subrainband structure and dynamic characteristics in the principal rainband of typhoon hagupit 2008 abstractthe principal rainband in tropical cyclones is currently depicted as a solitary and continuous precipitation region however the airborne radar observations of the principal rainband in typhoon hagupit 2008 reveal multiple subrainband structures these subbands possess many characteristics of the squall lines with trailing stratiform in the midlatitudes and are different from those documented in previous principal rainband studies the updraft and reflectivity cores are upright and elevated the updraft is fed by a low level radial outflow from the inner side the tangential wind speed shows a clear midlevel jet on the inner side of the reflectivity core except for the structural similarities the dynamics of the subbands is also similar to the squall lines the local environment near the subbands shows little convective inhibition modest instability and vertical wind shear the temperature retrieval shows a cold pool structure in the stratiform precipitation region the estimated vertical w

a comparison of inner and outer spiral rainbands in a numerically simulated tropical cyclone abstractthe simulated inner and outer spiral rainbands in a tropical cyclone are compared in this study the inner rainbands are generally active immediately outside the eyewall in the rapid filamentation zone while the outer rainbands are active in regions outside about 3 times the radius of maximum wind the inner rainbands are characterized by the convectively coupled vortex rossby waves the movement of the outer rainbands follows the low level vector winds associated with the azimuthally averaged low level flow and the radially outward cross band flow caused by the downdraft induced cold pool in the boundary layer convective cells in outer rainbands are typical of convective systems and move cyclonically and radially outward inward at large small radii net upward vertical mass transports vmts appear throughout the depth of the troposphere in the whole inner rainband region while net downward vmts are found below 4 km height in the outer rainband region in the whole inner rainband region on

an observational study of a coastal barrier jet induced by a landfalling typhoon abstractin this study the structure and evolution of a coastal barrier jet cbj along the east coast of taiwan is documented using operational doppler radars the formation of the cbj was control

u and th series disequilibria in coastal infill sediments from praia da rocha algarve region portugal a contribution to the study of late quaternary weathering and erosion u and th series disequilibria observed in a sequence of infill sediments from praia da rocha southern portugal were used in combination with geochemical and particle size data to investigate sediment provenance with a view to resolving the late quaternary weathering and erosion history of the algarve region and the stratigraphy of coastal karstic exposures of the faro quarteira fq formation the red infill units can be distinguished from the brown and buff units on the basis of their lower residual u and th concentrations their differing post depositional histories as revealed by u and th series disequilibria in sequentially extracted sediment phases and their greater degree of sediment processing hence the buff and brown infill units appear to be derived locally from weathering of the miocene limestone whilst the red infill may be linked to large scale mass movement of the fq formation from further inland but south of silves during the late pleistocene this sequence of events confirms a close association between the formation of karst topography and infilling by gravitational slumping debris flow and fluvial activity and hence accounts for the complex three stage sediment provenance of the infill material

bioprotection explored the story of a little known earth surface process abstract bioprotection is identified as an earth surface process however it has been little studied little acknowledged and yet may have major implications for the operation and management of geomorphic systems key early observations are traced back to darwin s voyage of the beagle geikie in the natural environment and watson for the built environment recent field observations and experimental work examining bioprotection are reviewed with a specific focus on lichens and the landscape as are its complex interactions with other processes a conceptual model of bioprotection is presented for the case of an epilithic lichen on a limestone surface

rapidly intensifying hurricane guillermo 1997 part i low wavenumber structure and evolution abstract the structure and evolution of rapidly intensifying hurricane guillermo 1997 is examined using airborne doppler radar observations in this first part the low azimuthal wavenumber component of the vortex is presented guillermo s intensification occurred in an environmental flow with 7 8 m s 1 of deep layer vertical shear as a consequence of the persistent vertical shear forcing of the vortex convection was observed primarily in the downshear left quadrant of the storm the greatest intensification during the 6 h doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left of shear semicircle of the eyewall some of the strongest convective bursts were triggered by azimuthally propagating low wavenumber vorticity asymmetries mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to guillermo s structural evol

rapid filamentation zones in intense tropical cyclones intense tropical cyclones often possess relatively little convection around their cores in radar composites this surrounding region is usually echo free or contains light stratiform precipitation while subsidence is typically quite pronounced in this region it is not the only mechanism suppressing convection another possible mechanism leading to weak echo moats is presented in this paper the basic idea is that the strain dominated flow surrounding an intense vortex core creates an unfavorable environment for sustained deep moist convection strain dominated regions of a tropical cyclone can be distinguished from rotationdominated regions by the sign of s 2 s 2 2 where s1 ux y and s2 x uy are the rates of strain and x uy is the relative vorticity within the radius of maximum tangential wind the flow tends to be rotation dominated 2 s 2 s 2 so that coherent structures such as mesovortices can survive for long periods of time outside the radius of maximum tangential wind the flow tends to be strain dominated s 2 s 2 2 resulting in filaments of anomalous vorticity in the regions of strain dominated flow the filamentation time is defined as fil 2 s 2 s 2 2 1 2 in a tropical cyclone an approximately 30 kmwide annular region can exist just outside the radius of maximum tangential wind where fil is less than 30 min and even as small as 5 min this region is defined as the rapid filamentation zone since the time scale for deep moist convective overturning is approximately 30 min deep convection can be significantly distorted and even suppressed in the rapid filamentation zone a nondivergent barotropic model illustrates the effects of rapid filamentation zones in category 1 5 hurricanes and demonstrates the evolution of such zones during binary vortex interaction and mesovortex formation from a thin annular ring of enhanced vorticity

coastal landscape evolution as a function of eustasy and surface uplift rate cascadia margin southern oregon we explore the relative importance of eustatic versus tectonic factors in sculpting preserving and modifying coastal landforms the study area is a 30 km coastal reach in southern oregon using degree of soil development as a means of correlating wave cut platforms along the coast we document that surface uplift rate is variable in a shore parallel sense variability being a function of differential vertical displacement of crustal blocks along faults and flexures in the upper plate of the cascadia subduction zone a consequence of this variability is that in areas of moderate uplift rate 0 7 0 9 m k y flights of up to seven emergent wave cut platforms are preserved along the interfluves of coastal drainages whereas in areas of low uplift rate 0 05 0 2 m k y only one wave cut platform commonly exists within a few meters of present sea level preservation of shore platforms in both areas is the result of the inter action of tectonic uplift and eustatic sea level changes operating on a high energy coast subject to platform planation platform reoccupation can be a consequence of late pleistocene eustatic sea level changes operating on low up lift rate coasts particularly in the cases of the 200 ka and 125 ka high sea stands reoccupation by the later highstand is probable when coastal uplift rates are about 0 2 m k y the same eustatic history operating on a higher uplift rate section of the coast results in multiple emergent platforms and no instances of reoccupation coastal drainage basins in the size range of 5 10 km2 have different hypsometries reflecting whether platforms in coastal basins are preserved over a range of altitudes or only near sea level the hypsometric differences are thus a product of differences in uplift rate the dominant mechanism of base level fall varies between the two areas coastal retreat during sea level highstands drives baselevel fall in lower uplift rate basins whereas tectonic uplift mainly drives base level fall in moderate uplift rate basins even though the magnitude of coastal retreat may be about the same in the two areas where coastal retreat largely provides the mechanism for base level fall steep coastal drainages discharge their debris onto coastal piedmonts benches and the resultant alluvial fans prograde over marine deposits in southern oregon the alluvial fan building episode was relatively short about 2 20 k y in duration fan aggradation ceased as a consequence of fan entrenchment most likely brought on by buildup and steepening of the fan over time

