interaction of a tropical cyclone with a high amplitude midlatitude wave pattern waviness analysis trough deformation and track bifurcation an idealized scenario of extratropical transition et is investigated in which a tropical cyclone interacts with a high amplitude upper level wave pattern and well developed surface cyclones early during the interaction the external forcing of the upper level wave by the et system is quantified based on a metric for the waviness of the midlatitude flow local amplification of the wave pattern is diagnosed associated prominently with the trough downstream of et this amplified trough however exhibits pronounced anticyclonic breaking and thus in contrast to many previous et studies it is not clear that the amplification of the upper level wave propagates into the farther downstream region subsequently the et system merges with the upstream cyclone the upstream trough undergoes strong deformation and cyclonic breaking associated with straining due to the cyclonic circulation of the et system with the decay of this trough the et system weakens considerably and the upper level wave pattern changes locally to a zonal flow orientation this zonal flow pattern then extends into the downstream region and promotes the decay of the downstream baroclinic systems as in previous studies the evolution of et exhibits large sensitivity to the initial location of the tropical cyclone examining the steering flow s topology i e identifying the stagnation points and the streamlines emanating from these points helps to identify three different regimes a no et regime and two et regimes reminiscent of the northwest and northeast patterns respectively introduced previously by harr et al a stagnation point located on the axis of the upstream trough governs the bifurcation into no et and et regimes a stagnation point located on the axis of the downstream ridge governs the bifurcation into northwest and northeast patterns

advances and problems in ordovician palynology of england and wales acritarchs and chitinozoa are used to date ordovician rocks in england and wales but the data base for both groups is poor study of chitinozoa has been neglected in the uk in contrast to north america and southwest europe where biozonations have been established formal definition of acritarcb biozones may soon be possible in the tremadoc arenig but acritarch biostratigraphy in the llanvirn ashgill is insufficiently documented

an analysis of hurricane opal s forecast track errors using quasigeostrophic potential vorticity inversion abstract hurricane opal s landfall in october 1995 forms the basis of a serious hurricane forecast problem the potential for hurricane conditions over land with insufficient warning time official national hurricane center nhc a division of the tropical prediction center forecasts predicted landfall and passage inland over the eastern united states at a later time than observed because of underestimation of the northward component of the steering flow by the national centers for environmental prediction s ncep operational models and other hurricane track models the goal of this paper is to isolate the cause of the poor forecast of meridional storm motion in ncep s early eta model by using quasigeostrophic potential vorticity qgpv inversion qgpv inversion permits decomposition of the steering flow into contributions from different synoptic scale features the inversion procedure is applied to the eta analysis and 48 h eta forecast valid at 1200 utc 5 october 1995 analyses from the european centre

on the role of a rossby wave train during the extratropical transition of hurricane helene 2006 three successive interactions of hurricane helene 2006 with a rossby wave train during the extratropical transition of helene over the north atlantic were investigated numerical experiments were performed with different horizontal resolutions and configurations over a domain that stretches from the eastern pacific to the western mediterranean to encompass helene and the whole rossby wave train in particular a cloud resolving run offered an explicit representation of strong diabatic effects involved in the three successive interactions while the circulation and moisture anomaly of helene were essential to its own reintensification it is shown that the rossby wave train played an important role in the track and intensity of helene and in explosive cyclogenesis downstream first the rossby wave train steered helene in such a way that a small difference in phasing resulted in large errors in the track of helene only a run at kilometre scale was able to correctly forecast the 5 day track of helene second through the formation of three filaments the rossby wave train created a quasi diurnal cycle in the intensity of helene helene responded with strong diabatic activity that prevented the superposition of an upstream trough and enhanced a downstream ridge finally model errors in the outflow of helene propagated downstream with the group speed of the rossby wave train leading to the loss of predictability of a tropical like cyclone over the mediterranean this study suggests that in addition to the horizontal resolution uncertainty from the model microphysics and from initial conditions need to be characterized to improve mid range forecast downstream from an extratropical transition copyright 2012 royal meteorological society

