volume | PIER Journals

Abstract

The distorted Born approximation (DBA) of volume scattering was previously combined with the numerical solution of Maxwell equations (NMM3D) for rough surfaces to calculate radar backscattering coefficients for the Soil Moisture Active Passive (SMAP) mission. The model results were validated with the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) data. In this paper, we extend the existing model to calculate the bistatic scattering coefficients for each of the three scattering mechanisms: volume, double bounce and surface scattering. Emissivities are calculated by integrating the bistatic scattering coefficients over the hemispherical solid angle. The backscattering coefficients and emissivities calculated using this approach form a consistent model for combined active and passive microwave remote sensing. This has the advantage that the active and passive microwave remote sensing models are founded on the same theoretical basis and hence allow the use of the same physical parameters such as crop density, plant height, stalk orientation, leaf radius, and surface roughness, amongst others. In this paper, this combined active and passive model is applied to four vegetation types to calculate both backscattering coefficients and brightness temperature: wheat, winter wheat, pasture and canola. This model uses a single-scattering and incoherent vegetation model, which is applicable for the vegetation fields studied in this paper but not suitable for vegetation types where collective scattering or multiple scattering effects are important. We demonstrate the use of the DBA/NMM3D for both active and passive using the same input parameters for matching active and passive coincident data. The model results are validated using coincident airborne Passive Active L-band System (PALS) low-altitude radiometer data and Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data taken during the SMAPVEX12 field campaign. Results show an average root mean squared error (RMSE) of 1.04 dB and 1.21 dB for backscatter at VV and HH, respectively, and 4.65 K and 6.44 K for brightness temperature at V-pol and H-pol, respectively. The results are comparable to those from the tau-omega model which is commonly used to compute the brightness temperature, though the physical parameters used in this model are different from the empirically adjusted parameters used in the tau-omega model.

1. Entekhabi, D., E. G. Njoku, P. E. O’Neill, K. H. Kellogg, W. T. Crow, W. N. Edelstein, et al. "The Soil Moisture Active Passive (SMAP) mission," Proceedings of the IEEE, Vol. 98, 704-716, May 2010.
doi:10.1109/JPROC.2010.2043918 Google Scholar

2. Jackson, T. J. and T. J. Schmugge, "Vegetation effects on the microwave emission of soils," Remote Sensing of Environment, Vol. 36, 203-212.
doi:10.1016/0034-4257(91)90057-D Google Scholar

3. Monerris, A. and T. Schmugge, "Soil moisture estimation using L-band radiometry," Advances in Geoscience and Remote Sensing, InTech, 2009. Google Scholar

4. Ulaby, F. T., D. G. Long, W. J. Blackwell, C. Elachi, A. K. Fung, C. Ruf, et al. Microwave Radar and Radiometric Remote Sensing, University of Michigan Press, 2014.

5. Entekhabi, D., S. Yueh, P. O’Neill, and K. Kellogg, SMAP Handbook, 400-1567, JPL Publication JPL, 2014.

6. Kerr, Y. H. and E. G. Njoku, "A semiempirical model for interpreting microwave emission from semiarid land surfaces as seen from space," IEEE Transactions on Geoscience and Remote Sensing, Vol. 28, 384-393, 1990.
doi:10.1109/36.54364 Google Scholar

7. Jackson, T. and T. Schmugge, "Vegetation effects on the microwave emission of soils," Remote Sensing of Environment, Vol. 36, 203-212, 1991.
doi:10.1016/0034-4257(91)90057-D Google Scholar

8. Tsang, L., J. A. Kong, and R. T. Shin, Theory of Microwave Remote Sensing, Wiley, 1985.

9. Oh, Y., K. Sarabandi, and F. T. Ulaby, "Semi-empirical model of the ensemble-averaged differential Mueller matrix for microwave backscattering from bare soil surfaces," IEEE Transactions on Geoscience and Remote Sensing, Vol. 40, 1348-1355, Jun. 2002.
doi:10.1109/TGRS.2002.800232 Google Scholar

10. Lang, R. H. and J. S. Sidhu, "Electromagnetic backscattering from a layer of vegetation — A discrete approach," IEEE Transactions on Geoscience and Remote Sensing, Vol. 21, 62-71, 1983.
doi:10.1109/TGRS.1983.350531 Google Scholar

11. Huang, S. and L. Tsang, "Electromagnetic scattering of randomly rough soil surfaces based on numerical solutions of Maxwell equations in three-dimensional simulations using a hybrid UV/PBTG/SMCG method," IEEE Transactions on Geoscience and Remote Sensing, Vol. 50, 4025-4035, 2012.
doi:10.1109/TGRS.2012.2189776 Google Scholar