cape in tropical cyclones abstractconvective available potential energy cape and the vertical distribution of buoyancy were calculated for more than 2000 dropsonde soundings collected by the noaa gulfstream iv aircraft calculations were done with and without the effects of condensate loading entrainment and the latent heat of fusion cape showed larger values downshear than upshear within 400 km of the center consistent with the observed variation of convective intensity the larger downshear cape arose from i higher surface specific humidity ii lower midtropospheric temperature and for entraining cape iii larger free tropospheric relative humidity reversible cape had only one half the magnitude of pseudoadiabatic cape as shown previously reversible cape with fusion closely resembled pseudoadiabatic cape without fusion entrainment had the most dramatic impact entraining cape was consistent with the observed radial distribution of convective intensity displaying the largest values downshear at inner radii with

objective convective updraft identification and tracking part 1 structure and thermodynamics of convection in the rainband regions of two hurricane simulations to better understand the life cycles of convective elements in numerical model simulations a convective updraft tracking algorithm dubbed the statistical and programmable objective updraft tracker spout is developed spout identifies updraft cores in horizontal slices through a given model data set links these cores in three dimensions to form vertically coherent updrafts and then tracks updrafts in time via estimates of the mean local advection spout is evaluated in idealized hurricane simulations from both the regional atmospheric modeling system rams and weather research and forecasting wrf in both simulations spout indicates most updrafts live less than 60 min but some can persist for over 2 h updrafts are typically manifested as shallow cumulus cumulus congestus and deep cumulonimbus overall there is reasonable agreement between the vigor of convection and the amount of localized conditional convective instability also the majority of updrafts attain a tilted structure that is in accordance with the localized vertical wind shear nonetheless there are striking differences between models with the higher resolution wrf simulation producing around twice as many updrafts as rams moreover the wrf updrafts are significantly weaker this paper highlights the utility of spout for studying convective life cycles in high resolution numerical simulations and provides some basic features of convection in two hurricane simulations

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

modeling the development of marine terraces on tectonically mobile rock coasts abstract a mathematical model was used to study the effect of glacially induced fluctuations in sea level on the formation of wave cut terraces on tectonically mobile rock coasts two deep water wave sets were used to calculate breaker height and depth which along with surf zone width bottom roughness and the gradient of the submarine slope dictated the force exerted at the shoreline an erosional force threshold was employed to represent the variable strength of the rocks the model also considered tidal range the time that the water level spent at each intertidal elevation and the protective effect of debris accumulation at the cliff foot three hundred runs were made with constant sea level and with different rates of rising and falling relative sea level rates of erosion increased with the rate of rising and falling sea level but eventually decreased in some runs with very rapid changes in relative sea level fifty five longer runs were also made with a quaternary sea level model that consisted of 26 glacial cycles representing the period from 2 million to 0 9 million years ago and nine cycles of approximately twice the amplitude and wavelength in the last 0 9 million years these runs were made on a landmass experiencing slow 0 11 mm yr 1 or fast 0 74 mm yr 1 positive or negative changes in the elevation of the land it was found that on rising landmasses erosional coastal terraces are formed during interglacial stages and on subsiding landmasses during glacial stages the number of terraces increased with the rate of uplift and subsidence and with the slope of the hinterland terrace gradient increased with tidal range and decreased with rock resistance the was an inverse relationship between terrace width and the strength of the rock

a convective cell in a hurricane rainband abstract on 10 october 1983 the two noaa wp 3d aircraft completed a mission designed to provide airborne doppler radar data for a convective cell embedded in a weak rainband on the trailing side of hurricane raymond comparisons of the wind field produced from the pseudo dual doppler radar technique with in situ wind measurements suggest that the larger convective scale feature may be resolved if the sampling time is kept to a minimum the convective cell was found to move downband faster than any environmental winds but slightly slower than the winds found in the reflectivity core that delineates the cell in the core of the cell the tangential wind is increased and the radial inflow turns to outflow with respect to the circulation center the flow field demonstrates that the downband stratiform portion of a rainband is not from cells currently active since the updraft detrains upwind relative to the cell but rather it is due to the fallout from ice particles placed into the upper troposphere by clouds t

modeling the development of wave cut shore platforms abstract a mathematical model was used to investigate the development of wave cut shore platforms with constant sea level the model considered the effects of deep water wave height spectra period and wavelength breaker height and depth breaker type the width and bottom roughness of the surf zone the gradient of the submarine slope an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot intertidal erosion rates were calculated according to the force of the surf reaching the shoreline whereas submarine erosion rates were determined using a depth decay variable each of the two hundred and fifty model runs consisted of 300 000 iterations platform width increased and gradient progressively decreased through model runs and states of static equilibrium were attained by the end of one hundred and nine runs when the wave induced force at each point in the intertidal zone had became too weak to continue eroding the rock runs with mesotidal spring tidal range 3 m generally produced subhorizontal platforms with cliff platform junctions at the mean low water neap tidal level a greater variety of profiles was produced in runs with macrotidal spring tidal ranges 9 m although almost 30 of these runs produced gently sloping platforms with average gradients of only 0 3 about two thirds of the simulated profiles had average gradients ranging from about 1 to 3 simulated platform width increased with tidal range and decreased with the rate of submarine erosion rock resistance the roughness or irregularity of the platform surface the amount and persistence of the cliff foot debris and wave period because higher waves break in deeper water than lower waves there was no consistent relationship between simulated platform width and wave height

dynamics of the stratiform sector of a tropical cyclone rainband abstractairborne doppler radar documented the stratiform sector of a rainband within the stationary rainband complex of hurricane rita the stratiform rainband sector is a mesoscale feature consisting of nearly uniform precipitation and weak vertical velocities from collapsing convective cells upward transport and associated latent heating occur within the stratiform cloud layer in the form of rising radial outflow beneath downward transport is organized into descending radial inflow in response to two regions of latent cooling in the outer upper regions of the rainband sublimational cooling introduces horizontal buoyancy gradients which produce horizontal vorticity and descending inflow similar to that of the trailing stratiform region of a mesoscale convective system within the zone of heavier stratiform precipitation melting cooling along the outer rainband edge creates a midlevel horizontal buoyancy gradient across the rainband that drives air farther inward beneath the brightband the organi

rapid filamentation zone in a numerically simulated tropical cyclone abstract in a recent study rozoff et al proposed a possible mechanism to explain the formation and maintenance of the weak echo annulus or moat outside of the primary eyewall of a tropical cyclone observed in radar images by this mechanism the moat is determined to be a region of the strain dominated flow outside of the radius of maximum wind in which essentially all fields are filamented and deep convection is hypothesized to be highly distorted and even suppressed this strain dominated region is defined as the rapid filamentation zone wherein the filamentation time is shorter than the overturning time of deep convection an attempt has been made in this study to test the hypothesis in a full physics tropical cyclone model under idealized conditions and to extend the concept to the study of the inner core dynamics of tropical cyclones the foci of this paper are the evolution of the rapid filamentation zone during the storm intensification the potential roles of rapid filamentation in the organiz

low wavenumber structure and evolution of the hurricane inner core observed by airborne dual doppler radar abstract the asymmetric dynamics of the hurricane inner core region is examined through a novel analysis of high temporal resolution three dimensional wind fields derived from airborne dual doppler radar seven consecutive composites of hurricane olivia s 1994 wind field with 30 min time resolution depict a weakening storm undergoing substantial structural changes the symmetric and asymmetric mechanisms involved in this transformation are considered separately to zeroth order the weakening of the primary circulation is consistent with the axisymmetric vortex spindown theory of eliassen and lystad for a neutrally stratified atmosphere vertical shear however increased dramatically during the observation period leading to a strong projection of the convection onto an azimuthal wavenumber 1 pattern oriented along the maximum vertical shear vector recent theoretical ideas elucidating the dynamics of vortices in vertical shear are used to help explain this asymmetry the role of asymmetric vorticity d

