Valery L. Mironov

Physically and Mineralogically Based Spectroscopic Dielectric Model for Moist Soils

In this paper, the error of dielectric predictions for moist soils was estimated, regarding the semiempirical mixing dielectric model (SMDM) developed by Dobson , which is a universally recognized one, and the generalized refractive mixing dielectric model (GRMDM) recently elaborated by Mironov The analysis is based on the measured dielectric data presented in by Curtis and the papers of Dobson These data cover a broad variety of grain-size distributions observed in 15 soils and the frequency range from 45 MHz to 26.5 GHz, with the temperature being from 20 degC to 22 degC. The SMDM was found to deliver predictions with substantially larger error for the soils, whose dielectric data were not used for its development, while the GRMDM ensured dielectric predictions for all the soils analyzed with as small error as the SMDM did in the case of the soils that it was based on. To secure the same convenience in application of the GRMDM, which the SMDM possesses, the spectroscopic parameters of that model were correlated with the clay percentages of the respective soils. As a result, a new mineralogy-based dielectric model was developed. For the moist soils other than those whose dielectric data were used for its development, this model was shown to demonstrate noticeably smaller error of dielectric predictions, with clay percentage being the only input parameter, as compared with the error observed in the case of the SMDM.

Evaluating an Improved Parameterization of the Soil Emission in L-MEB

In the forward model [L-band microwave emission of the biosphere (L-MEB)] used in the Soil Moisture and Ocean Salinity level-2 retrieval algorithm, modeling of the roughness effects is based on a simple semiempirical approach using three main “roughness” model parameters: HR, QR, and NR. In many studies, the two parameters QR and NR are set to zero. However, recent results in the literature showed that this is too approximate to accurately simulate the microwave emission of the rough soil surfaces at L-band. To investigate this, a reanalysis of the PORTOS-93 data set was carried out in this paper, considering a large range of roughness conditions. First, the results confirmed that QR could be set to zero. Second, a refinement of the L-MEB soil model, considering values of NR for both polarizations (namely, NRV and NRH), improved the model accuracy. Furthermore, simple calibrations relating the retrieved values of the roughness model parameters HR and (NRH - NRV) to the standard deviation of the surface height were developed. This new calibration of L-MEB provided a good accuracy (better than 5 K) over a large range of soil roughness and moisture conditions of the PORTOS-93 data set. Conversely, the calibrations of the roughness effects based on the Choudhury approach, which is still widely used, provided unrealistic values of surface emissivities for medium or large roughness conditions.

Temperature-Dependable Microwave Dielectric Model for an Arctic Soil

Dielectric measurements of an organic-rich permafrost soil over the range from 1.0 to 16 GHz and from -30°C to +25°C are presented. The measured shrub soil contains up to 90% organic matter and is the first soil of this composition for which the soil dielectric has been characterized. The measurements were fitted to the generalized refractive mixing dielectric model (GRMDM) recently proposed by Mironov et al., which combines the complex refractive indexes for the major components of the soil. These components were found to be the solid content, bound water, transient bound water, liquid capillary water, and moistened ice water. The dielectric properties of the frequency-dispersive components are each described by their own Debye relaxation spectrum. The GRMDM has been modified to incorporate the temperature dependence of the Debye parameters. The phase transformation of the soil water components at the freezing temperature is taken into account. As a result, a temperature-dependable GRMDM (TD GRMDM) has been developed, including model parameters which have a physical interpretation. This TD GRMDM predicts the dielectric for this soil in the whole range of moistures, frequencies, and temperatures measured. The model prediction errors are on the same order as that of dielectric measurements. The model proposed is the first of its kind to provide a physical basis for radar and radiothermal remote sensing algorithms that retrieve the freeze/thaw state and the volumetric moisture in the upper layer of an Arctic soil.

Generalized refractive mixing dielectric model for moist soils

In this paper, a technique for estimating the maximum bound water content and complex dielectric constants for both the bound and the free water in soil is presented. The thus attained dielectric properties for the water in soil, are used to derive the Debye spectroscopic parameters for both types of water. Empirical data sets for the soil complex dielectric constant as a function of moisture measured only at two frequencies are sufficient for applying this technique. As a result the model for predicting soil complex dielectric constant in the microwave band is proposed and validated.

Frozen soil dielectric model using unfrozen water spectroscopic parameters

In this paper, the generalized refractive mixing dielectric model (GRMDM) introduced in was extended over freezing temperatures. Two types of unfrozen soil water, bound either by hydrophilic soil particle or ice crystal surfaces, have been identified. With this approach, the soil unfrozen water spectroscopic parameters in the microwave band were retrieved using the bentonite soil dielectric data measured at 0.6, 1.11, and 1.43 GHz, and 25/spl deg/C down to -30/spl deg/C. Based on these results, a dielectric model for frozen soil was proposed which allows for predicting complex dielectric constant as a function of frequency and temperature.

