Abstract
Within the framework of the two-scale scattering model, the Doppler shift of C-band radar return signals from the nonlinear sea surface are numerically evaluated. As an analytical approximation method, the Bragg resonance scattering method cannot accurately describe the backscattering field from sea surface. Therefore, in the two-scale scattering model, more accurate scattering coefficient (the normalized radar cross section, NRCS) evaluated by the C-band dual-polarized (HH/VV) empirical geophysical model function (CSAR model) is employed to replace the traditional Bragg NRCS to weight the Doppler shift. The numerical results indicate that there are obvious differences between the Doppler shift weighted by the CSAR NRCS and that weighted by the traditional Bragg NRCS. The hydrodynamic modulation of the large-scale waves is one of the important factors that affect the difference between the Doppler shift predicted in upwind and downwind directions. If the relaxation rate in the hydrodynamic modulation is set to be the angular frequency of the dominant water waves, the Doppler shift predicted by the numerical method can fit the results of the empirical model (C-band empirical geophysical model function, CDOP) well at moderate wind speed. Under low wind condition, the comparison shows that the empirical CDOP model appears to overestimate the Doppler shift. In order to facilitate the application, at the end of this paper a semi-empirical CSAR-DOP model, which is a polynomial fitting formula, is developed for evaluating the Doppler shift of C-band signals from time varying sea surface.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Alpers W R, Ross D B, Rufenach C L. 1981. On the detectability of ocean surface waves by real and synthetic aperture radar. Journal of Geophysical Research, 86(C7): 6481–6498, doi: https://doi.org/10.1029/JC086iC07p06481
Apel J R. 1994. An improved model of the ocean surface wave vector spectrum and its effects on radar backscatter. Journal of Geophysical Research, 99(C8): 16269–16291, doi: https://doi.org/10.1029/94JC00846
Barrick D E. 1977. Extraction of wave parameters from measured HF radar sea-echo Doppler spectra. Radio Science, 12(3): 415–424, doi: https://doi.org/10.1029/RS012i003p00415
Bass F G, Fuks I, Kalmykov A I, et al. 1968. Very high frequency radiowave scattering by a disturbed sea surface Part II: scattering from an actual sea surface. IEEE Transactions on Antennas and Propagation, 16(5): 560–568, doi: https://doi.org/10.1109/TAP.1968.1139244
Caponi E A, Crawford D R, Yuen H C, et al. 1988. Modulation of radar backscatter from the ocean by a variable surface current. Journal of Geophysical Research, 93(C10): 12249–12263, doi: https://doi.org/10.1029/JC093iC10p12249
Chapron B, Collard F, Ardhuin F. 2005. Direct measurements of ocean surface velocity from space: interpretation and validation. Journal of Geophysical Research, 110(C7): C07008
Chen K S, Fung A K, Amar F. 1993. An empirical bispectrum model for sea surface scattering. IEEE Transactions on Geoscience and Remote Sensing, 31(4): 830–835, doi: https://doi.org/10.1109/36.239905
Crombie D D. 1955. Doppler spectrum of sea echo at 13.66Mc./s. Nature, 175(4459): 681–682, doi: https://doi.org/10.1038/175681a0
Elfouhaily T, Chapron B, Katsaros K, et al. 1997. A unified directional spectrum for long and short wind-driven waves. Journal of Geophysical Research, 102(C7): 15781–15796, doi: https://doi.org/10.1029/97JC00467
Fuks I M, Voronovich A G. 2002. Radar backscattering from Gerstner’s sea surface wave. Waves in Random Media, 12(3): 321–339, doi: https://doi.org/10.1088/0959-7174/12/3/305