12. Kim, S. B., L. Tsang, J. T. Johnson, S. Huang, J. J. van Zyl, and E. G. Njoku, "Soil moisture retrieval using time-series radar observations over bare surfaces," IEEE Transactions on Geoscience and Remote Sensing, Vol. 50, 1853-1863, May 2012.
doi:10.1109/TGRS.2011.2169454 Google Scholar

13. Kim, S.-B., M. Moghaddam, L. Tsang, M. Burgin, X. Xu, and E. G. Njoku, "Models of L-band radar backscattering coefficients over global terrain for soil moisture retrieval," IEEE Transactions on Geoscience and Remote Sensing, Vol. 52, 1381-1396, 2014.
doi:10.1109/TGRS.2013.2250980 Google Scholar

14. McNairn, H., T. J. Jackson, G. Wiseman, S. Belair, A. Berg, P. Bullock, et al. "The Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12): Prelaunch calibration and validation of the SMAP soil moisture algorithms," IEEE Transactions on Geoscience and Remote Sensing, Vol. 53, 2784-2801, 2015.
doi:10.1109/TGRS.2014.2364913 Google Scholar

15. Bolten, J. D., V. Lakshmi, and E. G. Njoku, "Soil moisture retrieval using the passive/active L- and S-band radar/radiometer," IEEE Transactions on Geoscience and Remote Sensing, Vol. 41, 2792-2801, Dec. 2003.
doi:10.1109/TGRS.2003.815401 Google Scholar

16. Bindlish, R., T. Jackson, R. J. Sun, M. Cosh, S. Yueh, and S. Dinardo, "Combined passive and active microwave observations of soil moisture during CLASIC," IEEE Geoscience and Remote Sensing Letters, Vol. 6, 644-648, Oct. 2009.
doi:10.1109/LGRS.2009.2028441 Google Scholar

17. Ferrazzoli, P., G. Luzi, S. Paloscia, P. Pampaloni, G. Schiavon, and D. Solimini, "Comparison between the microwave emissivity and backscatter coefficient of crops," IEEE Transactions on Geoscience and Remote Sensing, Vol. 27, 772-778, Nov. 1989.
doi:10.1109/TGRS.1989.1398244 Google Scholar

18. Guerriero, L., P. Ferrazzoli, and R. Rahmoune, "A synergyc view of L-band active and passive remote sensing of vegetated soil," 2012 12th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad), 1-3, 2012. Google Scholar

19. Chauhan, N. S. and D. M. Levine, "Discrete scatter model for microwave radar and radiometer response to corn — Comparison of theory and data," IEEE Transactions on Geoscience and Remote Sensing, Vol. 32, 416-426, Mar. 1994.
doi:10.1109/36.295056 Google Scholar

20. Lang, R. H., "Scattering from a layer of discrete random medium over a random interface: application to microwave backscattering from forests," Waves in Random Media, Vol. 14, S359-S391, Apr. 2004.
doi:10.1088/0959-7174/14/2/014 Google Scholar

21. Yueh, S. H., J. A. Kong, J. K. Jao, R. T. Shin, and T. Letoan, "Branching model for vegetation," IEEE Transactions on Geoscience and Remote Sensing, Vol. 30, 390-402, Mar. 1992.
doi:10.1109/36.134088 Google Scholar

22. Stiles, J. M. and K. Sarabandi, "Electromagnetic scattering from grassland Part I: A fully phasecoherent scattering model," IEEE Transactions on Geoscience and Remote Sensing, Vol. 38, 339-348, Jan. 2000.
doi:10.1109/36.823929 Google Scholar

23. Stiles, J. M., K. Sarabandi, and F. T. Ulaby, "Electromagnetic scattering from grassland Part II: Measurement and modelling results," IEEE Transactions on Geoscience and Remote Sensing, Vol. 38, 349-356, Jan. 2000.
doi:10.1109/36.823930 Google Scholar

24. Ulaby, F. T., K. Sarabandi, K. Mcdonald, M. Whitt, and M. C. Dobson, "Michigan microwave canopy scattering model," International Journal of Remote Sensing, Vol. 11, 1223-1253, Jul. 1990.
doi:10.1080/01431169008955090 Google Scholar

25. Tsang, L., J. Kong, and K.-H. Ding, Scattering of Electromagnetic Waves: Theories and Applications, John Wisley & Sons, ed: Inc, 2000.
doi:10.1002/0471224286

26. Liao, T.-H., S. B. Kim, S. R. Tan, L. Tsang, C. X. Su, and T. J. Jackson, "Multiple scattering effects with cyclical correction in active remote sensing of vegetated surface using vector radiative transfer theory," IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 9, 1414-1429, Apr. 2016.
doi:10.1109/JSTARS.2015.2505638 Google Scholar

27. Toure, A., K. P. B. Thomson, G. Edwards, R. J. Brown, and B. G. Brisco, "Adaptation of the mimics backscattering model to the agricultural context — Wheat and canola at L and C bands," IEEE Transactions on Geoscience and Remote Sensing, Vol. 32, 47-61, Jan. 1994.
doi:10.1109/36.285188 Google Scholar