Soil dielectric spectroscopic parameters dependence on humus content

The purpose of this paper is to apply generalized refractive mixing dielectric model (GRMDM) based on the Debye relaxation formula to soils with various humus contents. With this approach, the soil types containing 6.6% and 0.6% of natural humus. Complex dielectric constant or complex refractive index were measured as a function of moisture at the frequencies of 0.55; 1.1; 1.8, 3.0, 11.5, 13.5 and 16.3 GHz with the temperature being of 20-24 /spl deg/C. Using measured data only at 1.8, 3.0, 4.3 GHz, the GRMDM parameters - relaxation time, static dielectric constant, and conductivity for both types of water in soil were attained for both types of soil. Though variation in the relaxation parameters with humus content is moderate, this factor has to be taken into account when soil moisture remote sensing algorithms are being designed for agricultural areas. For this purpose, the GRMDM can be applied, with a soil humus content being one of its physical parameters.

Spectral dielectric properties of moist soils in the microwave band

In this work, the spectral dielectric properties of moist soils in the microwave band were analyzed, using the generalized refractive mixing dielectric model (GRMDM). First, for different types of soil, all available data on dielectric constant (DC) and loss factor (LF) at zero volumetric moisture, maximum bound water fraction (MBWF) values, relating to these types of soil, as well as the static dielectric constants, relaxation times, and conductivities of both the bound soil water (BSW) and free soil water FSW were systematized in the form of a spectroscopic data base for moist soils. Second, using such a data base, the spectroscopic parameters relating to BSW and FSW were analyzed in terms of their dependence on the type of soil. In addition, for each individual soil, the dielectric spectra of both types of soil water were calculated with the use of GRMDM, in order to demonstrate the variability of those as a function of soil type. Finally, the soil water dielectric spectra together with the other parameters of the moist soil dielectric data base were applied to evaluate the dependence of moist soil emissivity on the type of soil, in the whole microwave band. From this point of view, the study conducted can be considered as a new approach, that opens perspective for carrying out both the feasibility studies and developing data processing algorithms in radiometry or radar remote sensing, using an appropriate spectroscopic data base for moist soils.

UWB electromagnetic borehole logging tool

Based on a theoretical model of the geosteering borehole logging tool, which operates the broadband pulse, we demonstrate the possibility of detecting an interface between oil- and water-saturated layers in the oil-gas formation.

Multirelaxation Generalized Refractive Mixing Dielectric Model of Moist Soils

In this letter, a multirelaxation generalized refractive mixing dielectric model (GRMDM) for moist soil is proposed and substantiated in the frequency range from 0.04 to 26.5 GHz. This model is based on the methodology of a single-relaxation GRMDM which accounts only for the dipole relaxation of water molecules in the gigahertz frequency range. The proposed multirelaxation GRMDM takes into account both the dipole (Debye) and ionic (Maxwell-Wagner) relaxations of soil water molecules. For this purpose, it uses a two-frequency Debye relaxation equation for the dielectric spectra of bound water. The spectroscopic parameters of the multirelaxation GRMDM were derived by fitting the spectra calculated by this model to the respective measured ones. The main advantage of this model is that it predicts the complex dielectric constant of moist soils throughout the megahertz and gigahertz frequency ranges with the same error as the single-relaxation GRMDM does only in the gigahertz range.

Data Processing Technique for Deriving Soil Water Spectroscopic Parameters in Microwave

In this paper, the technique employed in the generalized refractive mixing dielectric model (GRMDM) (1), (2) for soil water spectroscopic analysis is extended to include fitting the refractive mixing dielectric model to moist soil complex dielectric constant (CDC) data in the frequency domain, with a restricted number of volumetric moistures being available. To reach this goal, the refractive mixing dielectric model was fitted to the moist soil CDCs measured first at volumetric moistures in the range below the maximum bound water fraction (MBWF). At this phase of data processing, spectroscopic parameters, that is, static dielectric constant, relaxation time, and conductivity, relating to the bound soil water were derived, along with the values of CDCs relating to a dry soil. Further fitting in frequency domain to the CDCs of moist soil, measured in the range of free soil water moistures, yielded the values of MBWF, as well as the spectroscopic parameters related to the free soil water. After this final stage of data processing, a full set of the GRMDM spectroscopic parameter became available to insure CDCs prediction as a function of soil moisture and frequency. The technique was validated on the basis of correlating the predicted moist soil dielectric data to those measured.