the separate roles of geostrophic vorticity and deformation in the midlatitude occlusion process abstract separate vector expressions for the rate of change of direction of the potential temperature gradient vector resulting from the geostrophic vorticity and geostrophic deformation referred to as qvr and qdr respectively are derived the evolution of the thermal structure and forcing for quasigeostrophic vertical motion in an occluded cyclone are investigated by examining the distributions of qvr and qdr and their respective convergences the dynamics of two common structural transformations observed in the evolution of occluded cyclones are revealed by consideration of these separate forcings first the tendency for the sea level pressure minimum to deepen northward and or westward into the cold air west of the triple point is shown to be controlled by the convergence of qvr which is mathematically equivalent to thermal wind advection of geostrophic vorticity a well accepted mechanism for forcing of synoptic scale vertical motion second the lengthening of the occluded thermal ridge and surf

meridional and downward propagation of atmospheric circulation anomalies part ii southern hemisphere cold season variability abstract as in the northern hemisphere there exists a simultaneous poleward propagation of temperature anomalies in the stratosphere and equatorward propagation in the troposphere in the southern hemisphere s cold season it takes about 110 days for anomalies of one polarity to propagate from the equator to the pole or half the period of the complete cycle nearly twice as long as in the northern hemisphere the earlier poleward propagation of temperature anomalies in upper levels compared with those in lower levels results in an apparent downward propagation in the stratosphere accompanying the poleward and downward propagating warm cold anomalies is a successive leveling steepening of isentropic surfaces reflecting a simultaneous reduction strengthening of the meridional temperature gradient and increase decrease of the vertical static stability following changes in the thermal fields are poleward and downward propagating zonal wind anomalies of the opposite sign the arrival of the pole

validation of models and empirical equations to estimate deformations in jointed rock through the monitoring of a 40 storey tower foundation abstract there is a pressing need in rock mechanics for the calculation of deformations and stresses of structures in rock with this aim the rock mass modulus must be estimated and a model chosen to perform the calculations monitoring the foundation of twin towers in tenerife island has allowed validating both the rock mass modulus estimated from empirical equations and the model in this paper only the second tower tower n with a structural height of 137 4 m above foundation has been studied because the first tower had been previously presented by justo et al int j rock mech min sci 2006 43 267 81 the foundations of both towers are supported by jointed vesicular and weathered basalt and scoria the parameters have been deduced from the simple empirical equations proposed by several authors as a function of geological strength index gsi or rock mass rating rmr three dimensional elastic and advanced elasto plastic finite element fe programs have permitted calculation of the displacements of tower n the stresses in the slab and the factor of safety fos of the excavation the installation of rod extensometers at different depths below the slab has permitted comparison between measured and calculated displacements good fit has been obtained in this type of rock these results increase our confidence in the use of classification schemes to estimate the deformations in jointed rock in construction processes that involve unloading reloading it is important to use a material model that considers these processes the use of advanced elasto plastic methods increases the calculated settlements even if there are no failure points as the pre consolidation stress and the mobilized angle reached during the excavation phase are exceeded at many points during the loading phase tension cut off points also increase deformations with respect to linear elastic behaviour the hardening soil model improves fit between measured and calculated settlements as well

a new look at deformation as a diagnostic for large scale flow abstractdeformation plays a key role in atmospheric dynamics because it provides a dynamical measure of the interaction between different scales such as in frontogenesis a climatology of deformation constructed from interim ecmwf re analysis era interim data 1979 2013 reveals four main processes associated with deformation 1 frontogenesis at lower levels 2 movement and evolution of jet streams in the upper troposphere 3 orographic blocking and 4 rossby wave breaking the merits of deformation as an additional perspective are discussed for these processes on the basis of case studies and composite analyses in conjunction with analytic solutions this study shows that deformation can be used to unambiguously detect orographic blocking through the local strength of the flow diversion around orography moreover the deformation signature for orographic blocking observed in case studies and composites closely resembles the analytic solution for two dimensional flow around an obstacle the climatolo

predicting the deformation moduli of rock masses abstract predictive empirical models for the mechanical properties of rock masses have been used in rock engineering because direct measurement of the properties is difficult due to the presence of discontinuities such empirical models are open to improvement because they are based on collected data the purposes of the present study are to assess the existing empirical equations and to develop a new empirical approach for this reason in the first stage of the study the prediction performance of the existing models proposed for predicting the deformation modulus of rock masses were evaluated statistically by using a database including 115 data values obtained from in situ plate loading and dilatometer tests a new empirical approach with higher prediction capacity than the existing empirical models was developed in the subsequent stage of the study the new empirical model considers the modulus ratio of intact rock e i ucs rock quality designation rqd and weathering degree wd although data obtained from very weak and weak rock masses were included in the development of the new empirical equation the type of rocks employed in the study were limited therefore a crosscheck between the new empirical equation and previous empirical approaches should be performed in the design stage

high archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3 5 ga swaziland supergroup south africa new and compiled oxygen isotope data combined with the results of geological and sedimentological studies demonstrate that enclaves of synsedimentary to very early diagenetic cherts are widely preserved in the 3 5 3 2 ga swaziland supergroup barberton greenstone belt south africa the low 1 8 o values of these cherts indicate extremely high ocean temperatures of 55 85 c previously the large depletion in 1 8 o shown by all barberton cherts relative to their phanerozoic counterparts has been attributed to low 1 8 o in archean oceans chert formation during late diagenesis wholesale loss of 1 8 o during alteration and or regional silicification of sediments around hot springs these alternative explanations are not compatible with the new results cherts in the onverwacht group display an isotopic stratigraphy that is inversely repeated in conglomerates in the overlying fig tree and moodies groups demonstrating that the chert 8 0 o values were fixed prior to archean uplift and erosion which started at 3 26 ga the maximum 1 8 o value in barberton cherts 22 is lower than the minimum values 23 in phanerozoic bedded cherts precluding late diagenesis as the explanation of the overall low 1 8 o values regional metamorphic hydrothermal or long term resetting of original 1 8 o values is also precluded by preservation of 1 8 o values across different metamorphic grades and by systematic 1 8 o differences among interbedded chert types stratigraphic units and conglomerate clasts the 7 1 8 o variation of these archean cherts is similar to that of phanerozoic deep sea cherts formed when opal converted to microquartz during burial but the actual archean values are 10 lower marine opal was apparently converted to microquartz during burial to depths of 1 km cherts with 1 8 o 15 reflect conversion during deepest burial or in local areas of enhanced geothermal gradient and or hydrothermal activity cherts with higher 1 8 o values formed during early diagenesis and indicate an extremely hot archean ocean and surface environment