Fung A K. 1994. Microwave Scattering and Emission Models and Their Applications. Norwood: Artech House
Hasselmann K, Hasselmann S. 1991. On the nonlinear map** of an ocean wave spectrum into a synthetic aperture radar image spectrum and its inversion. Journal of Geophysical Research, 96(C6): 10713–10729, doi: https://doi.org/10.1029/91JC00302
Hayslip A R, Johnson J T, Baker G R. 2003. Further numerical studies of backscattering from time-evolving nonlinear sea surfaces. IEEE Transactions on Geoscience and Remote Sensing, 41(10): 2287–2293, doi: https://doi.org/10.1109/TGRS.2003.814662
Johannessen J A, Kudryavtsev V, Akimov D, et al. 2005. On radar imaging of current features: 2. Mesoscale eddy and current front detection. Journal of Geophysical Research, 110(C7): C07017
Johnson J T, Burkholder R J, Toporkov J V, et al. 2009. A numerical study of the retrieval of sea surface height profiles from low grazing angle radar data. IEEE Transactions on Geoscience and Remote Sensing, 47(6): 1641–1650, doi: https://doi.org/10.1109/TGRS.2008.2006833
Johnson J T, Toporkov J V, Brown G S. 2001. A numerical study of backscattering from time-evolving sea surfaces: comparison of hydrodynamic models. IEEE Transactions on Geoscience and Remote Sensing, 39(11): 2411–2420, doi: https://doi.org/10.1109/36.964977
Karaev V, Kanevsky M, Meshkov E. 2008. The effect of sea surface slicks on the Doppler spectrum width of a backscattered microwave signal. Sensors, 8(6): 3780–3801, doi: https://doi.org/10.3390/s8063780
Keller W C, Plant W J, Alenzuela G R. 1986. Observation of breaking ocean waves with coherent microwave radar. In: Phillips O M, Hasselmann K, eds. Wave Dynamics and Radio Probing of the Ocean Surface. Boston: Springer, 285–293
Kudryavtsev V, Akimov D, Johannessen J, et al. 2005. On radar imaging of current features: 1. Model and comparison with observations. Journal of Geophysical Research, 110(C7): C07016
Leykin I A, Donelan M A, Mellen R H, et al. 1995. Asymmetry of wind waves studied in a laboratory tank. Nonlinear Processes in Geophysics, 2(3): 280–289, doi: https://doi.org/10.5194/npg-2-280-1995
Li **aoming, Lehner S. 2014. Algorithm for sea surface wind retrieval from TerraSAR-X and TanDEM-X Data. IEEE Transactions on Geoscience and Remote Sensing, 52(5): 2928–2939, doi: https://doi.org/10.1109/TGRS.2013.2267780
Lindgren G. 2009. Exact asymmetric slope distributions in stochastic Gauss-Lagrange ocean waves. Applied Ocean Research, 31(1): 65–73, doi: https://doi.org/10.1016/j.apor.2009.06.002
Lindgren G, Åberg Sofia. 2009. First order stochastic Lagrange model for asymmetric ocean waves. Journal of Offshore Mechanics and Arctic. Engineering, 131(3): 031602
Lipa B. 1978. Inversion of second-order radar echoes from the sea. Journal of Geophysical Research, 83(C2): 959–962, doi: https://doi.org/10.1029/JC083iC02p00959
Lyzenga D R. 1986. Numerical simulation of synthetic aperture radar image spectra for ocean waves. IEEE Transactions on Geoscience and Remote Sensing, GE-24(6): 863–872, doi: https://doi.org/10.1109/TGRS.1986.289701
Moiseev A, Johannessen J A, Johnsen H. 2022. Towards retrieving reliable ocean surface currents in the coastal zone from the sentinel-1 Doppler shift observations. Journal of Geophysical Research, 127(5): e2021JC018201
Moiseev A, Johnsen H, Johannessen J A, et al. 2020. On removal of sea state contribution to Sentinel-1 Doppler shift for retrieving reliable ocean surface current. Journal of Geophysical Research, 125(9): e2020JC016288
