Ocean wave directional spectrum measurement using microwave coherent radar with six antennas

Abstract:In this paper, a novel shore-based S-band microwave Doppler coherent wave radar (Microwave Ocean Remote SEnsor (MORSE)) is designed to improve wave measurements. Marine radars, which operate in the X band, have been widely used for ocean monitoring because of their low cost, small size and flexibility. However, because of the non-coherent measurements and strong absorption of X-band radio waves by rain, these radar systems suffer considerable performance loss in moist weather. Furthermore, frequent calibrations to modify the modulation transfer function are required. To overcome these shortcomings, MORSE, which operates in the S band, was developed by Wuhan University. Because of the coherent measurements of this sensor, it is able to measure the radial velocity of water particles via the Doppler effect. Then the relation between the velocity spectrum and wave height spectrum can be used to obtain the wave height spectra. Finally, wave parameters are estimated from the wave height spectra by the spectrum moment method. Comparisons between MORSE and Waverider MKIII are conducted in this study, and the results, including the non-directional wave height spectra, significant wave height and average wave period, are calculated and displayed. The correlation coefficient of the significant wave height is larger than 0.9, whereas that of the average wave period is approximately 0.4, demonstrating the effectiveness of MORSE for the continuous monitoring of ocean areas with high accuracy.

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“…The phases from two adjacent range cells acquired simultaneously are compared to solve the 180-degree ambiguity [27].…”

Section: Coherent Wave Measuring Methodsmentioning

confidence: 99%

S-Band Doppler Wave Radar System

et al. 2017

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“…Step 1: Calculation of the spatial-temporal velocity series. According to (7), the Doppler frequency shift can be calculated from the radar echo Doppler spectrum, and then the Doppler velocity can be obtained according to (8). A spatial-temporal velocity series v r (x, t, φ n ) can be obtained, where φ n is the azimuth angle of the nth antenna.…”

Section: Wave Parameter Inversion Flowmentioning

confidence: 99%

Inversion of Wave Parameters With Shore-Based Coherent $S$-Band Radar Using Quasi-Binary Variational Mode Decomposition

Hu,

Chen,

Zhao

et al. 2024

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Coherent microwave radar utilizes the direct relationship between the orbital wave velocity and the wave height spectrum to retrieve wave parameters. However, due to the broken wave and its evolution, the "Group-Line" is introduced in the radar-obtained wavenumber-frequency spectrum, and the dominant wave energy is reduced. Many methods have proposed to remove the "Group-Line" in the wavenumber-frequency spectrum, but these methods can only remove low-frequency energy and fail to compensate for the dominant wave energy. To solve this problem, a method for wave parameter inversion using the quasibinary variational mode decomposition (QB-VMD) is proposed. Firstly, the QB-VMD decomposes the spatial-temporal radial velocity series, and a series of modes are obtained, including the "Group-Line" and dominant wave modes. Secondly, the "Group-Line" mode is discarded, and the dominant wave mode is compensated appropriately to reconstruct the spatial-temporal radial velocity series. Finally, the wave parameters are retrieved according to the reconstructed spatial-temporal radial velocity series. The proposed method is verified by simulation. In addition, this paper uses on 8-day data set collected by the coherent Sband radar deployed at the Beishuang island for analysis. The significant wave height and mean wave period are retrieved from the data set. The wave parameters estimated by the proposed method are compared with the buoy results. The correlation coefficients are 0.97 and 0.80, and the root means square errors are 0.12 m and 0.49 s, respectively. The results show that the proposed method can invert wave parameters using the coherent S-band radar with a reasonable performance.

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“…In contrast to noncoherent radars, coherent radars do not need calibration. Typical coherent radar systems include the SM-050 MK III from the Norwegian MIROS and the shore-based S-band Doppler wave radar developed by the Radio Ocean Remote Sensing (RORSE) Laboratory at Wuhan University, China [9,10]. The SM-050 MK III radar is a pulsed radar and operates in the C-band [11].…”

Section: Introductionmentioning

confidence: 99%

Wave Height and Wave Period Derived from a Shipboard Coherent S-Band Wave Radar in the South China Sea

Chen

Zhao

et al. 2019

Remote Sensing

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To expand the scope of ocean wave observations, a shipboard coherent S-band wave radar system was developed recently. The radar directly measures the wave orbital velocity from the Doppler shift of the received radar signal. The sources of this Doppler shift are analyzed. After removing the Doppler shifts caused by the ocean current and platform, the radial velocities of water particles of the surface gravity waves are retrieved. Subsequently, the wavenumber spectrum can be obtained based on linear wave theory. Later, the significant wave height and wave periods (including mean wave period and peak wave period) can be calculated from the wavenumber spectrum. This radar provides a calibration-free way to measure wave parameters and is a novel underway coherent microwave wave radar. From 9 September to 11 September, 2018, an experiment involving radar-derived and buoy-measured wave measurements was conducted in the South China Sea. The Doppler spectra obtained when the ship was in the state of navigation or mooring indicated that the quality of the radar echo was fairly good. The significant wave heights and wave periods measured using the radar are compared with those obtained from the wave buoy. The correlation coefficients of wave heights and mean wave periods between these two instruments both exceed 0.9 while the root mean square differences are respectively less than 0.15 m and 0.25 s, regardless of the state of motion of the ship. These results indicate that this radar has the capability to accurately measure ocean wave heights and wave periods.

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Ocean wave directional spectrum measurement using microwave coherent radar with six antennas

Cited by 14 publications

References 7 publications

S-Band Doppler Wave Radar System

S-Band Doppler Wave Radar System

Inversion of Wave Parameters With Shore-Based Coherent $S$-Band Radar Using Quasi-Binary Variational Mode Decomposition

Wave Height and Wave Period Derived from a Shipboard Coherent S-Band Wave Radar in the South China Sea

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