location and interaction of upper and lower troposphere adiabatic frontogenesis abstract both upper air and surface frontogenesis have often been depicted as processes whose dynamics could he reduced to 2d balanced problems in which self sharpening configurations could be highlighted this paper reports on a 3d adiabatic simulation of a baroclinic wave life cycle great care has been devoted to the vertical resolution allowing for a good description of both surface and upper air frontogenesis the authors introduce a kinematic diagnostic q vector that permits the identification of frontogenetic areas in such complex 3d flows where classical low rossby number balance conditions can be violated relations and specificity with respect to frontogenetic forcing diagnostics are discussed first q is used for surface frontogenesis where it describes well the actual frontal activity including the complex warm frontal seclusion process upper air frontogenesis is also investigated both in terms of this kinematic diagnostic or in terms of potential vorticity displacements on isentr

far upstream precursors of heavy precipitation events on the alpine south side this study examines the upper level flow pattern that foreshadows the comparatively frequent co occurrence of heavy precipitation events on the alpine south side together with potential vorticity pv streamers aloft over western europe it is hypothesized that each streamer is itself preceded by a dynamically distinctive and a thermodynamically active flow associated with the space time development and the ultimate breaking over europe of synoptic scale rossby waves the ecmwf european centre for medium range weather forecasts era 40 dataset is used to examine the nature of a streamer s coherent precursor pattern by deriving seasonal composites of refined hovmoller diagrams the upper level pattern of the pv and its gradient and mid tropospheric diabatic heating for the autumn and winter seasons the composites reveal a significant and coherent wave packet precursor signal in the pv field that can be traced back 1 week to the central and eastern pacific contemporaneously the coherent signatures in the composite pv gradient field and diabatic heating fields are conducive to triggering and or supporting the wave signal and also contribute to subsequent downstream wave breaking in spring the composite precursor pv signal appears over and propagates eastward from the atlantic basin and its limited zonal extent is attributed to the lack of a coherent pv waveguide in summer the signal appears essentially in situ in the hovmoller analysis but extends across the atlantic basin in the pv composite results an indication is also provided of the extent to which the composite characteristics are evident in two individual events and note is made of the study s implications for medium range forecasting copyright 2008 royal meteorological society

palaeoclimatology evidence for hot early oceans reply robert chaussidon the possibility of a change in 18o values of the oceans has been discussed for the past 30 years1 and the comment by shields and kasting2 does not really bring any new insight into this issue the carbonate 18o curve3 is indistinguishable from that of cherts and shows a huge scatter caused by local geological processes this scatter in 18o up to 20 at a given age far exceeds the sensitivity of the isotope thermometer about 2 per 10 c it therefore prevents any precise additional test of the model and no consensus was ever reached in the literature on this debate from oxygen isotope data alone our approach4 by contrast was to try to find another isotopic proxy 30si that could bring new and independent constraints to test the hypothesis of hot oceans in the early precambrian our interpretation of the 30si values in terms of temperature is fully coherent not only with the 18o of cherts but also with that of marine carbonates and certainly does not overlook these data in addition we indicated4 that our sample set has not the time resolution that would be necessary to look for an effect on silicon isotopes of precambrian global glaciations no chert samples from such periods were analysed

method for estimating the deformability of heavily jointed rock masses determination of the deformability of jointed rock masses is an important and challenging task in rock mechanics and rock engineering in this paper simple expressions are derived for estimating the equivalent isotropic deformation properties of heavily jointed rock masses using the methodology of equivalent continuum approach the derived expressions are compared with two analytical relations in the literature and the field test data relating rock quality designation rqd and deformation modulus ratio em er where em and er are the deformation modulus of the rock mass and the intact rock respectively the derived expressions are in reasonable agreement with the existing analytical relations in the literature and satisfactorily predict the range of the field rqd versus modulus ratio em er data finally two examples are presented to demonstrate the application of the derived expressions by applying them to estimate the deformation modulus of jointed rock mass at two sites the results of the paper

in situ measurements of rock mass deformability using fiber bragg grating strain gauges abstract in order to examine how the mechanical properties of a rock mass vary from the centimeter to meter scale we performed two field point loading tests 89 kn and 890 kn to determine the in situ modulus of deformation of a rock mass the experimental setup is analogous to plate jacking type tests but instead using a point load the experiments were done in the poorman formation on the 4100 level 1250 m underground of the sanford underground research facility surf at the site of the former homestake gold mine in lead sd for comparison with in situ values we also conducted laboratory mechanical tests and used two geotechnical classification systems to evaluate rock stiffness the in situ modulus of deformation increases with depth into the rock mass this increase in stiffness is a result of the differences in mechanical properties due to the effect of excavation of the underground space near the surface 0 1 2 m depth the rock is softest due to induced fractures and damage from blasting beyond this damaged zone is the stress relief zone 1 2 1 5 m depth where open joint sets affect rock stiffness and beyond that lies the undisturbed zone 1 5 m depth where the rock is the stiffest if done properly in situ measurements of rock stiffness are a valuable tool to fully characterize the gradient in stiffness of a rock mass which laboratory tests or geotechnical classification systems do not fully capture

a review of the structure and dynamics of upper level frontal zones abstract this article presents a review of upper level fronts with the intent of synthesizing observational and modeling studies into a conceptual and dynamical description of these fronts and their evolution relative to the life cycle of midlatitude baroclinic waves the discussion begins by tracing present day concepts concerning the structure of upper level frontal systems which are based on composite analyses of radiosonde and aircraft data from their origins in the pioneering analyses of upper air data in the 1930s perspectives from scales both smaller and larger than upper level frontal systems are provided respectively by considering the effects of turbulent processes on frontal structure and dynamics and by relating variations in frontal structure to the evolution of the baroclinic waves that provide the dynamical environment for upper level frontogenesis the dynamics of upper level fronts are shown to comprise the interactions between the primary geostrophic and secondary ageostrophic cir