palynomorphs of the fezouata shale lower ordovician morocco age and environmental constraints of the fezouata biota abstract the present study documents new palynological investigations of the fezouata shale from the anti atlas morocco palynomorphs were extracted from samples collected from both outcrops and drill cuttings outcrop samples were taken near zagora and include some that were collected during excavation of stratigraphic horizons where exceptionally well preserved fossils of the fezouata lagerstatte occur subsurface samples were taken from the az 1 adrar zouggar mountain borehole which was extracted some 300 km to the southwest of zagora the palynological samples yielded acritarchs chitinozoans scolecodonts conodonts and fragments of graptolites the abundance and quality of preservation of palynomorphs varies greatly but rich and diverse assemblages were recovered from several samples the diversity and composition of the assemblages points to an open shelf environment generally mixed preservation states suggest resedimentation or differential transport histories the acritarchs can be assigned to the diagnostic messaoudensis trifidum acritarch assemblage which is typical of the tremadocian floian boundary interval of the gondwanan margin in high southern palaeolatitudes the acritarch taxa present in some of the lower parts of the fezouata shale including levels of exceptional preservation can be attributed to sub assemblages 1 2 of the messaoudensis trifidum assemblage and thus point to a late tremadocian age of the fezouata lagerstatte confirming biostratigraphic data provided by graptolites of the araneograptus murrayi graptolite biozone chitinozoans from the fezouata shale are from the e symmetrica and e brevis biozones and include various species that are well known from several localities on the gondwanan margin and from other palaeocontinents baltica laurentia and south china demarcating broad links between those regions the coincidence between index fossils of these three groups hitherto not all found in the same level suggests that the age assignments of chitinozoan biozones may be in need of revision

the impact of extratropical transition on the downstream flow an idealized modelling study with a straight jet the interaction of a tropical cyclone undergoing extratropical transition et with the midlatitude synoptic scale flow is investigated using full physics numerical experiments with idealized initial conditions the emphasis is on the impact on the midlatitude flow downstream of the et event the midlatitude flow is represented by a balanced straight jet stream as the tropical cyclone approaches the jet a ridge trough couplet and a distinct jet streak form in the upper level flow a midlatitude cyclone develops rapidly downstream of the et system and the further evolution is characterized by downstream baroclinic development based on hovmoller diagrams the upper level development is interpreted as the excitation and subsequent dispersion of a rossby wave train on the potential vorticity gradient associated with the jet the characteristics of this wave train are sensitive to the structure of the jet and to moist processes in the midlatitudes the tropical cyclone undergoing et acts as a sustained forcing for the wave train and the structure of the et system impacts the development most significantly one to two wavelengths downstream of et piecewise inversion of potential vorticity complemented by the partitioning of the flow into its rotational and divergent parts is applied to assess the impact of the et system quantitatively both the cyclonic circulation and the outflow of the tropical cyclone are important contributors to the formation and amplification of the ridge trough couplet the outflow anomaly reduces the eastward motion of the ridge trough couplet significantly and thus promotes phase locking between the tropical cyclone and the upper level pattern copyright 2008 royal meteorological society

the resonant interaction of a tropical cyclone and a tropopause front in a barotropic model part ii frontal waves abstract the influence of frontal waves on the interaction of a tropical cyclone and a tropopause front is investigated in an idealized framework in a nondivergent barotropic model the front is represented by a vorticity step with a superimposed sinusoidal perturbation this gives rise to a jet that meanders to the north and south and can be viewed as a sequence of upper level troughs and ridges the model evolution depends sensitively on the position of the cyclone relative to the troughs and ridges here a bifurcation point is identified that is located on the trough axis at a distance where the zonal speed of the background flow equals the phase speed of the wave arbitrarily small displacements from this position determine whether a cyclone is advected toward the front or repelled only a limited range of wavelengths can lead to track bifurcations the largest effects are obtained for resonant frontal waves propagating with a phase speed matching the initial zonal translation speed of the cyclone we

magma rates in feeding conduits of different volcanic centres abstract a quasi stationary magma flow rate in asthenospheric and crustal conduits of central type volcanoes and volcanic centres was studied analytically under the following conditions magma rises through cylindrical channels in which the magma temperature does not change with time but the wall rocks are gradually heated the magma rates were calculated for basaltic andesitic and dacitic volcanoes using the continental and oceanic geotherms it follows from these calculations that the magma supply rate may determine the kind of activity of a volcanic centre being constant for large and very active volcanoes intermittent for usual volcanic centres of island arcs or sporadic for volcamic fields clusters of cinder cones and areal volcanism theoretical conclusions are consistent with observational data

