Coupling between the Fluctuating Wind Field, Wave Field and the Momentum Flux.

1995 ◽  
Author(s):  
Larry Mahrt
Keyword(s):  
Wave Field ◽  
Wind Field ◽  
Momentum Flux ◽  
Fluctuating Wind ◽  
Field Wave

Statistical Analysis on the Extreme Events of Big Waves Under Wave Climate Change Around Taiwan Waters

2011 ◽  
Author(s):  
Ching-Her Hwang ◽  
Wen-Ching Lee ◽  
Wen-Fang Hsieh ◽  
Ching-Piao Tsai ◽  
Hwa Chien
Keyword(s):  
Climate Change ◽  
Wave Field ◽  
Extreme Events ◽  
Wind Field ◽  
Wave Climate ◽  
Model Parameters ◽  
Climate Change Research ◽  
Weather Bureau ◽  
Central Weather Bureau ◽  
Typhoon Wind

This study aimed to analyze the statistical characteristics of wave heights, wave energy and wave steepness, in order to investigate the wave climate changes around Taiwan Waters, especially for extreme events of big waves. The operational observation of Taiwan sea waves was initiated by the Central Weather Bureau in 1998; however, due to insufficient data length and low data space coverage, the data are unable to serve as references for long-term wave climate change research. Hence, this study adopted the SWAN (Simulation of Wave in Nearshore) Numerical Wave Hindcasting Method, which is a common method used in many studies, to hindcast the history of a wave field. The re-analysis on wind field data of the last 60 years (1948∼2008), published by the National Centers for Environmental Prediction (NCEP), was employed to make the wind field grid consistent with the hindcast wave field grid. Moreover, the Typhoon Wind Field Grid Down Scaling technique proposed by Winter & Chiou (2007) was applied to interpolate a U10 analysis field that better fits an actual typhoon wind field. The hindcast wave data were compared and validated with directional spectra, which were observed by the meteorological/oceanographic data buoys set up by the Central Weather Bureau and Water Resources Agency since 1997. Longdong, Hualien and Hsinchu Stations were chosen to represent the wave characteristics of sea areas around the island of Taiwan. According to observation data, model parameters were adjusted so that the hindcast results could be closer to observed data in Taiwan sea areas.

Application of the IDEMIX Concept for Internal Gravity Waves in the Atmosphere

2020 ◽  
Vol 77 (10) ◽  
pp. 3601-3618
Author(s):  
B. Quinn ◽  
C. Eden ◽  
D. Olbers
Keyword(s):  
Energy Balance ◽  
Wave Field ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Middle Atmosphere ◽  
Internal Gravity Waves ◽  
Wave Drag ◽  
Mean Flow ◽  
The Mean

AbstractThe model Internal Wave Dissipation, Energy and Mixing (IDEMIX) presents a novel way of parameterizing internal gravity waves in the atmosphere. IDEMIX is based on the spectral energy balance of the wave field and has previously been successfully developed as a model for diapycnal diffusivity, induced by internal gravity wave breaking in oceans. Applied here for the first time to atmospheric gravity waves, integration of the energy balance equation for a continuous wave field of a given spectrum, results in prognostic equations for the energy density of eastward and westward gravity waves. It includes their interaction with the mean flow, allowing for an evolving and local description of momentum flux and gravity wave drag. A saturation mechanism maintains the wave field within convective stability limits, and a closure for critical-layer effects controls how much wave flux propagates from the troposphere into the middle atmosphere. Offline comparisons to a traditional parameterization reveal increases in the wave momentum flux in the middle atmosphere due to the mean-flow interaction, resulting in a greater gravity wave drag at lower altitudes. Preliminary validation against observational data show good agreement with momentum fluxes.

Simulation of Wind Field on Long-Span Cable-Stayed Bridge Based on SPT

2011 ◽  
Vol 90-93 ◽  
pp. 2451-2455
Author(s):  
Yi Feng Huang ◽  
Ji Xin Yang
Keyword(s):  
Computational Efficiency ◽  
Physical Meaning ◽  
Wind Field ◽  
Basic Theory ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Matlab Program ◽  
Fluctuating Wind ◽  
High Computational Efficiency

The simplified of fluctuating wind field and the basic theory of Spectral Proper Transformation（SPT）were expatiated. SPT was used to simulate the random wind field on long-span cable-stayed bridge, then the random wind field of the bridge was simulated by MATLAB program, an actual example was used to validate the validity and correctness of the MATLAB program. The results showed that SPT had the advantage of explicit physical meaning, high computational efficiency. It is an effective method to simulate the random wind field.

