spreading of the western mediterranean deep water after winter 2005 time scales and deep cyclone transport this work is dedicated to the study of the propagation of the western mediterranean deep water wmdw formed in the gulf of lions during the exceptional winter 2005 a simulation of the 1998 2008 period has been carried out with an eddy resolving ocean general circulation model of the mediterranean sea driven by interannual high resolution air sea fluxes this study first presents a validation of the recently improved model configuration against satellite observations then we assess the ability of the model to reproduce the particularly intense deep convection event of winter 2005 in the gulf of lions a huge volume of very dense water is formed in the simulations at that time annual formation rate of about 3 sv the thermohaline characteristics of the new wmdw allow a monitoring of its deep propagation we identify several deep cyclones as mainly responsible of the fast spreading of the wmdw southwards in the western mediterranean by comparing eulerian and lagrangian approaches we estimate different transport times of the wmdw by these cyclonic eddies and compare them to those deduced from several observations finally we argue that these cyclones favour the propagation of the wmdw thermohaline characteristics towards the channel of sardinia and decrease the volume of wmdw which can reach the strait of gibraltar

fluid dynamics of oceanic thermocline ventilation abstract a flux form of the potential vorticity pv equation is applied to study the creation and transport of potential vorticity in an ocean gyre generalized pv fluxes j vectors and the associated pv flux fines are used to map the creation by buoyancy forcing of pv in the mixed layer and its transport as fluid is subducted through the base of the mixed layer into the thermocline the pv flux lines can either close on themselves recirculation or begin and end on the boundaries ventilation idealized thermocline solutions are diagnosed using j vectors which vividly illustrate the competing process of recirculation through western boundary currants and subduction from the surface potential vorticity flux vectors are then used to quantify the flux of mass passing invisidly through a surface across which potential vorticity changes discontinuously but at which potential density and velocity are continuous such a surface might be the base of the oceanic mixed layer or in a meteorological context

a pv approach for dense water formation along fronts application to the northwestern mediterranean the mechanisms of dense water formation 29 0 kg m 3 at work in the baroclinic cyclonic gyre of the north western mediterranean basin are investigated through a pv budget pv potential vorticity the pv budget is diagnosed from an eddy resolving 1 36 ocean simulation driven in surface by hourly air sea fluxes provided by a non hydrostatic atmospheric model at 2 5km resolution the pv budget is controlled by the diabatic frictional and advective pv fluxes around the gyre the surface diabatic pv flux dominates the pv destruction except along the northern branch of the north current where the surface frictional pv flux is strongly negative in this region the bathymetry stabilizes the front and maintains the current northerly in the same direction as the dominant northerly wind this configuration leads to optimal wind current interactions and explains the preponderance of frictional pv destruction on diabatic pv destruction this mechanical forcing drives a cross front ageostrophic circulation which subducts surface low pv waters destroyed by wind on the dense side of the front and obducts high pv waters from the pycnocline on the light side of the front the horizontal pv advections associated with the geostrophic cyclonic gyre and turbulent entrainment at the pycnocline also contribute to the pv refueling in the frontal region the surface non advective pv flux involves energy exchanges down to 1400 w m 2 in the frontal zone this flux is 3 5 times stronger than atmospheric buoyancy flux these energy exchanges quantify the coupling effects between the surface atmospheric forcing with the oceanic frontal structures at submesoscale this article is protected by copyright all rights reserved

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

intensification of ocean fronts by down front winds abstract many ocean fronts experience strong local atmospheric forcing by down front winds that is winds blowing in the direction of the frontal jet an analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by which down front winds lead to frontogenesis when a wind blows down a front cross front advection of density by ekman flow results in a destabilizing wind driven buoyancy flux wdbf equal to the product of the ekman transport with the surface lateral buoyancy gradient destabilization of the water column results in convection that is localized to the front and that has a buoyancy flux that is scaled by the wdbf mixing of buoyancy by convection and ekman pumping suction resulting from the cross front contrast in vertical vorticity of the frontal jet drive frontogenetic ageostrophic secondary circulations ascs for mixed layers with negative potential vorticity the most frontogenetic ascs select a preferred cross front width and do not translate with