convective scale downdrafts in the principal rainband of hurricane katrina 2005 abstract airborne doppler radar data collected during the hurricane rainband and intensity change experiment rainex document downdrafts in the principal rainband of hurricane katrina 2005 inner edge downdrafts ieds originating at 6 8 km altitude created a sharp reflectivity gradient along the inner boundary of the rainband low level downdrafts llds evidently driven by precipitation drag originated at 2 4 km within the heavy rain cells of each convective element the ied and lld were spatially separated by but closely associated with the updrafts within the rainband the ied was forced aloft by pressure perturbations formed in response to the adjacent buoyant updrafts once descending the air attained negative buoyancy via evaporative cooling from the rainband precipitation a convective scale tangential wind maximum tended to occur in the radial inflow at lower levels in association with the ied which enhanced the inward flux of angular momentum at lower levels convergence at the base of the

development of shore platforms on kaikoura peninsula south island new zealand ii the role of subaerial weathering the role of subaerial weathering in the development of shore platforms on kaikoura peninsula is investigated evidence for weathering came from a number of distinctive surface morphologies on platforms salt crystal growth water layer weathering and slaking schmidt hammer test data showed that weathering had occurred and that rock strength was reduced through weathering by as much as 50 weathering processes on shore platforms rely on repeated wetting and drying and for this reason the number of wetting and drying cycles was estimated it was found that the number of wetting and drying cycles depend not only on the pattern of tidal water levels but also on algae growth and desiccation the number of cycles ranged from 104 to 379 per year at elevations low in the tide range fewer cycles occurred the greatest number occurring between the peaks of spring and neap tides and where rainfall adds to the number the zone of most cycles was estimated to occur between 0 6 and 0 9 m above mean sea level on the more landward margins of platforms it is at these elevations that the highest rates of erosion occur based on these results it is argued that the development of shore platforms at kaikoura results from subaerial weathering caused by repeated wetting and drying this is contrary to the view that shore platforms result from marine erosion

structural and surface features of arc shaped radar echoes along an outer tropical cyclone rainband this study uses ground based dual doppler radar and surface observations to document the structural and surface features of the arc shaped radar echoes asres evident along an outer rainband of typhoon longwang as it approached northern taiwan on 1 october 2005 the particular aim of this study is to explore the possible distinction between the present case previously documented tropical cyclone rainbands tcrs and squall lines the dual doppler derived fields show that the leading precipitation of the studied asres exhibited a convective nature with a sharp horizontal gradient of reflectivity and a significant vertical extent theregionsbehindtheleadingconvectionwerecharacterizedbyband relativerear to frontflowatlowlevels and were associated with a broader area of stratiform precipitation the deep layer of front to rear flow extending from the surface to the upper troposphere was generally present ahead of the asres this flow appearstobeliftedupwardatandimmediatelyaheadoftheleadingedgeofthelow levelrear to frontflowto form rearward tilting updrafts these airflow patterns are similar to those of the convective region of squall lines but differ fundamentally from those of previously documented tcrs that were located closer to the inner core of cyclones the detailed analyses of surface fluctuations during the passage of one of the studied asresfurthershowanabruptpressurerise 2mb atemperaturedrop 48c andapronounceddeceleration of inflow air coincident with the leading heavy precipitation the evaluation presented suggests that the convectively generated cold pool may be important in influencing the structures and propagation of the studied asres

sheared deep vortical convection in pre depression hagupit during tcs08 1 airborne doppler radar observations from the recent tropical cyclone structure 2008 field campaign in the western north pacific reveal the presence of deep buoyant and vortical convective features within a vertically sheared westward moving pre depression disturbance that later developed into typhoon hagupit on two consecutive days the observations document tilted vertically coherent precipitation vorticity and updraft structures in response to the complex shearing flows impinging on and occurring within the disturbance near 18 north latitude the observations and analyses herein suggest that the low level circulation of the pre depression disturbance was enhanced by the coupling of the low level vorticity and convergence in these deep convective structures on the meso gamma scale consistent with recent idealized studies using cloud representing numerical weather prediction models further examination of these new observations is needed to quantify the relative role of these vortical convection features in the tropical cyclone spin up process

formation of mesoscale lines of pirecipitation severe squall lines in oklahoma during the spring abstract four distinct kinds of severe mesoscale convective line development are identified in oklahoma during the spring based on the analysis of an 11 year period of reflectivity data from the national severe storms laboratory s 10 cm radar in norman oklahoma the primary classes of fine formation are broken line back building broken areal and embedded areal each is described in detail along with illustrative examples comparisons are made with other observations and with numerical model simulations the former two classes of line formation have been previously documented while the latter two have not only the broken areal squall line has been realistically simulated numerically the environment for each of the types of line development was determined from data from the standard national weather service surface and upper air networks and from special rawinsonde launches it was found that broken line formation tends to occur along cold fronts in a multicell environment while back building occur

surface fluctuations associated with tropical cyclone rainbands observed near taiwan during 2000 08 with radar measurements and temporally high resolution surface observations this study investigates surface fluctuations associated with tropical cyclone rainbands tcrs observed in the vicinity of taiwan during 2000 08 a total of 263 tcrs identified from 37 typhoon eventsduring the studyperiod were analyzed to show the mean and common nature of perturbations of various meteorological variables associated with the passage of tcrs the main patterns of surface thermodynamic fluctuations as revealed from the composite analysis of all identified tcrs include a persistent decrease in temperature dewpoint temperature and equivalent potential temperature ue from the outer to inner edge of the rainband a wavelike variation of pressure perturbations associated with the rainband was evident with a minimum coincident with the outer edge and a maximum located inside the inner edge the kinematics of the rainband was characterized by an obvious decrease in cross band wind component relatively minor variations in along band wind component and the windveering quantitative analysesindicatethatthemajorityofthetcrs 80 90 exhibitedvariations in surface temperature pressure wind speed and wind direction less than 28c 1 5 mb 5 m s 21 and 208 respectively however acleartrendofthemagnitudeoftcrthermodynamicfluctuationsincreasingwiththe radial distance from the tropical cyclone center was observed the tcrs identified in this study were also classified into the outer and inner rainbands which are distinguishedbyaradialdistanceof3timestheradiusofmaximumwind thecompositeandmagnitudeanalyses of their surface fluctuations indicate that the outer rainbands had a higher potential than the inner rainbands to reduce the near surface ue values this observed characteristic is likely related to more pronounced evaporative cooling taking place in drier subcloud regions and the downward transport of low ue air aloft by more vigorous convective downdrafts for the outer rainband fundamentally different features of surface pressure fluctuations and mean frictional vertical velocity and relative vorticity between the outer and inner rainbands were also documented these results reflect a possibly different origin nevertheless there was no dramatic difference in the pattern of kinematic fluctuations between the outer and inner rainbands and their mean magnitudes were also found to be statistically identical which suggests that there is not an entirely clear distinction of surface characteristics for these two types of rainbands

