comparison of radar and in situ measurements of atmospheric turbulence 1 we compare measurements of refractive index structure constant cn2 and energy dissipation rate e by vhf radar with in situ observations by high resolution thermosondes during a campaign near adelaide australia in august 1998 a total of 17 thermosonde soundings was performed within a distance of 120 km to the radar site the variance between estimates of cn2 from backscattered radar power and in situ thermosonde observations is found to be comparable to the observed variance of the radar estimates due to temporal and spatial variations of the turbulent parameters angle brackets denote average over the radar range resolution of 1 km the high resolution thermosonde observations allow us to test the applicability of the turbulent volume fraction model to the estimation of e from cn2 the data indicate that the turbulent volume fraction should not be modeled as the fraction of unstable layers with gradient richardson number ri 0 25

a lagrangian model for boundary layer growth and bed shear stress in the swash zone abstract a new model for the boundary layer development and associated skin friction coefficients and shear stress within the swash zone is presented the model is developed within a lagrangian reference frame following fluid trajectories and can be applied to both laminar flow and smooth turbulent flow the model is based on the momentum integral approach for steady flat plate boundary layers with appropriate modifications to account for the unsteady flow regime and flow history the model results are consistent with previous measurements of bed shear stress and skin friction coefficients within the swash zone these indicate strong temporal and spatial variation throughout the swash cycle and a clear distinction between the uprush and backwash phase this variation has been previously attributed the unsteady flow regime and flow history effects both of which are accounted for in the new model fluid particle trajectories and velocity are computed using the non linear shallow water wave equations and the boundary layer growth across the entire swash zone is estimated predictions of the bed shear stress and skin friction coefficients agree reasonably well with direct bed shear stress measurements reported by barnes et al barnes m p o donaghue t alsina j m baldock t e 2009 direct bed shear stress measurements in bore driven swash coastal engineering 56 8 853 867 and for a given flow velocity give stresses which are consistent with the bias toward uprush sediment transport which has consistently been observed in measurements the data and modelling suggest that the backwash boundary layer is initially laminar which results in the late development of significant bed shear during the backwash with a transition to a turbulent boundary layer later in the backwash a new conceptual model for the boundary layer structure at the leading edge of the swash is proposed which accounts for both the no slip condition at the bed and the moving wet dry interface however further development of the lagrangian boundary layer model is required in order to include bore generated turbulence and to account for variable roughness and mobile beds

the role of bore collapse and local shear stresses on the spatial distribution of sediment load in the uprush of an intermediate state beach abstract spatial variations in sediment load in the swash uprush and textural properties of sediment in transport were evaluated to investigate the mechanisms responsible for sediment transport during wave uprush four streamer traps were deployed at 2 0 m intervals across the swash zone of a sheltered microtidal sandy beach at port beach western australia over a 4 day period during these trapping experiments offshore significant wave heights were 0 3 0 5 m and wave periods were about 10 s the average width of the uprush zone was 6 9 m and the average uprush duration was 5 9 s cross shore distributions of sediment load for 70 uprush events reveal a maximum in sediment load landward of the base of the swash at about 20 of swash width during single events and a maximum closer to mid swash at about 40 of swash width during multiple events characterized by swash interactions settling velocity distributions of trap samples during individual uprush events are similar to distributions found on the beach surface with the lowest settling velocities finest sediments near the base of the swash zone and maximum settling velocities coarsest sediments around the mid swash position it was found that sediment transport during wave uprush occurs through two distinct mechanisms 1 sediment entrainment during bore collapse seaward of the base of the swash zone and subsequent advection of this bore entrained sediment up the beach by wave uprush and 2 in situ sediment entrainment and transport induced by local shear stresses during wave uprush both mechanisms are considered important but the first mechanism is considered most significant during the early stages of wave uprush when sediment is transported mainly in suspension while the second mechanism is likely to dominate the mid to later stages of wave uprush when sediment is transported mainly by sheet flow the relative importance of the two mechanisms will vary between different beaches with the morphodynamic state of the beach reflective versus dissipative expected to play a major role

stability metastability and elastic properties of a dense silica polymorph seifertite 1 dense silica polymorphs with sixfold coordinated si have been found in snc and lunar meteorites and may be important minerals for silica rich components in the lower mantle however the stable crystal structure in the lower mantle and properties of dense silica remain controversial under stable heating and quasi hydrostatic stress conditions we found that the cacl2 type undergoes a phase transition to the pbo2type seifertite at 130 140 gpa and 2500 k our data suggest that this phase transition occurs at a greater depth than the perovskite postperovskite transition in the lowermost mantle the molar volume measured at 1 bar is the smallest among the reported silica polymorphs therefore having the highest calculated density and in excellent agreement with recent first principles calculations the greater molar volume of seifertite found in the shergottite meteorite and previous experiments supports a metastable synthesis of the phase outside its stability field our data combined with the hugoniots of silica polymorphs also rule out the possibility of the formation of seifertite in the meteorite within its stability field we found very little change in bulk sound speed across the cacl2 type seifertite transition if shear wave velocity decreases at the transition to seifertite as suggested by some computational studies this silica transition may provide an alternative explanation for the discontinuities with a shear wave velocity decrease found at depths greater than the d discontinuity

observations of gravel beach dynamics during high energy wave conditions using a laser scanner the work described in this publication was supported by the epsrc project arcoes adaptation and resilience of the uk energy system to climate change epsrc reference ep 1035390 1 and by epsrc grant ep h040056 1 in partnership with the channel coastal observatory cco the full text is under embargo until 01 01 16

net sediment transport and morphological change in the swash zone of a high energy sandy beach from swash event to tidal cycle time scales abstract a field experiment was conducted on a high energy sandy beach truc vert france to examine swash zone processes and shoreline erosion accretion in response to changing wave and tide conditions beachface morphological changes were measured at the swash by swash timescale using an array of ultrasonic bed level sensors and at the tidal timescale through total station surveys hydrodynamic and sediment dynamic data were collected using arrays of pressure transducers electromagnetic current meters optical backscatter sensors and total load sediment traps data were collected for 16 consecutive days 33 tides over a spring neap spring tidal cycle with offshore significant wave heights of 1 4 m and periods of 5 12 s the swash motion was predominantly at infragravity wave frequencies over the measurement period the upper beach experienced phases of accretion erosion and stability trapped sediment loads for the uprush and backwash were predicted reasonably well by cross shore velocity skewness but the prediction of net transport over individual swash events by velocity based models was more problematic particularly lower in the swash zone where swash interactions were more prevalent net sediment fluxes over individual swash events often exceeded 100 kg per unit meter beach width and such rates were only one order of magnitude less than the net transport typically experienced across the high tide swash zone over complete tidal cycles upper beach erosion accretion at the tidal timescale was reasonably well predicted by the dean criterion based on offshore wave steepness and dimensionless fall velocity but the beach gradient also played a significant role in controlling the occurrence of erosion and accretion

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

on the role of infiltration and exfiltration in swash zone boundary layer dynamics boundary layer dynamics are investigated using a 2 d numerical model that solves the volume averaged reynolds averaged navier stokes equations with a vof tracking scheme and a k turbulence closure the model is validated with highly resolved data of dam break driven swash flows over gravel impermeable and permeable beds the spatial gradients of the velocity bed shear stress and turbulence intensity terms are investigated with reference to bottom boundary layer bl dynamics numerical results show that the mean vorticity responds to flow divergence convergence at the surface that result from accelerating decelerating portions of the flow bed shear stress and sinking injection of turbulence due to infiltration exfiltration hence the zero up crossing of the vorticity is employed as a proxy of the bl thickness inside the shallow swash zone flows during the uprush phase the bl develops almost instantaneously with bore arrival and fluctuates below the surface due to flow instabilities and related horizontal straining in contrast during the backwash phase the bl grows quasi linearly with less influence of surface induced forces however the infiltration produces a reduction of the maximum excursion and duration of the swash event these effects have important implications for the bl development the numerical results suggest that the bl growth rate deviates rapidly from a quasi linear trend if the infiltration is dominant during the initial backwash phase and the flat plate boundary layer theory may no longer be applicable under these conditions

sediment transport and beach profile evolution induced by bi chromatic wave groups with different group periods abstract in this paper large scale experimental data are presented showing the beach profile morphological evolution induced by four different bi chromatic wave conditions characterized by very similar energy content between them but varying the modulation period important differences were observed in the resultant beach profiles as a function of the wave group periods larger variability in the profile evolution is generally observed for larger wave group periods and more importantly as the wave group period increases the distance between the generated breaker bar and the shoreline increases the measured primary wave height to depth ratio increases with the wave group period which is consistent with the observed larger wave height at the breaking location the primary wave breaking location is also observed at increasing distances with respect to the initial shoreline as the wave group period increases the variation in with wave group period is related to the selective energy dissipation of the higher primary frequency component f1 during the wave group shoaling broad bandwith conditions reduced wave group period lead to larger dissipation of wave heights at the f1 component relative to f2 resulting in a reduction in the wave modulation and primary wave height at the breaking location suspended sediment fluxes obtained from collocated velocity and sediment concentration measurements in the surf zone showed a consistently larger contribution of the mean return flow to the suspended sediment fluxes compared with the wave group and primary wave components the distinct beach profile evolution in terms of bar location is interpreted from an increasing distance of the mean breakpoint location and the location of maximum return flow with respect to the shoreline as the wave group period increases