friction frontogenesis and the stratification of the surface mixed layer the generation and destruction of stratification in the surface mixed layer of the ocean is understood to result from vertical turbulent transport of buoyancy and momentum driven by air sea fluxes and stresses in this paper it is shown that the magnitude and penetration of vertical fluxes are strongly modified by horizontal gradients in buoyancy and momentum a classic example is the strong restratification resulting from frontogenesis in regions of confluent flow frictional forces acting on a baroclinic current either imposed externally by a wind stress or caused by the spindown of the current itself also modify the stratification by driving ekman flows that differentially advect density ekman flow induced during spindown always tends to restratify the fluid while wind driven ekman currents will restratify or destratify the mixed layer if the wind stress has a component up or down front i e directed against or with the geostrophic shear respectively scalings are constructed for the relative importance of friction versus frontogenesis in the restratification of the mixed layer and are tested using numerical experiments of mixed layer fronts forced by both winds and a strain field the scalings suggest and the numerical experiments confirm that for wind stress magnitudes mixed layer depths and cross front density gradients typical of the ocean wind induced friction often dominates frontogenesis in the modification of the stratification of the upper ocean the experiments reveal that wind induced destratification is weaker in magnitude than restratification because the stratification generated by up front winds confines the turbulent stress to a depth shallower than the ekman layer which enhances the frictional force ekman flow and differential advection of density frictional destratification is further reduced over restratification because the stress associated with the geostrophic shear at the surface tends to compensate a down front wind stress

high velocity ring shear tests on sand ring shear tests on sand materials have been carried out to show whether there is a change in the behaviour of these materials at high shearing rates and normal stresses this question is relevant to the problem of the mobility of large rock avalanches sturzstroms but is also of more general academic interest a ring shear apparatus of unusual although simple design has been constructed capable of achieving circumferential velocities of 2 m s at normal stresses of up to 200 kpa tests were carried out on two types of coarse sand wet or dry sand rock flour mixtures and polystyrene beads perfect frictional behaviour was observed in all the tests uninfluenced by either velocity or normal stress over the entire range of these variables change in frictional behaviour due to high rate of shearing therefore cannot be used to explain the high observed mobility of sturzstroms des essais de cisaillement circulaire par torsion ont ete effectes afin de decouvrir si un changement ait lieu dans le comportem

dense water formation in the north western mediterranean area during hymex sop2 in 1 36 ocean simulations sensitivity to initial conditions the north western mediterranean sea is a key location where intense air sea exchanges occur in autumn and winter the succession of strong mistral and tramontane situations leading to significant evaporation and ocean heat loss is well known as the controlling factor in the dense water formation dwf with deep convection episodes during hymex sop2 1 february to 15 march 2013 several platforms sampled the area in order to document dwf and air sea exchanges this study investigates the ability of the nemo wmed36 ocean model 1 36 resolution driven in surface by the hourly air sea fluxes from the arome wmed forecasts 2 5 km resolution to represent dwf during hymex sop2 and focuses on the sensitivity to initial conditions after a short evaluation of the atmospheric forcing the high resolution oceanic simulations using three different data sets as initial and boundary conditions are compared to observations collected during the field campaign it evidences that using regional model outputs may lead to unrealistic thermohaline characteristics for the intermediate and deep waters which degrade the simulated new dense water formed using ocean analyses built from observations permits to obtain more realistic characteristics of the western mediterranean dense water however a low stratification favors an overestimation of the convective area and of the dwf rate the dwf chronology is also impacted nevertheless in every run sop2 is characterized by the production of water denser than 29 11 kg m 3 with a peak during the strong mistral event of 23 25 february followed by a period of restratification before a last event of bottom convection on 13 15 march

