scholarly journals Surface roughness and breaking wave properties retrieved from polarimetric microwave radar backscattering

2015 ◽  
Vol 120 (5) ◽  
pp. 3640-3657 ◽  
Author(s):  
Paul A. Hwang ◽  
Franco Fois
Keyword(s):  
Surface Roughness ◽  
Breaking Wave ◽  
Microwave Radar ◽  
Radar Backscattering ◽  
Wave Properties

A study of relation between non-Bragg microwave radar backscattering and decimeter-scale wind waves

2021 ◽  
Author(s):  
Irina A. Sergievskaya ◽  
Stanislav Ermakov ◽  
Olga Shomina ◽  
Alexander Kupaev ◽  
Ivan Kapustin
Keyword(s):  
Wind Waves ◽  
Microwave Radar ◽  
Radar Backscattering

scholarly journals Estimation of breaking wave properties and their interaction with a jacket structure

2019 ◽  
Vol 91 ◽  
pp. 102722 ◽  
Author(s):  
Ankit Aggarwal ◽  
Hans Bihs ◽  
Seimur Shirinov ◽  
Dag Myrhaug
Keyword(s):  
Breaking Wave ◽  
Wave Properties

Characteristics of the Wave Slamming Forces on Jacket Structures Under Plunging Breaking Waves Based on Experimental Data

2017 ◽  
Author(s):  
Jithin Jose ◽  
Olga Podrażka ◽  
Ove Tobias Gudmestad ◽  
Witold Cieślikiewicz
Keyword(s):  
Energy Demand ◽  
Clean Energy ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Wave Forces ◽  
Breaking Wave ◽  
Jacket Structures ◽  
Wave Slamming ◽  
Wave Properties

Due to increased energy demand and thrive for clean energy, offshore wind energy has become popular these days. A large number of offshore wind turbines supported by fixed type substructures have been installed, among which jacket structures are getting popular in recent times. The forces from breaking waves are a major concern in the design of offshore structures installed in shallow waters. However, there are only limited studies available regarding breaking wave forces on jacket structures and still there exist many uncertainties in this area. During the WaveSlam experiment carried out in 2013, a jacket structure of 1:8 scale was tested on a large number of breaking wave conditions. Wave properties and the forces on the structure were measured during the experiment. The total wave slamming forces are being filtered from the experimental measured force using the Empirical Mode Decomposition method and local slamming forces are obtained by the Frequency Response Function method. Based on these results, the peak slamming force and slamming coefficients on the jacket members are estimated. The wave parameters (wave height and period) and wave front asymmetry are obtained from measured wave properties. The variation of slamming forces and slamming coefficients with respect to these parameters are also investigated.

scholarly journals The Role of Micro Breaking of Small-Scale Wind Waves in Radar Backscattering from Sea Surface

2020 ◽  
Vol 12 (24) ◽  
pp. 4159
Author(s):  
Irina A. Sergievskaya ◽  
Stanislav A. Ermakov ◽  
Aleksey V. Ermoshkin ◽  
Ivan A. Kapustin ◽  
Olga V. Shomina ◽  
...  
Keyword(s):  
Wind Waves ◽  
Breaking Waves ◽  
Sea Surface ◽  
Small Scale ◽  
Breaking Wave ◽  
Generation Process ◽  
Bragg Scattering ◽  
Radar Backscattering ◽  
Radar Sensing ◽  
The Impact

The study of the microwave scattering mechanisms of the sea surface is extremely important for the development of radar sensing methods. Some time ago, Bragg (resonance) scattering of electromagnetic waves from the sea surface was proposed as the main mechanism of radar backscattering at moderate incidence angles of microwaves. However, it has been recently confirmed that Bragg scattering is often unable to correctly explain observational data and that some other physical mechanisms should be taken into consideration. The newly introduced additional scattering mechanism was characterized as non-polarized, or non-Bragg scattering, from quasi-specular facets appearing due to breaking wave crests, the latter usually occurring in moderate and strong winds. In this paper, it was determined experimentally that such non-polarized radar backscattering appeared not only for rough sea conditions in which wave crests strongly break and “white caps” occur, but also at very low wind velocities close to their threshold values for the wave generation process. The experiments were performed using two polarized Doppler radars. The experiments demonstrated that a polarization ratio, which characterizes relative contributions of non-polarized and Bragg components to the total backscatter, changed slightly with wind velocity and wind direction. Detailed analysis of radar Doppler shifts revealed two types of scatterers responsible for the non-polarized component. One type of scatterer, moving with the velocities of decimeter-scale wind waves, determined radar backscattering at low winds. We identified these scatterers as “microbreakers” and related them to nonlinear features in the profile of decimeter-scale waves, like bulges, toes and parasitic capillary ripples. The scatterers of the second type were associated with strong breaking, moved with the phase velocities of meter-scale breaking waves and appeared at moderate winds additionally to the “microbreakers”. Along with strong breakers, the impact of microbreaking in non-polarized backscattering at moderate winds remained significant; specifically the microbreakers were found to be responsible for about half of the non-polarized component of the radar return. The presence of surfactant films on the sea surface led to a significant suppression of the small-scale non-Bragg scattering and practically did not change the non-Bragg scatterer speed. This effect was explained by the fact that the nonlinear structures associated with dm-scale waves were strongly reduced in the presence of a film due to the cascade mechanism, even if the reduction of the amplitude of dm waves was weak. At the same time, the velocities of non-Bragg scatterers remained practically the same as in non-slick areas since the phase velocity of dm waves was not affected by the film.

scholarly journals Variations in sea surface roughness induced by the 2004 Sumatra-Andaman tsunami

2009 ◽  
Vol 9 (4) ◽  
pp. 1135-1147 ◽  
Author(s):  
O. A. Godin ◽  
V. G. Irisov ◽  
R. R. Leben ◽  
B. D. Hamlington ◽  
G. A. Wick
Keyword(s):  
Surface Roughness ◽  
Surface Wind ◽  
Early Warning Systems ◽  
Sea Surface Height ◽  
Open Ocean ◽  
Sea Surface ◽  
Near Surface ◽  
Sea Surface Roughness ◽  
Backscattering Strength ◽  
Radar Backscattering

Abstract. Observations of tsunamis away from shore are critically important for improving early warning systems and understanding of tsunami generation and propagation. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude there is much smaller than it is close to shore. Currently, tsunami observations in deep water rely on measurements of variations in the sea surface height or bottom pressure. Here we demonstrate that there exists a different observable, specifically, ocean surface roughness, which can be used to reveal tsunamis away from shore. The first detailed measurements of the tsunami effect on sea surface height and radar backscattering strength in the open ocean were obtained from satellite altimeters during passage of the 2004 Sumatra-Andaman tsunami. Through statistical analyses of satellite altimeter observations, we show that the Sumatra-Andaman tsunami effected distinct, detectable changes in sea surface roughness. The magnitude and spatial structure of the observed variations in radar backscattering strength are consistent with hydrodynamic models predicting variations in the near-surface wind across the tsunami wave front. Tsunami-induced changes in sea surface roughness can be potentially used for early tsunami detection by orbiting microwave radars and radiometers, which have broad surface coverage across the satellite ground track.

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