some aspects of mining under aquifers in china abstract a number of case studies of mining induced permeability enhancement are documented the extent of strata failure around active underground mines is determined through use of a borehole discharge test the test delimits zones and the severity of extraction induced fracturing from these data empirical relationships are developed to determine the vertical and horizontal extents of the caving and fracture zones induced by mining these relationships are developed for a variety of strata types and strengths and give quantitative recommendations applicable to similar mining conditions elsewhere these recommendations are particularly important for sub sea or sub aquifer mining to ensure hazard free operation

an improved void resistance model for abandoned coal mine gas reservoirs abstract previous studies have shown that the gas pressure behaviour of some abandoned coal mines may be described with the aid of a simple conceptual model the so called void resistance model in this study an improved void resistance model has been developed and validated using previously collected data two model parameters i e an apparent source sink pressure and a time constant which control the gas pressure behaviour during recharge and under certain gas production conditions are defined it has been shown that the two parameters can be determined via linear regression through analysing the historical abandoned mine gas pressure data during recharge the void resistance model developed has been successfully applied to analyse the historical pressure data recorded at two abandoned coal mines in europe

stress relief coalbed methane drainage by surface vertical wells in china abstract this paper summarizes the status of engineering practice technology and research related to stress relief coalbed methane cbm drainage using surface wells in china during the past 10 years comments are provided on the theory and technical progress of this method in high gas mining areas such as the huainan huaibei and tiefa mining areas characterized by heavily sheared coals with relatively low permeability stress relief cbm surface well drainage has been successfully implemented and has broad acceptance as a cbm exploitation technology the fundamental theories underpinning stress relief cbm surface well drainage were established in china and include elements relating to 1 rock layer deformation theory vertical zoning and horizontal partitioning and the change in the stress condition in mining stopes 2 a theory regarding an abscission circle in the development of mining horizontal abscission fracture and vertical broken fracture in overlaying rocks and 3 the theory of stress relief inducing permeability increase in protected coal seams during mining and the gas migration accumulation theory of stress relief cbm surface well drainage three kinds of technical drainage modes are described protected seam surface well drainage in areas influenced by mining represented mainly in the huainan mining area gob surface well drainage most prominently in the tiefa mining areas and the multipurpose surface well drainage used in the huaibei mining areas serial well allocation in which wells are used for different purposes as extraction and mining proceeds and well bore configurations and designs suitable for this purpose are described the development and utilization of cbm is significant to energy saving emission reduction and to ensure safety in coal production

comparative studies of the spreading of mediterranean water through the gulf of cadiz abstract a comparative study is made of observations and model results of the spreading of mediterranean water mw from the strait of gibraltar through the gulf of cadiz past cape st vincent into the eastern north atlantic the observations include a set of hydrographic sections from west of gibraltar to offshore of lisbon the tracking of rafos floats and current meter data the model is a very fine resolution limited area model of the region around cape st vincent and includes model floats both the observational data and the model results show the mw descending into two distinct layers around 800 and 1200 m depth in the gulf of cadiz as the mw leaves the slope meddies are generated and have been tracked by the rafos floats and can be seen in the paths of the model floats

a shared borehole approach for coal bed methane drainage and ground stabilization with grouting abstract in underground longwall coal mines the risks of surface subsidence and coal bed methane cbm emission are generally controlled separately e g subsidence mitigation by overburden stabilization using grout injection and pressure relief cbm drainage using surface boreholes however some longwall panels require both gas drainage and ground stabilization for this purpose we propose a shared borehole approach for ground stabilization grouting and adjacent seam pressure relief cbm drainage by using mining induced fractures and voids in this method overlying seam pressure relief cbm is drained through a surface borehole during extraction of a longwall panel whereas grout injection is applied to stabilize the ground using the same borehole following drainage a combined drainage injection model that determines the allowable lag distance for grout injection is proposed the effectiveness of the shared borehole approach was tested at a longwall panel in a chinese coal mine no obvious interactions between the injection and drainage processes were detected during the case study verifying the effectiveness of the shared borehole approach