diagnosing the observed seasonal cycle of atlantic subtropical mode water using potential vorticity and its attendant theorems analyzed fields of ocean circulation and the flux form of the potential vorticity equation are used to map the creation and subsequentcirculation of lowpotential vorticity waters known as subtropical mode water stmw in the north atlantic novel mapping techniques are applied to i render the seasonal cycle and annual mean mixed layer vertical flux of potential vorticity pv through outcrops and ii visualize the extraction ofpv from the mode water layer in winter over and to the south of the gulf stream both buoyancy loss and wind forcing contributetotheextractionofpv buttheauthorsfindthattheformergreatlyexceedsthelatter thesubsequent path of stmw is also mapped using bernoulli contours on isopycnal surfaces

observations of deep convection in the gulf of lions northern mediterranean during the winter of 1991 92 abstract during december 1991 to april 1992 measurements with moored acoustic doppler current profiler adcp stations and shipboard surveys were carried out in the convection regime of the gulf of lions northwestern mediterranean first significant mixed layer deepening and generation of internal waves in the stratified intermediate layer occurred during a mistral cooling phase in late december mixed layer deepening to about 400 m eroding the salinity maximum layer of saltier and warmer levantine intermediate water and causing temporary surface layer warming followed during a second cooling period of late january during a mistral cooling period from 18 to 23 february 1992 convection to 1500 m depth was observed where the size of the convection regime was 50 100 km extent vertical velocities 40 640 m deep recorded by four adcps of a triangular moored array of 2 km sidelength in the center of the convection regime exceeded 5 cm s 1 and were not correlated over the separation of the moorings hori

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

recent changes in deep water formation and spreading in the eastern mediterranean sea a review abstract observations of the last decade testify that the characteristics of the deep thermohaline circulation in the eastern mediterranean sea have changed thoroughly the source of the most dense waters of the basin has moved from the adriatic to the aegean sea this new source has proved to be very efficient since the estimated formation rate for the period 1989 95 was more than 1 sv about three times more than the dense water formation rate of the adriatic sea these new waters with hydrological characteristics that are warmer and more saline have replaced almost 20 of the older deep waters of the basin and have uplifted the deep isopycnals by about 500 m this major event can be attributed to important meteorological anomalies in the eastern mediterranean and to changes of circulation patterns the extended dry period of 1988 93 and the exceptionally cold winters of 1987 and 1992 93 created favorable conditions for increased formation of dense water in the aegean furthermore changes in the circulation patterns in the intermediate water range levantine intermediate water liw and cretan intermediate water themselves possibly linked to meteorological anomalies appear to have played an important role in the redistribution of salt as a result of an interruption to exchanges between the ionian and levantine basin the salinities in the latter started to rise high salinity waters were diverted into the aegean malanotte rizzoli p manca b b ribera dacala m theocharis a 1998 the eastern mediterranean in the 80s and in the 90s the big transition emerged from the poem bc observational evidence rapport du commission international de la mer medittanee 35 174 175 and the westward transport of liw was reduced an additional effect of the deep water discharge from the aegean and the resulting uplifting of mid depth waters was to lower salinities in the liw layer this effect is most strongly felt in the ionian sea a 3 d primitive equation numerical model for the eastern mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient these results indicate that the observed changes can be at least partially explained as a response of the eastern mediterranean and more specifically of the aegean to atmospheric forcing variability

wind ringing of the ocean in presence of mesoscale eddies 1 recent findings have highlighted the impact of high frequency hf winds on the inertial motions and the consequences on the large scale oceanic circulation wunsch and ferrari 2004 within this context the present study focuses on the role of intermediate scales related to oceanic mesoscale eddies results show that a turbulent eddy field does not affect the impact of hf winds on the inertial motions however the eddies efficiently and permanently concentrate the wind forced inertial motions in small scale anticyclonic structures this leads to a spatially heterogeneous vertical mixing strongly related to the eddy field properties