scholarly journals Mesoscale Eddy–Internal Wave Coupling. Part I: Symmetry, Wave Capture, and Results from the Mid-Ocean Dynamics Experiment

2008 ◽  
Vol 38 (11) ◽  
pp. 2556-2574 ◽  
Author(s):  
Kurt L. Polzin
Keyword(s):  
Internal Wave ◽  
Wave Field ◽  
Mesoscale Eddy ◽  
Horizontal Velocity ◽  
Ocean Dynamics ◽  
Energy Propagation ◽  
Wave Trapping ◽  
Inertial Wave ◽  
Parallel Shear Flow ◽  
Field Wave

Abstract Vertical profiles of horizontal velocity obtained during the Mid-Ocean Dynamics Experiment (MODE) provided the first published estimates of the high vertical wavenumber structure of horizontal velocity. The data were interpreted as being representative of the background internal wave field, and thus, despite some evidence of excess downward energy propagation associated with coherent near-inertial features that was interpreted in terms of atmospheric generation, these data provided the basis for a revision to the Garrett and Munk spectral model. These data are reinterpreted through the lens of 30 years of research. Rather than representing the background wave field, atmospheric generation, or even near-inertial wave trapping, the coherent high wavenumber features are characteristic of internal wave capture in a mesoscale strain field. Wave capture represents a generalization of critical layer events for flows lacking the spatial symmetry inherent in a parallel shear flow or isolated vortex.

scholarly journals Spectrally Resolved Energy Dissipation Rate and Momentum Flux of Breaking Waves

2008 ◽  
Vol 38 (6) ◽  
pp. 1296-1312 ◽  
Author(s):  
Johannes R. Gemmrich ◽  
Michael L. Banner ◽  
Chris Garrett
Keyword(s):  
Energy Dissipation ◽  
Wave Field ◽  
Wave Energy ◽  
Dissipation Rate ◽  
Momentum Flux ◽  
Phase Speed ◽  
Breaking Waves ◽  
Energy Dissipation Rate ◽  
Small Scale ◽  
Breaking Wave

Abstract Video observations of the ocean surface taken from aboard the Research Platform FLIP reveal the distribution of the along-crest length and propagation velocity of breaking wave crests that generate visible whitecaps. The key quantity assessed is Λ(c)dc, the average length of breaking crests per unit area propagating with speeds in the range (c, c + dc). Independent of the wave field development, Λ(c) is found to peak at intermediate wave scales and to drop off sharply at larger and smaller scales. In developing seas breakers occur at a wide range of scales corresponding to phase speeds from about 0.1 cp to cp, where cp is the phase speed of the waves at the spectral peak. However, in developed seas, breaking is hardly observed at scales corresponding to phase speeds greater than 0.5 cp. The phase speed of the most frequent breakers shifts from 0.4 cp to 0.2 cp as the wave field develops. The occurrence of breakers at a particular scale as well as the rate of surface turnover are well correlated with the wave saturation. The fourth and fifth moments of Λ(c) are used to estimate breaking-wave-supported momentum fluxes, energy dissipation rate, and the fraction of momentum flux supported by air-entraining breaking waves. No indication of a Kolmogorov-type wave energy cascade was found; that is, there is no evidence that the wave energy dissipation is dominated by small-scale waves. The proportionality factor b linking breaking crest distributions to the energy dissipation rate is found to be (7 ± 3) × 10−5, much smaller than previous estimates.

Multi-scale mountain waves observed with the ALIMA lidar during SOUTHTRAC-GW above the southern Andes

2021 ◽  
Author(s):  
Natalie Kaifler ◽  
Bernd Kaifler ◽  
Andreas Dörnbrack ◽  
Sonja Gisinger ◽  
Tyler Mixa ◽  
...  
Keyword(s):  
Wave Field ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Middle Atmosphere ◽  
Airborne Lidar ◽  
Horizontal Wind ◽  
Measured Temperature ◽  
Southern Andes ◽  
Mountain Waves

