Adiabatic transformation of a wave spectrum in a nonstationary medium with dispersion

The spaceborne interferometric synthetic aperture radar (InSAR) is expected to measure the sea surface height (SSH) with high accuracy over a wide swath. Since centimeter-level accuracy is required to monitor the ocean sub-mesoscale dynamics, the high accuracy implies that the altimetric errors should be totally understood and strictly controlled. However, for the dynamic waves, they move randomly all the time, and this will lead to significant altimetric errors. This study proposes an analytical method for the dynamic wave-related errors of InSAR SSH measurement based on the wave spectrum and electromagnetic scattering model. Additionally, the mechanisms of the dynamic wave-related errors of InSAR altimetry are analyzed, and the detailed numerical model is derived. The proposed analytical method is validated with NASA’s Surface Water and Ocean Topography (SWOT) project error budget, and the Root-Mean-Square Errors (RMSEs) are in good agreement (0.2486 and 0.2470 cm on a 0.5 km2 grid, respectively). Instead of analysis for a typical project, the proposed method can be applied to different radar parameters under multiple sea states. The RMSEs of Ka-band under low sea state, moderate sea state, and high sea state are 0.2670, 1.3154, and 6.6361 cm, respectively. Moreover, the RMSEs of X-band and Ku-band are also simulated and presented. The experimental results demonstrate that the dynamic wave-related errors of InSAR altimetry are not sensitive to the frequencies but are sensitive to the sea states. The error compensation method is necessary for moderate and higher sea states for centimetric accuracy requirements. This can provide feasible suggestions on system design and error budget for the future interferometric wide-swath altimeter.

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Millimeter-Wave Spectrum Utilization Improvement in Multi-Operator Networks: A Framework using the Equal Likelihood Criterion

IEEE Access ◽

10.1109/access.2021.3080326 ◽

2021 ◽

pp. 1-1

Author(s):

Rony Kumer Saha

Keyword(s):

Millimeter Wave ◽

Wave Spectrum ◽

Spectrum Utilization

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Primordial monopoles and strings, inflation, and gravity waves

Journal of High Energy Physics ◽

10.1007/jhep02(2021)114 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Joydeep Chakrabortty ◽

George Lazarides ◽

Rinku Maji ◽

Qaisar Shafi

Keyword(s):

Symmetry Breaking ◽

Gravity Waves ◽

Cosmic Strings ◽

Wave Spectrum ◽

Gauge Coupling ◽

String Tension ◽

Magnetic Monopoles ◽

Intermediate Scale ◽

Tension Parameter ◽

The Universe

Abstract We consider magnetic monopoles and strings that appear in non-supersymmetric SO(10) and E6 grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter Gμ spans the range 10−6− 10−30, where G is Newton’s constant and μ is the string tension. We show how intermediate scale monopoles with mass ∼ 1013− 1014 GeV and flux ≲ 2.8 × 10−16 cm−2s−1sr−1, and cosmic strings with Gμ ∼ 10−11− 10−10 survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio r lies between 0.06 and 0.003 depending on the details of the inflationary scenario.

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HF Radars for Wave Energy Resource Assessment Offshore NW Spain

Remote Sensing ◽

10.3390/rs13112070 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2070

Author(s):

Ana Basañez ◽

Vicente Pérez-Muñuzuri

Keyword(s):

Wave Energy ◽

Numerical Models ◽

Wave Spectrum ◽

Energy Resource ◽

Electrical Energy ◽

Resource Assessment ◽

Electricity Production ◽

Statistical Validation ◽

Wave Energy Converters ◽

Energy Converters

Wave energy resource assessment is crucial for the development of the marine renewable industry. High-frequency radars (HF radars) have been demonstrated to be a useful wave measuring tool. Therefore, in this work, we evaluated the accuracy of two CODAR Seasonde HF radars for describing the wave energy resource of two offshore areas in the west Galician coast, Spain (Vilán and Silleiro capes). The resulting wave characterization was used to estimate the electricity production of two wave energy converters. Results were validated against wave data from two buoys and two numerical models (SIMAR, (Marine Simulation) and WaveWatch III). The statistical validation revealed that the radar of Silleiro cape significantly overestimates the wave power, mainly due to a large overestimation of the wave energy period. The effect of the radars’ data loss during low wave energy periods on the mean wave energy is partially compensated with the overestimation of wave height and energy period. The theoretical electrical energy production of the wave energy converters was also affected by these differences. Energy period estimation was found to be highly conditioned to the unimodal interpretation of the wave spectrum, and it is expected that new releases of the radar software will be able to characterize different sea states independently.

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Sea State Monitoring by Ship Motion Measurements Onboard a Research Ship in the Antarctic Waters

Journal of Marine Science and Engineering ◽

10.3390/jmse9010064 ◽

2021 ◽

Vol 9 (1) ◽

pp. 64

Author(s):

Silvia Pennino ◽

Antonio Angrisano ◽

Vincenzo Della Corte ◽

Giampaolo Ferraioli ◽

Salvatore Gaglione ◽

...

Keyword(s):

Transfer Functions ◽

Wave Spectrum ◽

Weather Forecast ◽

Ship Motion ◽

State Monitoring ◽

Sea State ◽

Peak Period ◽

Research Ship ◽

Antarctic Waters ◽

The Antarctic

A parametric wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and significant wave height, based on the measurement and analysis of the heave and pitch motions of a vessel in a seaway, recorded by a smartphone located onboard the ship. The measurement system makes it possible to determine the heave and pitch acceleration spectra of the reference ship in the encounter frequency domain and, subsequently, the absolute sea spectra once the ship motion transfer functions are provided. The measurements have been carried out onboard the research ship “Laura Bassi”, during the oceanographic campaign in the Antarctic Ocean carried out in January and February 2020. The resembled sea spectra are compared with the weather forecast data, provided by the global-WAM (GWAM) model, in order to validate the sea spectrum resembling procedure.

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