relevance of era40 dynamical downscaling for modeling deep convection in the mediterranean sea 1 a strong open ocean convection event was observed in the northwestern mediterranean sea during the 1986 87 winter this period was used as a case study to evaluate the impact of the spatial resolution of atmospheric forcing on deep convection modeling twin numerical experiments were performed with an oceanic model forced by atmospheric forcing sets with different resolutions a low resolution atmospheric forcing extracted from the era40 reanalysis was compared with a high resolution forcing produced by a dynamical downscaling of era40 a high resolution climate model spectrally driven by era40 fields for the large scales provided the dynamical downscaling dataset covering the 1958 2001 period the oceanic simulation performed under low resolution meteorological forcing did not reproduce the observed convection the simulation performed under high resolution forcing correctly reproduced the convection event this was principally due to the enhancement of spatial and temporal meteorological extremes under the high resolution forcing

transformation of dilative and contractive landslide debris into debris flows an example from marin county california abstract the severe rainstorm of january 3 4 and 5 1982 in the san francisco bay area california produced numerous landslides many of which transformed into damaging debris flows the process of transformation was studied in detail at one site where only part of a landslide mobilized into several episodes of debris flow the focus of our investigation was to learn whether the landslide debris dilated or contracted during the transformation from slide to flow the landslide debris consisted of sandy colluvium that was separable into three soil horizons that occupied the axis of a small topographic swale failure involved the entire thickness of colluvium however over parts of the landslide the soil a horizon failed separately from the remainder of the colluvium undisturbed samples were taken for density measurements from outside the landslide from the failure zone and overlying material from the part of the landslide that did not mobilize into debris flows and from the debris flow deposits the soil a horizon was contractive and mobilized to flows in a process analogous to liquefaction of loose granular soils during earthquakes the soil b and c horizons were dilative and underwent 2 to 5 volumetric expansion during landslide movement that permitted mobilization of debris flow episodes several criteria can be used in the field to differentiate between contractive and dilative behavior including lag time between landsliding and mobilization of flow episodic mobilization of flows and partial or complete transformation of the landslide

numerical simulation of debris flows a key requirement in the assessment of landslide risk in such densely populated urban areas as hong kong consists of the prediction of potential runout distance or the extent of the subsequent debris flow this paper presents a three dimensional dynamic model of unsteady gravity driven debris flow the lagrangian galerkin finite element method is used to determine the nodal velocity and depth of soil column elements within the sliding mass with the momentum and mass conservation mathematically closed within the soil column elements the numerical solution also features a lumped mass matrix and a volume weighted procedure the method of least squares approximation plays a smoothing role which enhances stability and efficiency of the numerical solution scheme the nodal elevation during sliding is obtained via a dynamic bilinear interpolation of the elevation function for the base of the sliding mass furthermore the accuracy robustness and generality of this method are validated by experimental results

a new hypothesis about the surface circulation in the eastern basin of the mediterranean sea abstract in time the circulation of the atlantic water aw in the eastern basin of the mediterranean sea has been described differently according to two major representations the historical one which began with the scheme from nielsen in 1912 and has been refined up to the 1980s favours a counterclockwise circulation in the whole basin with aw flowing in its southern part as a broad flow off libya and egypt from the ionian to the levantine subbasins then continuing along middle east and turkey before flowing back westwards the more recent one issued in the 1990s favours a clockwise circulation in the northern part of the ionian continuing offshore across the basin from the cretan to the central part of the levantine as the so called mid mediterranean jet this jet is depicted then as splitting both clockwise in the southeastern part of the basin and counterclockwise off turkey where this representation agrees with the former because the recent representation cannot be considered as a refinement of the historical ones we have been interested in understanding why a given data set available to everybody is interpreted in such different ways in the algerian subbasin the combined use of satellite infrared images and a significant amount of in situ data sets hydrology and both eulerian and lagrangian current measurements allowed us to solve a similar controversy therefore we examined the circulation features in the eastern basin undertaking the detailed analysis of 1000 daily and weekly composite images spanning the period 1996 2000 and of monthly composite images available since 1985 whenever in situ observations were available we have confronted them with the satellite thermal signatures and have shown that both are consistent this paper focuses on the overall basin scale results while the detailed ones are published in an other paper the new scheme we propose is basically a refined version of the historical ones the circulation of aw is counterclockwise in the whole eastern basin but it is more constrained alongslope than previously thought and the broadening historically schematised appears to be due to intense mesoscale eddies mainly generated by the instability of this circulation