the habberley formation youngest tremadoc in the welsh borderlands the habberley formation overlies the shineton shale formation in the shelve inlier shropshire and includes the youngest tremadoc strata known from the welsh basin it probably represents deposition during the interval cut out by the sub arenig unconformity in north wales and removed by the sub caradoc unconformity in the wrekin district there is no angular unconformity between tremadoc and arenig in the shelve inlier the habberley formation is likely to correlate in part with the hunnebergian stage of scandinavia it was deposited probably in a largely stagnant basin and records a shallowing upwards sequence prior to the arenig transgression of the stiperstones quartzite a sparse trilobite fauna proves the presence of the angelina sedg vickii biozone and a succeeding interval is characterized by asaphellus cf graffi the trilobites are briefly described they include the first undistorted material of angelina sedgwvickii the brachiopod lingulella bella walcott hitherto known only from eastern newfoundland is described by a w a rushton

buoyancy driven instabilities of low viscosity zones as models of magma rich zones the low reynolds number dynamics of a thin layer of fluid bounded below by a flat horizontal boundary and above by a fluid of another viscosity and greater density is reported three distinct stages of growth were observed the first stage is a rayleigh taylor instability in which disturbances of one specific wave number grow most rapidly if e is the ratio of the viscosity of the thick layer to the viscosity of the thin layer fastest growth is for wave number e in the second stage distortion of the interface is large and it is found experimentally that the fluid moves out of the thick layer as circular columns surrounded by relatively broad regions of descending material in the third stage fully matured structures are formed if the upwelling material has less viscosity than the surrounding material the structure develops a rim syncline and a pronounced overhang and eventually ascends as a spherical pocket of fluid fed by a conduit two applications to geophysics are given the first application follows from the fact that a melt source must exist in the mantle below mid ocean ridges this source can be approximated as a cylindrical body with lower viscosity and density compared to the overlying mantle if the cylinder develops a gravitational instability it will develop regularly spaced vertical protrusions estimates of the spacing are compared to high resolution segmentation data and some constraints on viscosity of the mantle below spreading centers are made these are that viscosity of the mantle is 1018 1 p and the ratio of this viscosity to the viscosity of the cylinder is less than 100 in the second application the upwelling conduits are measured experimentally and solitary waves are observed a recently found analog with magma rising up through the pores of a viscous crystalline matrix is discussed

postlandfall tropical cyclone reintensification in a weakly baroclinic environment a case study of hurricane david september 1979 abstract an analysis is conducted from a potential vorticity pv perspective of the reintensification of tropical storm david over the northeastern united states in september 1979 david a major long lived hurricane originated near the cape verde islands in late august 1979 it made final landfall in georgia on 4 september 1979 and weakened rapidly thereafter the noteworthy aspect of david was its subsequent reintensification approximately 27 h after landfall as a warm core disturbance in a weakly baroclinic environment in this regard the redevelopment of david is unlike the classical extratropical transformation of a tropical storm in a strongly baroclinic environment that has been documented in the literature the authors analysis of the evolution of the dynamical tropopause subsequent to storm landfall revealed that david reintensified in response to tropopause lifting upward displacement of the dynamic tropopause ahead of a nondeepening and otherwise very weak upper tropospheric disturbance

resonance oscillations of the soufriere hills volcano montserrat w i magmatic system induced by forced magma flow from the reservoir into the upper plumbing dike abstract short period deformation cycles are a common phenomenon at active volcanoes and are often attributed to the instability of magma flow in the upper plumbing system caused by fluctuations in magma viscosity related to cooling degassing and crystallization here we present 20 min periodic oscillations in ground deformation based on high precision continuous borehole strain data that were associated with the 2003 massive dome collapse at the soufriere hills volcano montserrat west indies these high frequency oscillations lasted 80 min and were preceded by a 4 hour episode of rapid expansion of the shallow magma reservoir strain amplitude ratios indicate that the deformational changes were generated by pressure variations in the shallow magma reservoir and with reversed polarity the adjacent plumbing dike the unusually short period of the oscillations cannot be explained with thermally induced variations in magma properties we investigate the underlying mechanism of the oscillations via a numerical model of forced magma flow through a reservoir dike system accounting for time dependent dilation contraction of the dike due to a viscous response in the surrounding host rock our results suggest that the cyclic pressure variations are modulated by the dynamical interplay between rapid expansion of the magma chamber and the incapacity of the narrow dike to take up fast enough the magma volumes supplied by the reservoir our results allow us to place first order constraints on the viscosity of crustal host rocks and consequently its fractional melt content hence we present for the first time crustal scale in situ measurements of rheological properties of mush zones surrounding magmatic systems