<p>During the SOUTHTRAC-GW (Southern hemisphere Transport, Dynamics and Chemistry – Gravity Waves) field campaign, gravity waves above the Southern Andes mountains, the Drake passage and the Antarctic Peninsula were probed with airborne instruments onboard the HALO research aircraft. The Airborne Lidar for Middle Atmosphere research (ALIMA) detected particularly strong mountain waves in excess of 25 K amplitude in cross-mountain legs above the Southern Andes of research flight ST08 on 12 September 2019. The mountain waves propagated well into the mesosphere up to 65 km altitude with possible generation of smaller-scale secondary waves during wave breaking above 65 km. A superposition of mountain waves with horizontal wavelengths in the range 15-200 km and vertical wavelengths 7-24 km dominated the wave field between 18 and 65 km altitude. Vertical wavelengths predicted by the hydrostatic equation and horizontal wind from the European Center for Medium-Range Weather Forecasts’ Integrated Forecasting System are in good agreement with observed vertical wavelengths. We apply wavelet analysis to the measured temperature field along the flight track in order to identify and separate dominant scales, and estimate their relative contributions to the total gravity wave momentum flux as well as the local and zonal-mean gravity wave drag. Furthermore, we compare our observations to results obtained by Fourier ray analysis of the terrain of the Southern Andes. The Fourier model allows the investigation of the 3d-wave field and trapped waves which are not well sampled by the ALIMA instrument because of the relative alignment between the wave fronts and the flight track. These sampling biases are quantified from virtual flights through the model domain at multiple angles and taken into account in the estimation of the total momentum flux derived from ALIMA observations. The combination of high-resolution observations and model data reveals the significance of this and similar mountain wave events in the Southern Andes region for the atmospheric dynamics at ~60° S.</p>

scholarly journals Surface Wave Effects on the Translation of Wind Stress across the Air–Sea Interface in a Fetch-Limited, Coastal Embayment

2017 ◽  
Vol 47 (8) ◽  
pp. 1921-1939 ◽  
Author(s):  
Alexander W. Fisher ◽  
Lawrence P. Sanford ◽  
Malcolm E. Scully ◽  
Steven E. Suttles
Keyword(s):  
Surface Wave ◽  
Wave Field ◽  
Chesapeake Bay ◽  
Wind Stress ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Breaking Waves ◽  
Wave Direction ◽  
Mean Flow ◽  
Surface Wave Field

AbstractThe role of surface gravity waves in structuring the air–sea momentum flux is examined in the middle reaches of Chesapeake Bay. Observed wave spectra showed that wave direction in Chesapeake Bay is strongly correlated with basin geometry. Waves preferentially developed in the direction of maximum fetch, suggesting that dominant wave frequencies may be commonly and persistently misaligned with local wind forcing. Direct observations from an ultrasonic anemometer and vertical array of ADVs show that the magnitude and direction of stress changed across the air–sea interface, suggesting that a stress divergence occurred at or near the water surface. Using a numerical wave model in combination with direct flux measurements, the air–sea momentum flux was partitioned between the surface wave field and the mean flow. Results indicate that the surface wave field can store or release a significant fraction of the total momentum flux depending on the direction of the wind. When wind blew across dominant fetch axes, the generation of short gravity waves stored as much as 40% of the total wind stress. Accounting for the storage of momentum in the surface wave field closed the air–sea momentum budget. Agreement between the direction of Lagrangian shear and the direction of the stress vector in the mixed surface layer suggests that the observed directional difference was due to the combined effect of breaking waves producing downward sweeps of momentum in the direction of wave propagation and the straining of that vorticity field in a manner similar to Langmuir turbulence.

An Optimized Method for Transient Electromagnetic Field-Wave Field Conversion

2005 ◽  
Vol 48 (5) ◽  
pp. 1268-1275 ◽  
Author(s):  
Xiu LI ◽  
Guo-Qiang XUE ◽  
Jian-Ping SONG ◽  
Wen-Bo GUO ◽  
Jun-Jie WU
Keyword(s):  
Electromagnetic Field ◽  
Wave Field ◽  
Transient Electromagnetic ◽  
Field Wave

Numerical study on ergodic fluctuating wind field of long-span bridge

2012 ◽  
Vol 29 (5) ◽  
pp. 432-437
Author(s):  
Heng-bin ZHENG ◽  
Quan-sheng YAN ◽  
Wei-feng WANG ◽  
Jie WU
Keyword(s):  
Wind Field ◽  
Numerical Study ◽  
Long Span ◽  
Long Span Bridge ◽  
Fluctuating Wind
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