sand transport processes and bed level changes induced by two alternating laboratory swash events abstract sand transport processes and net transport rates are studied in a large scale laboratory swash zone bichromatic waves with a phase modulation were generated producing two continuously alternating swash events that have similar offshore wave statistics but which differ in terms of wave swash interactions measured sand suspension and sheet flow dynamics show strong temporal and spatial variability related to variations in flow velocity and locations of wave capture and wave backwash interactions suspended and sheet flow layer transport rates in the lower swash zone are generally of same magnitude but sheet flow exceeds the suspended load transport by up to a factor four during the early uprush the bed level near the inner surf zone is relatively steady during a swash cycle but changes of o cm s are measured near the mid swash zone where wave swash interactions lead to strongly non uniform flows the two alternating swash events produce a dynamic equilibrium with bed level changes up to a few mm induced by single swash events but with net morphodynamic change over multiple events that is two orders of magnitude lower most of the intra swash and the single event averaged bed level changes in the swash zone are caused by a redistribution of sediment within the swash the transport of sediment across the surf swash boundary is minor at intra swash time scale but becomes increasingly significant at swash averaged time scales or longer i e averaged over multiple swash events

direct bed shear stress measurements in bore driven swash direct measurements of bed shear in the swash zone are presented the data were obtained using a shear plate in medium and large scale laboratory bore driven swash and cover a wide range of bed roughness data were obtained across the full width of the swash zone and are contrasted with data from the inner surf zone estimates of the flow velocities through the full swash cycle were obtained through numerical modelling and calibrated against measured velocity data the measured stresses and calculated flow velocities were subsequently used to back calculate instantaneous local skin friction coefficients using the quadratic drag law the data show rapid temporal variation of the bed shear stress through the leading edge of the uprush which is typically two four times greater than the backwash shear stresses at corresponding flow velocity the measurements indicate strong temporal variation in the skin friction coefficient particularly in the backwash the general behaviour of the skin friction coefficient with reynolds number is consistent with classical theory for certain stages of the swash cycle a spatial variation in skin friction coefficient is also identified which is greatest across the surf swash boundary and likely related to variations in local turbulent intensities skin friction coefficients during the uprush are approximately twice those in the backwash at corresponding reynolds number and cross shore location it is suggested that this is a result of the no slip condition at the tip leading to a continually developing leading edge and boundary layer into which high velocity fluid and momentum are constantly injected from the flow behind and above the tip region finally the measured stress data are used to determine the asymmetry and cross shore variation in potential sediment transport predicted by three forms of sediment transport formulae crown copyright c 2009 published by elsevier b v all rights reserved

a semianalytical model for sheet flow layer thickness with application to the swash zone a new semianalytical model for the time dependent thickness of the sheet flow layer that includes the effects of pressure gradients bed slope boundary layer growth and bore turbulence is presented the shear stress and boundary layer growth are computed using the boundary layer integral method the model is expressed as two coupled ordinary differential equations that are solved numerically given a prescribed time series of free stream velocity horizontal pressure gradient and bore turbulence which together represent the hydrodynamic forcing the model was validated against two data sets of sheet flow layer thickness collected in oscillatory flow tunnels and one data set collected in the swash zone of a prototype scale laboratory experiment in the oscillatory flow tunnel data sets sheet flow is mostly generated by shear stress with pressure gradients providing an important secondary forcing around flow reversal in the swash zone pressure gradients and shear stresses alone are not sufficient to generate the large sheet flow layer thickness observed at the initial stages of uprush bore turbulence is most likely the dominant generation mechanism for this intense sheet flow

first observations of turbulence parameters in the troposphere over the bay of bengal and the arabian sea using radiosonde 1 this paper discusses the turbulence characteristics of the free atmosphere over the bay of bengal and the arabian sea during the premonsoon season of 2006 the turbulence scaling concepts developed over the past decades for application to oceanic mixing are used for retrieving turbulence properties in the free atmosphere from high resolution soundings as described by clayson and kantha 2008 the variability in the vertical turbulence structure over a large spatial region is studied using this novel method for the first time investigations revealed the presence of a highly turbulent band at upper troposphere below the cold point tropopause cpt with significant enhancements in thorpe length and eddy diffusion coefficient this increased turbulence is studied in conjunction with the observations of the tropical tropopause layer ttl it is seen that the lower and upper boundaries of this turbulence band nearly coincide with the height where the potential temperature lapse rate begins to show a decrease lrhmin and cold point tropopause respectively the ttl is the transition regime from convectively dominated troposphere to radiatively dominated stratosphere and is characterized by a decrease in the static stability the enhanced zonal and meridional wind shear observed in this region shows that the stability in this region is further weakened because of the breaking of kelvin helmholtz waves which results in the enhancement of turbulence the study reveals the potential of high resolution soundings to be used in the investigations of turbulence in the free atmosphere

high pressure minerals in shocked meteorites heavily shocked meteorites contain various types of high pressure polymorphs of major minerals olivine pyroxene feldspar and quartz and accessory minerals chromite and ca phosphate these high pressure minerals are micron to submicron sized and occur within and in the vicinity of shock induced melt veins and melt pockets in chondrites and lunar howardite eucrite diogenite hed and martian meteorites their occurrence suggests two types of formation mechanisms 1 solid state high pressure transformation of the host rock minerals into monomineralic polycrystalline aggregates and 2 crystallization of chondritic or monomineralic melts under high pressure based on experimentally determined phase relations their formation pressures are limited to the pressure range up to 25 gpa textural crystallographic and chemical characteristics of high pressure minerals provide clues about the impact events of meteorite parent bodies including their size and mutual collision velocities and about the mineralogy of deep planetary interiors the aim of this article is to review and summarize the findings on natural high pressure minerals in shocked meteorites that have been reported over the past 50 years

recent advances in modeling swash zone dynamics influence of surf swash interaction on nearshore hydrodynamics and morphodynamics the role of the swash zone in influencing the whole nearshore dynamics is reviewed with a focus on the interaction between surf and swash zone processes local and global hydromorphodynamic phenomena are discussed in detail and a description of the overall swash zone operation is given the effects of swash zone boundary conditions are highlighted together with the importance of surf zone boundary conditions major emphasis is placed on illustrating the interactions of various hydrodynamic modes which in turn control the swash and surf zone morphology finally methods to account for swash zone processes in coastal models with different temporal and spatial resolutions are proposed

experimental study of bore driven swash swash interactions on an impermeable rough slope abstract experimental measurements are obtained to investigate the detailed hydrodynamics of wave wave interactions in the swash zone two bores are generated using a double dam break mechanism and interact on a 1 10 impermeable rough slope measurements of the hydrodynamics are obtained via acoustic displacement sensors and a combined particle image velocimetry and laser induced fluorescent system two types of interactions are investigated wave capture with the second bore reaching the first one during the uprush and weak wave backwash interactions when interaction happens during the backwash of the first wave the relative strength of the bores at the initial shoreline and time between their arrivals determines the initial type of interaction however the type as well as the intensity of the interaction may vary throughout the swash zone for the same swash event during wave capture and weak wave backwash interactions the fluid of the first bore is advected upwards then mixed with the fluid of the second bore by intense shearing and highly turbulent vortices generated at the front of the second bore because of the relative velocity differences between the two bores the details of the hydrodynamics during interaction confirm the potential of swash swash interactions to suspend sediment and transport it shoreward or interrupt seaward sediment transport

sand suspension storage advection and settling in surf and swash zones a time dependent cross shore sediment transport model in the surf and swash zones on beaches is developed to predict both beach accretion and erosion under the assumptions of alongshore uniformity and normally incident waves the model is based on the depth integrated sediment continuity equation which includes sediment suspension by turbulence generated by wave breaking and bottom friction sediment storage in the entire water column sediment advection by waves and wave induced return current and sediment settling on the movable bottom the hydrodynamic input required for this sediment transport model is predicted using the finite amplitude shallow water equations including bottom friction the developed model is compared with three large scale laboratory tests with accretional neutral little and erosional beach profile changes under regular waves the model predicts sediment suspension under the steep front of breaking waves and due to bottom friction in the swash zone the computed depth averaged sediment concentration does not respond to local sediment suspension instantaneously because of the sediment storage and advection the mean sediment concentration becomes large in comparison to the oscillatory concentration with the decrease of the normalized sediment fall velocity the net cross shore sediment transport rate is shown to be the small difference between the onshore transport rate due to the positively correlated oscillatory components of the suspended sediment volume per unit area and the horizontal sediment velocity and the offshore transport rate due to the product of the mean suspended sediment volume and the mean horizontal sediment velocity relatedly the net accretion or erosion rate of the movable bottom is determined by the small difference between the mean sediment settling rate and the mean suspension rate caused by wave breaking and bottom friction the present computation is limited to the initial beach profile change but the numerical model is capable of predicting the accretional erosional and neutral profile changes

description of new shock induced phases in the shergotty zagami nakhla and chassigny meteorites the shergottite nakhlite and chassignite snc meteorites shergotty zagami nakhla and chassigny have been studied by analytical transmission electron microscopy new phases characteristic of strong shock conditions have been discovered calcium rich majorites in shergottty wadsleyite with anomalously elevated iron content in chassigny and impact melts in shergotty zagami and nakhla cristobalites and polymorphs observed in shergotty and zagami may also be related to shock and are interpreted as back transformation products of post stishovite silica polymorphs shocks corresponding to pressure and temperature conditions characteristic of the earth s transition zone and lower mantle have occurred in those meteorites moreover impact melts indicate high temperature conditions in localized areas on the other hand no massive impact melting is observed in those meteorites consistent with previous descriptions these observations provide evidence of highly heterogeneous shock conditions at the scale of few micrometers in these meteorites strongly heterogeneous conditions such as those suggested by the present study may help to explain the preservation in martian meteorites of phases practically unaffected by shock being very close to strongly shock metamorphized minerals