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

potential shoreline changes induced by three dimensional bathymetric anomalies with gradual transitions in depth abstract the development of an analytic model for nearshore wave propagation and shoreline change shoreward of a bathymetric anomaly is presented the three dimensional 3 d step model bender c j dean r g 2003 wave transformation by axisymmetric 3 dimensional bathymetric anomalies with gradual transitions in depth in review coastal engineering propagates a linear wave field in a region of uniform depth over an axisymmetric bathymetric anomaly to a region representing the nearshore zone the bathymetric anomaly is represented by a series of steps which can approximate uniform or nonuniform slopes this paper presents the development and application of an approximate shallow water analytic shoaling and refraction method analytic s r model which establishes the breaking wave height and angle for arbitrary nearshore slopes thus extending the 3 d step model to the nearshore region where the depth is nonuniform the 3 d step model determines the wave transformation caused by the processes of wave refraction diffraction and reflection the wave heights and directions for transects located shoreward of the bathymetric anomaly are combined with the analytic s r model to determine the wave propagation in a nearshore zone of arbitrary slope employing the shoreline change model calculates the longshore transport and shoreline evolution for the nearshore shoaled and refracted wave field that occurs shoreward of the anomaly through the methods developed in this paper the wave transformation nearshore shoaling and refraction longshore transport and shoreline evolution induced by a 3 d bathymetric anomaly with gradual transitions in depth are investigated comparisons of the analytic nearshore shoaling model with a numerical model verify the results for several bathymetries including both pits and shoals the analytic shoreline change model predicts shoreline response for areas shoreward of bathymetric anomalies comparison to the laboratory experiment of horikawa et al horikawa k sasaki t and sakuramoto h 1977 mathematical and laboratory models of shoreline change due to dredged holes journal of the faculty of engineering the university of tokyo xxxiv no 1 pp 49 57 indicates the shoreline change model is able to predict the equilibrium planform shoreward of a pit when the transport caused by the gradient in breaking wave height is included the results demonstrate the importance of the longshore transport term driven by the gradient in breaking wave height

modelling the effect of waves weathering and beach development on shore platform development a mathematical model was used to study shore platform development mechanical wave erosion was dependent on such variables as tidal range wave height and period breaker height and depth breaker type surf zone width and bottom roughness submarine gradient rock resistance and the elevational frequency of wave action within the intertidal zone also included were the effects of sand and pebble accumulation cliff height and debris mobility and downwearing associated with tidal wetting and drying the occurrence location and thickness of beaches often depended on initially quite minor variations in platform morphology but owing to their abrasive or protective effect on underlying rock surfaces they were able to produce marked differences in platform morphology generalizations are difficult but the model suggests that platform gradient increases with tidal range platform width also increases with tidal range with slow downwearing but it decreases with fast downwearing platform gradient decreases and width increases with wave energy and decreasing rock resistance and platform roughness with low tidal range platform gradient is generally lower and platform width greater with beaches of fine sand than with gravel but the relationship is more variable with a high tidal range platform width increases and platform gradient decreases with the rate of downwearing on bare surfaces particularly in low tidal range environments but the pattern is less clear on beach covered platforms platforms with large amounts of beach sediment tend to be narrower and steeper than bare platform surfaces platform gradient increases and platform width decreases with increasing cliff height and with decreasing cliff debris mobility copyright 2005 john wiley sons ltd

beach etching and shore platforms etch forms are widely recognised in continental landscapes but little attention has been given to the etch factor in the coastal context evidence mainly from south australia and the iberian peninsula is cited of weathering fronts fortuitously located within the tidal zone and exposed by the stripping of a regolith by waves in addition the possible effects of beach etching or weathering by waters retained by beach sediments are discussed such weathering is difficult to prove in detail but circumstantial evidence from south australian sites suggests it contributes to the development of shore platforms as well as to cliff foot depressions and an assemblage of minor forms such as basins rock doughnuts and fonts the zonation of basins and gutters noted on some coasts may also and in part reflect beach etching

mesoscale and convective structure of a hurricane rainband abstract the mesoscale thermodynamic kinematic and radar structure of a hurricane floyd rainband observed on 7 september 1981 is presented data are from 26 aircraft passes through the rainband from 150 to 6400 m a composite technique which presents rainband structure as a function of distance from the storm circulation center reveals inflow from the outer edge of the band and a partial barrier to this flow below 3 km in the direction parallel to rainband orientation radar reveals cellular reflectivity structure on the upwind and central portions of the rainband the frequency of cellular precipitation decreases in favor of stratiform precipitation further downwind as the band spirals gradually towards the eyewall in the radial direction a decrease of 12 k in e is observed across the rainband in the subcloud layer convective scale up and downdrafts that are associated with cellular reflectivity structure are hypothesized to be responsible for the thermodynamic modification of the cloud and subc

surface swelling of coastal bedrock on inter tidal shore platforms kaikoura peninsula south island new zealand this paper reports the occurrence of swelling of coastal bedrock measured with a traversing micro erosion meter tmem on inter tidal mudstone and limestone shore platforms while numerous micro erosion meter mem studies have been made only a small number have reported surface swelling during this study 24 055 measurements were made with a tmem of those 4047 indicated swelling or 17 of the total number of measurements vertical swelling of up to 8 9 mm was measured and values of 3 and 4 mm were common swelling displayed a complex pattern with minor swelling being superimposed on longer period episodes duration of swelling events in excess of 697 days were recorded while other events were commonly in the order of 3 to 4 months there is a distinct seasonal variation with greater and more frequent swelling occurring during summer months compared with winter explanation for swelling includes the growth of salt crystals in rock lattices and expansion from wetting and drying warm summer temperatures provide the best conditions for both processes swelling appears to be an important precursor to erosion of material from shore platform surfaces the conclusion drawn is that subaerial weathering makes an important contribution to the lowering of the shore platforms on the kaikoura peninsula

kinematic structure of convective scale elements in the rainbands of hurricanes katrina and rita 2005 1 airborne doppler radar data collected during the hurricane rainband and intensity change experiment rainex show the convective scale air motions embedded in the principal rainbands of hurricanes katrina and rita these embedded convective cells have overturning updrafts and low level downdrafts originating at 2 4 km that enter the rainband on its radially outward side and cross over each other within the rainband as well as a strong downdraft emanating from upper levels 6 km on the radially inward side these vertical motion structures repeat from one convective cell to another along each rainband the resulting net vertical mass transport is upward in the upwind portion of the band and greatest in the middle sector of the principal rainband where the updraft motions contribute generally to an increase of potential vorticity below the 3 4 km level because the convective cells in the middle sector are systematically located radially just inside the secondary horizontal wind maximum shwm the local increase in vorticity implied by the convective mass transport is manifest locally as an increase in the strength of the shwm at midlevels 4 km the overturning updrafts of the convective cells tilt stretch and vertically transport vorticity such that the convergence of the vertical flux of vorticity strengthens the vorticity anomaly associated with the shwm this process could strengthen the shwm by several meters per second per hour and may explain how high wave number convective scale features can influence a low wave number feature such as the principal rainband and subsequently influence the primary vortex

the loess deposits of buca dei corvi section central italy revisited loess deposits have been described in the past for the upper section of buca dei corvi succession central italy in this paper the deposits were re analysed to clarify the depositional environment and to attempt a paleoclimate reconstruction two radiocarbon dates on pedogenic carbonate constrain the ages to the late glacial and are consistent with previous osl dating of the top of the succession the non marine mollusc assemblage shows typical character of cold and dry climatic conditions testified by strong oligotypical composition mineralogy and geochemistry of the sediments indicate the abundant presence of exotic quartz mineral which can be explained only by wind transport probably wind transport was also responsible of deposition of carbonate which then dissolved and re precipitated producing pedogenic concretions stable isotopes 13c 12c and 18o 16o ratios of the concretions are consistent with a climate drier than present conditions with an environment characterized by sparse vegetation

