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Sample records for piecioletnia remisja guza

  1. Evolution of Random Nonlinear Infragravity Waves in Coastal Waters

    NASA Astrophysics Data System (ADS)

    Tian, Miao; Sheremet, Alex; Shrira, Victor

    2014-05-01

    The observed spectra of nearshore infragravity waves are typically mixed, with a discrete component (edge waves, trapped waves, propagating parallel to the coast) and a continuous one (leaky waves, that propagate from, and radiate back into, the deep ocean. See e.g., Oltman-Shay and Guza, 1987). The evolution of infragravity spectrum is driven by three general processes: 1) edge-leaky interactions, that transfer energy to the system from shorter waves; 2) energy redistribution through edge-edge and edge-leaky interactions; 3) and energy dissipation due to processes such as bottom friction. Previous studies treated either the edge and leaky system, in isolation from the other one, and focused on phase-resolving dynamical equation. Following Whitham (1976), who derived the nonlinear edge-wave solutions for the shallow water equations, theoretical work on the nonlinear edge-edge interaction resulted in many significant extensions (e.g., Kirby et. al. 1998, Pelinovsky et. al. 2010). The interaction between standing edge waves and a normally incident wave has been investigated both within the framework of the shallow-water equation (Guza and Davis 1974) and full water wave theory (Minzoni and Whitham, 1977). Here, we derive a general dynamical equation for the full mixed edge-leaky spectrum over a laterally uniform beach based on Zakharov's (1968, 1999) Hamiltonian formalism. The introduction of canonical variables in this formalism significantly simplifies the complicated derivation of the nonlinear interaction coefficient in the previous work (Kirby et. al. 1998, Pelinovsky et. al. 2010). The subharmonic resonance mechanism for edge-wave excitation (Guza and Davis, 1974) is retrieved from the model equation as a special case. The effects of dissipation induced by bottom friction are included using a perturbation approach. A kinetic equation for Zakharov's (1999) canonical variables can be derived, that reduces to the stochastic nonlinear mild-slope model of Agnon and

  2. Evolution of Random Nonlinear Infragravity Waves in Coastal Waters

    NASA Astrophysics Data System (ADS)

    Tian, M.; Sheremet, A.; Shrira, V. I.

    2014-12-01

    The observed spectra of nearshore infragravity waves are typically mixed, with a discrete component (edge waves, trapped waves, propagating parallel to the coast) and a continuous one (leaky waves, that propagate from, and radiate back into, the deep ocean. See e.g., Oltman-Shay and Guza, 1987). The evolution of infragravity spectrum is driven by three general processes: 1) edge-leaky interactions, that transfer energy to the system from shorter waves; 2) energy redistribution through edge-edge and edge-leaky interactions; 3) and energy dissipation due to processes such as bottom friction. Previous studies treated either the edge and leaky system, in isolation from the other one, and focused on phase-resolving dynamical equation. Following Whitham (1976), who derived the nonlinear edge-wave solutions for the shallow water equations, theoretical work on the nonlinear edge-edge interaction resulted in many significant extensions (e.g., Kirby et. al. 1998, Pelinovsky et. al. 2010). The interaction between standing edge waves and a normally incident wave has been investigated both within the framework of the shallow-water equation (Guza and Davis 1974) and full water wave theory (Minzoni and Whitham, 1977). Here, we derive a general dynamical equation for the full mixed edge-leaky spectrum over a laterally uniform beach based on Zakharov's (1968, 1999) Hamiltonian formalism. The introduction of canonical variables in this formalism significantly simplifies the complicated derivation of the nonlinear interaction coefficient in the previous work (Kirby et. al. 1998, Pelinovsky et. al. 2010). The subharmonic resonance mechanism for edge-wave excitation (Guza and Davis, 1974) is retrieved from the model equation as a special case. The effects of dissipation induced by bottom friction are included using a perturbation approach. A kinetic equation for Zakharov's (1999) canonical variables can be derived, that reduces to the stochastic nonlinear mild-slope model of Agnon and

  3. Abnormal strain changes of the 2008 Wenchuan, China, earthquak

    NASA Astrophysics Data System (ADS)

    Qiu, Z.

    2009-12-01

    The tenth Five-Year Project of China Earthquake Administration installed about 40 YRY-4 type high-resolution borehole strainmeters over the mainland China in order to enhance its capability of earthquake-forecasting attempt. The strainmeters are installed in rocks at a depth around 40m and resolve strain changes to the order of 10-11. Measurements are sampled every minute. There are four gauges horizontally placed, 45-degree apart, in an YRY-4 strainmeter, whose measurements are denoted as Si (i=1, 2, 3, 4) in our study. The similarity of the two curves of S1 +S3 and S2 +S4 of Guza recordings gives sufficient credit to the data. Among the sites, Guza is located the nearest (about 140km), from the epicentral area of the Wenchuan earthquake. Even months before the earthquake, it had already been noticed at Guza that the initially smooth curves had become badly interfered from time to time by minor steps or unsymmetrical pulses with periods of minutes~hours. The interferences were dominantly compressional and mostly on the order of 10-9. They were not corresponding to weather changes. Other sites are at least 300km away and did not observe such anomalies. A comparison of the interferences with the long-term and coseismic changes shows a good consistence in the sense of strain variety among them, which suggests a tectonic cause of the abnormal signals. High-passed data show obvious relevance of the abnormal signals to the Wenchuan quake in time. They became stronger as the great event approached, reached the highest at the main shock and diminishing while aftershocks have been dying away. We put forth an Overrun Rate Analysis (ORA) to give out a quantitative description of the interferences. The high-passed interferences can be depicted as positive or negative big values overrunning the normal level. Overrun Rate of Numbers, denoted as Ron, is defined as the total number of overrun points in one day, and Overrun Rate of Strength Ros the daily sum of amplitudes of