silica as a shock index in shergottites a cathodoluminescence study silica in shergottites is a minor phase of great significance determining its structural state as either silica glass quartz cristobalite tridymite coesite stishovite or post stishovite could provide informations about their shock history the purpose of this work is to assess the shock intensity in shergottites using two spectroscopic methods on a conventional polished section a scanning electron microscope sem enables us to study the cathodoluminescence cl of silica at variable magnification the results were crosschecked by systematic raman spectroscopy of the selected areas cl spectra differ substantially from one another and enable separating stishovite high and low pressure silica glass quartz and cristobalite we studied a set of five shergottites northwest africa nwa 480 nwa 856 zagami shergotty and los angeles stishovite is common in shergotty zagami nwa 856 and nwa 480 and absent in the studied section of los angeles high pressure glass is very common particularly in close association with stishovite according to the textural relationship it may be a product of the retromorphosis amorphization during decompression of stishovite large stishovite areas result from the transformation of preexisting low pressure silica crystals while needles result from the high pressure transformation of pyroxene to glass melt and silica in the latter case they are found in melt pockets and represent a small fraction of areas of overall pyroxene composition needles exhibit square sections of about 1 m silica spots identical to those described previously as poststishovite are found in shergotty zagami nwa 480 and nwa 856 at present the spectroscopic distinction of post stishovite from stishovite is difficult post stishovite is destroyed under the raman beam and cl spectra are possible mixtures of several phases e g glass and post stishovite it is concluded that the shock intensity is highly heterogeneous and the pressure probably exceeded 60 gpa in all shergottites studied here

swash zone sediment fluxes field observations abstract this paper describes newly obtained high frequency observations of beach face morphological change over numerous tidal cycles on a macrotidal sandy beach made using a large array of ultrasonic altimeters these measurements enable the net cross shore sediment fluxes associated with many thousands of individual swash events to be quantified it is revealed that regardless of the direction of net morphological change on a tidal time scale measured net fluxes per event are essentially normally distributed with nearly equal numbers of onshore and offshore directed events the majority of swash events cause net cross shore sediment fluxes smaller than 50 kg m 1 and the mean sediment flux per swash event is only o 1 kg m 1 leading to limited overall morphological change however much larger events which deposit or remove hundreds of kilograms of sand per meter width of beach occur at irregular intervals throughout the course of a tide it was found that swash swash interactions tend to increase the transport potential of a swash event and the majority of the swash events that cause these larger values of sediment flux include one or more interactions the majority of the larger sediment fluxes were therefore measured in the lower swash zone close to the surf swash boundary where swash swash interactions are most common despite the existence of individual swash events that can cause fluxes of sediment that are comparable to those observed on a tidal time scale frequent reversals in transport direction act to limit net transport such that the beach face volume remains in a state of dynamic equilibrium and does not rapidly erode or accrete

beach face and berm morphodynamics fronting a coastal lagoon this study documents two different modes of berm development i vertical growth at spring tides or following significant beach cut due to substantial swash overtopping and 2 horizontal progradation at neap tides through the formation of a proto berm located lower and further seaward of the principal berm concurrent high frequency measurements of bed elevation and the associated wave runup distribution reveal the details of each of these berm growth modes in mode i sediment is eroded from the inner surf and lower swash zone where swash interactions are prevalent the net transport of this sediment is landward only resulting in accretion onto the upper beach face and over the berm crest the final outcome is a steepening of the beach face gradient a change in the profile shape towards concave and rapid vertical and horizontal growth of the berm in mode 2 sediment is eroded from the lower two thirds of the active swash zone during the rising tide and is transported both landward and seaward on the falling tide sediment is eroded from the inner surf and transported landward to backfill the zone eroded on the rising tide the net result is relatively slow steepening of the beach face a change of the profile shape towards convex and horizontal progradation through the formation of a neap berm the primary factor determining which mode of berm growth occurs is the presence or absence of swash overtopping at the time of sediment accumulation on the beach face this depends on the current phase of the spring neap tide cycle the wave runup height and indirectly offshore wave conditions and the height of the pre existing berm a conceptual model for berm morphodynamics is presented based on sediment transport shape functions measured during the two modes of berm growth c 2006 elsevier b v all rights reserved

large scale experimental observations of sheet flow on a sandbar under skewed asymmetric waves a novel large wave flume experiment was conducted on a fixed barred beach with a sediment pit on the sandbar allowing for the isolation of small scale bed response to large scale forcing concurrent measurements of instantaneous sheet layer sediment concentration profiles and near bed velocity profiles were obtained on a sandbar for the first time two sediment distributions were used with median grain diameters d50 of 0 17 mm and 0 27 mm sheet flow occurred primarily under wave crests where sheet thickness increased with increasing wave height a proportionality constant was used to relate maximum shields parameter to maximum sheet thickness normalized by d50 with bed shear stress computed using the quadratic drag law an enhanced sheet layer thickness was apparent for the smaller sediment experiments 18 7 when directly compared to closed conduit oscillatory flow tunnel data 10 6 however varied significantly 5 31 depending on the procedure used to estimate grain roughness ds and wave friction factor fw three models for ks were compared keeping the model for fw fixed constant ks 2 5d50 and two expressions dependent on flow intensity derived from steady and oscillatory sheet flow experiments values of ks d50 varied by two orders of magnitude and exhibited an inverse relationship with where 30 for ks d50 of o 1 while 5 for ks d50 of o 100 two expressions for fw were also tested with the steady flow based model for ks yielding a difference of 69 13 versus 22

advances in numerical modelling of swash zone dynamics we present a comprehensive and critical review of work on the numerical modelling of swash zone processes between 2005 and 2015 a wide range of numerical models has been employed for the study of this region and hence only phase resolving approaches i e depth averaged and depth resolving models are analyzed the current advances in the modelling of swash zone processes are illustrated by comparing different numerical models against laboratory experiments of a dam break driven swash event depth averaged and depth resolving models describe well the swash flow for both coarse sand and gravel impermeable beach cases depth averaged models provides a practical tool for engineering use whereas depth resolving models improve the flow description especially for the backwash phase with a significantly higher computational cost the evolution and magnitude of bed shear stresses predicted by all models is reasonable when compared with laboratory estimates based on the log law however differences between modelling approaches cannot be rigorously evaluated owing to the uncertainty in shear stress estimates while employing such approximation furthermore small scale processes such as turbulence evolution are investigated with depth resolving models finding differences between the two dimensional and three dimensional approaches numerical models allow us to investigate other processes such as beach morphology changes the evolution of the turbulence coherent structures and the infiltration exfiltration effects on the swash flow a discussion on the advantages and limitations of each model is presented the future of swash zone modelling depends on the increase of the computational power and more importantly on the improvement of the current capability to obtain intra wave measurements for model validation calibration and greater resolution of physical processes

the swash of solitary waves on a plane beach flow evolution bed shear stress and run up the swash of solitary waves on a plane beach is studied using large scale experiments ten wave cases are examined which range from non breaking waves to plunging breakers the focus of this study is on the influence of breaker type on flow evolution spatiotemporal variations of bed shear stresses and run up measurements are made of the local water depths flow velocities and bed shear stresses using a shear plate sensor at various locations in the swash zone the bed shear stress is significant near the tip of the swash during uprush and in the shallow flow during the later stages of downrush in between the flow evolution is dominated by gravity and follows an explicit solution to the nonlinear shallow water equations i e the flow due to a dam break on a slope the controlling scale of the flow evolution is the initial velocity of the shoreline immediately following waveform collapse which can be predicted by measurements of wave height prior to breaking but also shows an additional dependence on breaker type the maximum onshore directed bed shear stress increases significantly onshore of the stillwater shoreline for non breaking waves and onshore of the waveform collapse point for breaking waves a new normalization for the bed shear stress which uses the initial shoreline velocity is presented under this normalization the variation of the maximum magnitudes of the bed shear stress with distance along the beach which is normalized using the run up follows the same trend for different breaker types for the uprush the maximum dimensionless bed shear stress is approximately 0 01 whereas for the downrush it is approximately 0 002

video derived near bed and sheet flow sediment particle velocities in dam break driven swash abstract this short communication considers a video based approach to quantify near bed and sheet flow swash zone sediment particle velocities over a mobile bed in a laboratory setting and relate the profile shape to sheet thickness and a velocity that can be measured outside the sheet layer by for instance a current meter near bed high speed imagery was recorded during a dam break driven swash event in a flume with optically clear walls repeated swash events for two different median sediment sizes were tested optical current meter ocm analysis was applied to bed parallel image time stacks extracted at elevations from below the at rest bed to within the lower water column ocm results were compared to in situ velocity measurements where possible obtained with an acoustic doppler profiling velocimeter adpv ocm results compared well with adpv measurements for moderate suspended sediment concentrations based on visual observation sediment concentrations were not measured too high of a sediment concentration over saturated the image and did not provide distinct sediment particle trajectories in a consistent direction for ocm analysis this saturation occurred during uprush for both sediment sizes too little of a sediment concentration provided an inadequate number of sediment particle trajectories to track such as during flow reversal for the coarser sediment for coarser sediment backwash velocities were well resolved in ocm analysis with velocities comparing well correlation coefficient 0 8 to adpv estimates the dimensionless backwash sheet flow sediment particle velocity profile normalized by the velocity at the top of the sheet scaled with the dimensionless elevation normalized by the sheet layer thickness to the 0 62 power with 95 confidence intervals for the exponent ranging from 0 47 to 0 76

flow convergence at the tip and edges of a viscous swash front experimental and analytical modeling the details of flow at the tip of a viscous swash front are important to describe the propagation of the wave the bed shear and to estimate material transport rates and impact forces this paper presents novel experimental data illustrating the convergence of fluid at swash fronts generated by dam break flows very viscous fluids detergents were used to slow the flow sufficiently to enable video tracking of particles on the free surface and within the interior of the flow the experiments were performed both up a slope and on a horizontal bed the particle tracking shows that surface particles travel faster than the mean flow converge on the swash tip and then rapidly decelerate a process that will induce a high bed shear stress at the swash tip as observed in recent experiments particles also converge on the wall boundaries because of the no slip condition a simple analytical model is developed to estimate the ratio of the velocity of surface particles and the wave front for laminar flows this ratio is found to be 3 2 independent of the bed slope and flow depth and is in good agreement with the experimental data the same model approach suggests a ratio of 8 7 for turbulent flows this flow convergence does not appear to be included in either analytical modeling of the tip region or in basal resistance laws for the swash front and would modify the momentum equation at the swash tip c f hogg and pritchard 2004 and the kinematic boundary condition at the shoreline the flow convergence is consistent with observations of the behavior and build up of buoyant debris at the leading edge of tsunami wave front and can be observed in natural swash flows on beaches