Mouche A, Chapron B. 2015. Global C-Band Envisat, RADARSAT-2 and Sentinel-1 SAR measurements in copolarization and cross-polarization. Journal of Geophysical Research, 120(11): 7195–7207, doi: https://doi.org/10.1002/2015JC011149
Mouche A A, Chapron B, Reul N, et al. 2008. Predicted Doppler shifts induced by ocean surface wave displacements using asymptotic electromagnetic wave scattering theories. Waves in Random and Complex Media, 18(1): 185–196, doi: https://doi.org/10.1080/17455030701564644
Mouche A A, Collard F, Chapron B, et al. 2012. On the use of Doppler shift for sea surface wind retrieval from SAR. IEEE Transactions on Geoscience and Remote Sensing, 50(7): 2901–2909, doi: https://doi.org/10.1109/TGRS.2011.2174998
Shao Weizeng, Zhang Zheng, Li **aoming, et al. 2016. Sea surface wind speed retrieval from TerraSAR-X HH polarization data using an improved polarization ratio model. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 9(11): 4991–4997, doi: https://doi.org/10.1109/JSTARS.2016.2590475
Tayfun M A. 1986. On narrow-band representation of ocean waves: 1. Theory. Journal of Geophysical Research, 91(C6): 7743–7752, doi: https://doi.org/10.1029/JC091iC06p07743
Toporkov J V, Brown G S. 2000. Numerical simulations of scattering from time-varying, randomly rough surfaces. IEEE Transactions on Geoscience and Remote Sensing, 38(4): 1616–1625, doi: https://doi.org/10.1109/36.851961
Verspeek J, Stoffelen A, Verhoef A, et al. 2012. Improved ASCAT wind retrieval using NWP ocean calibration. IEEE Transactions on Geoscience and Remote Sensing, 50(7): 2488–2494, doi: https://doi.org/10.1109/TGRS.2011.2180730
Wang Yunhua, Zhang Yanmin. 2011. Investigation on Doppler shift and bandwidth of backscattered echoes from a composite sea surface. IEEE Transactions on Geoscience and Remote Sensing, 49(3): 1071–1081, doi: https://doi.org/10.1109/TGRS.2010.2070071
Wang Yunhua, Zhang Yanmin, Guo Lixin. 2013. Microwave Doppler spectra of sea echoes at high incidence angles: influences of large-scale waves. Progress in Electromagnetics Research B, 48: 99–113, doi: https://doi.org/10.2528/PIERB12123004
Wang Yunhua, Zhang Yanmin, He Mingxia, et al. 2012. Doppler spectra of microwave scattering fields from nonlinear oceanic surface at moderate- and low-grazing angles. IEEE Transactions on Geoscience and Remote Sensing, 50(4): 1104–1116, doi: https://doi.org/10.1109/TGRS.2011.2164926
Wang Yunhua, Zhang Yanmin, Li Huimin, et al. 2016. Doppler spectrum of microwave SAR signals from two-dimensional time-varying sea surface. Journal of Electromagnetic Waves and Applications, 30(10): 1265–1276, doi: https://doi.org/10.1080/09205071.2016.1186575
Wright J W, Keller W C. 1971. Doppler spectra in microwave scattering from wind waves. The Physics of Fluids, 14(3): 466–474, doi: https://doi.org/10.1063/1.1693458
Zavorotny V U, Voronovich A G. 1998. Two-scale model and ocean radar Doppler spectra at moderate- and low-grazing angles. IEEE Transactions on Antennas and Propagation, 46(1): 84–92, doi: https://doi.org/10.1109/8.655454
Author information
Authors and Affiliations
Corresponding authors
Additional information
Foundation item: The National Natural Science Foundation of China under contract No. 41976167; the Key Research and Development Program of Shandong Province (International Science and Technology Cooperation) under contract No. 2019GHZ023.
Rights and permissions
About this article
Cite this article
Cui, J., Wang, Y., Zhang, Y. et al. A new model for Doppler shift of C-band echoes backscattered from sea surface. Acta Oceanol. Sin. 42, 100–111 (2023). https://doi.org/10.1007/s13131-022-2144-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13131-022-2144-8