ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa
CURRENT PROBLEMS IN REMOTE SENSING OF THE EARTH FROM SPACE

  

Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2025, V. 22, No. 4, pp. 187-204

Comparison of brightness temperature models for layered non-isothermal bare soils with smooth boundary

K.V. Muzalevskiy 1 
1 Kirensky Institute of Physics SB RAS, Krasnoyarsk, Russia
Accepted: 05.05.2025
DOI: 10.21046/2070-7401-2025-22-4-187-204
The article compares incoherent and coherent models of brightness temperature (BT) for layered, non-isothermal bare soils with smooth boundary. BT models include incoherent models obtained on the basis of phenomenological radiative transfer theory (with and without considering a single reflection of the wave from the lower boundary of partial layers of the layered medium), and exact coherent models: Wilheit, Njoku, Klepikov–Sharkov. As non-isothermal layered-inhomogeneous dielectric half-spaces, thawed and frozen soils are considered with modeled and synchronously measured moisture and temperature profiles in the active layer. The complex permittivity of soils is modeled using proven dielectric models. The statistical analysis is based on synchronous calculation of the BT (using all the models under consideration) at frequencies of 409 MHz and 1.4 GHz in the range of viewing angles from 0 to 60° at vertical and horizontal polarizations. As a result, it is shown that coherent BT models (Wilheit, Njoku, Klepikov–Sharkov) have the same accuracy within the limits of computation error or digitization of graphic data from third-party origins. The average absolute difference between the BT calculated by incoherent and coherent models for all considered sets of moisture and temperature profiles can reach 20 and 8 K at frequencies of 409 MHz and 1.4 GHz, respectively, if the condition of smoothness of the refractive index profile at the soil surface is not met (large scale of vertical dielectric inhomogeneities in relation to the wavelength). If this condition is met, then the error does not exceed several degrees Kelvin. It is shown that the modification of the incoherent model by introduction into the reflectivity of a coefficient of coherent reflection from the air-soil interface allows achieving accuracy close to coherent models, even for freezing soils with a sharp jump in the complex permittivity between the freezing and thawed parts of the active layer. This study corroborates the applicability of a partially coherent emission model for calculating, in a wide frequency range, the angular dependencies of BT at horizontal and vertical polarizations of bare soils with smooth boundary and virtually any moisture and temperature profiles observed in the active layer.
Keywords: radiothermal emission, layered heterogeneous media, non-isothermal media, soil, moisture profiles, temperature profiles, permittivity
Full text

References:

  1. Basharinov A. E., Gurvich A. S., Egorov S. T., Radioizluchenie Zemli kak planety (Radio emission of the Earth as a planet), Moscow: Nauka, 1974, 187 p. (in Russian).
  2. Bogorodskii V. V., Kozlov A. I., Tuchkov L. T., Radioteplovoe izluchenie zemnykh pokrovov (Thermal radio emission from the Earth’s covers), Leningrad: Gidrometeoizdat, 1977, 224 p. (in Russian).
  3. Born M., Wolf E., Principles of Optics, 2nd ed., London, New York: Pergamon Press, 1964, 836 p.
  4. Brekhovskikh L. M., Volny v sloistykh sredakh (Waves in layered media), Moscow: Izd. AN SSSR, 1957, 502 p. (in Russian).
  5. Klepikov I., Sharkov E., Teplovoe izluchenie sloisto-neodnorodnykh neizotermicheskikh sred (Thermal radiation of layered inhomogeneous non-isothermal media), Moscow: IKI AN SSSR, 1983, 31 p. (in Russian).
  6. Kondrat’ev K. Ya., Grigor’ev Al. A., Rabinovich Yu. I., Shul’gina E. M., Meteorologicheskoe zondirovanie podstilayushchei poverkhnosti iz kosmosa (Meteorological sounding of the underlying surface from space), Leningrad: Gidrometeoizdat, 1979, 248 p. (in Russian).
  7. Levin M. L., Rytov S. M., Teoriya ravnovesnykh teplovykh fluktuatsii v ehlektrodinamike (Theory of equilibrium thermal fluctuations in electrodynamics), Moscow: Nauka, 1967, 310 p. (in Russian).
  8. Rytov S. M., Teoriya ehlektricheskikh fluktuatsii i teplovogo izlucheniya (Theory of electrical fluctuations and thermal radiation), Moscow: Izd. AN SSSR, 1953, 232 p. (in Russian).
  9. Finkel’shtein M. I., Mendel’son V. L., Kutev V. A., Radiolokatsiya sloistykh zemnykh pokrovov (Radiolocation of layered Earth’s covers), Moscow: Sovetskoe radio, 1977, 176 p. (in Russian).
  10. Sharkov E. A., Radioteplovoe distantsionnoe zondirovanie Zemli. Fizicheskie osnovy (Radiothermal Remote Sensing of the Earth. Physical Principles), V. 1, Moscow: IKI RAN, 2014, 544 p. (in Russian).
  11. Shul’gina E. M., Radio emission of vertically inhomogeneous media, Trudy Gosudarstvennoi geofizicheskoi observatorii, 1975, Iss. 331, pp. 64–72 (in Russian).
  12. Brakhasi F., Walker J. P., Ye N. et al., Towards soil moisture profile estimation in the root zone using L- and P-band radiometer observations: A coherent modelling approach, Science of Remote Sensing, 2023, V. 7, Article 100079, DOI: 10.1016/j.srs.2023.100079.
  13. Brakhasi F., Walker J. P., Judge J. et al. (2024a), Soil moisture profile estimation under bare and vegetated soils using combined L-band and P-band radiometer observations: An incoherent modeling approach, Remote Sensing of Environment, 2024, V. 307, Article 114148, DOI: 10.1016/j.rse.2024.114148.
  14. Brakhasi F., Walker J. P., Judge J. et al. (2024b), A comparison of passive microwave emission models for estimating brightness temperature at L- and P-bands under bare and vegetated soil conditions, IEEE J. Selected Topics in Applied Earth Observations and Remote Sensing, 2024, V. 17, pp. 2570–2585, DOI: 10.1109/JSTARS.2023.3344764.
  15. Burke W. J., Schmugge T., Paris J. F., Comparison of 2.8‐ and 21‐cm microwave radiometer observations over soils with emission model calculations, J. Geophysical Research: Ocean, 1979, V. 84, No. C1, pp. 287–294, DOI: 10.1029/JC084iC01p00287.
  16. Chandrasekhar S., Radiative transfer, London: Oxford University Press, 1950, 393 p.
  17. Gaikovich K. P., Simultaneous solution of emission transfer and thermal conductivity equations in the problems of atmosphere and subsurface radiothermometry, IEEE Trans. Geoscience and Remote Sensing, 1994, V. 32, No. 4, pp. 885–889, DOI: 10.1109/36.298016.
  18. Gaikovich K. P., Reznik A. N., Troitskii R. V., A radiometry method of determining the subsoil temperature profile and depth of soil freezing, Radiophysics and Quantum Electronics, 1989, V. 32, No. 12, pp. 1082–1088, DOI: 10.1007/BF01038633.
  19. Li M., Lang R., Cosh M., P-band and L-band radiometry retrieval of soil moisture and temperature profiles, IEEE Trans. Geoscience and Remote Sensing, 2024, V. 62, Article 5301715, 15 p., DOI: 10.1109/TGRS.2024.3416988.
