Wind‐stress coefficients over sea surface from breeze to hurricane

Wu, Jin

doi:10.1029/jc087ic12p09704

Cited by 464 publications

(308 citation statements)

References 16 publications

(18 reference statements)

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“…The second (α=0.0144) was that used by Janssen (1989) to model the impacts of waves on the surface roughness. The third (α=0.0185) was found by Wu (1982) to give good surface stress prediction for all sea states (wind conditions). Brown and Wolf (2009) found the optimum constant and spatially uniform value for the eastern Irish Sea to be 0.0185 although this might be dependent on model resolution.…”

Section: Surface Roughnessmentioning

confidence: 99%

“…Although α = 0.0185 seems to provide accurate representation of the surface stress for all sea states (Wu, 1982), a larger constant value (0.0275) has also been found to be appropriate for surge modelling and is applied in the UK operational surge model (Williams and Flather, 2000). To model the surface drag to accurately predict the surge events both the methods of Smith and Banke (1975) (S&B) and Charnock (1955) were previously investigated.…”

Section: Surface Roughnessmentioning

confidence: 99%

“…(1) Charnock's (1955) method parameterises the roughness length, z 0 , on dimensional grounds and has been found to be applicable from light to extreme (hurricane) wind conditions up to 60m/s (Wu, 1982). By assuming momentum transfer from air to ocean is mainly through short surface gravity waves, then the roughness length is scaled by the acceleration of gravity, g, and u * :…”

Section: Surface Roughnessmentioning

confidence: 99%

“…Wu (1982) has shown that using a constant Charnock parameter captures most of the variation in surface roughness without the need for including wave effects over a range of winds speeds (0 − 55m/s), and thus sea states. Brown and Wolf (2009) have shown that within the eastern Irish Sea, where the waves are locally generated and shoaling a constant spatially-uniform Charnock parameter of 0.0185 is adequate for hindcasting surge events.…”

Section: Introductionmentioning

confidence: 99%

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Surge modelling in the eastern Irish Sea: present and future storm impact

2009

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It is believed that in the future the intensity and frequency of extreme coastal flooding events may increase as a result of climate change. The NERC-FREE project (CoFEE) and EU FP7 project (MICORE) are investigating the flood risks in the eastern Irish Sea, an area that includes most of England's coastal types. Using a previously modelled and validated historical extreme surge event, in November 1977, we now investigate the changes in peak surge as a result of possible future climate conditions. In order to simulate the surge, we have set up a one-way nested approach, using the POLCOMS 3D baroclinic model, from a domain covering the whole NW European continental shelf, through to a 1.85km Irish Sea model, both areas are forced by tides, atmospheric pressure and winds. We use this modelling system to investigate the impact of enhanced wind velocities and increased sea levels on the peak surge elevation and residual current pattern. The results show that sea level rise has greater potential to increase surge levels than increased wind speeds. IntroductionFuture extreme coastal flooding events are expected to increase (in intensity and frequency) as a result of climate change. The NERC-FREE Coastal Flooding by Extreme Events (CoFEE) project and EU FP7 Morphological Impacts and COastal Risks induced by Extreme storm events (MICORE) project are investigating past, present and future storm events in Liverpool Bay and especially along the Sefton coastline (see Fig.1), where the mobile dunes exposed to the prevailing SW winds and depressions moving across the UK from west to east are at risk of enhanced erosion. The present-day surge conditions due to extreme events are being investigated using wave and surge modelling over an 11 year period (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). This paper uses a hindcast simulation of the November 1977 surge event, which caused significant flooding on the Sefton coast. We then study the sensitivity of the system by considering changes in the peak surge elevation resulting from this storm under future climate conditions. The future scenarios include increasing the mean sea level (by 0.7m and 1.4m) and the wind strength (by 5% and 10%) to look at the new surge levels that could arise in the future. The resulting surges are investigated at ports in the eastern Irish Sea. We present results for Hilbre, Heysham and Douglas (located in Fig. 3). Hilbre and Heysham represent shallow locations either side of the Sefton coastline, and thus give insight to the surge conditions that may occur along this stretch of coast. The Liverpool tide gauge had timing errors in its data, which is why we have concentrated on the results at Hilbre and not Liverpool. The surge results at Douglas have also been presented to show how the surge behaves at a deep location within the Liverpool Bay study area. To allow investigation of the full picture results are presented for both elevation and velocity.