neoarchean deep marine paleotemperature evidence from turbidite successions abstract numerous studies using various proxies have been conducted to ascertain the temperature of the archean ocean if as some of these investigations indicate the archean ocean was relatively hot with a cooling trend through time to the phanerozoic this would have had consequences for sediment erosion transport and deposition substantially higher surface temperatures would cause the viscosity of water an important variable in defining flow hydrodynamics to be lowered in particular less viscous water would have affected the development of current ripples these are dependent on the existence of the laminar sublayer as the sweeps of turbulent eddies impinging on this layer build small mounds that evolve into ripples the laminar sublayer thins at higher temperatures allowing sand grains of smaller sizes to destroy it at modern surface temperatures current ripples cannot form in coarse grained sands and if a hotter ocean existed in the archean it would have inhibited current ripple formation in medium grained sands and possibly even fine grained sands examination of numerous neoarchean deep water turbiditic successions in western superior province led to the realization that ripple cross lamination is rare in all these units as the formation of current ripples is dependent on the flow depositing sediment of the proper grainsize velocities in the appropriate range and existence of a viscous sublayer and the first two prerequisites were met during deposition from these decelerating turbidity currents the existence of the viscous sublayer during the majority of flows must be questioned the occurrence of current ripple cross lamination in well exposed turbidites of the neoarchean mckellar harbour formation was quantified and found to be substantially less than the abundance of ripple cross lamination present in phanerozoic turbidites indicating that the neoarchean deep ocean may have been considerably warmer than the deep ocean of today

palaeoclimatology evidence for hot early oceans arising from f robert m chaussidon 969 972 2006 10 1038 nature05239 robert chaussidon reply the oxygen isotopes in sedimentary cherts siliceous sediments have been used to argue that the precambrian oceans were hot with temperatures of up to 70 c at 3 3 gyr before present1 robert and chaussidon2 measure silicon isotopes in cherts and arrive at a similar conclusion we suggest here that both isotope trends may be caused by variations in seawater isotope composition rather than in ocean temperatures if so then the climate of the early earth may have been temperate as it is today and therefore more consistent with evidence for precambrian glaciations and with constraints inferred from biological evolution

an example of estimating rock mass deformation around an underground opening using numerical modeling abstract in rock engineering rock strength is regarded as an important rock mass parameter and it is widely estimated using the uniaxial compressive strength ucs test a ucs test in laboratory requires sampling and preparation of core samples which necessitates time consuming and expensive studies furthermore preparation of cores is almost impossible for a weak rock material taken from foliated laminated or thinly bedded rock masses of low rock quality designation rqd values 0 20 in this case determination of ucs by laboratory test may be impossible in compliance with isrm or astm standards to overcome this difficulty indirect tests such as point load index pli schmidt hammer sh rebound number tests are often employed to predict the ucs however indirect tests are likely to yield ucs values with large standard deviations depending on the geological origin of the rock mass the block punch index bpi has recently been developed to overcome the drawbacks of ucs and indirect tests and to minimize the errors arisen from the structural deficiencies and large standard deviations in this study determination of rock mass behavior in laminated foliated bornova melange yellowish brown flysch and grayish black flysch and well jointed yamanlar volcanics altindag formation where the second phase of the izmir metro tunnels was excavated is aimed the bpi ratings were directly used in rmr calculations and indirectly used to estimate the ucs values of rock materials then the obtained results were input into numerical models along with the rock mass strength ucs rm and deformation modulus of rock mass e rm the results obtained from the numerical models agreed with that obtained results from inner tunnel convergence and ground settlement measurements

tropopause folds in era interim global climatology and relation to extreme weather events tropopause folds are intimately linked to upper level frontogenesis and jet stream dynamics they play an important role for stratosphere troposphere exchange the dynamical coupling of upper and lower tropospheric levels and for generating severe weather events this study presents a global climatology of tropopause folds using era interim reanalysis data from 1979 to 2012 and a refined version of a previously developed 3 d labeling and fold identification algorithm this algorithm objectively separates stratospheric and tropospheric air in complex situations e g in regions with strong low level inversions and in extratropical cyclones where diabatically generated potential vorticity anomalies typically occur three classes of tropopause folds are defined shallow medium and deep and their geographical distribution vertical extent and seasonal cycle are investigated most shallow folds occur along the subtropical jet stream in agreement with previous studies hot spots of medium and deep tropopause folds are found west of australia and along the coast of antarctica in the southern hemisphere and around the east coast of north america in the northern hemisphere seasonal cycles show maxima in winter for all fold classes medium and deep folds are frequently associated with surface wind gust and precipitation extremes as quantified for folds over the southern indian ocean wind gust extremes occur mainly in an elongated band upstream and equatorward of folds whereas precipitation extremes occur mainly east and poleward of folds overall in the considered region about 20 of medium folds and 33 of deep folds are associated with surface wind or precipitation extremes in the vicinity of the fold

the gulf stream north wall ageostrophic circulation and frontogenesis abstracteastward zonal jets are common in the ocean and atmosphere for example the gulf stream and jet stream they are characterized by atypically strong horizontal velocity baroclinic vertical

frontal wave cyclogenesis in the north atlantic a climatological characterisation the ambient conditions during cyclogenesis on fronts in the north atlantic na are characterised climatologically in the era interim dataset these secondary cyclones which grow from frontal waves are typically small in scale shallow and deepen rapidly and pose a challenge to forecasters and numerical weather prediction models frontal wave development has been studied intensively in the past based on observations e g fastex real case studies or analytical models in this study frontal wave cyclogenesis is studied from a climatological perspective and is detected by a combination of two automated identification methods for the period between 1979 and 2014 a climatology of frontal wave cyclogenesis is presented horizontal composites provide an estimate of the climatological mean of conditions during frontal wave cyclogenesis which may prove useful in the assessment of the realism of proposed idealized models of frontogenesis the findings are also compared with assumptions made in earlier idealized studies of frontal waves the composites reveal coherent structures of diabatically generated low level pv in the lower troposphere neutral moist static stability at cyclogenesis and an ambient lower troposphere close to saturation the vertical pv structure in the east na is more vertically aligned than in the west na and pv anomalies from the upper and lower levels reach deeper into the mid troposphere which indicates an enhanced phase lock between the two anomalies previous studies suggest the existence of an upper limit of along frontal stretching above which frontal wave development is strongly suppressed the presented multi decadal analysis confirms its existence in a range between 0 6 and 0 8 10 5 s 1 finally a climatology of along frontal stretching for the na is presented and compared to the fraction of cyclogenesis forming on frontal waves