laboratory study of the cross shore flow structure in the surf and swash zones 1 the flow structure of oscillatory broken waves within surf and swash zones was investigated using particle image velocimetry piv in the laboratory with the resolved spatial distribution of the velocity field vorticity was computed directly the results show that flow separation at the bed occurs during the interaction between the uprush bore front and the downwash flow the separation point advances in the onshore direction with the bore front until the bore reaches the lowest point of the moving shoreline the bore front continues to climb up onshore and collapses at the highest point of the moving shoreline in the swash zone flow attachment to the bed occurs during the transition from the uprush to downwash process an internal flow circulation is generated at the flow reversal phase as the flow near the bed responds to the gravitational force earlier than the flow in the upper water column where the uprush momentum is sustained later in phase the magnitude of the downwash velocity in the swash zone is greater than that of the uprush process the swash zone flow observed in the experiments should be erosive in the lower part of the swash and accretive in the upper part where flow attachment occurs

morphological hysteresis in the evolution of beach profiles under sequences of wave climates part 1 observations abstract novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates the experiments were conducted in a wave flume at medium scale using both monochromatic and random waves representing 2d conditions beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler from which shoreline location bar position and sediment transport rates were derived experiments were conducted for sequences of wave climates where a sequence comprised of 6 13 sequential tests each commencing with the beach profile from the preceding test each test was run until equilibrium conditions were obtained and had a constant wave height increased or decreased relative to the preceding test cyclical conditions were also included with erosive and accretive wave conditions of short durations alternating through multiple cycles so that equilibrium conditions were not reached during a test with a sequence of increasing wave heights the relationship between the shoreline position and the bulk cross shore sediment transport at equilibrium was non monotonic indicating a maximum in the landward sediment transport rate for test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights morphological hysteresis was observed in the equilibrium shoreline position and bulk cross shore sediment transport such that shoreline recession or offshore transport continued in some instances after reductions in wave height this is inconsistent with classical equilibrium type shoreline evolution models however when equilibrium conditions were not reached in the cyclic sequences no such morphological hysteresis was observed and a dynamic equilibrium is reached the morphological hysteresis occurs because of the decay stranding or increased relative depth of the breaker bar following a reduction in wave height often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone similar sequences of morphological response are evident in field data and larger scale tests in the literature finally it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of wright et al 1985 by introducing the concept of a subsequent alternate active beach state which may occur following a change in wave conditions

integral flow properties of the swash zone and averaging the swash zone is that part of a beach over which the instantaneous shoreline moves back and forth as waves meet the shore this zone is discussed using the nonlinear shallow water equations which are appropriate for gently sloping beaches a weakly three dimensional extension of the two dimensional solution by carrier greenspan 1958 of the shallow water equations for a wave reflecting on an inclined plane beach is developed and used to illustrate the ideas thereafter attention is given to integrated and averaged quantities the mean shoreline might be defined in several ways but for modelling purposes we find the lower boundary of the swash zone to be more useful a set of equations obtained by integrating across the swash zone is investigated as a model for use as an alternative boundary condition for wave resolving studies comparison with sample numerical computations illustrates that they are effective in modelling the dynamics of the swash zone and that a reasonable representation of swash zone flows may be obtained from the integrated variables the longshore flow of water in the swash zone is in many ways similar to the stokes drift of propagating water waves further averaging is made over short waves to obtain results suitable as boundary conditions for longer period motions including the effect of incident short waves in order to clearly present the work a few simplifications are made the main result is that in addition to the kinematic type of boundary condition that occurs on a simple e g rigid boundary two further conditions are found in order that both the changing position of the swash zone boundary and the longshore flow in the swash zone may be determined models of the short waves both outside and inside the swash zone are needed to complete a full wave averaged model only brief indication is given of such modelling

the sources of water in martian meteorites clues from hydrogen isotopes abstract h isotope measurements of carbonate phosphate feldspathic and mafic glasses and post stishovite silica phase in the shergottites zagami shergotty sau 005 dag 476 alha 77005 and eeta 79001 as well as in chassigny and alh 84001 show that all these phases contain deuterium enriched water of extraterrestrial origin the minerals and glasses analyzed may contain an initial primary hydrogen component but their isotopic composition was modified to varying degrees by three different processes interaction with a fractionated exchangeable water reservoir on mars hydrogen devolatilization by impact melting and terrestrial contamination positive correlations between d and water abundance in feldspathic glass and post stishovite silica in zagami shergotty and sau 005 is indicative of mixing of a high d component 3000 4000 and a less abundant low d component 0 the high d component is primarily derived from the martian exchangable reservoir but may also have been influenced by isotopic fractionation associated with shock induced hydrogen loss the low d component is either a terrestrial contaminant or a primary magmatic component the negative correlation between d and water abundances in mafic and feldspathic glasses in alh 84001 alha 77005 and eeta 79001 is consistent with the addition of a low d terrestrial contaminant to a less abundant high deuterium martian component the low d of magmatic glass in melt inclusions suggests that the d of martian parent magma was low and that the initial h isotope signature of mars may be similar to that of earth

suspended sediment transport mechanisms in high energy swash abstract measurements of suspended sediment concentration at three heights above the bed and cross shore velocity at a single height were obtained using miniature optical backscatter sensors and a miniature electromagnetic current meter from the swash zone of a high energy macrotidal dissipative beach time series from relatively low h s 0 8 m and high h s 2 2 m energy conditions were chosen for analysis possible onshore and offshore sediment transport mechanisms are identified as a sudden offshore to onshore velocity transition and turbulence in the swash front leading to subsequent onshore advection by the uprush and b low frequency high velocity backwashes exceeding a certain threshold for sediment suspension these mechanisms are related to the velocity field through skewness and asymmetry an increase in negative infragravity skewness in high energy conditions suggests a potential shift towards offshore net transport time averaged vertical profiles of cross shore suspended sediment flux were calculated from the velocity and concentration time series these show a tendency towards offshore transport in high energy conditions particularly at low levels in the water column the actual sediment fluxes are believed to be more offshore than those calculated one reason for this discrepancy is the inability of the instruments to detect swash activity at very low levels in the water column

a stereoscopic method for rapid monitoring of the spatio temporal evolution of the sand bed elevation in the swash zone abstract a stereoscopic technique is developed in order to measure the sand bed elevation in the swash zone at the wave time scale the present technique allows one to perform highly resolved measurements both in time and in space an accuracy and a precision of less than 300 m and 600 m respectively are obtained in each direction this technique has been used during a large scale wave flume experiment where an erosive process of a plane beach is studied the stereoscopic technique allows one to accurately measure the long term evolution of the beach profile in addition spatially dependent variability on shorten time scales is observed featuring accretion as well as erosion at the wave time scale

suspended sediment transport and beach dynamics induced by monochromatic conditions long waves and wave groups abstract this study presents the analysis of the water surface elevation velocity and suspended sediment concentration measurements obtained at a large wave flume under mobile bed conditions the wave reproduced erosive and accretive conditions and included monochromatic short waves perturbed with a free long wave bichromatic and random conditions each tested condition started from a handmade 1 15 slope and lasted for an approximate time period of 2 4 h 6 runs of the selected wave condition to compare the different beach profile developments and in particular the events that control sediment transport in the swash and surf zones all erosive tested conditions produced a shoreline retreat and a bar at the breaking area whose development in time is directly correlated to the length of the breaking area on the other hand not all accretive conditions present a shoreward transport and random conditions do not seem to alter the initial profile the processed data show the suspended sediment event control produced by the existence or absence of wave backwash interactions in the swash zone the existence of these interactions and their number within the wave group will be a key parameter in controlling the sediment stirring water velocity magnitudes and therefore the suspended sediment fluxes in the inner surf and outer swash

rans based simulation of wave induced sheet flow transport of graded sediments abstract a one dimensional vertical 1dv turbulence closure flow model coupled with sediment transport capabilities is extended to incorporate graded sediment mixtures the hydrodynamic model solves the horizontal component of the incompressible reynolds averaged navier stokes rans equations coupled with k turbulence closure the sediment transport description includes both bed and suspended load descriptions so called high concentration effects turbulence damping and hindered settling velocities are likewise included the sediment transport model treats the bed and suspended load individually for each grain fraction including effects associated with increased exposure of larger particles within a mixture the suspended sediment transport model also makes use of modified reference concentration approach wherein reference concentrations computed individually for each fraction are translated to a common level conveniently enabling use of a single computational grid for the simulation of suspended sediments parametric study shows that these two effects combine to help alleviate an otherwise systematic tendency towards over under predicted transport rates for fine coarse sand fractions the sediment transport model is validated against sheet flow experimental oscillatory tunnel measurements beneath velocity skewed wave signals and demonstrates similar accuracy transport rates generally within a factor of two for both graded and uniform sands the model is likewise validated against an extensive data set involving sheet flow transport beneath acceleration skewed wave signals limited to uniform sands it is then utilized to study potential effects of gradation on the net transport beneath such flows the simulations suggest that gradation effects can both increase as well as decrease the total transport rate depending largely on the behavior of the fine sand fraction the model is implemented within the matlab environment and is freely available upon request to the corresponding author

x ray diffraction study of phase stability in sio2 at deep mantle conditions the stability of sio2 phases were examined by x ray diffraction at pressure up to 131 gpa and temperature n1300 k corresponding to earth s deep lower mantle conditions three materials stishovite cristobalite and silica glass were used as starting materials and an argon pressure transmitting medium was loaded with the sample for five out of six sets of laser heated diamond cell experiments x ray fluorescent crystals were loaded with the sample to ensure alignment of x ray beam and heating laser our results from three different staring materials indicate that the cacl2 type phase is the stable phase throughout our studied p t range we observe the a pbo2 type phase for cristobalite starting material at pressures greater than 48 gpa at room temperature however this transforms to the cacl2 type structure upon heating between 72 113 gpa transition kinetics and metastability may be important in explaining differences in results reported above 75 gpa and key experimental variables are discussed d 2005 elsevier b v all rights reserved