  4. Optical Estimation of Depth Induced Wave Breaking Distributions over Complex Bathymetry

    NASA Astrophysics Data System (ADS)

    Keen, A. S.; Holman, R. A.

    2012-12-01

    Parametric depth-induced-breaking dissipation models have shown great skill at predicting time averaged wave heights across the surf zone. First proposed by Battjes & Janssen (1978), these models balance the incoming wave energy flux with a roller dissipation term. This roller dissipation term is estimated by calculating the dissipation for one characteristic broken wave and then multiplying this quantity by the fraction of broken waves. To describe the fraction of broken waves, a typical assumption asserts that wave heights are nearly Rayleigh distributed [Thornton & Guza (1983)] allowing a sea state to be described by only a few parameters. While many experiments have validated the cross shore wave height profiles, few field experiments have been performed to analyze the probability distribution of breaking wave heights over a barred beach profile. The goal of the present research is to determine the distribution of broken and unbroken wave heights across a natural barred beach profile. Field data collected during the Surf Zone Optics experiment (a Multi-disciplinary University Research Initiative) in Duck, North Carolina, consisted of an array of in-situ pressure sensors and optical remote sensing cameras. Sea surface elevation time series from the in-situ pressure sensors are used here to resolve wave height distributions at multiple locations across the surf zone. Breaking wave height distributions are resolved based upon a combination of the pressure sensor and optically based breaker detection algorithm. Since breaking is easily able to be tracked by video imaging, breaking waves are flagged in the sea surface elevation series and binned into a broken wave height distribution. Results of this analysis are compared with model predictions based upon the Battjes & Janssen (1978), Thornton & Guza (1983) and Janssen & Battjes (2007) models to assess the validity of each wave height distribution model.

  5. Edge wave response on a barred beach with wind-sea and swell forcing

    NASA Astrophysics Data System (ADS)

    Contardo, Stephanie; Symonds, Graham; Segura, Laura

    2015-04-01

    The occurrence of short period wind-sea associated with a diurnal sea breeze, superimposed on longer period swell in South West Western Australia provides an opportunity to observe the response of infragravity (0.01-0.05 Hz) waves, in the nearshore, to both wind-sea and swell forcing. An alongshore array of pressure sensors and a cross-shore array of current velocity and pressure sensors are deployed at Secret Harbour, a barred beach near Perth. The observations show a stronger infragravity response to longer period incident swell than to short period wind-sea. Infragravity waves at Secret Harbour are generated by two mechanisms: breakpoint forcing and bound wave release. Breakpoint forcing is observed with both swell and wind-sea forcing while bound wave release is only observed in the presence of swell. Two mechanisms generate free infragravity waves during swell periods while only one mechanism is in place during wind-sea periods, providing an explanation for the stronger response to swell than wind-sea. Free infragravity waves propagating offshore after reflection at the shoreline are called leaky waves; those which are trapped to the shoreline by refraction are called edge waves. At Secret Harbour, both edge waves and leaky waves are detected. Leaky waves dominate with swell forcing while edge waves dominate with wind-sea forcing. Amongst edge waves, mode 0 waves are found to dominate in the absence of wind-sea, while higher mode edge waves dominate when wind-sea is present. We calculate the expected wavenumber-frequency distribution of edge wave and leaky wave energy, based on resonance conditions, using wave period, incidence angle and directional spreading, as proposed by Bowen and Guza (1978). Observations and predictions are in good agreement. However the model can be improved by quantifying the infragravity energy generated by both infragravity wave generation mechanisms. Bowen, A. J., and R. T. Guza (1978), Edge waves and surf beat, Journal of

  6. Vertical structure of mean cross-shore currents across a barred surf zone

    USGS Publications Warehouse

    Haines, John W.; Sallenger, Asbury H., Jr.