vortex vortex interaction between hurricane nadine 2012 and an atlantic cut off dropping the predictability over the mediterranean operational ensemble forecasts for the western mediterranean exhibited high uncertainty while hurricane nadine was moving slowly over the eastern north atlantic in september 2012 the forecasts showed a bifurcation in the track of nadine a significant fraction predicting its landfall over the iberian peninsula and a high spread in the synoptic conditions downstream the forecast uncertainty was a major issue for planning observations during the first special observation period sop1 of the hydrological cycle in the mediterranean experiment hymex clustering the ensemble forecast of the european centre for medium range weather forecasts reveals two scenarios for interaction between nadine and an atlantic cut off which controls both the track of nadine and the synoptic conditions downstream the observed scenario of weak interaction is characterized by nadine moving westward and the cut off moving eastward the cut off then triggers precipitation over the cevennes in southeastern france the contrasting scenario of strong interaction is characterized by nadine and the cut off rotating around each other over the atlantic nadine then either merges with the cut off or makes landfall over the iberian peninsula the interaction between nadine and the cut off mimics the vortex vortex interaction previously observed between two tropical cyclones or two upper level vortices it differs from the usual interaction between a tropical cyclone and a larger trough during extratropical transition a critical distance of about 1000 km between nadine and the cut off distinguishes between the cases of weak and strong interaction in the ensemble forecast shifting the initial position of nadine in meso nh numerical experiments confirms the critical distance and suggests a bifurcation point in the relative position of nadine and the cut off the high forecast sensitivity to the vortex vortex interaction resulted in the lowest predictability over the mediterranean during the whole hymex sop1

nonlinear visco elastic volcanic model and its application to the recent eruption of mt unzen abstract a volcanic model is proposed the model consists of a magma reservoir which is a spherical hole in an elastic medium and is being replenished from below and a conduit which is a circular cylinder in a visco elastic medium the model is expressed by a system of two coupled nonlinear differential equations we solve the system as an initial value problem with a source term corresponding to the magma supply the supply rate is expressed by a bell shape function with a constant part this model works as follows supplied magma to the reservoir at a given rate increases pressure inside the reservoir the increased pressure expands the conduit through which the magma is discharged with the rate determined by poiseuille s flow law although the system eventually goes to a steady state in which the in and out flows are balanced the difference between response times of the reservoir and conduit causes the oscillation of the discharge rate this means that a volcanic activity oscillates for a pulse input expressed by a bell shape function the number of oscillations increases when the amount of inflow magma increases this model is applied to the recent volcanic activities of mt unzen the model well simulates the semi long term few years variation of the discharge rate of lava with a plausible replenishment rate of magma geometrical factors of the volcanic system the volume and radius of the reservoir the maximum and average radii of the conduit and some physical constants the maximum excess pressure viscosity of the country rock and mogi s coefficient are estimated under assumptions on the following quantities density difference between the country rock and magma rigidity of the country rock bulk modulus and viscosity of magma all quantities calculated except the viscosity agrees with corresponding values determined by independent methods within a factor of two or three we discussed physical background of these results together with the model itself

physics based models of ground deformation and extrusion rate at effusively erupting volcanoes 1 we present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time dependent data sets including ground deformation and extrusion rate the model involves a deflating chamber which supplies newtonian magma through a cylindrical conduit solidification is approximated as occurring at fixed depth producing a solid plug that slips along its margins with rate dependent friction changes in tractions acting on the chamber and conduit walls are used to compute surface deformations given appropriate material properties and initial conditions the model predicts the full evolution of an eruption allowing us to examine the dependence of observables on initial chamber volume overpressure and volatile content employing multiple data sets in combination with a physics based model allows for better constraints on these parameters than is possible using kinematic idealizations modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources we compare numerical results to analytical approximations and to data from the 2004 2008 eruption of mount st helens for nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption with little contribution from the fluid magma below the idealized crystallization depth while rate dependent plug friction influences the time dependent evolution of the eruption it has no control on the final chamber pressure or extruded volume