clinogenesis and frontogenesis in jet stream waves part i analytical relations to wave structure abstract the circulations that alter the baroclinic structure along wave shaped currents are investigated for gradient and nongradient flow in the case of deformations which result in an increase of baroclinity and vertical shear and with a jet stream lateral shear the process is called clinogenesis in distinction to frontogenesis fg in which static stability is also increased in gradient flow convergence and confluence are related to curvature variations and are also wind speed dependent hence in a wave on the jet stream lateral shears result in solenoidally indirect tilting on the cyclonic flank in the midtropospheric airstream from a ridge to a trough this and the other clinogenetic processes of confluence and canting turning of wind with height are related to the structure and dimensions of a jet stream wave these features are numerically simulated in part ii where additional consequences of ageostrophic flow upon fg are examined clinogenesis is also discussed in more general te

poisson s ratio values for rocks abstract compared to other basic mechanical properties of rocks poisson s ratio is an elastic constant of which the significance is generally underrated yet in rock mechanics there is a considerable number of diverse areas which require a prior knowledge or estimation of the value of poisson s ratio this paper examines the values and applications of poisson s ratio in rock mechanics following an historical account of the initial controversy whether it was a material constant or not the effects of poisson s ratio in the elastic deformation of materials intact rocks and rock masses are briefly reviewed also the reported values of poisson s ratio for some elements materials and minerals are compiled while typical ranges of values are presented for some rocks and granular soils finally poisson s ratio classifications are recommended for isotropic intact rocks

microscale oxygen isotope variations in 1 9 ga gunflint cherts assessments of diagenesis effects and implications for oceanic paleotemperature reconstructions abstract variations in the oxygen isotope composition 18 o of five cherts from the 1 9 ga gunflint iron formation canada were studied at the micrometer scale by ion microprobe to try to better understand the processes that control 18 o values in cherts and to improve seawater paleotemperature reconstructions gunflint cherts show clearly different 18 o values for different types of silica with for instance a difference of 15 between detrital quartz and microquartz microquartz in the five samples is characterized by large intra sample variations in 18 o values 18 o of quartz varies from 4 6 to 6 6 at the 20 m scale and from 12 to 14 at 2 m scale isotopic profiles in microquartz adjacent to hydrothermal quartz veins demonstrate that microquartz more than 200 m away from the veins has preserved its original 18 o value at the micrometer spatial resolution of the ion probe data reveal that microquartz has preserved a considerable 18 o heterogeneity that must be regarded as a signature inherited from its diagenetic history modelling of the 18 o variations produced during the diagenetic transformation of sedimentary amorphous silica precursors into microquartz allows us to calculate seawater temperature t sw at which the amorphous silica precipitated and diagenesis temperature t diagenesis at which microquartz formed that reproduce the 18 o distributions mean range and shape measured at micrometer scale in microquartz the two critical parameters in this modelling are the 18 o value and the mass fraction of the diagenetic fluid under these assumptions the most likely ranges for t sw and t diagenesis are from 37 to 52 c and from 130 to 170 c respectively

determination of deformation modulus in a weak rock mass by using menard pressuremeter abstract the deformation modulus of heavily jointed andesitic rock mass was investigated by using 41 menard pressuremeter test results and geotechnical information obtained from seven geotechnical boreholes the geotechnical borehole logs and laboratory test results provided by a mining company were used for the assessment of rock mass characterization the log and the test results were taken into account in the rock mass classification work the well known empirical equations were employed to predict the deformation modulus of the rock mass the predictions and the pressuremeter test results were compared and their performance indicators were presented non linear multiple regression methods were used for predictive modelling of the deformation modulus of the rock mass by considering the available data rock quality designation rqd discontinuity condition rating dc of the rock mass rating rmr system and uniaxial compressive strength of the intact rock ci were taken into consideration as input parameters in four new prediction equations to be used for determination of deformation modulus one more equation was proposed by the addition of the depth as a predictive parameter the influence of the depth and vertical to horizontal stress ratio k on the deformation modulus was preliminarily examined by using finite element modelling initially the rock mass was assumed to be an isotropic elastic brittle plastic medium later on the rock mass was modelled as a discontinuum by imposing a discrete fracture network dfn keeping all of the mechanical properties constant different depth and k parameters were applied to the pressuremeter models no influence of the depth and k on the deformation modulus was observed for the isotropic medium while the depth contributed to an increase in the modulus in the anisotropic discontinuum analysis the numerical modelling findings constituted a basis for the inclusion of the depth parameter into the new predictions

why the oxygen isotopic composition of sea water changes with time the oxygen isotopic composition of oxygen in minerals and oxygen in water this sea water is determined by interactions with equilibrium fractionation is a strong function of fresh silicate rocks interactions at high temperature varying for many minerals from about

pv frontogenesis and upper tropospheric fronts abstract upper tropospheric fronts and frontogenesis are viewed from a potental vorticity pv perspective the rudiments of this approach are to regard such a front as a zone of strong pv gradient on isentropic surfaces and to treat the accompanying frontogenesis as the process whereby this gradient is enhanced on tropopause transcending isentropic surfaces a case study suggests that this concept of pv frontogenesis provides a concise dynamically based definition of upper level frontal zones and a compact and transparent approach for diagnosing the frontogenesis the concept provides fresh insight on the dynamics of the upper level fronts and has the potential to shed light on related phenomena and processes