mining induced strata stress changes fractures and gas flow dynamics in multi seam longwall mining abstract this paper presents key findings from a recent comprehensive study of longwall mining induced strata movement stress changes fractures and gas flow dynamics in a deep underground coal mine in anhui china the study includes field monitoring of overburden displacement stress and water pressure changes at the longwall panel 1115 1 of the guqiao mine in addition 3d modelling of strata behaviour at the longwall panel using a 3d finite element code and goaf gas flow simulations with a cfd code are carried out this research has resulted in many new insights into the complex dynamic interaction between mining induced strata stress changes fractures and gas flow patterns based on the findings from the field monitoring and numerical modelling a three dimensional annular shaped overlying zone along the perimeter of the longwall panel is identified for optimal methane drainage during mining a practical method that helps define the geometry and boundary of this zone is proposed this study provides a new methodology and a set of engineering principles for the design of optimal co extraction of coal and methane

a new study of the mediterranean outflow air sea interactions and meddies using multisensor data previous studies of the mediterranean sea outflow and meddies o m were limited by the poor spatial and temporal resolution of conventional in situ observations as well as the confinement of satellite observations to the ocean s surface accordingly little is known about the formation and transport of meddies and the spatial and temporal variation of o m trajectories which are located on average at a depth of 1000 m however a new remote sensing method has been developed by the authors to observe and study the o m through unique approaches in satellite multisensor data integration analyses satellite altimeter scatterometer infrared satellite imagery and xbt data were used to detect and calculate the trajectories and the relative transport of the o m january 1993 december 2002 two experiments covering 1993 95 a mediterranean undercurrent seeding experiment amuse and structures des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore and xbt temperature measurements were used to directly validate the method presented herein the monthly mean features derived from floats and xbts for multiple meddies and the results of the presented method were significantly correlated based on a statistical chi square test in addition the complex singular value decomposition method was used to identify the propagating features and their phase speeds it was found that saltier water from the mediterranean sea was transported into the north atlantic ocean over the strait of gibraltar in boreal spring and summer relative to boreal autumn and winter streamfunctions using altimetry and time frequency energy distributions using the hilbert huang transform were computed to evaluate the meddy interactions with the sea surface variation since the o m play a significant role in carrying salty water from the mediterranean sea into the atlantic such new knowledge about their trajectories transport and life histories is important to the understanding of their mixing and interaction with north atlantic water this may lead to a better understanding of the global ocean circulation and global climate change

characteristics of surface signatures of mediterranean water eddies in this work we obtain new results on the manifestation of meddies or of other deep eddies at the sea surface further developing the results by bashmachnikov and carton 2012 the quasi geostrophic equations are used to describe a near axisymmetric vortex in the upper ocean forced at its lower boundary by the isopycnal elevation of a moving meddy the solution thus obtained provides a better approximation of the characteristics of meddy surface signals the results show that in subtropics large meddies with dynamic radius rm 30 km are always seen at the sea surface with aviso altimetry that medium size meddies with rm 20 km may be seen at the sea surface only if they are sufficiently shallow and strong while small meddies with rm 10 km generally cannot be detected with the present accuracy of altimetry data the intensity of meddy surface signals decreases to the south with the decrease of the f n ratio the seasonal variation in intensity of the surface signal for northern meddies 45 n is on the order of 2 3 cm but for subtropical meddies 35 n it can be on the order of 5 10 cm the radii of meddy surface signals range from 1 to 2 times the radii of the corresponding meddies for most of the observed subtropical meddies the upper limit should be used numerical experiments show that surface signals of meddies translated with drift are efficiently dispersed by the radiation of rossby waves at the same time for meddies translated by a background current the surface signal does not show strong dissipation