    1994-01-01

    Mean cross-shore currents observed across a barred surf zone are compared to model predictions. The model is based on a simplified momentum balance with a turbulent boundary layer at the bed. Turbulent exchange is parameterized by an eddy viscosity formulation, with the eddy viscosity Aυ independent of time and the vertical coordinate. Mean currents result from gradients due to wave breaking and shoaling, and the presence of a mean setup of the free surface. Descriptions of the wave field are provided by the wave transformation model of Thornton and Guza [1983]. The wave transformation model adequately reproduces the observed wave heights across the surf zone. The mean current model successfully reproduces the observed cross-shore flows. Both observations and predictions show predominantly offshore flow with onshore flow restricted to a relatively thin surface layer. Successful application of the mean flow model requires an eddy viscosity which varies horizontally across the surf zone. Attempts are made to parameterize this variation with some success. The data does not discriminate between alternative parameterizations proposed. The overall variability in eddy viscosity suggested by the model fitting should be resolvable by field measurements of the turbulent stresses. Consistent shortcomings of the parameterizations, and the overall modeling effort, suggest avenues for further development and data collection.

  7. A new 3D fully wave-current model MARS-WAVEWATCH : development, validation and application to the rip currents

    NASA Astrophysics Data System (ADS)

    Bennis, A.; Ardhuin, F.; Dumas, F.; Bonneton, P.

    2010-12-01

    The interaction of waves with three-dimensional current structure is investigated using a two-way coupled modelling system combining MARS3D (Lazure and Dumas 2008) with WAVEWATCH III (Tolman 2008, Ardhuin et al. 2009) , a wave model (NOAA/NCEP, Tolman 2008). After a basic validation in two dimensions, the flow model MARS3D was adapted with three options that solve for the total momentum (Mellor 2003, 2008) or the quasi-Eulerian momentum (Ardhuin et al. 2008b). Adiabatic model results show that, as expected from theory (Ardhuin et al. 2008a), the total momentum fluxes parameterized by Mellor are not self-consistent and can lead to very large errors (Bennis and Ardhuin 2010). We thus use the model option to solve for the quasi-Eulerian momentum, including sources of momentum and turbulent kinetic energy (TKE). The influence of these TKE sources is investigated in the case of the NSTS experiment (Thornton and Guza, 1986). The feedback of the currents on the waves is negligible in this case. The sources of TKE from wave breaking and wave bottom friction are found to have strong influence on the bottom friction, in a way consistent with the parameterizations by Longuet-Higgins (1970) and Mellor (2002). The complete model is then applied to a real case of a large rip current on the South-West coast of France (Bruneau et al., Cont. Shelf Res. 2009). The breaking of waves on the opposed current generates a strong coupling on the rip current that partially controls the strength of the current and it three-dimensional shape.

  8. On the long waves disturbing ship operations in Ferrol (Spain)

    NASA Astrophysics Data System (ADS)

    Lopez, Mario; Iglesias, Gregorio

    2013-04-01

    focused on the long waves at the Port of Ferrol and their implications for the operations at the port. References Candella, R.N., Rabinovich, A.B., Thomson, R.E., 2008. The 2004 Sumatra tsunami as recorded on the Atlantic coast of South America. Adv. Geosci. 14, 117-128. Cecioni, C., Bellotti, G., 2010. Modeling tsunamis generated by submerged landslides using depth integrated equations. Appl. Ocean Res. 32(3), 343-350. de Jong, M.P.C., Battjes, J.A., 2004. Low-frequency sea waves generated by atmospheric convection cells. Journal of Geophysical Research-Oceans 109(C1), C01011. López, M., Iglesias, G., 2013. Artificial Intelligence for estimating infragravity energy in a harbour. Ocean Eng. 57(0), 56-63. López, M., Iglesias, G., Kobayashi, N., 2012. Long period oscillations and tidal level in the Port of Ferrol. Appl. Ocean Res. 38(0), 126-134. Okihiro, M., Guza, R.T., Seymour, R.J., 1993. Excitation of Seiche Observed in a Small Harbor. J. Geophys. Res. 98(C10), 18201-18211. Sepic, J., Orlic, M., Vilibic, I., 2008. The Bakar Bay seiches and their relationship with atmospheric processes. Acta Adriat. 49(2).

  9. Equilibrium Beach Profiles on the East and West U.S. Coasts

    NASA Astrophysics Data System (ADS)

    Ludka, B. C.; Guza, R. T.; McNinch, J. E.; O'Reilly, W.

    2012-12-01

    variations of the wave field (measured immediately offshore) are large, but shoreline changes (usually <30cm) are smaller than in Southern California. Maximum vertical variations occur just seaward of the shoreline and the nearshore bathymetry is often barred. Plant (1999) show that bar crest position at Duck has equilibrium-like behavior. We will present the results of equilibrium shoreline and profile modeling at Duck. At both sites, we diagnose sources (e.g. grain size and incident waves) of the sometimes strong observed alongshore variations in sand level change patterns. Funding was provided by the US Army Corps of Engineers and the California Department of Boating and Waterways. REFERENCES Plant, N. G., R. A. Holman, M. H. Freilich, and W. A. Birkemeier (1999), A simple model for interannual sandbar behavior, J. Geophys. Res., 104(C7), 15,755-15,776. Yates, M. L., R. T. Guza, and W. C. O'Reilly (2009), Equilibrium shoreline response: Observations and modeling, J. Geophys. Res., 114, C09014.