possible evidence for episodic epeiric marine and fluvial sedimentation and implications for palaeoclimatic conditions c 2 3 1 8 ga kaapvaal craton south africa abstract the debate on palaeoproterozoic atmospheric composition climate and the timing and nature of the postulated great oxidation event possibly at c 2 3 ga remain matters of debate within precambrian geology this paper contributes to the debate through examination of physical sedimentary structures preserved within two separate groups of sedimentary deposits from the central and northern portions of the kaapvaal craton south africa within the c 2 3 2 1 ga pretoria group study of epeiric marine sandstones and mudrocks magaliesberg and silverton formations c 2 1 ga suggests that fluvial input was predominant over low energy reworking by waves winds and tides this together with extensive evidence for microbial mat growth within the littoral sandstones of the magaliesberg formation points to strongly episodic sedimentation by both marine and fluvial processes within two younger basins belonging to the c 2 05 1 8 ga waterberg group anomalously high palaeoslopes calculated according to standard palaeohydrological methods combined with direct field evidence for sediment gravity flows and sheetflood deposition within an overall braided fluvial setting again suggest episodic sedimentation strongly episodic sedimentation can most easily be reconciled with a greenhouse palaeoclimate at least for that part of kaapvaal at that time taken together these data sets point to the postulate that the generally accepted change from a palaeoproterozoic greenhouse through a great oxidation event c 2 3 ga to less extreme climatic conditions may have been gradational and even diachronous across the earth s cratons at that time

origin and mechanisms of k si metasomatism of ca 3 4 3 3ga volcaniclastic deposits and implications for archean seawater evolution examples from cherts of kittys gap pilbara craton australia and msauli barberton greenstone belt south africa abstract the effects of k si metasomatism during the formation of early archean replacement cherts have been quantified in this study by the investigation of two well known stratigraphic sections the msauli chert mc barberton greenstone belt south africa and the kittys gap chert kgc pilbara craton western australia the kgcs have a dacitic precursor similar to duffer formation dacites pilbara craton while the mcs are derived from al depleted komatiites similar to those from the weltevreden formation barberton greenstone belt mass balance calculations reveal that the volcaniclastic deposits had initial porosities of up to 85 vol for the kgc and of 65 vol for the mc secondary porosities 27 vol mc 8 vol kgc produced during k metasomatism are proportional to the dissolution of fe ca mg rich glass and precursor minerals komatiites have a higher chemical exchange potential than dacites each gram releasing 1 2 mmol fe2 2 8 mmol mg2 1 4 mmol ca2 and 1 1 mmol na to seawater together with 4 4 mmol o2 k metasomatism of 1 g of komatiite further implies an uptake of 0 67 mmol of k and 2 7 mmol of h the highest silica uptake is achieved for the kgc 82 mmol g of precursor this silica enrichment most likely operated in the water column and at the sediment water interface by sorption mechanisms on the surface of detrital particles and particulate organic matter as a result of seawater silica saturation acidic conditions ph 5 5 6 5 and hot temperatures 70 c favored the formation of k rich phyllosilicates by interaction with seawater during the early diagenetic alteration of the volcaniclastic particles the widespread occurrence of k si metasomatism in volcanic and sedimentary rocks can be regarded as a general alteration process of the early archean seafloor with a major influence on seawater composition the highly k selective metasomatism confirms previous studies suggesting that the archean ocean was acidic and probably in equilibrium with a co2 rich atmosphere

determination of geomechanical properties and collapse potential of a caliche by in situ and laboratory tests working in complex grounds have always been difficult for engineering geologists because of the heterogenous nature of such geo materials which results in different behaviors under stresses the caliches outcropping in the adana basin and its close vicinity are selected as the study material because of their highly complex nature and also understanding their mechanical behaviour and collapse potential is too difficult although their aerial extent is large in the region for this reason investigation of the collapse potential and mechanical behaviour of the caliches by applying new approaches besides the conventional in situ and laboratory tests is the purpose of the study the study includes five main stages such as measurements of caliche profiles in situ tests plate loading sampling shooting photographs for photoanalyses and laboratory studies four different levels such as hard pan silty sandy layer gravelly blocky layer and clayey level are described for the caliches employed the hard pan level is a weak rock with an average uniaxial compressive strength of 11 89 mpa while the others have typical soil characteristics a series of plate loading tests are applied on the blocky gravelly level of the caliche to determine the modulus of elasticity the modulus of elasticity and the allowable bearing capacity are determined between 28 6 65 3 and 1 5 2 0 mpa respectively to determine the grain size distribution curve in addition to sieve analyses a photoanalysis technique is also applied and a combination procedure between the results from both sieve analyses and photoanalyses is introduced and the grain size curves for the blocky gravelly level of the caliche are obtained according to the results of collapse potential index tests performed on the samples collected from 20 locations of the study area the soft pan level of the caliche has slight to moderate degree of collapse indices in the final stage various simple and statistically meaningful empirical equations are proposed for the indirect determination of the collapse index by employing simple paramateres

an analysis of frontogenesis in numerical simulations of baroclinic waves abstract using a primitive equation pe model we revisit two canonical flows that were previously studied using a semigeostrophic equation sg model in a previous paper the authors showed that the pe and the sg models can have significantly different versions of the large scale dynamics here they report on the implications of this difference for frontogenesis the program for the study of frontogenesis developed by b j hoskins and collaborators is followed to show how in the pe version of the canonical cases the surface warm front develops before the cold front and why the upper level front is a long nearly continuous feature going from ridge to trough the frontogenesis experienced by an air parcel is computed following the parcel to illustrate better the mechanisms involved as the present calculations are carried out longer than most previous ones the relation of the upper frontogenesis to the formation of the upper level cutoff cyclone is also examined trajectory and three dimensional g