turbulence at the tropopause due to breaking kelvin waves observed by the equatorial atmosphere radar 1 the equatorial atmosphere radar ear installed in sumatra island indonesia observed significant enhancement of turbulence in the tropopause region 15 17 km intermittently for 5 days in november 2001 the turbulence intensity was estimated with the spectral width of the radar echo power spectrum and the turbulence during the period was a factor of up to 5 larger in kinetic energy than that in other periods further analyses confirm that the enhanced turbulence was convectively generated in the breaking phase of an equatorial kelvin wave between july and december 2001 we observed at least three more prominent cases of the turbulence generation by breaking kelvin waves in the tropopause region

sediment suspension events in the inner surf and swash zone measurements in large scale and high energy wave conditions abstract the present study presents a database of hydrodynamic properties and suspended sediment concentration collected within the inner surf and swash zones aiming to improve the current understanding of the sediment dynamics occurring within the beach area closest to the shoreline experimental measurements were conducted in a large scale wave flume under high energy wave conditions at three cross shore locations representing inner surf and swash zone conditions 47 tests each one comprising 500 wave trains with identical wave conditions were measured obtained hydrodynamic properties and suspended sediment concentrations were observed to be highly repeatable between successive tests despite the sediment suspension event like pattern the beach evolution between tests and the apparent randomness of the sediment suspension phenomenon the hydrodynamics close to the shoreline inner surf and swash zone is dominated by short incident broken waves and long wave water level oscillations induced by wave grouping the analyzed time series of measured water surface elevation horizontal velocity computed turbulent kinetic energy tke and sediment concentration revealed that the suspended sediment concentration in this coastal zone does not correlate strongly with either the incident bore height or the short wave horizontal velocity or the tke in other words high low values of these variables do not always promote high low values of sediment suspension in contrast the highest suspended sediment concentrations were observed to occur by the combined action of incident bores and the trough of long period water level oscillations this pattern was more apparent in the inner surf than in the swash zone high suspended sediment concentrations were also observed to coincide with negative peaks in long wave horizontal velocity modulation resulting in enhanced negative sediment transport rates and beach erosion close to the shoreline

an experimental study of the interaction of two successive solitary waves in the swash a strongly interacting case and a weakly interacting case abstract the interaction of successive solitary waves in the swash zone have been studied using large scale experiments with a simple bathymetry of a constant depth region where the water depth was 1 72 m and a plane beach whose slope was 1 12 two wave cases were considered where two successive solitary waves of the same height were generated one after the other so that the wave crests were separated by the effective wavelength associated with a single solitary wave in the weakly interacting case the swash period associated with a single solitary wave is smaller than the time period separating the successive wave crests which leads to similar run ups for the first and second wave whereas in the strongly interacting case the swash period associated with a single solitary wave is larger than the time period separating the successive wave crests which leads to a significant reduction in the run up of the second wave the degree to which there is an interaction between the swash uprush of the second wave and the downrush of the first wave is found to be related to the solitary wave slope parameter which predicts breaker type of the first wave previous data from literature are found to support this claim measurements of bed shear stress bed pressure and the free surface displacement at a location near the stillwater shoreline are used to describe how the dynamics of the boundary layer differ when the downrush of the first wave meets the incoming second wave in both cases

characterization of a high pressure phase of silica from the martian meteorite shergotty recently there has been substantial interest in post stishovite high pressure polymorphs of sio 2 discovered as extraterrestrial minerals or synthesized in the laboratory previous investigators reported the presence of pbo 2 like and baddeleyite like sio 2 in the martian meteorite shergotty and also the synthesis of an pbo 2 like phase at pressures of 60 80 gpa in a laser heated diamond anvil cell to provide definitive information about the nature of the natural pbo 2 phase we recovered a small sample from the shergotty meteorite obtained powder x ray diffraction patterns and performed a rietveld refinement of the structure the resulting cell parameters and space group are a 4 097 1 a b 5 0462 9 a c 4 4946 8 a and pbcn the structure refinement confirms that this sample does have the pbo 2 structure

infragravity wave modulation of short wave celerity in the surf zone the cross shore evolution of individual wave celerity is investigated using two high resolution laboratory experiments on bichromatic waves individual waves are tracked during their onshore propagation and their characteristics including celerity are estimated the intrawave variability in celerity is low in the shoaling zone but increases strongly after breaking it is maximum when the infragravity wave height to water depth ratio is the largest that is to say close to the shoreline there the observed range of individual wave celerity can be as large as the mean celerity value this variability can be largely explained by the variations in water depth and velocity induced by the infragravity waves the differences in celerity are such that they lead to the merging of the waves in the inner surf zone for most of the wave conditions considered again the location at which the first waves start merging strongly correlates with the infragravity wave height to water depth ratio the consequences of these findings for celerity based depth inversion techniques are finally discussed surprisingly accounting for the infragravity wave modulation of the velocity field in the celerity estimate does not significantly improve depth estimation in the surf zone however it is shown that the occurrence of bore merging decreases significantly the coherence of the wavefield in the surf zone this loss of coherence could hamper celerity estimation from pixel intensity time series and explain at least partly the relatively poor performance of depth inversion techniques in the inner surf zone

measurements of the time varying free surface profile across the swash zone obtained using an industrial lidar the use of an industrial lidar instrument to measure time varying water surface elevations within the swash zone is investigated the propagation of the swash lens across the beach face was measured simultaneously by a lidar instrument and a network of precision ultrasonic altimeters at a sandy beach comparison of the two datasets indicates that the time varying swash free surface profile obtained using a lidar compare favourably with point measurements obtained using ultrasonic altimeters significantly the use of a continuously scanning laser beam enables a single lidar instrument to obtain measurements of free surface elevation near synchronously at several hundred points throughout the swash zone this high spatial resolution permits small scale flow features such as the swash front gradient and the presence of secondary bores to be detailed and negates the need for the deployment of a large multi sensor array

laboratory apparatus for calibrating optical suspended solids sensors abstract an apparatus for testing and calibrating miniature to medium sized optical suspended solids sensors is described stable suspensions of sedimentary particles ranging in size from 10 6 to 4 10 3 m can be produced in water with concentrations exceeding 100 g 1 1 flow velocities in the test volume can be varied continuously from 0 1 to 1 5 m s 1 and samples of suspensions can be withdrawn directly with a peristaltic pump for gravimetric and particle size analyses the apparatus has been used to evaluate the effects of particle size flow speed and air bubbles on the performance of optical backscatterance sensors and transmissometers

bed level motions and sheet flow processes in the swash zone observations with a new conductivity based concentration measuring technique ccm detailed measurements of bed level motions and sheet flow processes in the lower swash are presented the measurements are obtained during a large scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves a new instrument ccm provides detailed phase averaged measurements of sheet flow concentrations particle velocities and bed level evolution during a complete swash cycle the bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase sheet flow occurs during the early uprush and mid and late backwash phases sheet flow sediment fluxes during these instances are highest in the pick up layer sediment entrainment from the pick up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave backwash interactions as opposed to oscillatory sheet flow the pivot point elevation of the sheet flow layer is time varying during a swash event moreover the upper sheet flow layer concentrations do not mirror the concentrations in the pick up layer both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange such as in oscillatory sheet flows but are strongly affected by horizontal advection processes induced by the non uniformity of the flow

modeling swash zone hydrodynamics and shear stresses on planar slopes using reynolds averaged navier stokes equations 1 a numerical model solving the reynolds averaged navier stokes equations with a volume of fluid tracking scheme and turbulence closure is employed for estimating hydrodynamics in the swash zone model results for run up distance water depth and near bed velocity are highly correlated r2 0 97 with ensemble averaged dam break driven swash data moreover modeled bed shear stresses are within 20 of estimates derived from measured velocity profiles dam break driven swash simulations are conducted to determine the effect of foreshore characteristics bed roughness and foreshore slope on bore induced swash zone hydrodynamics and bed shear stresses numerical results revealed that the boundary layer vanishes during flow reversal grows during the backwash and becomes depth limited at the end of the swash cycle in general the uprush experiences larger shear stresses but for a shorter duration than the backwash some variability in this pattern is observed depending on the bed roughness foreshore slope and cross slope location in the swash zone implying that large spatial gradients in shear stresses can occur on the foreshore the mean tangential force per unit area supplied to the bed is offshore directed for the simulated cases with the exception of the mild slope 1 25 cases owing to the skewed nature of swash flows the temporal evolution of the momentum balance inside the swash zone shows an important contribution to the total force from turbulence and advection at the early final stage of the swash cycle whereas the local acceleration does not appear to be a significant contribution

morphodynamical modelling of field scale swash events in the present work data for three single swash events are selected from those available for an accretive tide that occurred at le truc vert beach france during a measurement field campaign at that location these events are primarily chosen because of the different final bed change they produced namely variable accretion seaward erosion landward deposition and variable erosion along the swash zone these data are compared to results obtained from a state of the art numerical fully coupled 1d morphodynamical shallow water solver driven by measurements made of those events in the lower swash inner surf zone it is found that the hydrodynamics is reasonably well represented although the computed results exhibit reduced maximum inundations in comparison with the observed ones the model reproduces the correct order of magnitude of the morphodynamic change after each event and sometimes the pattern of erosion and deposition but this change is generally underestimated sensitivity analyses are conducted with respect to more uncertain physical parameters and assumed initial conditions they suggest that initial spatial distributions for velocity and pre suspended sediment concentration play a key role in the quantitative and qualitative prediction of the bed change