subsurface and deeper ocean remote sensing from satellites an overview and new results satellite remote sensors cannot see far beneath the surface layers of the ocean yet many important ocean processes and features are located well below the surface and at considerable depths examples include mediterranean eddies meddies mixed layer depth internal waves and bottom topography deeper ocean remote sensing is becoming even more important because recent data seem to indicate that the deeper ocean is responding to climate variability and change many of these subsurface phenomena have surface manifestations which can be interpreted with the help of models to derive key parameters of deeper ocean processes the objective of this paper is to provide an overview of satellite remote sensing and modeling techniques which enable scientists to characterize subsurface and deeper ocean processes and features and to present some new results

zircon age constraints on sediment provenance in the caspian region sensitive high resolution ion microprobe shrimp u pb ages for detrital zircons from the caspian region reveal the age ranges of basement terrains that supplied the sediment one sample from the modern volga river has groupings at c 340 370 ma c 900 1300 ma and c 1450 1800 ma with a small number of older zircons this is consistent with derivation from the precambrian basement of the east european craton and palaeozoic arcs in the urals mid and late proterozoic components may be derived from beyond the present volga drainage basin such as the sveconorwegian orogen a bajocian sandstone from the greater caucasus has 73 zircons that post date 350 ma ages cluster at c 165 185 ma c 220 260 ma c 280 360 ma and c 440 460 ma this pattern suggests derivation from palaeozoic basement of the greater caucasus itself and or the scythian platform and igneous rocks generated at a jurassic arc in the lesser caucasus four samples from the lower pliocene productive series of the south caspian basin have common phanerozoic grains and groups between c 900 1300 ma and 1500 2000 ma each sample contains zircons dated to c 2700 ma the overall age patterns in the productive series samples suggest a combination of east european craton and greater caucasus source components

observations and numerical modelling of the mediterranean outflow splitting and eddy generation during the canigo project the generation of dipolar eddies in the mediterranean water mw layers off south portugal was recorded by subsurface floats from february to november 1998 the role of the bottom topography on the spreading of the mw in the gulf of cadiz and on the generation of these mw eddies was studied in the framework of the medtop project some of the hydrological and velocity observations collected during medtop in 2001 and 2002 also revealed the association of anticyclones meddies and cyclones in the region just south of the portimao canyon the evolution of these structures is studied with subsurface floats deployed in the vortices the splitting of the mw plume in the gulf of cadiz and the generation mechanisms of the mw vortices in the region from portimao canyon to the estremadura promontory are investigated using a bottom following numerical primitive equations model in a regional ocean configuration incorporating the realistic topography of the iberian continental slope the model reproduces the mw division into different cores in the gulf of cadiz as well as the generation of baroclinic dipoles downstream of portimao canyon the role of the bottom topography in the eddy generation process is discussed

observations of layering under a warm core ring in the gulf of mexico abstracttwo glider transects in the gulf of mexico reveal fine vertical scale thermohaline structures within a loop current eddy lce partially compensating temperature and salinity anomalies are

submesoscale anomalies in the north pacific subarctic front data analysis of the experiment megapolygon 87 targeted at large scale and mesoscale currents revealed a submesoscale coherent eddy with a core of anomalously cold water south of the north pacific subarctic front sf ts characteristics of the core water are similar to the ones of the subarctic water mass north of sf the core occupies a depth range from 950 through at least 1500 m and has an outer diameter of 40 km the maximum value of thermal anomaly of 0 5 c is located at 1000 m depth anticyclonic orbital velocity reaches 30 cm s at 10 km radius at the edge of the internal core rotating nearly as a solid body the 7 cm s translating eddy is governed by the larger scale currents significant seawater density anomalies above the lens are explained by the interaction of the lens with a mean horizontal flow with strong vertical shear the lens was probably formed either by upper layer cooling during the previous winter spring season able to generate deep convection processes and move surface water to the middle and lower part of the main thermocline or by instability of the countercurrent existing below sf no direct observations of those processes in the northwestern pacific are available at present other similar submesoscale anomalies have been found in the area south of sf