the impact of typhoon jangmi 2008 on the midlatitude flow part ii downstream evolution extratropical transition et of a tropical cyclone tc can modify the midlatitude flow and thus have implications for the weather and predictability in downstream regions such as north america or europe albeit recurving and undergoing et the downstream impact of typhoon jangmi in september 2008 during the thorpex pacific asian regional campaign t parc was weak in this study we explore the physical processes inhibiting the reintensification of jangmi and governing the forecast uncertainty during et the focus is on the relative contribution of the tc and the midlatitude flow quasi geostrophic diagnostics reveal that jangmi is located south of and in phase with a midlatitude trough jangmi does not couple with the region favourable for reintensification ahead of the trough and subsequently decays instead a weak frontal wave like cyclone develops the role of the phasing of typhoon jangmi and the midlatitude rossby wave pattern is tested in sensitivity experiments with the cosmo model in which jangmi has been relocated the simulations reveal two contrasting groups of scenarios the first group reflects the weak actual et and subsequent decay accompanied by a broad ridge over the pacific the second group is characterized by a strong et with extratropical reintensification the triggering of a pronounced rossby wave train and downstream cyclogenesis the displacement of jangmi s initial position in the two contrasting groups is less than 1 25 130 km in the frame moving with the environmental background flow a critical bifurcation point for the track of jangmi exists the relative position to this bifurcation point determines whether jangmi decays or reintensifies and triggers a rossby wave train a simple discrimination parameter is derived that allows for classifying the scenarios the observed behaviour gives a simple explanation for the reduced predictability of the track and of the midlatitude flow in downstream regions during et

acritarch dating of latest tremadoc earliest arenig early ordovician sediments in the carmarthen district south wales an acritarch assemblage from beds beneath the ogof hen formation near carmarthen the login beds resembles assemblages from the watch hill grits and underlying sediments of latest tremadoc or earliest arenig age in the skiddaw group of the english lake district we conclude that the login acritarch assemblage is younger than at least some part of the late tremadoc angelina sedgwickii biozone but older than the early arenig didymograptus deflexus biozone its occurrence may therefore coincide with that of the graptolite tetragraptus approximatus this is of particular significance in any attempt to define an internationally correlatable base for the arenig series in britain

rheological properties of dome lavas case study of unzen volcano abstract transitions between effusive and explosive styles of lava dome eruptions are likely accompanied by changes in lava rheology the common presence of crystals in dome lavas produces a complex non newtonian rheology thus models of such complex rheology are essential for volcanic eruption models here we have measured the rheology of natural unzen lavas with a compressive uniaxial press operating at stresses between 1 and 70 mpa and temperatures between 940 and 1010 c crystal rich unzen lavas are characterised by two essential rheological features which produce non newtonian effects the first is an instantaneous response of the apparent viscosity to applied stress which requires that the magma be described as a visco elastic fluid that exhibits shear thinning the second effect takes the form of a time dependence of the viscosity at moderate to high stress 10 mpa in this regime the apparent viscosity slowly decreases as increasing fracturing of the phenocrysts and the groundmass occurs fragmentation of crystals and alignment of crystal fragments are observed to produce flow banding effects which in turn lower the apparent viscosity of natural dome lavas ultimately deformation may lead to complete rupture of the lava if the stress is sufficient cracking thus stands as an important process in natural dome lava rheology the ubiquitous non newtonian rheology of dome lavas observed experimentally here needs to be adequately treated in order to generate appropriate eruption models

a phase locking perspective on rossby wave amplification and atmospheric blocking downstream of recurving western north pacific tropical cyclones abstractthe extratropical transition et of tropical cyclones tcs can significantly influence the evolution of the midlatitude flow however the interaction between recurving tcs and upstream u

the messaoudensis trifidum acritarch assemblage and correlation of the base of ordovician stage 2 floian the global stratotype section and point gssp for stage 2 of the ordovician system now the floian stage and approximately equivalent to the lower and middle arenig of england and wales is defined by the first appearance datum fad of the graptolite tetragraptus approximatus in the diabasbrottet quarry section at mount hunneberg sweden one of the issues this raises is how to correlate the base of stage 2 at the gssp with areas and successions that do not contain a correlative graptolite fauna the distinctive cymatiogalea messaoudensis stelliferidium trifidum acritarch assemblage is present in the upper tremadocian araneograptus murrayi graptolite biozone of nw england and ranges across the tremadocian stage 2 boundary there the tremadoc arenig boundary of anglo welsh nomenclature it also occurs widely at other high southern ordovician palaeolatitudes around the margin of gondwana being reported from ireland wales the isle of man belgium germany spain and turkey and may also be present in bohemia and argentina eastern cordillera it therefore has the potential to contribute towards the recognition and correlation of the base of stage 2 in those areas of particular interest are the first appearance datums of various taxa within the stratigraphical range of the messaoudensis trifidum assemblage notably that of aureotesta clathrata simplex which is considered to be close to the base of stage 2 in nw england elements of the messaoudensis trifidum assemblage also occur in baltica the palaeoplate on which the gssp for the base of stage 2 is located however many of the taxa used to subdivide the messaoudensis trifidum assemblage around gondwana have not been recorded from baltica and may be restricted palaeobiogeographically to the gondwanan margin furthermore acritarch microfloras have not been reported from the diabasbrottet quarry section itself and there are hiatuses across the base of stage 2 in the two sections from baltica considered in this paper hence direct correlation of the base of stage 2 between the gssp and other sections using acritarchs is not yet possible nevertheless some taxa for example the genera peteinosphaeridium and rhopaliophora are shown to have fads at similar stratigraphical levels in the late tremadocian stage of both baltica and gondwana and therefore have the potential to correlate time slices in the late tremadocian stage between palaeoplates