measurement and modelling of the influence of grain size and pressure gradient on swash uprush sediment transport the paper examines the dependency between sediment transport rate q and grain size d i e q dp in the swash zone experiments were performed using a dam break flow as a proxy for swash overtopping on a mobile sediment beach the magnitude and nature of the dependency i e p value is inferred for different flow parameters the initial dam depth or initial bore height do the integrated depth averaged velocity u3 dt and against the predicted transport qp using the meyer peter muller mpm transport model experiments were performed over both upward sloping beds and a horizontal bed the data show that negative dependencies p 0 are obtained for u3 dt this indicates that a given do and qp transport less sediment as grain size increases whereas transport increases with grain size for a given u3 dt the p value is expected to be narrow ranged 0 5 p 0 5 a discernible difference observed between the measured and predicted transport on horizontal and sloping beds suggests different modes of transport the incorporation of a pressure gradient correction dp dx using the surface water slope i e piezometric head in the transport calculation greatly improved the transport predictions on the horizontal bed where dp dx is positive on average the incorporation of a pressure gradient term into the mpm formulation reduces qp in the uprush by 4 fine sand to 18 coarse sand and increases qp over a horizontal bed by 1 fine sand to two orders of magnitude coarse sand the measured transport for fine and coarse sand are better predicted using mpm and mpm dp dx respectively poor predictions are obtained using nielsen 2002 because the pressure gradient in the uprush is of opposite sign to that inferred from velocity data in that paper it is suggested that future swash sediment transport models should incorporate the grain size effect partly through the pressure gradient although the dp dx influence is small for fine sands because of the grain size scaling contained in the stress term

experimental study of bore driven swash hydrodynamics on impermeable rough slopes abstract a detailed experimental investigation of the hydrodynamics of large scale bore driven swash on impermeable rough beach slopes is described the experiments were carried out on 1 10 impermeable rough slopes with three different surface roughnesses based on 1 3 mm sand 5 4 mm gravel and 8 4 mm gravel the large scale discrete swash event was produced by the collapse of a dambreak generated bore on the beach simultaneous depths and velocities were measured using lif laser induced fluorescence and piv particle image velocimetry respectively yielding better resolution of the hydrodynamics than previous studies depth time series instantaneous velocity profiles depth averaged velocities instantaneous turbulent kinetic energy profiles depth averaged turbulent kinetic energy reynolds stress profiles and bed shear stresses are presented for five cross shore measurement locations in the swash the measurements resolve the backwash shoreline position and the late backwash period when depths are shallow and velocities are high the detailed data can be used to test and develop advanced numerical models for bore driven waves on rough slopes

concentrations in oscillatory sheet flow for well sorted and graded sands in wave generated sheet flow conditions oscillatory near bed flow is large ripples are washed out and sand is mainly transported in a thin layer a few centimetres thick close to and below the no flow bed level new experiments in the aberdeen oscillatory flow tunnel have produced a comprehensive dataset of transport processes for well sorted and graded sands in large scale sinusoidal and asymmetric oscillatory sheet flow conditions in this paper detailed time and height varying concentration measurements are analysed the range and level of detail in the measurements make it possible to quantitatively analyse concentration behaviour more rigorously than before a new empirical equation is presented which characterises the time dependent concentration profile in the sheet flow layer the equation involves two time dependent parameters erosion depth and reference concentration the dependence of both parameters on flow and bed conditions is analysed new results are presented which make it possible to estimate time dependent erosion depth reference concentration and therefore concentration profile the effects of grading on sheet flow concentrations are analysed by comparing results from the large range of sand beds tested

small scale wind fluctuations in the tropical tropopause layer from aircraft measurements occurrence nature and impact on vertical mixing abstractthe contribution of turbulent mixing to heat and tracer transport in the tropical tropopause layer ttl is poorly constrained partly due to a lack of direct observations here the authors use high resolution 20 hz airborne measurements to study the occurrence and properties of small scale 100 m wind fluctuations in the ttl 14 19 km over the tropical pacific the fluctuations are highly intermittent and appear localized within shallow 100 m patches furthermore active turbulent events are more frequent at low altitude near deep convection and within layers of low gradient richardson number a case study emphasizes the link between the turbulent events and the occurrence of inertio gravity waves having small horizontal or vertical scale in order to evaluate the impact of the observed fluctuations on tracer mixing their characteristics are examined during active events they are in broad agreement with inertial range turbulence theory the motions are close to 3d isotropic and the sp

the morphodynamics of a swash event on an erodible beach a high accuracy numerical solution coupling one dimensional shallow water and bed evolution equations with for the first time a suspended sediment advection equation thereby including bed and or suspended load is used to examine two swash events on an initially plane erodible beach the event of peregrine williams j fluid mech vol 440 2001 pp 391 399 and that of a solitary wave approaching the beach equations are solved by the method of characteristics and the numerical model is verified full coupling of suspended load to beach change for peregrine williams j fluid mech vol 440 2001 pp 391 399 yields only slightly altered swash flows depending on beach mobility and sediment response time a series of similar final beach change patterns results for different beach mobilities suspended and bed load transport have distinct morphodynamical signatures for the solitary wave a backwash bore is created hibberd peregrine j fluid mech vol 95 1979 pp 323 345 this morphodynamical bore propagates offshore initially and leads to the creation of a beach bed step larson sunamura j sedimentary petrology vol 63 1993 pp 495 500 primarily due to bed load transport its height is directly related to bed load mobility and also depends strongly on the bed friction coefficient the shock dynamics of this bed step is explained and illustrated bed and suspended load mobilities are quantified using field data and an attempt is made to relate predictions to measurements of single swash events on a natural beach average predicted bed change magnitudes across the swash are of the order of 2 mm with maximum bed changes of up to approximately 10 cm at the bed step

tropospheric turbulence over the tropical open ocean role of gravity waves a large set of soundings obtained in the indian ocean during 3 field campaigns is used to provide statistical characteristics of tropospheric turbulence and its link with gravity wave gw activity the thorpe method is used to diagnose turbulent regions of a few hundred meters depth above the mixed layer turbulence frequency varies from 10 in the lower troposphere up to 30 around 12km heights gw are captured by their signature in horizontal wind normalized temperature and balloon vertical ascent rate these parameters emphasize different parts of the wave spectrum from longer to shorter vertical wavelengths respectively composites are constructed in order to reveal the vertical structure of the waves and their link with turbulence the relatively longer wavelength gw described by their signature in temperature gwt are more active in the lower troposphere where they are associated with clear variations in moisture turbulence is then associated with minimum static stability and vertical shear stressing the importance of the former and the possibility of convective instability conversely the short waves described by their signature in balloon ascent rate gww are detected primarily in the upper troposphere and their turbulence is associated with a vertical shear maximum suggesting the importance of dynamic instability furthermore gww appear to be linked with local convection whereas gwt are more active in suppressed and dry phases in particular of the madden julian oscillation these waves maybe associated with remote sources such as organized convection or local fronts such as those associated with dry air intrusions

bed level fluctuations in the inner surf and swash zone of a dissipative beach abstract a field study was conducted on a dissipative beach to quantify inner surf and swash zone bed level change during periods of inundation and throughout a tidal cycle elevation changes were acquired at millimeter resolution with a new conductivity concentration profiler that allowed quantification of the bed level throughout the duration of the wave swash cycle and also during periods of bed exposure bed level change spectra showed the highest energy at low frequencies even though event scale net bed level changes were observed to exceed the tidal scale net bed level change net bed level change for individual events was nearly normally distributed with most individual events displaying little or no net bed level change large erosion and accretion events with bed level elevation magnitudes that exceeded net tidal elevation change occurred with similar frequency the similarity between the frequency of large erosion and large accretion events suggests that a few events may be ultimately responsible for the observed net elevation change over the tidal cycle the large events displayed different hydrodynamic characteristics erosion events had longer duration onshore directed flow and higher maximum onshore directed velocity magnitude than offshore directed velocity magnitude the opposite was found for accretion events that had longer duration offshore directed flow and a higher maximum offshore directed velocity magnitude than onshore directed velocity magnitude

first observations of elevated ducts associated with intermittent turbulence in the stable boundary layer over bosten lake china nocturnal radiative cooling is a main driver for atmospheric duct formation within this atmospheric process the impacts of intermittent turbulence on ducting have seldom been studied in this paper we reported two confusing ducting events observed in the early morning in august 2014 over bosten lake china when a stable boundary layer sbl still survived by using tethered high resolution gps radiosondes elevated ducts with strong humidity inversions were observed during the balloon ascents but were absent during observations made upon the balloon descent several minutes later this phenomenon was initially hypothesized to be attributable to turbulence motions in the sbl and the connection between the turbulence event and the radar duct was examined by the statistical thorpe method turbulence patches were detected from the ascent profiles but not from the descent profiles the possible reasons for the duct formation and elimination were discussed in detail the turbulent transport of moisture in the sbl and the advection due to airflows coming from the lake are the most probable reasons for duct formation in one case the downward transport of moisture by turbulence mixing within a kelvin helmholtz billow at the top of the low level jet resulted in duct elimination in another case the passage of density currents originating from the lake may have caused the elimination of the duct few studies have attempted to associate intermittent turbulence with radar ducts thus this work represents a pioneering study into the connection between turbulent events and atmospheric ducts in a sbl