life and demise of intrathermocline mesoscale vortices abstractthis study is focused on finescale dissipation mechanisms of intra thermocline mesoscale vortices exemplified by meddies large anticyclonic salt lenses of mediterranean origin commonly observed in the lower north atlantic thermocline high resolution numerical experiments are diagnosed to quantify the rates of temperature t and salinity s dispersion in salt lenses and to determine the relative contribution of various mixing processes in the decay of their thermohaline signatures we find in agreement with observations that meddies dissipate on the characteristic timescale of several years and that their ultimate disintegration can be attributed to thermohaline interleaving driven by double diffusive mixing mechanically generated turbulence on the other hand tends to suppress the interleaving and therefore has an adverse net effect on eddy dispersion it is found that the dispersion properties of static lenses characterized by density compensated t s patterns and their rapidly rotating

meddy seamount interactions implications for the mediterranean salt tongue abstract a quasigeostrophic point vortex numerical model is used to explore interactions of eddies and seamounts the ultimate objective of this study is to assess the role of meddy seamount interaction as an input to mediterranean salt tongue maintenance secondary objectives are to clarify the dynamics of meddy seamount interaction the results suggest that meddies survive seamount collisions with 60 70 of their initial cores remaining intact as coherent vortices given observed formation rates it appears meddies in their interactions with seamounts inject between one quarter and one half of the salt anomaly necessary to sustain the mediterranean salt tongue other considerations suggest the anomalous mass flux by meddies is comparable to that due to the mean flow in summary meddies are important to the maintenance of the salt tongue although other mechanisms are needed coherent vortex transport of which meddies are one example is a mesoscale process not well described by the downgradient mix

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

looping rafos floats in the california current system abstract looping motions of rafos floats deployed off the central california coast between 1992 and 2010 are described most floats were deployed in the california undercurrent floats at 300 m were observed to loop 26 of the time with anticyclonic rotation observed about twice as often as cyclonic rotation characteristics of anticyclonic rotation at 300 m included median swirl speeds of 14 cm s for diameters of 59 km and 14 day periods long lived 70 days and at least 8 consecutive loops anticyclonic loopers are identified as california undercurrent eddies or cuddies one cuddy was observed to move southwestward 1650 km over a period of 520 days before observations ended kinematically cuddies are similar to mediterranean water eddies meddies in the iberian basin except that meddies are somewhat stronger larger and deeper over the slope most cuddies were formed between either pt sur and pt reyes or cape mendocino and cape blanco the region north of cape mendocino is estimated to generate six cuddies each year these eddies form from waters on the inshore side of the california undercurrent as they move past cape mendocino topographic drag is the most likely formation mechanism two of eight deep floats were observed to loop one anticyclonically 1545 m for 279 days and the other cyclonically 1167 m for 192 days looping for these floats ended near taney seamounts

baroclinic eddy interaction with isolated topography point vortex and finite difference methods are used to study baroclinic eddies advected into weak and strong encounters with topography it is argued that weak interactions often scatter radially symmetric eddies into generalized hetons the dipole moments so generated within the eddy result in eddy propagations at various angles to the current strong interactions can result in the complete separation of the upper and lower layer circulations subsequent evolution in this case depends on many factors although strong topographic obstacles i e seamounts permit a reorganization of the centers into a coherent structure weaker topography confined to the deep ocean can disrupt the lower center although the upper center typically survives disassociation of the centers with both retaining their integrity is also possible heton generation can occur for eddies with weak lower layer expressions demonstrating a potentially strong control of shallow eddy propagation by deep sea bathymetry analytical and numerical estimates of the induced propagation speeds are sizable arguing topographic scattering is a potentially powerful mechanism influencing eddy propagation