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

clouds in tropical cyclones abstract clouds within the inner regions of tropical cyclones are unlike those anywhere else in the atmosphere convective clouds contributing to cyclogenesis have rotational and deep intense updrafts but tend to have relatively weak downdrafts within the eyes of mature tropical cyclones stratus clouds top a boundary layer capped by subsidence an outward sloping eyewall cloud is controlled by adjustment of the vortex toward gradient wind balance which is maintained by a slantwise current transporting boundary layer air upward in a nearly conditionally symmetric neutral state this balance is intermittently upset by buoyancy arising from high moist static energy air entering the base of the eyewall because of the radial influx of low level air from the far environment supergradient wind in the eyewall zone and or small scale intense subvortices the latter contain strong erect updrafts graupel particles and large raindrops produced in the eyewall fall out relatively quickly while ice splinters left

postglacial sea level rise and sedimentary response in the guadiana estuary portugal spain border abstract the study of sedimentological features foraminifera and molluscan fauna in samples recovered from four rotary boreholes permitted after 14 c dating the first assessment of the post glacial transgression in guadiana river estuary the holocene sequence is underlain by coarse sediments from delta fan enclosing continental swamp deposits dated 16 980 year bp the holocene sedimentary sequence was deposited either directly on this delta fan gravels or on top of fluvial sands deposited probably between 11 000 and 10 000 yr bp an accelerated phase of the estuary infilling by clayey sediments containing the salt marsh foraminifer trochammina began ca 9800 year bp when sea level was about 39 m below present between 7500 and 7000 year bp the central part of the estuary started to accommodate coarser sediments partially introduced from the continental shelf the first phase of holocene sea level rise at a rate of 0 85 m century terminated ca 6500 year bp since then lagoonal sediments in the vicinity of the estuary have been enclosed behind sand spits and predominantly sandy sedimentation was initiated within the estuary after a second phase of slower rise at the rate of 0 3 m century which lasted until ca 5000 year bp the sea approached the present level

a squall line like principal rainband in typhoon hagupit 2008 observed by airborne doppler radar this study examines the structure and dynamics of typhoon hagupit s 2008 principal rainband using airborne radar and dropsonde observations the convection in hagupit s principal rainband was organized into a well defined line with trailing stratiform precipitation on the inner side individual convective cells had intense updrafts and downdrafts and were aligned in a wavelike pattern along the line the line averaged vertical cross section possessed a slightly inward tilting convective core and two branches of low level inflow feeding the convection the result of a thermodynamic retrieval showed a pronounced cold pool behind the convective line the horizontal and vertical structures of this principal rainband show characteristics that are different than the existing conceptual model and are more similar to squall lines and outer rainbands the unique convective structure of hagupit s principal rainband was associated with veering low level vertical wind shear and large convective instability in the environment a quantitative assessment of the cold pool strength showed that it was quasi balanced with that of the low level vertical wind shear the balanced state and the structural characteristics of convection in hagupit s principal rainband were dynamically consistentwith the theory ofcold pooldynamicswidely appliedtostrong andlong livedsquall lines theanalyses suggest that cold pool dynamics played a role in determining the principal rainband structure in addition to storm scale vortex dynamics

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

the 12 13 january 1988 narrow cold frontal rainband observed during mfdp fronts 87 part i kinematics and thermodynamics abstract the kinematic and thermodynamic structure of a narrow cold frontal rainband ncfr observed during the english french german mfdp fronts 87 experiment is presented radiosonde data indicated a very weak convective instability below 1500 m altitude and a low level jet of 30 m s 1 from ssw before the arrival of the front a cooling of about 1 c associated with an airflow of 13 m s 1 from wsw after its passage a composite of wind and reflectivity fields from 17 dual doppler radar analyses shows high reflectivity values large convergence and relatively intense vertical motions associated with this ncfr at the 1000 m altitude a mean vertical cross section perpendicular to the surface front derived from three successive high resolution dual doppler scans is used to examine the general characteristics of the air circulation a structure apparently similar to that of a density current is observed above the 2 km altitude however air flowing at a speed faster than the surface front appreciably mod

beach morphodynamics in a strong wind bay a low energy environment abstract the morphodynamic behaviour of a multibarred beach in a fetch limited strong wind bay seaford beach se australia was examined during both high and low energy conditions and considered in the context of a definition of low energy provided in the literature measurements of nearshore waves currents and morphology revealed a bimodal behaviour under initial low energy conditions the beach exhibited a low tide terrace state and waves and currents were of very low magnitude during subsequent high energy conditions the beach demonstrated dynamic behaviour through the formation of a transitional transverse bar and rip rhythmic bar and beach and migration of the middle bar with the morphology remaining in an arrested high energy state during intervening low energy periods although broadly conforming to the morphodynamic model the beach did exhibit some distinct characteristics attributable to its fetch limited location limited progression through the morphodynamic model and the importance of wind direction and magnitude in governing morphodynamic behaviour furthermore rip currents were not significant in driving beach change through intermediate states the presence of infragravity energy in the storm wave spectra a dissipative multibarred surf zone dynamic inner and middle bars and the attainment of a transitional transverse bar and rip rhythmic bar and beach state during rising wave conditions underline seaford beach as bimodal exhibiting process and morphologic features of both higher and lower energy beaches as an example of a beach in a strong wind bay seaford illustrates that not all fetch limited beaches are low energy furthermore the presence of infragravity energy in a highly fetch limited environment indicates that infragravity energy may occur commonly in fetch limited environments that are subject to periodic strong winds a process that has remained largely unrecognised

evolution and inheritance of a rock coast western galicia northwestern spain there is increasing evidence that shore platforms and other elements of rock coasts may be inherited at least in part from interglacial stages when sea level was similar to today s most of this evidence which includes ancient beaches and datable terrestrial deposits has been obtained from areas of resistant slowly eroding rock where the platforms often appear to be much too wide to have developed since the sea reached its present level it is much more dif cult to demonstrate that inheritance has occurred in areas of weaker rock which generally lack any datable material the coast of western galicia in northwestern spain has shore platforms in igneous and metamorphic rocks that were deeply weathered during the tertiary these platforms are closely associated with ancient beaches from the last interglacial stage and associated periglacial and uvio nival deposits that covered and fossilized most of the eemian platforms and cliffs during the late middle and late weichselian glacial stage the sedimentary processes and the thickness and facies of the sediments were determined by the height aspect and gradient of the coastal mountains and their distance from the coast radiocarbon dating sedimentary analysis and platform morphology indicate that the shore platforms of galicia have been inherited from at least the last interglacial stage they were fossilized in places beneath thick weichselian deposits and then exhumed during the holocene transgression the abundant evidence for inheritance in galicia has important implications for other coasts in fairly weak rocks where such evidence is generally lacking copyright 2003 john wiley sons ltd

development of shore platforms on kaikoura peninsula south island new zealand abstract the role of waves in shore platform development has been investigated on kaikoura peninsula by direct measurement of waves in deep water and on platforms at high tide this showed that the deepwater wave environment off the kaikoura peninsula is very energetic but the amount of energy delivered to platforms is very low in deep water wave power ranged from 5900 to 106 700 n m s 1 per m of crest when calculated from mean significant wave height and when calculated from maximum wave height it ranged from 31 400 to 5 370 000 n m s 1 per m of crest a comparison of deep water wave energy flux with wave energy flux at the high tide cliff of platforms showed that there was a reduction by as much as five orders of magnitude during storm conditions an analysis of the role of breaking waves revealed that these are ineffective as an erosional agent because the depth of water offshore causes breaking before waves arrive on platform surfaces depth of water controlling wave breaking causes larger storm waves to break further from shore preventing direct attack at the cliff base shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms this showed that these forces never exceeded the compressive strength of the platform rocks at kaikoura it is concluded that wave forces are not directly capable of causing erosion on shore platforms at kaikoura

rock coasts with particular emphasis on shore platforms rock coasts are one of the most common elements of the world s littoral zone and they are often important sources of sediment for estuaries and beaches economic development growing populations and the potential effects of rising sea level provide a practical need to understand the dynamics of these coasts although there have been significant advances in our understanding of rocky coastal systems further progress has been hindered by a lack of researchers and by the often imperceptible changes that generally occur within human time scales this paper reviews rock coast processes and landforms in a variety of morphogenic environments one of our most fundamental challenges is to determine the degree to which rock coasts are contemporary rather than inherited features from the quaternary when changes in sea level and climate were responsible for marked variations in the nature intensity and elevational distribution of the marine and subaerial processes that sculpture rock coasts