suspended sediment transport in the swash zone of a dissipative beach abstract simultaneous high frequency field measurements of water depth flow velocity and suspended sediment concentration were made at three fixed locations across the high tide swash and inner surf zones of a dissipative beach the dominant period of the swash motion was 30 50 s and the results are representative of infragravity swash motion suspended sediment concentrations loads and transport rates in the swash zone were almost one order of magnitude greater than in the inner surf zone the vertical velocity gradient near the bed and the resulting bed shear stress at the start of the uprush was significantly larger than that at the end of the backwash despite similar flow velocities this suggests that the bed friction during the uprush was approximately twice that during the backwash the suspended sediment profile in the swash zone can be described reasonably well by an exponential shape with a mixing length scale of 0 02 0 03 m the suspended sediment transport flux measured in the swash zone was related to the bed shear stress through the shields parameter if the bed shear stress is derived from the vertical velocity gradient the proportionality coefficient between shear stress and sediment transport rate is similar for the uprush and the backwash if the bed shear stress is estimated using the free stream flow velocity and a constant friction factor the proportionality factor for the uprush is approximately twice that of the backwash it is suggested that the uprush is a more efficient transporter of sediment than the backwash because the larger friction factor during the uprush causes larger bed shear stresses for a given free stream velocity this increased transport competency of the uprush is necessary for maintaining the beach otherwise the comparable strength and greater duration of the backwash would progressively remove sediment from the beach

on the transport of suspended sediment by a swash event on a plane beach we develop solutions for the transport of suspended sediment by a single swash event following the collapse of a bore on a plane beach and we investigate the morphodynamical role that such transport may play although the intrinsic asymmetry between uprush and backwash velocities tends to encourage the export of sediment we find that swash events may be effective in distributing across the swash zone much or all of the sediment mobilised by bore collapse additionally settling lag effects may promote a weak onshore movement of sediment we quantify both effects in terms of the properties of the sediment and of the swash event and comment on the relationship between our findings and recent field studies of swash zone sediment transport

seasonal variability of vertical eddy diffusivity in the middle atmosphere 1 three year observations by the middle and upper atmosphere radar the vertical eddy diffusivity k due to atmospheric turbulence with spatial scales of 100 102 m has been computed from the echo power spectral width observed by the middle and upper atmosphere radar for almost every month from january 1986 to december 1988 the method of analysis follows lilly et al 1974 sato and woodman 1982 and hocking 1983a 1985 1988 and the contamination due to beam broadening vertical shear and transience has been removed although observations for horizontal wind speeds larger than approximately 40 m s such as occur near the tropopause jet stream in winter have been omitted because of excessive beam broadening sufficient numbers of observations have been accumulated to produce a reasonable climatology for the upper troposphere and lower stratosphere 6 20 km altitude and for the mesosphere 60 82 km altitude the monthly median of k shows a local maximum near the tropopause jet stream altitude it becomes larger in the mesosphere increasing gradually with height maxima of k are observed in winter near the tropopause and in summer in the mesosphere and the seasonal variability of k reaches approximately an order of magnitude a semiannual variability is apparent in the mesosphere with minima in the equinoctial seasons

unified view of sediment transport by currents and waves i initiation of motion bed roughness and bed load transport attention is given to the properties of sediment beds over the full range of conditions silts to gravel in particular the effect of fine silt on the bed composition and on initiation of motion critical conditions is discussed high quality bed load transport data sets are identified and analyzed showing that the bed load transport in the sand range is related to velocity to power 2 5 the bed load transport is not much affected by particle size the prediction of bed roughness is addressed and the prediction of bed load transport in steady river flow is extended to coastal flow applying an intrawave approach simplified bed load transport formulas are presented which can be used to obtain a quick estimate of bed load transport in river and coastal flows it is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions the proposed model is fully predictive in the sense that only the basic hydrodynamic parameters dep

laboratory and numerical study of dambreak generated swash on impermeable slopes new laboratory experiments have produced detailed measurements of hydrodynamics within swash generated by bore collapse on a steep beach the experiments are based on a dambreak rig producing a highly repeatable large scale swash event enabling detailed measurements of depths and velocities at a number of locations across the swash zone experiments were conducted on two beaches differentiated by roughness results are presented for uprush shoreline motion flow depths depth averaged velocity velocity profiles and turbulence intensity estimates of the time and spatially varying bed shear stress are obtained via log law fitting to the velocity profiles and are compared with the shear plate measurements of barnes et al 2009 for similar experimental conditions experimental results are compared with model predictions based on a nlswe model with momentum loss parameterised using the simple quadratic stress law in terms of the depth averaged velocity predicted and measured flow depths and depth averaged velocities agree reasonably well for much of the swash period but agreement is not good at the time of bore arrival and towards the end of the backwash the parameterisation of total momentum loss via the quadratic stress law cannot adequately model the swash bed shear stress at these critical times

swash zone sediment suspension and transport and the importance of bore generated turbulence a study of swash zone sediment transport was conducted at gleneden beach oregon during february 25 28 1994 the data collected included suspended sediment concentration ssc sea surface elevation and velocity initially 4 and 8 cm above the bed at three cross shore locations within the swash zone spanning high tides ensemble averages of 6 9 and 12 s duration swash events showed that the uprush suspension was high concentrated in the leading edge and nearly vertically uniform above the lower 1 2 cm of the water column shortly after the sensors were inundated by run up the sediment rapidly settled out of the water during flow reversal the ssc was small but increased again in the backwash backwash vertical profiles were markedly different from uprush profiles with much of the suspension being confined to very near the bed where strong vertical gradients in ssc existed these marked differences show that the backwash is not simply the reverse of the uprush implying significant differences in the underlying fluid dynamics and sediment transport mechanisms backwash sediment suspension increased with flow duration however ensemble averaged ssc profiles of varying duration showed that the backwash concentrations were not consistent at the same temporal phases which suggests that water depth in addition to flow duration may be a controlling factor strong cross shore gradients in ssc suggest that bore derived turbulence may affect local sediment transport specifically our data show this bore generated turbulence turbulent kinetic energy directly influences local sediment suspension hence standard bed shear bagnold type sediment transport models may no longer be valid in the vicinity of the bore in the vicinity of the bore a higher correlation between bore generated turbulence and suspended sediment transport was found than between a bagnold type formulation and suspended sediment transport

an experimental study on sediment transport and bed evolution under different swash zone morphological conditions in this study new large scale experimental data are presented showing evidences of a link between the swash zone dynamics and the surf zone morphodynamics two sets of large scale experiments are presented the first set of experiments investigates the swash and surf dynamics under the same hydrodynamic forcing but with two different swash zone morphological conditions one of which was created by manual reshaping of the sub aerial beach face it is shown that more dissipative swash zone conditions a more mildly sloping beach face significantly reduce the rate of seaward sandbar migration such that it almost ceases during the performed experimentation time this behavior is compared to a second set of experiments which shows the natural sand bar offshore migration under almost identical hydrodynamic forcing the changes in the sandbar migration are investigated in terms of the differences in the swash zone dynamics the more reflective swash zone is characterized by more intense backwashes that in turn promote significant quantities of sediment suspension during the interaction of the backwash with the subsequent bore the dissipative swash zone leads to a larger number of wave swash interactions reducing the backwash magnitudes and the magnitude of suspended sediment concentration events in the swash zone with a corresponding reduction in the offshore suspended sediment transport the total offshore sediment transport rates are also shown to reduce leading to the observed modification of the sandbar migration

sand transport beneath waves the role of progressive wave streaming and other free surface effects recent large scale wave flume experiments on sheet flow sediment transport beneath stokes waves show more onshore directed sediment transport than earlier sheet flow experiments in oscillating flow tunnels for fine sand this extends to a reversal from offshore tunnels to onshore flumes directed transport a remarkable hydrodynamic mechanism present in flumes with free water surface but not in tunnels rigid lid is the generation of progressive wave streaming an onshore wave boundary layer current this article investigates whether this streaming is the full explanation of the observed differences in transport in this article we present a numerical model of wave induced sand transport that includes the effects of the free surface on the bottom boundary layer with these effects and turbulence damping by sediment included our model yields good reproductions of the vertical profile of the horizontal mean velocities as well as transport rates of both fine and medium sized sediment similar to the measurements the model reveals the reversal of transport direction by free surface effects for fine sand a numerical investigation of the relative importance of the various free surface effects shows that progressive wave streaming indeed contributes substantially to increased onshore transport rates however especially for fine sands horizontal gradients in sediment advection in the horizontally nonuniform flow field also are found to contribute significantly we therefore conclude that not only streaming but also inhomogeneous sediment advection should be considered in formulas of wave induced sediment transport applied in morphodynamic modeling we propose a variable time scale parameter to account for these effects

large eddy simulation of dam break driven swash on a rough planar beach turbulence characteristics in the swash zone are investigated using a 3d large eddy simulation model the numerical model is implemented based on openfoam which solves the filtered navier stokes equations for two immiscible fluids with a standard smagorinsky sub grid scale closure the numerical model is validated with laboratory data for swash flow driven by a dam break apparatus the model results demonstrate that the main characteristics of turbulence in the swash zone are different from those in the surf zone which are mainly induced by surface wave breaking during uprush phase bore generated turbulence has 2d turbulence characteristics because of limited water depth near bed generated turbulence is mainly observed during backwash turbulence production and turbulent dissipation rate estimated from the model results indicate an imbalance possibly due to advection at swash front and large roughness used touching down of turbulent coherent structure tcs is observed during uprush which drives intense bed shear stress during the backwash interaction between tcs and bed is less clear however finger like patterns in the spatial extent of bed shear stress and vertical components of vorticity are predicted during the backwash the location of the strongest finger patterns in the vertical direction is collocated with that of maximum turbulence production these finger patterns are likely caused by boundary layer instabilities injected vertically from the bed this article is protected by copyright all rights reserved