eddy generation in the mediterranean undercurrent abstract in the framework of the european union mast iii project canary islands gibraltar azores observations 24 rafos floats were deployed in the mediterranean water mw undercurrent off south portugal between september 1997 and september 1998 a preliminary analysis of this lagrangian approach complemented with xbt and current meter data show some of the major aspects of the flow associated with the undercurrent as well as associated eddy activity floats that stayed in the undercurrent featured a downstream deceleration and a steering by bottom topography three meddy formations at cape st vincent could be isolated from the float data the dynamical coupling of meddies and cyclones was observed for a considerable period of time the generation of two dipolar structures in the portimao canyon region also was observed with the float data a major bathymetric relief gorringe bank was not only an important constraint to the eddy trajectories and of the flow at the mw levels but also a site for meddy formation

kinematics and dynamics of a mediterranean salt lens abstract two surveys of the absolute velocity field of an eddy of mediterranean water meddy in the eastern north atlantic were conducted one year apart in 1984 and 1985 two velocity regimes were revealed within the radius of maximum velocity the meddy rotated anticyclonically as a solid body with a depth dependent rotation period near 6 days at its mid depth 1000 m one year later the radius of the core had decreased by one third the rotation rate of the lens also decreased except at its mid depth where there was a small but perceptible increase there was a sharp 5 km or less transition between the core and the outer region where the velocity decayed exponentially with radius a strong potential vorticity front due to the abrupt change in sign of horizontal shear kept the core isolated from the outer region potential vorticity was nearly constant within the upper confines of the core over the study period whereas there was a notable increase in potential vorticity in the lower portion of

in situ study of intensity of weathering induced fractures and methane emission to the atmosphere through these fractures abstract the width and length of weathering induced fractures horizontal distances between through channels formed due to weathering number of through channels in a very weak sandy shale surface layer and methane emission through these fractures to the atmosphere are studied sampling from the studied weathered sandy shale exhibiting very low rock quality rqd in situ directly in the walls of five surface vertical boreholes 1 5 m deep using an original measurement device the radial expansion of measurement devise due to air pressure is used to press wet gypsum into the fractures in borehole surface in order to make gypsum casts of the fractures semi empirical relations between methane volumetric flow rate into the atmosphere through weathering induced fractures and dimensions area and number of weathering induced fractures and gas pressure difference are obtained the comparison between the values of gas seepage through the fractures and rock matrix is performed

formation of fractured zones in overburden due to longwall mining the fractured zones caused by mining were studied in the overburden of the torezko snezhnyanskaya area ukraine through the change in natural gas emission from these zones during longwall coal excavation zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings the maximum heights of the zone of interconnected fractures and separate horizontal fractures may reach 19 41 and 53 92 times the thickness of the coal seam respectively it was found that the ratio between the maximum height of the zone of interconnected fractures and the thickness of the extracted coal seam increases with the increasing number of rock layer interfaces and decreases with the increasing stiffness of immediate roof it is shown that the growth of the zone of interconnected fractures occurred during 17 39 days at an average rate of 0 94 1 97 m day 1 and it was accompanied by increasing methane emission from overburden observation shows that the formation of separate horizontal fractures began only 11 49 5 days after the height of the zone of interconnected fractures reached its maximum value formation of separate horizontal fractures in overburden over the longwall excavation occurred as a stepped process from lower to upper sandstone sandy shale layer interfaces in the direction of the ground surface

observed evolution of a california undercurrent eddy abstracta california undercurrent eddy cuddy was repeatedly surveyed using multiple seagliders for over three months found and tracked off of the washington vancouver island coasts this cuddy t