where is the seaward edge a review and definition of shore platform morphology abstract shore platforms are erosional coastal landforms that have attracted scientific attention since the mid 19th century the defining element of a platform is width that is used in many calculations such as determining a platform s evolutionary state or inferring how wave energy is distributed along the shore although a critical variable there are no uniform criteria for defining the seaward edge quantification of platform width has been driven by site specific variables with the seaward edge defined on the basis of tides morphology biology processes and sediment coverage the lack of a uniform definition has meant that comparative studies are difficult and results are possibly spurious as widths derived from very different criteria can vary by an order of magnitude just on the basis of which criteria is used to determine its edge in this review a combination of morphologic and process elements is used to define the seaward edge of a shore platform the development of strict criteria is especially needed in an environment of rising sea levels if measurements of landscape change are to be made in addition the advent of seamless datasets that cross the land sea boundary means that the delineation of platform morphology is no longer limited by physical access this review concludes that the seaward edge of a shore platform will occur at or landward of wave base and should be defined as the point where active erosion of the bedrock ceases characterised by erosional features such as notches and block plucking scars or the deposition of sediment of such a thickness that the underlying bedrock is not exposed during storm events

surface pressure features of landfalling typhoon rainbands and their possible causes abstract this study uses temporally high resolution surface observations doppler radar and micro rain radar to document the finescale features of the two landfalling rainbands associated with typhoon longwang 2005 as they passed over northern taiwan the present case allows a unique opportunity to investigate well defined convectively active tropical cyclone rainbands over land in particular the surface pressure fluctuations observed during the passage of the two rainbands and their possible causes are explored the rainbands were predominantly convective in nature with embedded stratiform precipitation outside their inner outer edge analyses of surface observations show similar surface pressure fluctuations during the rainband s passage low high pressure with relatively strong weak cross band flow and warmer colder temperature was located inside the outer inner edge maximum minimum pressure perturbations were observed to be 1 5 1 mb with smaller magnitudes 0 4 mb outside th

a new technique for evaluating short term rates of coastal bioerosion and bioprotection a multi scale and multi method approach has been developed to evaluate the nature and effects of short term biological colonisation this method has been used at falasarna on the western coast of crete to investigate bioprotection and bioerosion on a microtidal rocky coast eighteen blocks of limestone 5 5 2 cm were exposed for 7 months september 1998 to april 1999 at mean sea level at two exposed sites and one sheltered site biological colonization and its impacts were assessed by optical microscopy om scanning electron microscopy sem and multiphoton laser scanning microscopy mplsm exposed sites became colonized more quickly than the sheltered site and once a cover of foliose and filamentous algae had become established bioerosion by cyanobacteria biological etching and chemical weathering were reduced consequently there appears to be an inverse relationship between macroalgal abundance and bioerosion of experimental substrata after 7 months of colonisation thus some level of bioprotection appears to be provided by macro algae under exposed site conditions and would probably become increasingly apparent in longer term research trials

morphological features and processes in the central algarve rocky coast south portugal morphological features along the algarve rocky coast south portugal are identified and described with an emphasis on shore platforms and notches the contributions of processes such as wave attack chemical weathering and bioerosion to sculpting the shore platforms are discussed the preferential localization of shore platforms on sites exposed to waves and the lack of significant chemical weathering point to wave erosion as the first order factor in platform formation whilst bioerosion bioprotection lithology and geological structure determine platform morphological variations in addition platforms above the present intertidal zone appear to have a polygenetic evolution being inherited from former sea level highstands and currently undergoing chemical weathering the occurrence of notch features is independent of the degree of exposure to waves but they mostly occur where the substratum is sand hydrostatic pressure appears to be an important factor in the formation of marine caves in the more sheltered sites

a physical model for the rate of coastal tafoni development to explain the temporal change in growth rates of tafoni on homogeneous insoluble rocks modeling is carried out based on a formulated relationship for weathering induced reduction of rock strength the model is expressed by z z c 1 sqrt t ast t where z is the depth of tafoni z c is the ultimate depth t is the time and t is the time lag application of the model to the pacific coast of japan reveals that 1 the model accurately describes tafoni development 2 average growth rates presented by most previous studies are underestimated and 3 an exponential decrease in growth rates stems from strength reduction by inherent rock weathering

the morphosedimentary behaviour of a headland beach system quantifying sediment transport using fluorescent tracers abstract embayed beaches occurring along rocky coasts with headlands controlling hydrosedimentary processes are considered to be constrained sedimentary systems with little longshore sediment transfer between them such beaches are likely to narrow under rising sea level and a deficit of fluvial sediment and because beaches act to dissipate wave energy cliff erosion is expected to increase knowledge of hydrosedimentary processes in fetch limited environments such as embayed beaches is therefore a fundamental management tool in erosion prone coastal areas such as the algarve region southern portugal the main objective of this work is to quantify longshore sediment transport lst using a sedimentary tracer and compare the results with the ones derived via empirical formulae from several authors to achieve this we establish the spatial and temporal patterns of stained sediment and relate these to marine climate data over six tidal cycles for three adjacent embayed beaches the values of displaced sand estimated using tracer and scaled to mixed layer depth were compared with the results of five well known lst formulae to assess the applicability of each model to mesotidal environments of the lst formulae used the cerc 2013 shows to be the most accurate in our study area this study demonstrates the efficacy of using tracers for tracking and quantifying the sediment transport and as a basis for assessing the viability of different lst formulae for representing transport in these types of environments the work also shows the importance of the morphological control of hydrosedimentary processes including the disruption of longshore drift and the sediment transfer promoted by shore platforms

the organization of convection in the rainbands of tropical cyclone laurence abstract a slow moving weak tropical cyclone passed near darwin australia in december 1990 rainbands were observed by a doppler weather radar and a 50 mhz wind profiler for over 24 h the principal bands were seen to be organized on two distinct scales bands of stratiform precipitation formed at a radius of about 100 km from the center of the storm and moved outward at about 6 m s 1 these decayed after they moved past darwin over land a distinct midlevel jet extended along the bands within the bands convective lines formed at regular intervals propagated against and outward with respect to the mean flow and acted as a partial barrier to the radial inflow deep active convection was confined to these lines the vertical motion in the convection showed a distinct acceleration above the freezing level with measured updrafts of up to 10 m s 1 the convection elevated the tropopause height over the rainband it is hypothesized that an inertia gravity wave propagating from near the storm eye was resp

structural changes of an outer tropical cyclone rain band encountering the topography of northern taiwan this study utilized ground based doppler radar observations to document the detailed structures of an outer tropical cyclone rainband tcr of typhoon longwang 2005 as the rainband passed over the topography of northern taiwan on 1 october 2005 the tcr was oriented northeast southwest and was roughly parallel to the mountain barrier with a higher lower terrain height in its southern northern landfalling segment during the pre landfall stage the tcr was characterized by convective precipitation on its inner side where the front to rear flow met with the rear to front flow to lift air upward with overturning updraft like signatures significant relatively minor changes in the tcr s structures were evident in the southern northern landfalling segment during the landfalling stage in particular the southern landfalling segment exhibited a much stronger front to rear flow that passed through the region of the rainband resulting in the absence of low level organized convergence and a relatively disorganized nature of precipitation this structural change was shown to be closely related to a significant decrease in the cross barrier flow due to the orographic blocking that occurred as easterly ambient winds encountered local high mountains in the vicinity of the rainband segment as the tcr propagated over the western side of the major topography the low level rear to front flow reappeared due to the collapse of low level orographic blocking and the convergence between the front to rear flow and the rear to front flow tended to rebuild a well organized convective circulation along the rainband results from this case study provide insight into processes that contribute to rapid structural changes in a landfalling tcr over mountainous regions