hillslope infiltration divergent and convergent slopes this perturbation analysis of divergence convergence effects on hillslope infiltration and downslope unsaturated flow indicates that in general these effects are unimportant for usual hillslope topography only where the radius of the contour is less than about 10 times the characteristic infiltration length lgrav or 10 times the sorptive length need the perturbation be taken into account this result opens up a considerable extension of applicability of the analysis of infiltration on planar hillslopes to embrace slopes with curved contours such as ridge noses and hollows

newtonian fluid mechanics treatment of debris flows and avalanches calculations are carried out first for steady fully developed laminar flow on a slope application of this result to field data published in a previous paper by another author suggests that many debris flows are laminar then singular perturbation techniques are used to obtain first order solutions for unsteady non uniform flow from a point source on a steep slope solutions are obtained for both laminar and turbulent flows and it is found that the laminar flow model gives the best description of laboratory data obtained by a previous investigator a number of differences are observed in the behavior of the outer kinematic wave solutions for laminar and turbulent flow and it is suggested that it is probably not possible to describe all debris flows and avalanches with laminar flow models it is also suggested that more comparisons need to be made between theoretical results and field data measurements

continuum simulation of flow failures dynamic aspects of several catastrophic slope failures have been evaluated by unsteady flow modelling assuming two dimensional or quasi three dimensional transient flow of an incompressible bivi

on the role of interior mixing and air sea fluxes in determining the stratification and circulation of the oceans abstract the problem of determining the eastern boundary basic stratification and the buoyancy driven circulation of the oceans is addressed a global integral constraint relating the interior stratification and the air sea heat fluxes is derived based on the condition that the total mass of water of given density is constant in a steady state ocean this constraint is then applied to two simple analytic models the first is a continuous nonlinear diffusive model of the lower mid depth and bottom circulation below the influence of the wind driven circulation it shows the tendency of the vertical density profile to look like an exponential profile in the presence of mixing the integral constraint is used to relate the stratification and circulation of the bottom and mid depth waters to the air sea heat fluxes at the surface where the deep densities outcrop the second model is a layered one of the wind driven circulation mid depth and bottom water the eastern boundary stratification of the model i

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

modeling the deep convection in the northwestern mediterranean sea using an eddy permitting and an eddy resolving model case study of winter 1986 1987 1 in the northwestern mediterranean sea winter 1986 1987 was particularly cold inducing a strong open ocean convection event in order to investigate the impact of numerical models spatial resolution on the convection representation and the effects of deep convection on the northwestern mediterranean circulation we perform two numerical three dimensional simulations eddy permitting versus eddy resolving models are forced at the surface by the era40 atmospheric fluxes with a simple heat flux correction to better mimic the observed value we examine the characteristics of the deep convection mixed layer water masses characteristics convection zone and mesoscale structures and perform temporal analysis of this event in terms of kinetic energy buoyancy equilibrium and deep water dw evolution the convection characteristics are similarly represented on a global scale by both models and are in good agreement with observations except for the size of the convection region however the eddy resolving model better reproduces the mesoscale structures whose role in the dw formation mixing and transport is shown to be essential the boundary circulation and the overturning are enhanced during the convection event sixty six percent of the dw spreading is due to the bleeding effect into the catalan sea during the convection event whereas 33 is due to the mesoscale structures southwestward advection after the event sixty percent of the restratification with respect of the water column initial structure occurs before july 1987 and is due to light water advection afterward restratification is due to the mixing and is not complete before next year convection