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

volcanic tremor induced by gas liquid two phase flow implications of density wave oscillation 1 we model the source mechanism of volcanic tremor at shallow depths of a volcano by hydrothermal dynamics steam water two phase flow in the pipe is formulated and its instability known as density wave oscillation can produce monotonic characteristics similar to those of a volcanic tremor the oscillation is closely related to the heat supplied to the system and we quantitatively obtain the upper and lower limits of the heating quantity to realize this monotonic oscillation this source mechanism can be realized only when the effect of gravity is small i e horizontal flow since the effect of depressurization due to upwelling is significant for bubble growth with vertical flow including gravity and heating and vaporization are less important

cyclic fluid effusion accompanied by pressure change implication for volcanic eruptions and tremor magma effusion and tremor sometimes occur in quite regular intervals with periodic pressure changes as observed in volcanic eruptions at kilauea volcano lava dome growth at unzen volcano and tremor episodes at izu oshima volcano these events have more or less asymmetric pressure change of quasi sinusoidal to saw toothed shape with longer time elapsing in build up of the fluid pressure than in its relaxation such cyclic fluid effusion can be explained systematically by a simple model in which fluid is supplied at a constant rate accumulates in an elastic chamber and flows out in a cylindrical vent that may widen or narrow due to viscous deformation of the surrounding country rock

the extratropical transition of tropical cyclones part i cyclone evolution and direct impacts abstractextratropical transition et is the process by which a tropical cyclone upon encountering a baroclinic environment and reduced sea surface temperature at higher latitudes transforms into an extratropical cyclone this process is influenced by and influences phenomena from the tropics to the midlatitudes and from the meso to the planetary scales to extents that vary between individual events motivated in part by recent high impact and or extensively observed events such as north atlantic hurricane sandy in 2012 and western north pacific typhoon sinlaku in 2008 this review details advances in understanding and predicting et since the publication of an earlier review in 2003 methods for diagnosing et in reanalysis observational and model forecast datasets are discussed new climatologies for the eastern north pacific and southwest indian oceans are presented alongside updates to western north pacific and north atlantic ocean climatologies advances in understanding and in some cases mode

arenig biostratigraphy and correlation in the welsh basin recent work on the arenig series in the welsh basin is reviewed it is now known to be far more complete and richly fossiliferous than has been supposed three regional stages moridunain whitlandian and fennian and seven trilobite based biozones have been defined outstanding problems are highlighted among which remains the definition of a stratotype for a base for the series for which there appears to be only one feasible candidate in this area in the shelve inlier

downstream development associated with the extratropical transition of tropical cyclones over the western north pacific abstract the movement of a tropical cyclone into the midlatitudes involves interactions among many complex physical processes over a variety of space and time scales furthermore the extratropical transition et of a tropical cyclone may also result in a high amplitude rossby wave response that can extend to near hemispheric scales after an et event occurs over the western portion of a northern hemisphere ocean basin the high amplitude downstream response often forces anomalous midlatitude circulations for periods of days to a week these circulations may then be related to high impact weather events far downstream of the forcing by the et event in this study downstream development following et events over the western north pacific ocean is examined local eddy kinetic energy analyses are conducted on four cases of north pacific tropical cyclones of varying characteristics during et into varying midlatitude flow characteristics during 15 july 30 september 2005 the goal is to examine the impact of e