large scale experiments on beach profile evolution and surf and swash zone sediment transport induced by long waves wave groups and random waves new large scale laboratory data are presented on the influence of long waves bichromatic wave groups and random waves on sediment transport in the surf and swash zones physical model testing was performed in the large scale ciem wave flume at upc barcelona as part of the susco swash zone response under grouping storm conditions experiment in the hydralab iii program vicinanza et al 2010 fourteen different wave conditions were used encompassing monochromatic waves bichromatic wave groups and random waves the experiments were designed specifically to compare variations in beach profile evolution between monochromatic waves and unsteady waves with the same mean energy flux each test commenced with approximately the same initial profile the monochromatic conditions were perturbed with free long waves and then subsequently substituted with bichromatic wave groups with different bandwidth and with random waves with varying groupiness beach profile measurements were made at half hourly and hourly intervals from which net cross shore transport rates were calculated for the different wave conditions pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross shore sediment transport patterns giving high confidence to the data set consistent with recent small scale experiments the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions the random waves have a similar influence to the bichromatic wave groups promoting offshore transport in comparison to the monochromatic conditions the data also indicate that the free long waves promote onshore transport but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time the experiments suggest that the inclusion of long wave and wave group sediment transport is important for improved near shore morphological modeling of cross shore beach profile evolution and they provide a very comprehensive and controlled series of tests for evaluating numerical models it is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups as much as the presence of the forced and free long waves induced by the groupiness the equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic waves with the same incident energy flux

flow tunnel measurements of velocities and sand flux in oscillatory sheet flow for well sorted and graded sands oscillatory flow tunnel measurements of velocities and fluxes for sands in oscillatory sheet flow conditions are presented the experiments involved a range of well sorted and graded sands in two asymmetric flows velocities were measured using an ultrasonic velocity profiler uvp capable of measuring deep within the sheet flow layer velocity profiles are found to be similar for the same flow but different sand beds and display expected features of oscillatory boundary layer flow the near bed velocity leads the main flow velocity by approximately 21 and a small offshore directed current is generated near the bed measures of the boundary layer thickness are in good agreement with those predicted using an equation formulated for the boundary layer thickness over fixed beds velocity data have been combined with concentration data to produce time dependent sand flux profiles covering the sheet flow and suspension regions there are fundamental differences in the transport processes of sands of different size and grading caused by unsteady effects which dominate in the case of fine sand and are largely absent in the case of coarse sand 1 time averaged flux is onshore directed positive in the case of coarse sand and is confined to a region immediately above the bed in contrast time averaged flux in the case of fine sand extends high above the bed is offshore directed negative in the sheet flow layer and becomes onshore directed in the suspension layer 2 net transport in the case of coarse sand is directed onshore as the percentage of fine sand in the bed increases offshore transport becomes increasingly dominant as the percentage of fine sand increases 3 net transport in the suspension layer is onshore while net transport in the sheet flow layer may be onshore or offshore depending on sand size and grading

swash zone sediment transport modes abstract the result of field experiments designed to investigate the relative proportions of bedload and suspended load are described the ratio of bedload to suspended sediment load in the swash zone is examined in both swash and backwash on four beaches by measuring the amounts collected in a sediment trap bedload transport is found to dominate the backwash the relative proportions of bedload and suspended load change over the tidal cycle with increasing bedload dominance at low tide the total amount of sediment transported as swash and backwash is noticeably greater at high tide than at low tide more sediment is transported on the flood tide than on the ebb

non linear shallow water modelling of bore driven swash description of the bottom boundary layer abstract the paper presents a simple approach to estimate the bottom shear stress in the swash zone by coupling the non linear shallow water equations with the momentum integral equation for the bottom boundary layer the approach allows not only the computation of the frictional dissipation term in the equations but also to have an insight into the flow structure in the water column during a swash event the numerical results have been compared with a new set of experiments involving a single dam break generated swash event three different grain sizes ranging from coarse sand to gravel have been tested in the laboratory a sensitivity analysis on the only calibration parameter of the model the bed roughness is presented and its optimal value is chosen the numerically predicted free surface depth averaged velocity and velocity profiles have been compared with the measured ones results are very good in the run up stage where also the bottom shear stress is well modelled in the backwash the frictional energy dissipation is better modelled for the gravel beach than for the coarse sand one results show that the simple model accurately predicts the flow parameters during the swash event also the velocity profiles are reasonably well predicted especially during the run up

sediment suspension and turbulence in the swash zone of dissipative beaches abstract this paper investigates mechanisms for stirring and transport of suspended sediment by infragravity scale swash using high frequency field measurements of horizontal and vertical flow velocities water depths and sediment concentration profiles the field data suggest that vertical velocity fluctuations generated by coherent eddies can be important to the process of sediment suspension and can contribute to asymmetrically distributed sediment transport rates between the uprush and backwash phases of the swash cycle this result indicates that the traditional and often used proxy for bed shear stress based solely on measurements of the horizontal component of flow u i e b fu 2 where is the water density and f is a friction factor may be inadequate when used in energetics type sediment transport models applied to the swash which is indeed the case we demonstrate that a bed shear stress formulation which is more consistent with the physics leads to improved predictive capability for energetics type transport models this formulation is based on the correlation between the horizontal and turbulent vertical components of the flow i e b uw despite the improvement it is evident that considerable amounts of calibration data are still required before each application of this model type moreover our data shows that the issue of calibration coefficients is more problematic than generally appreciated the calibration coefficients for energetics type models on a given beach not only differ between uprush and backwash but also vary with position within the swash zone particularly on the uprush phase

measurements and modelling of the advection of suspended sediment in the swash zone by solitary waves novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone an experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse the advection scales and settling of this sediment were measured during the uprush along a rigid sediment free beach face by a sediment trap located at varying cross shore positions measurements were made using a number of repeated solitary broken waves or bores approximately 25 of the pre suspended sediment picked up by the bores reaches the mid swash zone 50 of the horizontal run up distance indicating the importance of the sediment advection in the lower swash zone the pre suspended sediment is sourced from a region seaward of the shoreline still water line which has a width of about 20 of the run up distance an eulerian lagrangian numerical model is used to model the advection scales of the suspended sediment the model resolves the hydrodynamics by solving the non linear shallow water equations in an eulerian framework and then solves the advection diffusion equation for turbulence and suspended sediment in a lagrangian framework the model provides good estimates of the measured mass and distribution of sediment advected up the beach face the results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre suspended sediment to the net sediment transport in the swash zone c 2009 elsevier b v all rights reserved

sediment transport partitioning in the swash zone of a large scale laboratory beach abstract swash zone sheet flow and suspended sediment transport rates are estimated on a coarse sand beach constructed in a large scale laboratory wave flume three test cases under monochromatic waves with wave heights of 0 74 m and wave periods of 8 and 12 2 s were analyzed sediment flux in the sheet flow layer exceeds several hundred kg m 2 s 1 during both uprush and backwash suspended sediment flux is large during uprush and can exceed 200 kg m 2 s 1 instantaneous sediment flux magnitudes in the sheet layer are nearly always larger than those for suspended sediment flux however sediment transport rates those integrated over depth indicate that suspended load transport is dominant during uprush for all cases and during the early stages of backwash except in the case for the 12 2 s wave case when the foreshore was steeper results could not be obtained for an entire swash event and were particularly truncated during backwash when water depths fell below the elevation of the lowest current meter

intra swash hydrodynamics and sediment flux for dambreak swash on coarse grained beaches the paper reports on dambreak type swash experiments in which intra swash hydrodynamics and sediment flux are measured for swash on a coarse sand beach and a gravel beach flow velocity and depth are measured using piv and lif respectively the intra swash sediment flux is measured using sediment traps comparison of measured hydrodynamics with the immobile permeable bed experiments of kikkert et al 2013 indicates that bed mobility impacts on the swash hydrodynamics reducing the maximum run up by approximately 8 for both beaches compared to the maximum run up on the corresponding immobile beach the measured intra swash sediment flux at a given location is characterised by high flux at the moment of bore arrival followed by rapid decay during uprush becoming zero at some time before flow reversal for the gravel beach the backwash sediment flux is negligibly small while for the sand beach the backwash flux increases slowly as the flow accelerates down the beach and peaks at about the time of maximum backwash velocity intra swash sediment flux calculated using the meyer peter and muller bed load transport formula with measured hydrodynamics as input and bed shear stress estimated using both the swart and colebrook formulae is within a factor 2 of the measured intra swash flux the agreement between the calculated and measured flux is better for the sand beach than for the gravel beach and better for uprush than for backwash for the sand beach there is good agreement between calculated and measured total uprush and total backwash sediment volumes the agreement is less good for the gravel beach for which calculated and measured uprush volumes show a similar trend but the calculated backwash volumes over estimate the negligible volumes observed in the experiments

sediment transport and morphodynamics generated by a dam break swash uprush coupled vs uncoupled modeling the present work analyzes the hydro morphodynamics characterizing the swash region during the uprush stage a comparison is illustrated between the sediment transport measured in a series of dam break experiments and that predicted by the numerical hydro morphodynamic model of postacchini et al 2012 the primary aim is to investigate the differences arising between the weakly coupled or uncoupled model and the measurements in terms of hydrodynamics tip celerity and sediment transport the hydrodynamics are well described by the model and results have been used to calibrate both friction factor and subgrid turbulent viscosity comparison of numerically computed tip celerity with experimental data reveals a fairly good agreement i e a mean error of about 10 while modeled sediment transport differs by about 40 from the available data no evident differences are found between results obtained from the coupled and uncoupled model runs 2 for the celerity and 11 for the sediment transport rate at the tip suggesting that for the specific flow under investigation at the leading edge of the swash front hydro morphological coupling is not an issue of fundamental importance however for the special case here of a swash forced by a dam break scour occurs at the dam location and in this case the erosion of the bed is significantly larger in the uncoupled model

kelvin helmholtz instability around the tropical tropopause observed with the equatorial atmosphere radar 1 in november 2001 the equatorial atmosphere radar 0 20 s 100 32 e observed a continuous strong eastward wind shear 10 50 m s 1 km 1 westward wind 2 27 m s 1 and the radar echo layer tilted downward to the west in the region 0 1 km above the tropopause during the same period the richardson number calculated with hourly averaged horizontal wind and radiosonde temperature data was almost continuously 0 5 and sometimes 0 25 which seems to indicate that the kelvin helmholtz instability khi frequently occurs in that region the existence of the tilted radar echo layer can be explained by khi billows a spurious updraft caused by the khi induced tilted echo layer and by the strong westward wind was also observed in the region