the downstream impact of tropical cyclones on a developing baroclinic wave in idealized scenarios of extratropical transition the interaction of a tropical cyclone with a developing baroclinic wave is investigated in an idealized scenario of extratropical transition et the impact of et is examined by comparing and analyzing two numerical baroclinic wave experiments a traditional experiment in which baroclinic development is excited by a localized upper level perturbation on a realistic jet profile and an experiment in which additionally a model tropical cyclone is inserted south of the jet at the initial time et occurs in a wavy upper level flow while baroclinic surface systems are still weak the characteristic direct impact of et on the midlatitude flow is the formation of a distinct jet streak and the amplification of a ridge trough couplet in the adjacent downstream region the subsequent rapid cyclogenesis downstream is a direct consequence of these upper level flow modifications this faster and stronger development constitutes the amplification of the leading edge of downstream development both the upper level wave pattern and the surface development are subsequently amplified in the region further downstream the formation of the ridge adjacent to the intensified downstream cyclone is analyzed in detail to elucidate the next stage in the downstream dispersion of the et impact ridge building in the et scenario exhibits characteristics distinct from those in the life cycle experiment wave breaking feedback from the modified low level frontal structure and diabatic processes all contribute to the high amplitude wave pattern downstream of et the downstream impact of et is highly sensitive to the initial storm location and intensity the considerable amplification of the leading edge found in the reference experiment is the most widespread and rapidly propagating impact we thus speculate that this leading edge represents an optimal location of the midlatitude circulation where et can lead to the most significant impact on the downstream flow copyright 2010 royal meteorological society

indirect determination of the modulus of deformation of rock masses based on the gsi system today as a result of the increase in the number of large tunnel constructions and underground excavations required for civil engineering and waste disposal and the operation of deep open pit mines determination of rock mass properties has become one of the most important stages in design and construction for rock engineering when rocks and rock masses are classified for geotechnical purposes this needs to be on the basis of strength or static modulus of deformation to give an indication of their stability or deformational response in addition the strength and modulus of deformation are the necessary input parameters of the rock masses to be utilized by numerical methods the modulus of elasticity of the rock material is undoubtly the geomechanical parameter that best represents the mechanical behaviour of rock material a similar conclusion can also be made for rock masses however the modulus of deformation of rock masses should be determined in situ by carrying out special tests which normally implies considerable costs and operational difficulties because of such difficulties the determination of the modulus of deformation of the rock masses continues to attract the attention of rock engineers and engineering geologists given the importance of having the value of the modulus of deformation available and at the same time the operational and economical difficulties mentioned above many researchers mentioned below were led to consider several cost effective and not too time consuming indirect procedures that can provide information on the modulus of deformation these attempts

predictive model for uniaxial compressive strength for grade iii granitic rocks from macao abstract determination of the uniaxial compressive strength ucs of rocks is an important task for rock and geotechnical engineering applications direct measurement is expensive time consuming and even infeasible in some circumstances due to the difficulty in obtaining core samples therefore empirical models are particularly favorable to engineers especially in the preliminary design stage however there is a lack of predictive ucs model for granite of weathering grade iii but it is well recognized to be crucial to the design of pile foundations on granitic bedrocks in this study a reliable predictive model will be developed under the bayesian framework an extensive experimental program was performed in this study to construct a comprehensive database of the measurements of uniaxial compressive strength point load index schmidt rebound hammer value p wave velocity effective porosity specific gravity and dry density it has been proven that the proposed model possesses satisfactory predictive performance

a comparative study of the determination of rock mass deformation modulus by using different empirical approaches abstract the increase in rock engineering projects over the last decade has made an increase in the importance of the determination of the rock mass parameters although properties of rock material are usually determined at laboratory it can also be determined by special in situ tests these in situ tests are both expensive and time consuming therefore empirical equations are developed to estimate rock mass properties by several researchers in numerical modelling rock mass properties are important furthermore controlling the results of models making back analysis and taking the feedback are very important comparison of different empirical equations of deformation modulus of rock mass suggested by different researchers by using field displacement measurements and numerical modelling results is aimed in this study

the palette of fronts and cyclones within a baroclinic wave development abstract a study is undertaken of the concurrent development of fronts and cyclones within a growing baroclinic wave the dynamical framework for the study is that of the semigeostrophic adiabatic flow of a uniform potential vorticity atmosphere that is sandwiched between two horizontal plates on an f plane a three dimensional spectral model is used to examine the growth to finite amplitude of the normal modes of this system for basic states that comprise of a symmetric jetlike baroclinic flow with and without a superposition of a uniform barotropic shear of either cyclonic or anticyclonic vorticity it is demonstrated that the presence of such lateral shear in the ambient environment exerts a profound influence upon the ensuing palette of fronts and cyclones on the synoptic scale this flow component influences the scale and strength of the individual surface highs and lows and also modifies the extent of their lateral drift away from and their relative movement along the baroclinic zone aloft t

analysis and diagnosis of the composition of ageostrophic circulations in jet front systems abstract diagnostic case studies of ageostrophic circulations in upper tropospheric jet front systems are presented using the numerical analyses of the ecmwf model as data sources the impact of the ecmwf analysis procedure on the retrieved ageostrophic fields is first discussed upper level fields of the ageostrophic wind and its divergence are computed in the natural coordinates system in order to analyze the composition of the transverse cross stream and the alongstream ageostrophic components that are induced by alongstream wind variations and curvature effects respectively the analysis shows that the curvature effects can contribute in a predominant way to the upper tropospheric divergence field in entrance or exit regions of jet streaks so as to sometimes inhibit the expected transverse circulations several transverse indirect circulations are displayed in the exit regions of jet streaks a case of lateral shift towards the anticyclonic side of the jet axis of an indirect circulation is discus

the foundation of a 40 storey tower in jointed basalt abstract a 132 70 m high tower above foundation has been successfully completed at tenerife island the foundation of the tower a 2 m thick reinforced concrete slab is supported by jointed vesicular and weathered basalt and scoria a three dimensional elastic finite element program has permitted to calculate the displacements of the tower and the stresses in the slab the installation of rod extensometers at different depths below the slab and clinometers at the lower basement has provided comparison between measured and calculated displacements and the estimation of in situ deformation moduli a first stage prediction before construction has allowed establishment of an upper limit based upon pressuremeter modulus and a lower limit based upon bieniawski s equation the geomechanics classification in rock engineering applications in proceedings of the fourth cong isrm congress montreux vol 2 1979 p 41 48 of the settlements of the tower slab the geometric mean of these values comes close to the measured settlement the moduli deduced from the simple empirical equation proposed by gokceoglu et al predicting the deformation modulus of rock masses a comparative study int j rock mech min sci 2003 40 701 10 and hoek and brown practical estimates of rock mass strength int j rock mech min sci 1997 40 701 10 as a function of gsi provide a good fit with the measured settlements in this type of rock a good correlation is also obtained with the empirical equation presented by verman et al effect of tunnel depth on modulus of deformation of rock mass rock mech rock eng 1997 30 3 121 7 that incorporates the influence of the confining stress in the deformation modulus