a three dimensional numerical study of deep water formation in the northwestern mediterranean sea abstract deep water formation dwf in the northwestern mediterranean sea and the subsequent horizontal circulation are investigated in a rectangular basin with a three dimensional primitive equation model the basin is forced by constant climatological heat and salt fluxes convective motion is parameterized by a simple nonpenetrative convective adjustment process plus richardson number dependent vertical eddy viscosity and diffusivity a homogeneous column of dense water is progressively formed in the forcing area meanders of 40 km wavelength develop at the periphery of the column these features agree with observations energy studies show that the meanders are generated mainly through a baroclinic instability process these meanders and the associated cells of vertical motion contribute to the process of dwf they generate vertical advection while the associated horizontal advection tends to restratify the surface water of the column and thus to inhibit very deep convection just before the end o

modeling the mediterranean sea interannual variability during 1961 2000 focus on the eastern mediterranean transient 1 this work is dedicated to the study of the climate variability of the mediterranean sea in particular the study of the eastern mediterranean transient emt which occurred in the early 1990s simulations of the 1961 2000 period have been carried out with an eddy permitting ocean general circulation model of the mediterranean sea driven by realistic interannual high resolution air sea fluxes using different databases for the river runoff black sea inflow and atlantic thermohaline characteristics at climatological or interannual scales we assess the effects of the non atmospheric hydrological forcings on the simulation of the interannual variations of the mediterranean circulation the evolution of the basin scale heat content is in very good agreement with the observations especially in the surface and intermediate layers while the agreement is lower for the evolution of the salt content convection events in the aegean sea are noticed in the simulations between 1972 and 1976 in the late 1980s and around the emt period the formation rates of cretan deep water cdw are different during these periods allowing or preventing the spreading of cdw into the eastern mediterranean the sequence of the emt events is well reproduced the high winter oceanic surface cooling and net evaporation over the aegean sea in the early 1990s the high amount of dense cdw formed during these winters and then the overflow and the spreading of this cdw in the eastern mediterranean among the preconditioning processes suggested in the literature we find that changes in the levantine surface circulation possibly induced by the presence in the cretan passage of anticyclonic eddies and a lasting period with reduced net precipitation over the eastern mediterranean lead to an increase of the salt content of the aegean sea changes in the black sea freshwater inflow or in the characteristic of the atlantic water entering at the gibraltar strait also modify the thermohaline state of the aegean sea before the emt but as none of these preconditioning factors has a lasting impact on lowering the vertical stratification of the aegean sea we conclude that concerning the emt the major triggering elements are the atmospheric fluxes and winds occurring in winters 1991 1992 and 1992 1993

a model for the runout analysis of rapid flow slides debris flows and avalanches runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows debris avalanches rockslide avalanches large scale liquefaction failure

intraseasonal mixed layer heat budget in the equatorial atlantic during the cold tongue development in 2006 1 estimating the mixed layer heat budget is a key issue for understanding the cold tongue development in the eastern equatorial atlantic a high resolution ocean regional model is used to diagnose the mixed layer heat budget online during the egee 3 experiment from may to august 2006 the heat budget shows the major role of the horizontal advection and turbulent mixing in the mixed layer temperature balance in the cold tongue the surface net heat flux and entrainment processes play a minor role the equatorial cooling is mainly induced by low frequency advection which is balanced by high frequency zonal and meridional advections the high frequency advections are organized in patterns along the northern edge of the cold tongue where they are associated with strong sea surface temperature gradients and well developed tropical instability waves in the western atlantic special attention is paid to the wind energy flux which controls horizontal advection and turbulent mixing we suggest that the wind energy flux drives the vertical velocity which in turn adjusts the mixed layer depth its stratification and the vertical shear of the horizontal current although vertical advection is not essential in providing cold water in the atlantic cold tongue it is shown that the vertical velocity plays a central role in preconditioning the mixed layer and maximizes the turbulent mixing

experiments on the flow behaviour of granular materials at high velocity in an open channel a series of laboratory flume experiments has been conducted to investigate the flow behaviour of dry sand at high velocities the first incentive for this experimental programme was an attempt to explain the high mobility of apparently dry masses of rapidly moving broken rock during rock avalanches sturzstroms test velocities of over 5 m s and most other parameters of the tests were found to be dimensionally similar to those for a typical rock avalanche yet the conclusion was negative even the most rapid of the experiments indicated flow behaviour which is in conformity with the constant volume uniform coulomb friction relationship as applicable to slow shearing this conclusion was confirmed independently both by direct measurements of base friction and mean density of the flows and by detailed observations of flow uniformity acceleration and velocity profiles the surprising mobility of st umlrzstroms therefore requires a different explanation une serie de tests a canaux a ete entreprise dans le