modeling the effect of late quaternary interglacial sea levels on wave cut shore platforms abstract a mathematical wave erosional model was used to study the effect of high sea levels during the penultimate oxygen isotopic stage 7 and last interglacials substage 5e and in the late holocene stage 1 on the present morphology of wave cut shore platforms sea level was considered to have been either the same as today or 2 25 m lower during the penultimate interglacial and 2 25 4 5 or 6 75 m higher than today during the last interglacial stage the model suggested that inherited gently sloping shore platforms in resistant rocks may be essentially protected today from erosion by high storm waves the lowest platform gradients were in runs with mesotidal 3 m range and usually with low wave periods low surf attenuation rates and weak rocks modern platform gradients increased with the difference in elevation between sea levels during successive interglacial stages shore platforms were widest in runs in which sea level was the same as today in the penultimate interglacial and 4 5 m higher than today during the last interglacial constant sea level and high last interglacial sea levels with considerable overlapping between the zones of high duration values between the mean neap high and low tidal levels in stages 7 5e and 1 were conducive to the development of wide shore platforms whereas sea levels lower than today s in stage 7 tended to produce narrower platforms in general higher sea levels during the last interglacial tended to produce higher cliff platform junctions than constant sea level unless the sea was lower than today during the penultimate interglacial stage there was a lack of supratidal ledges in macrotidal 9 m model runs with high initial gradients this suggests that gently sloping inherited shore platforms are essential for the subsequent development of supratidal nonstructural ledges in high tidal environments during periods of higher sea level intertidal ledges developed in the upper portion of the modern intertidal zone under a variety of tidal and sea level conditions these ledges can develop independently of lithological or structural influences and without any change in sea level a single high sea level may also simultaneously produce two ledges at different supratidal elevations in mesotidal environments

hurricane intensity and eyewall replacement observations made during the historic 2005 hurricane season document a case of eyewall replacement clouds outside the hurricane eyewall coalesce to form a new eyewall at a greater radius from the storm center and the old eyewall dies the winds in the new eyewall are initially weaker than those in the original eyewall but as the new eyewall contracts the storm reintensifies understanding this replacement mechanism is vital to forecasting variations in hurricane intensity processes in the moat region between the new and old eyewall have been particularly unclear aircraft data now show that the moat becomes dynamically similar to the eye and thus is converted into a region inimical to survival of the inner eyewall we suggest that targeting aircraft to key parts of the storm to gain crucial input to high resolution numerical models can lead to improvements in forecasting hurricane intensity

a theory for strong long lived squall lines revisited based on the analysis of idealized two and three dimensional cloud model simulations rotunno et al hereafter rkw and weisman et al hereafter wkr put forth a theory that squall line strength and longevity was most sensitive to the strength of the component of low level 0 3 km agl ambient vertical wind shear perpendicular to squall line orientation an optimal state was proposed by rkw based on the relative strength of the circulation associated with the storm generated cold pool and the circulation associated with the ambient shear whereby the deepest leading edge lifting and most effective convective retriggering occurred when these circulations were in near balance since this work subsequent studies have brought into question the basic validity of the proposed optimal state based on concerns as to the appropriate distribution of shear relative to the cold pool for optimal lifting as well as the relevance of such concepts to fully complex squall lines especially considering the potential role of deeper layer shears in promoting system strength and longevity in the following the basic interpretations of the rkw theory are reconfirmed and clarified through both the analysis of a simplified two dimensional vorticity streamfunction model that allows for a more direct interpretation of the role of the shear in controlling the circulation around the cold pool and through an analysis of an extensive set of 3d squall line simulations run at higher resolution and covering a larger range of environmental shear conditions than presented by wkr

episodic uplift deduced from holocene shorelines in the perachora peninsula corinth area greece four raised shorelines between 1 1 m and 3 5 m have been identified at two localities on the perachora peninsula and were dated by ams 14c to between 6400 and 1500 calibrated years ago uplift movements seem to have occurred in increments of 0 8 0 3 m with a return period of about 1600 years the last uplift coincided with a regional tectonic paroxysm which has already been documented in several areas of the eastern mediterranean the average uplift rate was probably faster during the holocene than the average since the last interglacial period no important vertical displacement occurred in this area at the time of or after the 1981 earthquake but a new episode of coseismic uplift may be in preparation

modelling the quaternary evolution of shore platforms and erosional continental shelves a mathematical model was used to investigate the effect of glacially induced fluctuations in sea level on the evolution of wave cut shore platforms and erosional continental shelves during the quaternary the model used two deep water wave sets which were used to calculate breaker height and depth and the force of the waves at the waterline according to the width and bottom roughness of the surf zone and the gradient of the submarine slope the model also incorporated an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot most runs were made using a sea level model that consisted of 26 glacial cycles from 2 million to 0 9 million years ago and nine of approximately twice the amplitude and wavelength in the last 0 9 million years the model emphasized the dynamic association between the contemporary intertidal platform and the continental shelf both surfaces trend towards a state of static equilibrium under oscillating sea level conditions when attenuated waves are unable to continue eroding the rock if there has not been enough time to reduce the gradient of the shallower portions of the continental shelf however intertidal shore platforms can be in a temporary though possibly long lasting state of dynamic equilibrium the model suggests that most platforms are at least in part inherited from one or in many cases more interglacial stages when sea level was similar to today s copyright 2001 john wiley sons ltd

comprehensive characterization of elevated coastal platforms in the north iberian margin a new template to quantify uplift rates and tectonic patterns abstract the cantabrian margin at the northern iberian peninsula shows elevated coastal platforms extending from west to east for 200 km these erosional surfaces are several kilometers wide and are bounded inland by a paleoshoreline and towards the sea by the retreating current cliff the origin and evolution of these geomorphologic markers remains controversial one of the main challenges arising from the difficulties in correlating the patchy distribution of the platforms and their variable heights along the margin due to lithological differences local tectonism and varying degrees of preservation with the aim of understanding recent coastal evolution a systematic quantitative gis analysis of lidar elevation models 5 m resolution was carried out along 4 000 km2 of the cantabrian coast between 4 15 w and 7 30 w longitude the coastline runs parallel to the cantabrian mountains which are supported by an orogenic root present only beneath the eastern half of the coastline under study the integration on the gis template of the crust mantle boundary as a controlling factor of landscape development has helped in the understanding of the recent evolution of the coastal platforms and in the interpretation of previously unexplained features of their distribution the two main outcomes of this multiscale approach are 1 the correlation of most of the fragmented rasas as part of an original unique coastal platform along the cantabrian margin and 2 the differentiation of two sectors separated by a highly tectonized area associated to the ventaniella fault the western sector has one main continuous surface showing a 0 08 tilt towards the west sometimes interrupted by local and recent minor faults with net slips of meters to tens of meters the eastern sector has several steps of erosional surfaces spread out at various heights without tilt the ventaniella fault separating both sectors produces an apparent vertical offset of 50 m in the main erosional surface our study shows that this fault also separates two distinct evolutions in the elevation of the coastal platform 1 the western coast which has risen continuously probably in response to a lateral gradient in crustal thickness and 2 the eastern coast where uplift is discontinuous over time since several of these surfaces formed below the main paleoshoreline the cantabrian coast captures the influence that crustal structure has on the expression and evolution of geomorphologic markers at the surface and vice versa landform features at the surface can be very sensitive to differential crustal thickness while responding to the same external and climatic forces in the context of the western european framework our work provides a regional template within which future absolute geochronological dating can be based to improve our knowledge of the recent evolution of the atlantic margins

tidal wetting and drying on shore platforms an experimental assessment abstract rocks were subjected to wetting and drying cycles with de ionized water under real time conditions using tidal simulators one third of the samples experienced 11 h of exposure and 1 h of inundation over a 12 h tidal cycle representing high tidal conditions one third experienced 6 h of exposure and 6 h of inundation representing mid tidal conditions and one third experienced 1 h of exposure and 11 h of inundation representing low tidal conditions we obtained 324 cores from igneous metamorphic and sedimentary rocks from ontario which were exposed to more than 930 wetting and drying cycles over 16 months we obtained 675 cores and cubes from basalts sandstones and argillites from shore platforms in eastern canada which were exposed to about 700 cycles over 12 months many of the cores and cubes experienced very little to no breakdown particularly those from the igneous and metamorphic rocks of ontario sandstones from a sloping platform in the macrotidal bay of fundy and argillites from a horizontal mesotidal platform in gaspe quebec were the most susceptible rock types with equivalent surface downwearing rates ranging from 0 to 4 mm year 1 the results suggest that downwearing rates decrease with elevation within the intertidal zone probably because rocks require much longer to desorb than to absorb water the experiments demonstrated that wetting and drying can be an important process on shore platforms in some types of rock helping to lower the height and reduce the gradient of sloping macrotidal platforms and to reduce the height of horizontal micro and mesotidal platforms