a shallow subtropical subducting westward propagating eddy swesty swesty is a shallow subtropical subducting westward propagating eddy that was observed to move across the eastern basin of the north atlantic at a latitude near 25 n the eddy was first detected by the movement and temperature of a drogued argos buoy near 23 w 26 n in february 1993 by december 1993 the drogued buoy had moved 1000 km westward to 33 w and a winter eddy survey was made from rrs charles darwin the eddy was about 100 km in diameter and had a centre water mass core at a depth of 190 m with characteristic temperature 19 9 c and salinity 37 06 psu but was best resolved by properties related to vertical gradient structure e g brunt vaisala frequency temperature perturbation structure the eddy was particularly flat with a height to width aspect ratio of only ca 0 14 and a vertical decay scale of ca 250 m for temperature displacements maximum azimuthal currents were ca 16 cm s 1 at a depth of 175 m and the eddy azimuthal transport was only 3 sv however the potential vorticity in the eddy core was 1 5 x 10 11 rad ms 1 comparable with other deep anticyclonic lenses and lower than background values by a factor of ten the eddy appeared slightly elliptical with a detectable sea surface cooling ca 0 2 c over its centre three argos buoys with drogues set at a depth of 200 m were deployed near the centre of the eddy and one buoy continued looping westward for a further ca 800 km the drogued argos buoy results showed that the eddy moved westward at ca 100 km month 1 and about half this westward rate was attributed to self propagation during this ca 1650 km continuously drogued journey the eddy only slipped southward by about one degree of latitude and so was perhaps resisting the southward component of flow of the subtropical gyre the buoy results suggested that the central rotation rate increased with time but the eddy became smaller the initial rotation period of the central core was ca 8 d giving a corresponding normalized relative vorticity of 0 3 about 400 d later the period of core rotation was ca 5 d with normalized relative vorticity of 0 5 some of the increase in central rotation rate was attributed to subduction effects variance spectra and filtered components of velocity were derived from the buoy positions kinetic energy levels in the eddy ca 73 cm 2 s 2 were markedly elevated with respect to background levels ca 29 cm 2 s 2 the core properties of the eddy indicated a winter formation near 27 n 22 w and hydrographic sections showed that the eddy would be sinking at a rate of about 40 m a 1 by the second year the subducted water parcel the eddy core was sufficiently deep below the surface of the ocean to escape further effects of winter mixing

prediction of the height of destressed zone above the mined panel roof in longwall coal mining abstract longwall mining is one of the most widely used underground mining methods most suitable in relatively flat lying thick and uniform coalbeds due to extraction of the coal seam the panel roof strata above the mined zone will be destressed and then the roof loads will be redistributed and transferred to the front abutment and neighboring solid sections with higher load bearing capacity where the adjacent access tunnels and the corresponding barrier pillars are located the height of destressed zone hdz in this paper is taken as equivalent to the combined height of the caving and fracturing zones above the mined panel roof induced due to longwall mining the height of destressed zone plays a vital role in accurate determination of the amount of loads being transferred towards front abutment and panel sides the paper describes the mechanism of development of the height of this zone finally five new simple yet conclusive mathematical approaches to estimate the height of destressed zone are presented the results of the methods proposed are compared with each other and with the comparable methods the methods proposed are further compared and verified with in situ measurements reported in the literatures the comparative results confirm the agreement that exist among the methods and those with the in situ measurements as well finally the methods have shown that in short term the height of destressed zone ranges from 6 5 to 24 times the extraction coal seam height while in long term the height of destressed zone ranges from 11 5 to 46 5 times the extraction coal seam height therefore beyond this height the overburden pressure will be transferred towards the front abutment the adjacent access tunnels the intervening barrier pillars as well as the panel rib sides

localization of mining induced horizontal fractures along rock layer interfaces in overburden field measurements and prediction the locations of mining induced horizontal fractures along rock interfaces in the overburden of donetsk coal basin were identified using an original experimental device the device traps methane from horizontal fracture zone 100 fold coal seam thickness over an active longwall mining excavation presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden such as thickness uniaxial compressive strength of overburden rock layers location of rock layer interfaces and thickness of extracted coal seams as a result a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations

an algorithm to detect isolated anomalies in three dimensional stratified data fields with an application to density fields from four deep basins of the baltic sea 1 a new approach to describe the mesoscale variability caused by eddies in terms of the integral properties of all eddies contained in a certain ocean volume is suggested for this purpose a pattern recognition algorithm to detect isolated anomalies in three dimensional stratified data fields was developed and is introduced in detail an application to 12 eddy resolving density fields acquired in the framework of the german russian project mesodyn in four deep basins of the baltic sea namely the arkona basin the bornholm basin the stolpe furrow and the eastern gotland basin demonstrates that the algorithm works properly the most remarkable finding of this application is that the volume fraction occupied by the isolated anomalies or eddies is constant it amounts to about 12 of the total volume for each data field no matter whether the stratification corresponds to a summer or a winter situation many possible applications of the pattern recognition are proposed to document its general usefulness finally the main features of the algorithm and possible extensions are discussed extensively

observations and laboratory modeling of meddy generation at cape st vincent abstract the amuse canigo and ampor observations provided a large amount of subsurface float data showing evidence of several distinctly different flow behaviors within the mediterranean water layers in the vicinity of cape st vincent southwest portugal some of the floats followed the coastline and moved northward and some were trapped either in anticyclonic lenses of mediterranean water meddies generated at cape st vincent or in cyclonic structures these observations clearly indicated that the anticyclones were accompanied by cyclones at least during their early stages as the dipolar structure moves away from the cape the cyclone tends to shift slowly away from the anticyclone while decaying so that after some time only the meddy persists these in situ observations are compared with large scale laboratory experiments and the agreement between the two sets of observations is remarkably good near the cape and shortly after the generation the nondimensional radius relative vorticity and r

a tale of two eddies diagnosing coherent eddies through acoustic remote sensing 1 a 38 khz vessel mounted acoustic doppler current profiler is used to explore in detail the dynamics of an anticyclonic and a cyclonic eddy during two transits of the cruise vessel explorer of the seas from the caribbean to new jersey in july 2007 the radial scale of the two eddies is similar but whereas the cyclone is strongly surface intensified the anticyclone has its maximum expression with near solid body rotation between 200 and 800 m depth the anticyclone has a minimum in relative vorticity very close to f at 800 m depth and the cyclone has a maximum of about 1 6 f close to the surface where f is the local coriolis parameter by integrating the momentum equation the geopotential anomaly field and hence the potential energy of the eddies can be determined quite accurately which means that the kinetic and potential energy of the eddies can be determined purely through acoustic remote sensing given a density profile just outside the eddy one can integrate the gradient wind equation to obtain an estimate of the density and hence potential vorticity fields through the two eddies the acoustic backscatter patterns in the eddies are quite distinct from the surrounding waters the backscatter intensity of the main scattering layer at 600 m depth decreases by 10 db in the core of both eddies in the cyclonic eddy three identifiable scattering layers in the main thermocline show a strong tendency for the scattering layer to track the shoaling density structure toward the center of the eddy

meddies and decadal changes at the azores front from 1980 to 2000 twenty years of time series observations from the deep sea mooring kiel276 are used to obtain information on the frequency and propagation of meddies mediterranean water eddies on long term changes in flow properties and on a possible relation to the north atlantic oscillation the mooring was set at the nominal position 33 n 22 w at a water depth of more than 5200 m in the northern canary basin it is located near the southern boundary of the azores current ac which is part of the north atlantic subtropical gyre and also in the large scale mediterranean water mw tongue originating from the strait of gibraltar the amplitudes of time varying vertical quasi geostrophic modes and the correlation of current and temperature changes at levels in the mw and the north atlantic central water above are used to identify meddies a total of 10 meddies passed the mooring during the period 1980 2000 half of the events can be related to earlier observations directional changes in meddy related velocities are used to estimate speeds and directions of meddy propagation directions of propagation are very homogeneous with all the 10 meddies observed propagating with a southward velocity component within a sector of 90 and typical speeds are 2 3 cm s meddy occurrence was uneven in time with six meddies found during the first four years and only four meddies during the remaining 16 years decadal changes show the annual mean and the fluctuating kinetic energy levels at the site changing from lower values in the 1980s to high values in the 1990s this change appears to be correlated with variations in the north atlantic oscillation nao index with a delay in oceanic response of about 3 years a conceptual model of ac meanders is used to identify meander signals in the upper layer time series the ac axis appears to be closer to the site during the 1990s than during the preceding decade and indicates a southward or southwestward displacement of the ac with increasingly positive values of the nao index meddy frequency is lower when the ac gets closer from the north a reduction in meddy occurrence in the region just south of the ac is possibly caused by the shear induced blocking of some meddies crossing the front from the north