  20. Liu P.-W., De Roo R. D., England A. W., Judge J., Impact of moisture distribution within the sensing depth on L- and C-band emission in sandy soils, IEEE J. Selected Topics in Applied Earth Observations and Remote Sensing, 2013, V. 6, No. 2, pp. 887–899, DOI: 10.1109/JSTARS.2012.2213239.
  21. Mironov V. L., Muzalevskiy K. V., Savin I. V. (2013a), Retrieving temperature gradient in frozen active layer of Arctic tundra soils from radiothermal observations in L-band—theoretical modeling, IEEE J. Selected Topics in Applied Earth Observations and Remote Sensing, 2013, V. 6, No. 3, pp. 1781–1785, DOI: 10.1109/JSTARS.2013.2262108.
  22. Mironov V. L., Bobrov P. P., Fomin S. V. (2013b), Multirelaxation generalized refractive mixing dielectric model of moist soils, IEEE Geoscience and Remote Sensing Letters, 2013, V. 10, No. 3, pp. 603–606, DOI: 10.1109/LGRS.2012.2215574.
  23. Mironov V. L., Muzalevskiy K. V., Ruzicka Z., Retrieving profile temperatures in a frozen topsoil near the TFS, Alaska, based on SMOS brightness temperatures at the 1.4-GHz frequency, IEEE Trans. Geoscience and Remote Sensing, 2016, V. 54, No. 12, pp. 7331–7338, DOI: 10.1109/TGRS.2016.2599272.
  24. Mironov V. L., Karavayskiy A. Yu., Lukin Yu. I., Molostov I. P., A dielectric model of thawed and frozen Arctic soils considering frequency, temperature, texture and dry density, Intern. J. Remote Sensing, 2020, V. 41, No. 10, pp. 3845–3865, DOI: 10.1080/01431161.2019.1708506.
  25. Muzalevskiy K. V., Heat equation-based temperature profiles retrieval in frozen tundra soil using dual-polarized multi-angular brightness temperature observations in L-band, Intern. J. Remote Sensing, 2024, V. 46, No. 4, pp. 1864–1884, DOI: 10.1080/01431161.2024.2440670.
  26. Njoku E. G., Kong J.-A., Theory for passive microwave remote sensing of near-surface soil moisture, J. Geophysical Research, 1977, V. 82, No. 20, pp. 3108–3118, DOI: 10.1029/JB082i020p03108.
  27. Njoku E. G., O’Neill P. E., Multifrequency microwave radiometer measurements of soil moisture, IEEE Trans. Geoscience and Remote Sensing, 1982, V. GE-20, No. 4, pp. 468–475, DOI: 10.1109/TGRS.1982.350412.
  28. Schmugge T. J., Choudhury B. J., A comparison of radiative transfer models for predicting the microwave emission from soils, Radio Science, 1981, V. 16, No. 5, pp. 927–938, DOI: 10.1029/RS016i005p00927.
  29. Soil temperature dataset. University of Alaska Fairbanks. Geophysical Institute. Permafrost laboratory, permafrost.gi.alaska.edu, 21.03.2025, https://permafrost.gi.alaska.edu/site/fbn.
  30. Stogryn A., The brightness temperature of a vertically structured medium, Radio Science, 1970, V. 5, No. 12, pp. 1397–1406, DOI: 10.1029/RS005i012p01397.
  31. Tsang L., Njoku E., Kong J. A., Microwave thermal emission from a stratified medium with nonuniform temperature distribution, J. Applied Physics, 1975, V. 46, No. 12, pp. 5127–5133, DOI: 10.1063/1.321571.
  32. Ulaby F. T., Moore R. K., Fung A. K., Microwave remote sensing: Active and passive. V. 3. From theory to applications, Dedham, MA: Artech House, 1986, 1120 p.
  33. Wang J. R., Shiue J. C., McMurtrey J. E., III, Microwave remote sensing of soil moisture content over bare and vegetated fields, Geophysical Research Letters, 1980, V. 7, No. 10, pp. 801–804, DOI: 10.1029/GL007i010p00801.
  34. Wang J. R., O’Neill P. E., Jackson T. J., Engman E. T., Multifrequency measurements of the effects of soil moisture, soil texture, and surface roughness, IEEE Trans. Geoscience and Remote Sensing, 1983, V. GE-21, No. 1, pp. 44–51, DOI: 10.1109/TGRS.1983.350529.
  35. Wigneron J.-P., Jackson T. J., O’Neill P. et al., Modelling the passive microwave signature from land surfaces: A review of recent results and application to the L-band SMOS and SMAP soil moisture retrieval algorithms, Remote Sensing of Environment, 2017, V. 192, pp. 238–262, DOI: 10.1016/j.rse.2017.01.024.
  36. Wilheit T. T., Radiative transfer in a plane stratified dielectric, NASA Technical reports, No. NASA-TM-X-71051, Greenbelt, MD: Goddard Space Flight Center, 1975, 19 p.
  37. Wilheit T. T., Radiative transfer in a plane stratified dielectric, IEEE Trans. Geoscience Electronics, 1978, V. 16, No. 2, pp. 138–143, DOI: 10.1109/TGE.1978.294577.