28. Huang, S. W., L. Tsang, E. G. Njoku, and K. S. Chan, "Backscattering coefficients, coherent reflectivities, and emissivities of randomly rough soil surfaces at L-band for SMAP applications based on numerical solutions of maxwell equations in three-dimensional simulations," IEEE Transactions on Geoscience and Remote Sensing, Vol. 48, 2557-2568, Jun. 2010.
doi:10.1109/TGRS.2010.2040748 Google Scholar

29. Njoku, E. G. and D. Entekhabi, "Passive microwave remote sensing of soil moisture," Journal of Hydrology, Vol. 184, 101-–129, Oct. 1, 1996.
doi:10.1016/0022-1694(95)02970-2 Google Scholar

30. Colliander, A., E. G. Njoku, T. J. Jackson, S. Chazanoff, H. McNairn, and J. Powers, "Retrieving soil moisture for non-forested areas using PALS radiometer measurements in SMAPVEX12 field campaign," Remote Sensing of Environment, Vol. 184, 86-100, Oct. 2016.
doi:10.1016/j.rse.2016.06.001 Google Scholar

31. Hensley, S., K. Wheeler, G. Sadowy, C. Jones, S. Shaffer, H. Zebker, et al. "The UAVSAR instrument: Description and first results," 2008 IEEE Radar Conference, Vol. 1–4, 827-832, 2008. Google Scholar

32. Mladenova, I. E., T. J. Jackson, R. Bindlish, and S. Hensley, "Incidence angle normalization of radar backscatter data," IEEE Transactions on Geoscience and Remote Sensing, Vol. 51, 1791-1804, Mar. 2013.
doi:10.1109/TGRS.2012.2205264 Google Scholar

33. Colliander, A., T. Jackson, H. McNairn, S. Chazanoff, S. Dinardo, B. Latham, et al. "Comparison of airborne Passive and Active L-band System (PALS) brightness temperature measurements to SMOS observations during the SMAP Validation Experiment 2012 (SMAPVEX12)," IEEE Geoscience and Remote Sensing Letters, Vol. 12, 801-805, Apr. 2015.
doi:10.1109/LGRS.2014.2362889 Google Scholar

34. Jester, W. and A. Klik, "Soil surface roughness measurement — Methods, applicability, and surface representation," Catena, Vol. 64, 174-192, Dec. 30, 2005.
doi:10.1016/j.catena.2005.08.005 Google Scholar

35. Rowlandson, T. L., A. A. Berg, P. R. Bullock, E. R. Ojo, H. McNairn, G. Wiseman, et al. "Evaluation of several calibration procedures for a portable soil moisture sensor," Journal of Hydrology, Vol. 498, 335-344, Aug. 19, 2013.
doi:10.1016/j.jhydrol.2013.05.021 Google Scholar

36. Cosh, M. H., T. J. Jackson, R. Bindlish, J. S. Famiglietti, and D. Ryu, "Calibration of an impedance probe for estimation of surface soil water content over large regions," Journal of Hydrology, Vol. 311, 49-58, Sep. 15, 2005.
doi:10.1016/j.jhydrol.2005.01.003 Google Scholar

37. Ulaby, F. T. and M. A. Elrayes, "Microwave dielectric spectrum of vegetation. 2. Dual-dispersion model," IEEE Transactions on Geoscience and Remote Sensing, Vol. 25, 550-557, Sep. 1987.
doi:10.1109/TGRS.1987.289833 Google Scholar

38. Huang, H., S.-B. Kim, L. Tsang, X. Xu, T.-H. Liao, T. J. Jackson, et al. "Coherent model of L-band radar scattering by soybean plants: Model development, evaluation, and retrieval," IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 9, No. 1, 272-284, Jan. 2016.
doi:10.1109/JSTARS.2015.2469717 Google Scholar

39. Njoku, E. G. and J. A. Kong, "Theory for passive microwave remote-sensing of near-surface soilmoisture," Transactions-American Geophysical Union, Vol. 58, 554-554, 1977. Google Scholar

40. Huang, H., L. Tsang, E. G. Njoku, A. Colliander, T.-H. Liao, and K.-H. Ding, "Propagation and scattering by a layer of randomly distributed dielectric cylinders using monte carlo simulations of 3D Maxwell equations with applications in microwave interactions with vegetation," IEEE Access, Vol. 5, 11985-12003, 2017.
doi:10.1109/ACCESS.2017.2714620 Google Scholar

Dr. Huanting Huang

Dr. Tien-Hao Liao

Professor Leung Tsang

Dr. Eni Gerald Njoku

Dr. Andreas Colliander

Professor Thomas J. Jackson

Dr. Mariko Burgin

Dr. Simon Yueh