intermittent generation of mafic enclaves in the 1991 1995 dacite of unzen volcano recorded in mineral chemistry mafic enclaves in the 1991 1995 dacite of unzen volcano show chemical and textural variability such as bulk sio2 contents ranging from 52 to 62 wt and fine to coarse grained microlite textures in this paper we investigated the mineral chemistry of plagioclase and hornblende microlites and distinguished three enclave types type i mafic enclaves contain high mg plagioclase and low cl hornblende as microlites whereas type iii enclaves include low mg plagioclase and high cl hornblende type ii enclaves have an intermediate mineral chemistry type i mafic enclaves tend to show a finer grained matrix have slightly higher bulk rock sio2 contents 56 60 wt when compared with the type iii mafic enclaves sio2 53 59 wt but the overall bulk enclave compositions are within the trend of the basalt dacite eruptive products of quaternary monogenetic volcanoes around unzen volcano the origin of the variation of mineral chemistry in mafic enclaves is interpreted to reflect different degree of diffusion controlled re equilibration of minerals in a low temperature mushy dacitic magma reservoir mafic enclaves with a long residence time in the dacitic magma reservoir whose constituent minerals were annealed at low temperature to be in equililbrium with the rhyolitic melt represent type iii enclaves in contrast type i mafic enclaves result from recent mafic injections with a mineral assemblage that still retains the high temperature mineral chemistry taking temperature ca ca na ratio of plagioclase and water activity of the hydrous unzen magma into account the mg contents of plagioclase indicate that plagioclase microlites in type iii enclaves initially crystallized at high temperature and were subsequently re equilibrated at low temperature conditions compositional profiles of mg in plagioclase suggest that older mafic enclaves type iii had a residence time of 100 years at 800 c in a stagnant magma reservoir before their incorporation into the mixed dacite of the 1991 1995 unzen eruption presence of different types of mafic enclaves suggests that the 1991 1995 dacite of unzen volcano tapped mushy magma reservoir intermittently replenished by high temperature mafic magmas

the key role of diabatic outflow in amplifying the midlatitude flow a representative case study of weather systems surrounding western north pacific extratropical transition abstractrecurving tropical cyclones tcs undergoing extratropical transition et may substantially modify the large scale midlatitude flow pattern this study highlights the role of diabatic outflow in midlatitude flow amplification within the context of a review of the physical and dynamical processes involved in et composite fields of 12 western north pacific et cases are used as initial and boundary conditions for high resolution numerical simulations of the north pacific north american sector with and without the tc present it is demonstrated that a three stage sequence of diabatic outflow associated with different weather systems is involved in triggering a highly amplified midlatitude flow pattern 1 preconditioning by a predecessor rain event pre 2 tc extratropical flow interaction and 3 downstream flow amplification by a downstream warm conveyor belt wcb an ensemble of perturbed simulations demonstrates the robustness of these stages beyond earlier studies investigating pres recurv

effects of gas escape and crystallization on the complexity of conduit flow dynamics during lava dome eruptions 1 we investigated the coupled effects of gas escape and crystallization on the dynamics of lava dome eruptions using a one dimensional conduit flow model the relationship between chamber pressure pch and mass flow rate q for steady conduit flow commonly has a regime of negative differential resistance i e dpch dq 0 5 feedback 1 is the main mechanism that forms negative differential resistance in this case the transition from lava dome to explosive eruption occurs when the magma supply rate exceeds a fixed critical value for low phenocryst content magma volume fraction 0 5 feedback 2 plays a key role so that the transition is controlled by the permeability of the surrounding rocks the critical magma supply rate remarkably decreases with decreasing permeability transition due to feedback 2 is associated with a change in the chemical composition of volcanic gas a drastic increase in magma porosity from nearly 0 to greater than 0 8 and overpressure at a shallower level which can be detected from geochemical and geophysical field observations

the age and correlation of skiddaw group early ordovician sediments in the cross fell inlier northern england the skiddaw group in the cross fell inlier comprises the catterpallot formation of latest tremadoc or earliest arenig age the murton formation of arenig age and the kirkland formation of early llanvirn age each of these formations can be correlated with formations in the skiddaw group of the lake district the faulted contact of the catterpallot and kirkland formations is the probable extension of the causey pike fault cpf which separates two distinct sequences in the skiddaw inlier of the northern lake district contrasts across the cpf in the cross fell inlier reflect those seen in the skiddaw inlier the cpf is a major basement structure separating markedly different successions in the ordovician strata of northern england