observations of open ocean deep convection in the northwestern mediterranean sea seasonal and interannual variability of mixing and deep water masses for the 2007 2013 period we present here a unique oceanographic and meteorological data set focus on the deep convection processes our results are essentially based on in situ data mooring research vessel glider and profiling float collected from a multiplatform and integrated monitoring system moose mediterranean ocean observing system on environment which monitored continuously the northwestern mediterranean sea since 2007 and in particular high frequency potential temperature salinity and current measurements from the mooring lion located within the convection region from 2009 to 2013 the mixed layer depth reaches the seabed at a depth of 2330m in february then the violent vertical mixing of the whole water column lasts between 9 and 12 days setting up the characteristics of the newly formed deep water each deep convection winter formed a new warmer and saltier vintage of deep water these sudden inputs of salt and heat in the deep ocean are responsible for trends in salinity 3 3 0 2 10 3 yr and potential temperature 3 2 0 5 10 3 c yr observed from 2009 to 2013 for the 600 2300 m layer for the first time the overlapping of the three phases of deep convection can be observed with secondary vertical mixing events 2 4 days after the beginning of the restratification phase and the restratification spreading phase still active at the beginning of the following deep convection event

impact of the spatial distribution of the atmospheric forcing on water mass formation in the mediterranean sea the impact of the atmospheric forcing on the winter ocean convection in the mediterranean sea was studied with a high resolution ocean general circulation model the major areas of focus are the levantine basin the aegean cretan sea the adriatic sea and the gulf of lion two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared the first simulation med16 era40 was forced by air sea fields from era40 which is the ecmwf reanalysis the second simulation med16 ecmwf was forced by the ecmwf analyzed surface fields that have a horizontal resolution twice as high as those of era40 the analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns comparing the companion ocean simulation results with available observations in the adriatic sea and in the gulf of lion shows that med16 ecmwf is more realistic than med16 era40 in the eastern mediterranean although deep water formation occurs in the two experiments the depth reached by the convection is deeper in med16 ecmwf in the gulf of lion deep water formation occurs only in med16 ecmwf this larger sensitivity of the western mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time space resolutions of the forcing on the intense winter convection event in winter 1998 1999 the sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography which can only be reproduced in atmospheric models of sufficient resolution thus well positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter

unsteady nonuniform landslide motion 1 theoretical dynamics and the steady datum state unsteady nonuniform motion of persistently active landslides is a process of widespread importance a general three dimensional theory aimed at elucidating this process is developed from physical principles and field measurements of landslide behavior the theory employs a versatile constitutive model that represents landslides as deformable bodies composed of frictional nonlinear viscoplastic material the three dimensional theory is reduced to a mathematically tractable form by defining an ideal landslide datum state that consists of steady unidirectional shear flow driven by ground water seepage and gravitational forces solution of the datum state equation of motion yields vertical landslide velocity profiles that can represent deformation styles ranging from shear thickening viscoplastic flow to perfectly plastic frictional slip this range of theoretical profiles encompasses the range of profiles measured in four persistently active northern california landslides also obtained from the datum st