the mediterranean water tongue and its chlorofluoromethane signal in the iberian basin in early summer 1989 hydrographic observations from the iberian basin demonstrate the variability of water masses in upper and intermediate layers the surveyed area embraces the internal front between water masses from higher latitudes and the mediterranean outflow exhibits several isolated mediterranean eddy meddy structures at middepth and displays the virtual source region for the mediterranean water mw tongue off the portuguese continental slope the description is enhanced by additional chlorofluoromethane measurements which show anomalously high concentrations at middepth due to mixing of mw with the overlying atlantic waters in the gulf of cadiz the geostrophic stream function shows several meddylike features that not only are remarkably extended in the depth range of the mw but are also correlated with surface height anomalies

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

bulking factors and extents of caved zones in weathered overburden of shallow abandoned underground workings abstract a comparison between the bulking factor and height of the caved zone for different weathered subsurface rocks over shallow abandoned mines and for strong rocks at intermediate and large depths of longwall mining is performed in this study vertical boreholes drilled from the ground surface have been used to detect the height of caving in weathered w and very weathered vw rock mass overlying abandoned underground workings at a shallow depth and then to calculate the bulking factor it is found that key parameters that control the bulking factor k and the ratio between the heights of caving and mining h h are different for w and vw rocks in w rocks such parameters are the rock strength of immediate roof and rock porosity whereas those for vw rocks are rock quality designation rqd and standard linear fracture intensity p10 it is argued that h h in vw rocks increases according to linear logarithmic law with an increasing ratio p10 rqd in the immediate roof and p10 in four rock layers over the immediate roof observations show that vw rocks exhibit smaller values of k 1 06 1 165 and larger h h 6 07 15 6 compared to w rocks having 1 09

estimation of methane emission from shallow gas bearing sandstones abstract this paper presents exponential model created by the author to estimate gas flow time relationships for shallow methane bearing donetsk sandstones in donetsk ukraine such estimation is indispensable in case of passing subway tunnels through these sandstones the proposed model involves not only time but also a ratio between average widths of shallow fractures in sandstones and average horizontal distances between these fractures it is revealed that an increase in this ratio leads to an increase in gas volumetric flow rate acceleration of gas emission and an increase in the volume of methane emitted from borehole it is shown that gas flow vs time curves obtained for 17 boreholes drilled from the ground surface through sandstones are similar to those estimated by the proposed model observations show that the volume of methane extracted from each borehole is between 161 m3 and 673 m3 and maximum value of volumetric flow rate is ranged from 0 00265 m3 min to 0 0455 m3 min

meddy trajectories in the canary basin measured during the semaphore experiment 1993 1995 as part of the structures des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore experiment four mediterranean water eddies meddies were identified in the canary basin and tracked with freely drifting rafos floats one large and energetic meddy discovered 1700 km west of cape saint vincent portugal set a distance and speed record as it translated another 1700 km southwestward at 3 9 cm s during 1 5 years this meddy traveled 57 of the distance from cape saint vincent toward the spot mcdowell and rossby 1978 found a possible meddy north of the dominican republic two meddies were observed to interact with the azores current as they passed underneath or through it three meddies collided with tall seamounts which seemed to disrupt the normal swirl velocity perhaps fatally in two cases one meddy appeared to bifurcate when it collided with seamounts