a model for late archean chemical weathering and world average river water abstract interpretations of the geologic record of late archean near surface environments depend very strongly on an understanding of weathering and resultant riverine transport to the oceans the late archean atmosphere is widely recognized to be anoxic p o 2 g 10 5 to 10 13 bars p h 2 g 10 3 to 10 5 bars detrital siderite feco3 pyrite fes2 and uraninite uo2 in late archean sedimentary rocks also suggest anoxic conditions however whether the observed detrital minerals could have been thermodynamically stable during weathering and riverine transport under such an atmosphere remains untested similarly interpretations of fluctuations recorded by trace metals and isotopes are hampered by a lack of knowledge of the chemical linkages between the atmosphere weathering riverine transport and the mineralogical record in this study we used theoretical reaction path models to simulate the chemistry involved in rainwater and weathering processes under present day and hypothetical archean atmospheric boundary conditions we included new estimates of the thermodynamic properties of fe ii smectites as well as smectite and calcite solid solutions simulation of present day weathering of basalt calcite by world average rainwater produced hematite kaolinite na mg saponite and chalcedony after 10 4 moles of reactant minerals kg 1 h2o were destroyed combination of the resultant water chemistry with results for granitic weathering produced a water composition comparable to present day world average river water warw in contrast under late archean atmospheric conditions p co 2 g 10 1 5 and p h 2 g 10 5 0 bars weathering of olivine basalt calcite to the same degree of reaction produced kaolinite chalcedony and na fe ii rich saponite late archean weathering of tonalite trondhjemite granodiorite ttg formed fe ii rich beidellite and chalcedony combining the waters from olivine basalt and ttg weathering resulted in a model for late archean warw with the composition na ca2 fe2 mg2 cl hco 3 sio2 aq the ph of the water was 6 3 and it is much richer in hco 3 and in mg fe relative to ca na compared to present day warw at higher ph2 g e g 10 4 0 bars organic acid anions could be metastable our results are consistent with the thermodynamic stability of fe ii clays pyrite uraninite and under some conditions siderite during weathering and riverine transport overall our results provide a basis for assessing the formation of organic hazes and the mobility of trace elements and nutrients due to fluctuations of the late archean atmosphere

a technique for representing three dimensional vertical circulations in baroclinic disturbances abstract the problem of representing vertical circulations in frontal zones is reexamined with the objective of devising a methodology sufficiently general to apply in situations where these circulations are no longer confined to the cross front transverse vertical plane and therefore must be viewed as fully dimensional the proposed methodology which builds upon the earlier work of hoskins and draghici and of eliassen consists of adopting a vector streamfunction that describes the vertical velocity and the horizontal irrotational flow this generalized streamfunction referred to as the psi vector may be determined uniquely from the vertical velocity field over a limited region provided that suitable lateral boundary conditions on the velocity potential for the irrotational part of the horizontal velocity can be specified a key property of the psi vector is that its projections onto arbitrary orthogonal vertical planes yield two independent vertical circulations providing an objective means for se

alternating si and fe deposition caused by temperature fluctuations in precambrian oceans precambrian banded iron formations contain thin alternating layers of iron and silica rich minerals microbial culture experiments show that these alternations could be caused by changes in the relative dominance of microbial iron oxidation and abiotic silica precipitation driven by fluctuating ocean temperature

influence of upstream diabatic heating upon an alpine event of heavy precipitation abstract narrow extended troughs associated with elongated streamers of potential vorticity pv are a frequent feature of upper tropospheric flow and they can instigate or modify surface weather systems in this study consideration is given to the generation of one particular pv streamer that was itself a dynamical precursor of a heavy precipitation event in the alpine region it is shown that the streamer s parturition over the eastern north atlantic is linked to a prior event of cyclo and frontogenesis upstream over the western north atlantic diagnostic trajectory analysis and heuristic simulations with a limited area nwp model suggest that the streamer s origin is influenced crucially by the following chain of physical processes cloud diabatic heating associated with the upstream cyclogenesis enhances a downstream negative pv anomaly in the upper troposphere and the flow associated with this anomaly subsequently helps transform a farther downstream preexisting broad positive pv anomaly into an elo

comments on dynamics of upper level frontogenesis in baroclinic waves abstracta recent paper by mak et al grants the opportunity to discuss two different definitions of the frontogenetical function proposed in the literature to study the formation and evolution of upper level fronts this comment exposes some problems that in this author s opinion are related to the use of the lagrangian tendency of the 3d in place of horizontal gradient of potential temperature as adopted in the mak et al paper

estimating the deformation modulus of rock masses a comparative study although the modulus of deformation of rock masses has crucial importance for geotechnical projects such as tunnels and dams the determination of this parameter by in situ tests requires considerable costs and involves difficult operational processes for this reason empirical equations for the indirect estimation of the modulus of deformation are an interesting issue for rock engineers and engineering geologists this study includes assessment of the prediction performances of some existing empirical equations using in situ plate loading test data and rock mass properties producing an empirical equation depending on the new data construction of a fuzzy inference system for the estimation of modulus of deformation and making a comparison between results obtained from the empirical equations and fuzzy inference system a series of calculations and statistical analyses were undertaken it is concluded that the performance of the empirical equations and fuzzy inference system obtained in this study is satisfactory however the prediction models developed in this study are limited by the number of the data used and the rock types employed for these reasons a cross check should be performed before using these prediction models for design purposes