numerical high resolution air sea coupling over the gulf of lions during two tramontane mistral events 1 the near sea surface meteorological conditions associated with strong wind events over the mediterranean sea constitute a strong forcing on the ocean mixed layer the present study addresses the question of the sea surface scheme used in high resolution and short range atmospheric numerical modeling to represent the ocean mixed layer response under these severe mistral wind events in the gulf of lions area several slab ocean models have been used coupled with the weather research and forecasting wrf model and applied on two mistral cases 1 a slab model based on the transport divergence equation where the mixed layer evolution is only driven by the wind stress 2 a slab model where the temperature is the only prognostic variable and evolves according to the net surface heat flux and 3 a complete slab scheme from price 1981 the coupled simulations are also compared to two basic simulations one using a constant sea surface temperature sst field during all of the model integration and another using a 6 hourly update sea surface temperature reanalysis in this study we mainly focus on the slab model performances we identify the processes involved in the ocean mixed layer response under strong wind situations i e local and fast cooling and deepening the feedbacks of an interactive ocean mixed layer on the atmospheric simulation are also investigated

radon health and natural hazards a signpost for assessment and protection in the 21st century this volume draws together the final outputs of the five year unesco iugs igcp project 571 and presents new data on radon in the built and natural environments radon as a diagnostic tool of geophysical phenomena reflections and recommendations on the future of radon research and a critique of radon s asserted use as a therapy in recent years there has been an increasing interest in radon from a range of different aspects and we would suggest that radon science has the potential to be a useful tool in understanding our environment as well as its impacts on human health

multiscale observations of deep convection in the northwestern mediterranean sea during winter 2012 2013 using multiple platforms during winter 2012 2013 open ocean deep convection which is a major driver for the thermohaline circulation and ventilation of the ocean occurred in the gulf of lions northwestern mediterranean sea and has been thoroughly documented thanks in particular to the deployment of several gliders argo profiling floats several dedicated ship cruises and a mooring array during a period of about a year thanks to these intense observational efforts we show that deep convection reached the bottom in winter early in february 2013 in a area of maximum 28 3 109 m2 we present new quantitative results with estimates of heat and salt content at the subbasin scale at different time scales on the seasonal scale to a 10 days basis through optimal interpolation techniques and robust estimates of the deep water formation rate of 2 0 0 2 sv we provide an overview of the spatiotemporal coverage that has been reached throughout the seasons this year and we highlight some results based on data analysis and numerical modeling that are presented in this special issue they concern key circulation features for the deep convection and the subsequent bloom such as submesoscale coherent vortices scvs the plumes and symmetric instability at the edge of the deep convection area

a sliding consolidation model for flow slides a model is proposed for the behaviour of flow slides in loose cohesionless materials in which the debris spreads out as a uniform sheet excess pore fluid pressures are assumed to be generated for example by undrained loading arising from the collapse of metastable structure in the source area of the flow slide under the influence of these the leading element of the debris moves downslope by basal sliding consolidating as it does so by single upward drainage as a result the pore pressure at the base of the element eventually decays to a value that brings the element to rest hence defining the run out of the flow slide the model is applicable in principle to subaqueous and subaerial flow slides and to pore fluids consisting of water gas or both of these the predictions of the model are tested against the observed behaviour and measured properties of the 1966 flow slide at aberfan south wales the results show that a sliding consolidation model provides a possible mechanism for that event

indoor radon concentrations in relation to geology in slovenia for this study 330 instantaneous indoor radon concentrations were selected from the database assembled during the slovenian national radon programme a relationship was found between indoor radon concentrations rock type tectonic faults and age of buildings indoor radon concentrations were elevated in buildings that were older than 50 years and in those with a fault under foundations when these data were eliminated elevated indoor radon levels were found only in buildings built on limestone our conclusions were confirmed by using the machine learning methods clustering and multiple regression

routing debris flows with particle segregation a computer simulation method is developed to predict the temporal variations of debris flow discharge solids concentration and vertical mean particle size distribution a single finite step in the simulation is divided into two stages in the first stage a sediment bed composed of a well graded mixture is eroded by surface water introduced at the head of a channel thereby generating a debris flow in the second stage larger particles in the debris flow move upward because of dispersive force and are then transported forward faster than smaller particles which remain in the lower part of the flow because the velocity is slower in the lower layer another numerical simulation method is also developed to predict simultaneously the shape of the debris deposit area the distribution of the deposit thicknesses within the area and the three dimensional distribution of the mean diameters of the deposited particles both simulation methods are verified using laboratory experiments