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Section: Surface Roughnessmentioning

confidence: 99%

Section: Surface Roughnessmentioning

confidence: 99%

Section: Surface Roughnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surge modelling in the eastern Irish Sea: present and future storm impact

2009

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“…Let us consider the friction force on a bunch. Figure 3 shows a case where an ice floe bunch A is in contact with the bunch C. Ff is the axial interaction force between the bunch A and C. The shear force exerted on the ice floe bunch A is expressed as, (11) However, in case that the velocity of the bunch A relative to bunch C at time t + dt has the opposite direction compared with that at time t, the direction of the shear force would be altered within one time step of dt. In order to take into consideration the change of the direction of shear force, we construct a semi-implicit scheme.…”

Section: Ice Internal Forcementioning

confidence: 99%

Numerical Simulation of Rectangle Ice Floes Movement Using a Distributed Mass/Discrete Floe Model

Rheem

Yamaguchi

Kato

1994

J. SNAJ, Nihon zousen gakkai ronbunshu

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SummaryA new model, named "Distributed Mass/Discrete Floe model" is proposed for numerical simulation of short term and narrow area pack ice movement. This model possesses the advantages of both the continuum and the discrete element ones : it can express the discrete nature of pack ice which is difficult for a continuum model to treat, and it can realize much shorter computation time than a discrete element model. The pack ice is divided into ice floe bunches in which the floes, assumed to be distributed uniformly, are modeled as inelastic rectangles floating on the water. The ice interaction forces are formulated from the relation between the impulse on the bunch and the variation of the bunch momentum.The ocean flow is calculated by a multi-layer model simultaneously with the ice floe movement. The model formulation and the improvement of the computation accuracy are described in detail.The computations were made for simplified ocean conditions driven by a uniform wind field in the marginal ice zones between the coast and offshore. The results showed some characteristics of ice and water combined flow and force acting on an ocean structure, as follows ;1. The water surface velocity distribution is distorted by the difference in the shear stress between the water/ice interface and the water/air interface. This causes the diffusion of pack ice.3. In the case of no major current for a deep ocean, the water surface velocity can be determined from the computation only for a scale of the Ekman layer. If the water depth is less than the scale of Ekman layer, the direction of water surface flow, which is essential for the ice flow calculation, is highly affected by the water depth.3. Many spike-like peaks appeard in the time variation of ice load on an ocean structure. This is caused by the discrete nature of the present model. Also, the results showed the rational movement of pack ice around the structure.

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Deep water renewal in Lake Baikal: A model for long‐term analyses

Piccolroaz

Toffolon

2013

JGR Oceans

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[1] The phenomenon of deep water renewal in the South Basin of Lake Baikal is investigated by means of a simplified one-dimensional model. The downwelling process, whereby large volumes of superficial, cold, and oxygenated water periodically sink to the lake bottom (>1400m) due to thermobaric instability, is simulated by means of three main submodules: a reaction-diffusion equation for temperature and other tracers, and two Lagrangian algorithms, the first for the vertical stabilization of unstable density regions (including thermobaric effects) and the second handling the downwelling mechanism. A self-consistent procedure for the dynamical reconstruction of the diapycnal diffusivity profile is included to account for the effect of the variability of external conditions. The model has been developed aimed at providing a detailed description of deep-ventilation and a quantification of its consequences at the basin scale; the core algorithms have been designed suitably to perform long-term simulations (hundreds of years) and to deal with a limited amount of information about boundary conditions, which are expressed in terms of wind forcing and surface water temperature. The main parameters have been calibrated using measured profiles of temperature and chlorofluorocarbons (CFC-12) concentration over a 40 year historical period. A long-term simulation (one millennium), in which the current meteorological conditions have been kept statistically unchanged, has been used to determine the asymptotic dynamics. The results are consistent with previous measurements and estimates, suggesting that the model is suitable to qualitatively and quantitatively simulate deep water renewal in deep, temperate lakes, capturing the relative contribution and interaction of the different processes involved.Citation: Piccolroaz, S., and M. Toffolon (2013), Deep water renewal in Lake Baikal: A model for long-term analyses, J. Geophys.

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Wind‐stress coefficients over sea surface from breeze to hurricane

Cited by 464 publications

References 16 publications

Surge modelling in the eastern Irish Sea: present and future storm impact

Surge modelling in the eastern Irish Sea: present and future storm impact

Numerical Simulation of Rectangle Ice Floes Movement Using a Distributed Mass/Discrete Floe Model

Deep water renewal in Lake Baikal: A model for long‐term analyses

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