biostratigraphy taxonomic diversity and patterns of morphological evolution of ordovician acritarchs organic walled microphytoplankton from the northern gondwana margin in relation to palaeoclimatic and palaeogeographic changes abstract acritarchs the fossilizable resting cysts of phytoplanktonic algal protists are the dominant component of marine organic walled microfossils in the palaeozoic the majority of acritarchs show strong similarities with dinoflagellate cysts in morphological and biogeochemical features as well as distributional patterns in the sediments the production of these organic walled microfossils and their distribution and survivorship in the sediments were controlled by differences in ecological tolerances and life cycle autecology of the planktonic parent organisms calculation of evolutionary rates and development of a detailed diversity curve at specific level form the basis for discussing the influence of global palaeoenvironmental perturbations on the evolution of organic walled microphytoplankton in northern gondwana during latest cambrian through ordovician times the potential of acritarchs for biostratigraphic correlation at the regional scale northern gondwana domain is much improved by our detailed revision of distributional patterns of 245 acritarch taxa the most important cambro ordovician acritarch bio events are short periods of diversification which also correspond to introduction of morphological innovations observed in latest cambrian and earliest tremadoc late tremadoc early arenig basal llanvirn and latest ashgill and an important extinction phase in the early caradoc overall acritarch diversity increased from the basal ordovician up to the middle llanvirn then declined in the early and middle caradoc during ashgill times the assemblages are poorly diversified at the generic level as a result of a combined effect of sea level drawdown and onset of glacial conditions but no major extinction event is observed in connection with the end ordovician biotic crisis the peak in acritarch diversity during middle ordovician times appears to be correlated to maximum spread of palaeogeographical assembly acritarch dynamics appear largely uncorrelated to second order sea level oscillations the primary abiotic controls on acritarch evolution were palaeogeographical and the associated palaeoceanographic changes especially during middle ordovician and the end ordovician palaeoclimatic shift the acritarch fossil record provides important information on the evolution of oceanic primary producers however the relationships between acritarch diversity oceanic productivity and evolution of invertebrate animals are proving much more complex than previously thought in particular the hypothesis of a causal relationship between changes in acritarch diversity and metazoan evolution in the palaeozoic is not supported by our data

a stability analysis of a conduit flow model for lava dome eruptions abstract periodic variations in magma discharge rate and ground deformation have been commonly observed during lava dome eruptions we performed a stability analysis of a conduit flow model by barmin et al barmin a melnik o sparks r s j 2002 periodic behavior in lava dome eruptions earth and planetary science letters 199 1 2 173 184 in which the periodic variations in magma flow rate and chamber pressure are reproduced as a result of the temporal and spatial changes of the magma viscosity controlled by the kinetics of crystallization the model is reduced to a dynamical system where the time derivatives of the magma flow rate dq dt and the chamber pressure dp dt are functions of q and p evaluated at a shifted time t t here the time delay t represents the time for the viscosity of fluid particle to increase in a conduit the dynamical system with time delay is approximated by a simple two dimensional dynamical system of q and p where t is given as a parameter the results of our linear stability analyses for these dynamical systems indicate that the transition from steady to periodic flow depends on nonlinearities in the steady state relation between q and p the steady state relation shows a sigmoidal curve in q p phase plane its slope has negative values at intermediate flow rates the steady state solutions become unstable and hence p and q oscillate periodically when the negative slope of the steady state relation dp dq s exceeds a critical value that is dp dq s

sawtooth wave like pressure changes in a syrup eruption experiment implications for periodic and nonperiodic volcanic oscillations this study is based on the observation of sawtooth wave like pressure changes stw observed during repetitive gas emissions in a syrup eruption experiment similar waveforms are observed at many active volcanoes as geodetic signals by studying the physics of such experiments we often find new ideas and insights that are applicable to natural volcanic phenomena we consequently try identifying the features common to both our experimental system and natural volcanic systems we infer that the oscillatory mechanism in our experiment is similar to flow induced oscillation controlled by a coupling between elastic capacitance and variable flow resistance we developed an elementary pipe chamber system to quantitatively test this hypothesis we observed three distinct oscillatory patterns periodic stw non stw and nonperiodic stw a mathematical model is constructed to support the hypothesis and to enable comparison with existing models of volcanic systems models of flow induced volcanic oscillations are mathematically similar to the model derived from our experimental system our results indicate that flow pattern transitions are essential for oscillatory behavior during gas emission an important finding is that cycle periodicity and fluctuation are controlled by interactions between upward and downward flow within the pipe especially during the termination of gas emission and the transition to the next cycle similar interactions occur in natural volcanoes during the termination of an explosive eruption fall back or drain back of ejected materials may modulate the explosivity and periodicity of the next eruption cycle our experimental system may provide a useful tool for understanding the oscillatory behavior of natural volcanic systems this study may also give a proof that the original eruption experiment provides a useful tool for explaining the dynamics of oscillatory and eruptive behaviors of natural volcanic systems in educational e g open day demonstrations