model ◽  
Moisture Profile ◽  
The Usa ◽  
Moisture Profiles ◽  
Semi Arid

Abstract. Aboveground cosmic-ray neutron measurements provide an opportunity to infer soil moisture at the sub-kilometer scale. Initial efforts to assimilate those measurements have shown promise. This study expands such analysis by investigating (1) how the information from aboveground cosmic-ray neutrons can constrain the soil moisture at distinct depths simulated by a land surface model, and (2) how changes in data availability (in terms of retrieval frequency) impact the dynamics of simulated soil moisture profiles. We employ ensemble data assimilation techniques in a "nearly-identical twin" experiment applied at semi-arid shrubland, rainfed agricultural field, and mixed forest biomes in the USA The performance of the Noah land surface model is compared without and with assimilation of observations at hourly intervals and every 2 days Synthetic observations of aboveground cosmic-ray neutrons better constrain the soil moisture simulated by Noah in root zone soil layers (0–100 cm) despite the limited measurement depth of the sensor (estimated to be 12–20 cm). The ability of Noah to reproduce a "true" soil moisture profile is remarkably good regardless of the frequency of observations at the semi-arid site. However, soil moisture profiles are better constrained when assimilating synthetic cosmic-ray neutrons observations hourly rather than every 2 days at the cropland and mixed forest sites. This indicates potential benefits for hydrometeorological modeling when soil moisture measurements are available at relatively high frequency. Moreover, differences in summertime meteorological forcing between the semi-arid site and the other two sites may indicate a possible controlling factor to soil moisture dynamics in addition to differences in soil and vegetation properties.

scholarly journals A quality assessment of spatial TDR soil moisture measurements in homogenous and heterogeneous media with laboratory experiments

2010 ◽  
Vol 7 (1) ◽  
pp. 269-311 ◽  
Author(s):  
T. Graeff ◽  
E. Zehe ◽  
S. Schlaeger ◽  
M. Morgner ◽  
A. Bauer ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Laboratory Experiments ◽  
Heterogeneous Media ◽  
Clay Content ◽  
Reconstruction Algorithm ◽  
Telegraph Equation ◽  
Moisture Profile ◽  
Near Surface ◽  
Small Influence ◽  
Moisture Profiles

Abstract. Investigation of transient soil moisture profiles yields valuable information of near- surface processes. A recently developed reconstruction algorithm based on the telegraph equation allows the inverse estimation of soil moisture profiles along coated, three rod TDR probes. Laboratory experiments were carried out to prove the results of the inversion and to understand the influence of probe rod deformation and solid objects close to the probe in heterogonous media. Differences in rod geometry can lead to serious misinterpretations in the soil moisture profile but have small influence on the average soil moisture along the probe. Solids in the integration volume have almost no effect on average soil moisture but result in locally slightly decreased moisture values. Inverted profiles obtained in a loamy soil with a clay content of about 16% were in good agreement with independent measurements.

scholarly journals Improving soil moisture profile reconstruction from ground-penetrating radar data: a maximum likelihood ensemble filter approach

2013 ◽  
Vol 17 (7) ◽  
pp. 2543-2556 ◽  
Author(s):  
A. P. Tran ◽  
M. Vanclooster ◽  
S. Lambot
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Ground Penetrating Radar ◽  
Time Lapse ◽  
Loamy Sand ◽  
Moisture Profile ◽  
Ground Penetrating ◽  
Maximum Likelihood Ensemble Filter ◽  
Moisture Profiles ◽  
Soil Moisture Profile

Abstract. The vertical profile of shallow unsaturated zone soil moisture plays a key role in many hydro-meteorological and agricultural applications. We propose a closed-loop data assimilation procedure based on the maximum likelihood ensemble filter algorithm to update the vertical soil moisture profile from time-lapse ground-penetrating radar (GPR) data. A hydrodynamic model is used to propagate the system state in time and a radar electromagnetic model and petrophysical relationships to link the state variable with the observation data, which enables us to directly assimilate the GPR data. Instead of using the surface soil moisture only, the approach allows to use the information of the whole soil moisture profile for the assimilation. We validated our approach through a synthetic study. We constructed a synthetic soil column with a depth of 80 cm and analyzed the effects of the soil type on the data assimilation by considering 3 soil types, namely, loamy sand, silt and clay. The assimilation of GPR data was performed to solve the problem of unknown initial conditions. The numerical soil moisture profiles generated by the Hydrus-1D model were used by the GPR model to produce the "observed" GPR data. The results show that the soil moisture profile obtained by assimilating the GPR data is much better than that of an open-loop forecast. Compared to the loamy sand and silt, the updated soil moisture profile of the clay soil converges to the true state much more slowly. Decreasing the update interval from 60 down to 10 h only slightly improves the effectiveness of the GPR data assimilation for the loamy sand but significantly for the clay soil. The proposed approach appears to be promising to improve real-time prediction of the soil moisture profiles as well as to provide effective estimates of the unsaturated hydraulic properties at the field scale from time-lapse GPR measurements.

scholarly journals A quality assessment of Spatial TDR soil moisture measurements in homogenous and heterogeneous media with laboratory experiments

2010 ◽  
Vol 14 (6) ◽  
pp. 1007-1020 ◽  
Author(s):  
T. Graeff ◽  
E. Zehe ◽  
S. Schlaeger ◽  
M. Morgner ◽  
A. Bauer ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Laboratory Experiments ◽  
Heterogeneous Media ◽  
Clay Content ◽  
Reconstruction Algorithm ◽  
Telegraph Equation ◽  
Moisture Profile ◽  
Near Surface ◽  
Small Influence ◽  
Moisture Profiles

Abstract. Investigation of transient soil moisture profiles yields valuable information of near- surface processes. A recently developed reconstruction algorithm based on the telegraph equation allows the inverse estimation of soil moisture profiles along coated, three rod TDR probes. Laboratory experiments were carried out to prove the results of the inversion and to understand the influence of probe rod deformation and solid objects close to the probe in heterogeneous media. Differences in rod geometry can lead to serious misinterpretations in the soil moisture profile, but have small influence on the average soil moisture along the probe. Solids in the integration volume have almost no effect on average soil moisture, but result in locally slightly decreased moisture values. Inverted profiles obtained in a loamy soil with a clay content of about 16% were in good agreement with independent measurements.

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