Mapping coastal winds with HF radar
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Over-water wind speeds and directions derived from a ground-wave high frequency radar-the Multi-frequency Coastal Radar (MCR)-are compared to in-situ observations to examine the skill of the radar measurements. Conventional beam formation processing of radar data collected from two sites around Monterey Bay during summer 1997 is used to produce wind directions based on the relative strength of the positive and negative Bragg-resonant peaks, which correspond to wind-driven waves approaching and receding from the radar, respectively. The functional relationship that converts these signal levels, which primarily reflect surface wave conditions, to a wind direction are a central research issue. To address this issue, the remotely sensed estimates are compared against moored observations under variable wind conditions. Wind direction algorithms based on Bragg ratios applied to this or any HF radar cannot detect wind speed. However, the unique capability of the MCR to, simultaneously, measure at four Bragg-resonant frequencies is used to assess the sensitivity of near-surface current shear to the measured wind speed.Keywords:
Wave radar
Estimating ocean wave height is vital for coastal activities. Herein, we propose a method for the estimation of wave height using a phase time series of the frequency-modulated continuous-wave (FMCW) millimeter-wave (MMW) radar. We simulated a one-dimensional wavy ocean surface under different wind speeds and the electromagnetic echo of MMW radar on the ocean surface. The simulation results show that the unwrapping phase time series-based wave heights are highly consistent with the actual wave heights. This shows that the phase time series of the FMCW MMW radar is effective for estimating wave height, and the FMCW MMW radar can be used to monitor ocean states.
Wave radar
Extremely high frequency
Continuous wave
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The ocean wave spectrum is an essential parameter to fully describe the dynamic ocean waves. Although the spaceborne Synthetic Aperture Radar (SAR) is a potential instrument to measure the ocean wave spectrum, its retrieval is intricated by the complicated non-linear SAR-wave imaging mechanisms. This study introduced a deep learning (DL) method to address the ocean wave spectrum retrieval tasks from SAR images. The DL-based framework modifies the classical CNN architecture according to the multiple outputs of the target parameters and imposes a soft constraint based on the characteristics of the ocean wave spectrum. Trained and evaluated by the measurements of in-situ buoys deployed in the global ocean, the proposed model achieved root-mean-square errors of 0.53 m for significant wave heights and 1.24 s mean wave periods, demonstrating a generalized and robust performance. Our study represents a significant breakthrough in the longstanding challenge of SAR retrievals in ocean remote sensing.
Wave radar
Electromagnetic spectrum
Significant wave height
Wave height
Ocean dynamics
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The paper deals with the investigations of wind characteristics of local winds in the coastal area of Croatia. The measurements of wind speed and direction were carried out on an antenna column at heights of 10, 20 and 35 m. The objective of these measurements was to determine the wind characteristics for dominant winds (bura, jugo, levant) according to the wind rose defined from the measured days. The investigations showed that there are three dominant wind directions for which the relations between the wind shear factor and the wind speed and direction have been analyzed. The obtained values of the wind shear coefficient WSC are relevant considering the social and national interest since a wind-park is planned to be built on the mentioned location These investigations were carried out in order to determine the National Annex for the norms 1991-2-4: Wind action upon the structure.
Maximum sustained wind
Prevailing winds
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Sensors for remote sensing of ocean wave directional spectra are needed for global wave forecasting application. Backscatter from off-nadir, short pulse, radar-illuminated ocean waves gives the wave impulse response. Wave slope and wave length can be determined from the applitude time radar signature. Analysis of some preliminary wave spectral data taken with a 10 nanosecond aircraft mounted radar will be compared with wave spectra derived from laser prolifometer measurements.
Wave radar
Backscatter (email)
Nadir
Radar altimeter
Significant wave height
Wave height
Pulse repetition frequency
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Wind sea and swell indicating different wave field characteristics generally coexist in both coastal areas and open waters, which results in bimodal or multi-peaked features in directional wave spectrum. Separation and identification of mixed wave conditions into wind sea and swell present a more detailed description of the sea states, and they turn wave parameters such as significant weight height and mean wave period of the detached wave components more meaningful. With directional wave spectrum and wind velocity, wind sea and swell separation results can be obtained using a commonly used method named Wave Age (WA). Wuhan University has developed an S-band Doppler radar based on FMICW since 2011. Directional wave spectra derived from the Doppler radar deployed on the coast of the South China Sea have been utilized to investigate the results of wind sea and swell by WA.
Swell
Wave radar
Significant wave height
Infragravity wave
Sea state
Wind wave model
Wave height
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Ocean wave in-situ measurement is limited only to measure temporal sea surface information. In order to measure spatial surface information a radar system is suitable; however, radar image includes many noises. In this study both temporal and spatial ocean surface characteristics were measured by a X-band radar and a wave buoy. Radar scattering waves were analyzed by WaMosII (Wave Monitoring System II) system which gives spatial surface elevations in a measuring region. Wave parameters such as significant wave height, maximum wave height, peak wave period, wave age were estimated and verified by the X-band radar. It was shown that the radar measurements gave narrower directional spectra than the buoy observations.
Buoy
Wave radar
Significant wave height
Wave height
Wind wave model
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This paper discusses methods for using measurements of the backscattered power and the Doppler shift of radar signals scattered from the ocean surface to compute maps of phase resolved ocean wave fields. Results are compared with buoy and lidar measurements of ocean surface waves off the coast of southern California.
Wave radar
Buoy
Early-warning radar
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