millennial scale oceanic climate variability off the western iberian margin during the last two glacial periods high resolution palaeoclimate records recovered from the iberian margin in core md95 2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka large scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer neogloboquadrina pachyderma sinistral and in some instances the occurrence of ice rafted debris ird ice rafting episodes were prevalent in both of the last two glacials with greater intensity in stages 2 through 4 than in stage 6 the six youngest heinrich events are well defined during the last glacial but detrital carbonate is absent from heinrich layers hl6 hl5 and hl3 dansgaard oeschger stadial equivalent sub millennial ird deposition events have been detected in particular during stage 3 allowing a good match with the cooling displayed in the greenland ice core gisp2 sea surface temperature off portugal in stage 6 was in general warmer than during the last glacial pointing towards a weaker southward influence of polar water masses ice rafting occurred mainly in mid mis marine isotope stage 6 between 173 and 153 kyr as a group of poorly differentiated short duration quasi continuous events mainly marked by the high abundance of sinistral n pachyderma differences exist in ird composition relative to the last glacial with a reduced canadian derived detrital carbonate component combined with an important contribution of volcanic particles the lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas

surface cold pools in the outer rainbands of tropical storm hanna 2008 near landfall surface mesonet observations were used to document the structure of prominent cold pools associated with twoconvectiveouterrainbandsoftropicalstormhannaon5september2008 thedevelopingrainbandswere located 400 kmnorth ofthestormcenterastheycrossedthecarolinacoastlineandpassedover themesonet the combination of moderate cape moderate low level cross band vertical shear and dry midlevel air provided an environment supportive of surface cold pool formation and long lived quasi linear convection both rainbands exhibited multiple outward tilting convective cells and discrete line segments centered within a narrow zone of nearly continuous stratiform precipitation the mesonet observations provided a unique along and cross band perspective of discrete cold pools situated beneath andbehind the convection portions of each rainband prominentcold pools extended 40 80 km behind the rainband s leading edge and exhibited maximum potential temperature mixing ratio and equivalentpotentialtemperaturedeficitsof2 4 k 1 2 g kg 21 and4 10 k respectively inthecross banddirection convergence of storm relative inflow along the cold pool leading edge was coincident with a modest high pressure anomaly while inflow divergence prevailed through the cold pool and rainfall maxima several cold pools expanded along band while being advected downband by the prevailing cyclonic flow cold pool wakes were observed more than 50 km behind the rainband leading edge and up to 20 km downband from intense convection variations in cold pool intensitywerenotwell correlated with convectiveintensity rainfallrate or the degree of midlevel dryness implications of prominent cold pools on tropical cyclone convection size and intensity are discussed

sedimentology of rocky shorelines 3 hydrodynamics of megaclast emplacement and transport on a shore platform oahu hawaii abstract megaclasts of well cemented coralgal limestone have been emplaced onto a shore platform by large waves on the north shore of oahu hi emplacement and movements of the largest ca 96 ton megaclast have been dated using aerial photographs hydrodynamic forces at the low submerged shoreline cliff are computed using design wave characteristics based on linear wave theory and experimental results considering the local wave climate and near shore bottom topography force exerted by a tsunami has been estimated based on the 1946 aleutian tsunami the computed forces are evaluated in terms of the initial fracturing along a given failure plane that is required in order for the detachment to occur the analysis shows that tsunami as well as large swell waves are capable of quarrying the megaclast provided that sufficient initial fracturing is present dislodgement and emplacement most likely occurred in a sequence during impact of a single wave on the shoreline cliff swell waves however are seldom capable of emplacing large blocks onto the platform due to their rapid disintegration after breaking so that most blocks quarried from the cliff edge fall back onto the submarine terrace emplacement of large boulders seems to require extreme sea waves with periods longer than storms or north pacific swells usually produce transport mechanisms on the shore platform vary depending on megaclast shape sliding is a common mechanism of transport for larger and irregular megaclasts whereas somewhat smaller and platy megaclasts are occasionally found in overturned positions

multiscale analysis of tropical cyclone kinematic structure from airborne doppler radar composites abstractthe multiscale inner core structure of mature tropical cyclones is presented via the use of composites of airborne doppler radar analyses the structure of the axisymmetric vortex and the convective and turbulent scale properties within this axisymmetric framework are shown to be consistent with many previous studies focusing on individual cases or using different airborne data sources on the vortex scale these structures include the primary and secondary circulations eyewall slope decay of the tangential wind with height low level inflow layer and region of enhanced outflow radial variation of convective and stratiform reflectivity eyewall vorticity and divergence fields and rainband signatures in the radial wind vertical velocity vorticity and divergence composite mean and variance fields statistics of convective scale fields and how they vary as a function of proximity to the radius of maximum wind show that the inner eyewall edge is associated with stronger updrafts and higher refl

holocene emerged notches and tectonic uplift along the jalisco coast southwest mexico this paper presents the preliminary results from a study of holocene emerged shorelines marine notches and their tectonic implications along the jalisco coast the pacific coast of jalisco sw mexico is an active tectonic margin this coast has been the site of two of the largest earthquakes to occur in mexico this century the 1932 mw 8 2 jalisco earthquake and the 1995 mw 8 0 colima earthquake measurement and preliminary radiocarbon dating of emergent paleoshorelines along the jalisco coast provide the first constraints upon the timing for tectonic uplift along this coastline uplifted holocene marine notches and wave cut platforms occur at elevations ranging from ca 1 to 4 5 m amsl in situ intertidal organisms dated with radiocarbon the first ever reported for the jalisco area provide preliminary results that record tectonic uplift during at least the past 1300 years bp at an average rate of about 3 mm year we propose a model in which coseismic subsidence produced by offshore earthquakes is rapidly recovered during the postseismic and interseismic periods the long term period is characterized by slow tectonic uplift of the jalisco coast we found no evidence of coastal interseismic and long term subsidence along the jalisco coast

convective scale variations in the inner core rainbands of a tropical cyclone airborne doppler radar documented a variety of convective scale structures within the inner core rainbands of hurricane rita 2005 as predicted by past studies wind shear determined azimuthal variations in the convection all convective scale circulations had radial inflow at low levels upward motion and outflow in the midtroposphere convective cells at smaller radii contained a low level tangential jet determined largely by tangential acceleration due to angular momentum conservation uy r term while cells at larger radii contained a low level and or midlevel jet determined jointly by the uy r and vertical advection terms the outflow was at a higher lower altitude for the outer inner cells radial variations in the convective cells are attributable to differencesin buoyancy and vertical shear of the radial wind u z more buoyant updrafts at larger radii enhance vertical advection of y creating local tangential jets at midlevels at smaller radii the stronger low level radial inflow contributes to a greater u z confining convectively generated jets to low levels the low level tangential jet and convectively generated pressure gradients produce outward pointing supergradient acceleration that decelerates the boundary layer inflow consequently this supergradient flow will enhance convergence and convection at the radius of inner rainbandcells increasing the likelihoodof secondary eyewall formation it is hypothesized that a critical zone for secondary eyewall formation exists where sufficiently high u z consistently constrains the altitudes of convectively generated supergradient flow so that convection in this radial zone leads to a newly developed eyewall once an incipient secondary eyewall forms at a certain radius subsidence occurring along its inner edge separates it from the primary eyewall