rossby wave initiation by recurving tropical cyclones in the western north pacific abstractthe interaction of recurving tropical cyclones tcs with midlatitude rossby waves during extratropical transition et can significantly alter the midlatitude flow configuration this study provides a climatological investigation of rossby wave initiation rwi by transitioning tcs in the specific configuration of an initially zonal midlatitude waveguide and elucidates physical processes governing ab initio flow amplification during et recurving tcs interacting with a zonally oriented waveguide in the western north pacific wnp basin from 1979 to 2013 are categorized into cases initiating rossby waves tc rwi or not tc norwi interactions with a zonally oriented waveguide occurred for 22 7 of the recurving tcs and one third of these resulted in tc rwi in the presence of a tc the probability of rwi on a zonally oriented waveguide is 3 times larger than in situations without a tc the occurrence of tc rwi exhibits a seasonality and is relatively more common during boreal summer than in aut

the structure and evolution of lower stratospheric frontal zones part 1 examples in northwesterly and southwesterly flow the structure evolution and dynamics of two lower stratospheric frontal zones are examined from a basic state variables perspective the case studies highlight the asynchronous evolution of the lower stratospheric and upper tropospheric frontal portions of upper level jet front uljf systems as well as some substantial differences in lower stratospheric frontal development that occur in southwesterly and northwesterly flow the evolution of the uljf in northwesterly flow was characterized by an initially intense but weakening lower stratospheric front along with an initially weak but intensifying upper tropospheric front throughout the evolution geostrophic cold air advection in cyclonic shear characterized a substantial portion of the lower stratospheric front this circumstance supported subsidence through the local jet core within the cold upper troposphere weakening the lower stratospheric front via tilting this subsidence extended downward below the jet core where it is suggested to have played a role in the early stages of upper tropospheric frontogenesis in the southwesterly flow case the evolution of the uljf was characterized by a strengthening lower stratospheric front and a weakening upper tropospheric front a deep column of upward vertical motion resulted from the superposition of lower tropospheric ascent associated with convection along a surface cold front and upper tropospheric lower stratospheric utls ascent through the jet core coincident with geostrophic warm air advection in cyclonic shear along large sections of the lower stratospheric front the utls ascent located on the cold edge of the lower stratospheric baroclinicity served to intensify the lower stratospheric frontal zone via tilting the implications of these lower stratospheric frontal processes on the topography of the tropopause and downstream sensible weather are discussed copyright 2012 royal meteorological society

an empirical method for determining the mechanical properties of jointed rock mass using drilling energy abstract characterization of jointed rock masses and evaluation of their mechanical properties are challenging tasks in rock engineering this paper presents an experimental investigation of the response characteristics of drilling energy to the discontinuity of rock mass using a drilling method the linear relationship between the drilling energy and discontinuity frequency is revealed which only depends on the rock type and is independent of calculation units a new empirical method for determining the rock quality designation rqd versus the variation of drilling energy is proposed based on the discontinuity frequency comparison between the prediction and in situ investigation results demonstrates that the rqd can be estimated from this empirical method the em er modulus ratio and cm c strength ratio versus rqd relations are modified for the determination of rock mass strength and deformation modulus in order to consider the continuous variation of em er and cm c with the model parameter which is related to the drilling energy and modulus of elasticity of intact rock and the variation of drilling energy for rock mass the results show that the modified em er cm c versus rqd relations can give proper values compared with the field test results as well as compared with the various proposed relations from rmr q and gsi the modified relations can provide a practical fast and easy to use method for the estimated rock mass strength and deformation modulus but they are only a first approximation

a potential vorticity diagnostic approach to upper level frontogenesis within a developing baroclinic wave the process of tropopause folding is studied in the context of the life cycle of baroclinic waves previous studies of upper level frontogenesis have emphasized the role of the vertical circulation in driving stratospheric air down into the midtroposphere here a potential vorticity based approach is adopted that focuses on the generation of a folded tropopause to facilitate comparison of the two approaches the diagnosis is applied to the upper level front previously simulated and studied by rotunno et al the potential vorticity approach clarifies the primary role played by the horizontal nondivergent wind in producing a fold and explains why folding should be a common aspect of baroclinic development between the trough and upstream ridge prolonged subsidence within a region of weak system relative flow generates a tropopause depression oriented at an angle to the large scale flow the large scale vertical shear then locally increases the slope of the tropopause eventually leading to a tropopause fold in contrast tropopause folding in the base of the trough is caused by the nondivergent cyclonic circulation associated with the surface thermal wave the winds associated with the thermal wave amplify the potential vorticity wave aloft and these winds which decrease with height rapidly generate a tropopause fold within the trough

initiation and evolution of an intense upper level front abstract within confluent northwesterly flow of an intensifying baroclinic wave over north america in late october 1963 an intense frontal zone developed in 12 h near the inflection point in the middle and upper troposphere by 24 h after its initial appearance the zone extended roughly from 400 to 700 mb and from the inflection point to just beyond the downstream trough horizontal gradients of potential temperature reached 15 20 k 100 km 1 air within the frontal zone was extremely dry as the accompanying trough approached the east coast of he united states surface frontogenesis occurred offshore remaining distinct from the upper level front a region of subsidence elongated in the direction of the upper level flow displayed maximum descent on the warm edge of the frontal zone and played a frontogenetical role through tilting of the isentropic surfaces analysis of isentropic potential vorticity showed significant increase of this quantity near the cold base and a probable decrease near the top

modeling deformation modulus of a stratified sedimentary rock mass using neural network fuzzy inference and genetic programming abstract this paper investigates a series of experimental results and numerical simulations employed to estimate the deformation modulus of a stratified rock mass the deformation modulus of rock mass has a significant importance for some applications in engineering geology and geotechnical projects including foundation slope and tunnel designs deformation modulus of a rock mass can be determined using large scale in situ tests this large scale sophisticated in situ testing equipments are sometimes difficult to install plus time consuming to be employed in the field therefore this study aims to estimate indirectly the deformation modulus values via empirical methods such as the neural network neuro fuzzy and genetic programming approaches a series of analyses have been developed for correlating various relationships between the deformation modulus of rock mass rock mass rating rock quality designation uniaxial compressive strength and elasticity modulus of intact rock parameters the performance capacities of proposed models are assessed and found as quite satisfactory at the completion of a comparative study on the accuracy of models in the results it is seen that overall genetic programming models yielded more precise results than neural network and neuro fuzzy models