on cyclonic tracks over the eastern mediterranean abstract in this study an updated and extended climatology of cyclonic tracks affecting the eastern mediterranean region is presented in order to better understand the mediterranean climate and its changes this climatology includes intermonthly variations classification of tracks according to their origin domain dynamic and kinematic characteristics and trend analysis the dataset used is the 1962 2001 2 5 2 5 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 the identification and tracking of the cyclones was performed with the aid of the melbourne university algorithm it was verified that considerable intermonthly variations of track density occur in the eastern mediterranean consistent with previous studies for the entire mediterranean while further interesting new features have been revealed the classification of the tracks according to their origin domain reveals that the vast majority originate within the examined area itself mainly in the cyprus

frontogenesis and the development of secondary wave cyclones in fastex two major mechanisms of frontogenesis deformation and shear are important in frontal wave cyclone development horizontal deformation can suppress the nonlinear wave development using an analytic model bishop and thorpe have shown that large strain rates inhibit any wave slope amplification for real cases this ambient strain can be measured using the vorticity divergence attribution method developed by bishop this technique permits us to confirm the crucial role of such strain on the evolution of cases of wave development during the fronts and atlantic storm track experiment fastex horizontal shear in the presence of an along front thermal gradient is also an important mechanism of frontogenesis using an eady model joly and thorpe have shown that in cases of large along front thermal gradient frontal waves have growth rates smaller than the front itself and thus would not develop the domain independent attribution method developed by bishop is here extended to a geopotential field partition this leads via a nonlinear balance condition to the estimation of the ambient along front potential temperature gradient the role of such an along front potential temperature gradient is discussed as well as the relative contributions of the two frontogenesis mechanisms for the fastex cases

p wave tomographic imaging of the crust and upper mantle beneath the japan islands more than 50 000 high accuracy arrival times from 1200 shallow and deep earthquakes selected from the japan university network earthquake catalog are used to investigate the three dimensional 3 d seismic velocity structure beneath japan travel times and ray paths are accurately calculated by using an efficient 3 d ray tracing technique p wave tomographic images of the crust and upper mantle to a depth of 500 km beneath the japan islands are determined with spatial resolutions of 25 50 km the obtained p wave velocity in the crust and uppermost mantle is slightly higher and relatively homogeneous in western japan in contrast with an average lower velocity and a large heterogeneity in eastern japan where many active volcanoes exist this feature correlates well with the distributions of heat flow and gravity anomalies low velocity low v zones are imaged in the crust and uppermost mantle beneath active volcanoes the low v zones in the mantle wedge dip toward the west and extend continuously to a depth of about 200 km a high velocity high v zone corresponding to the subducted pacific plate is delineated the thickness of the high v zone is estimated to be 80 90 km in southwestern japan the descending philippine sea plate is also delineated its thickness is estimated to be 30 km

a global climatology of atmospheric fronts 1 atmospheric fronts in the lower troposphere often mark regions of significant weather and serve as an important conceptual tool that is frequently used and well understood by the public this study uses an objective method to identify fronts in the era 40 reanalysis and to compile a quantitative global climatology of their occurrence the climatology confirms the mid latitude storm tracks as the regions of highest front frequency and identifies slow moving frontal boundaries in the subtropics corresponding to major climate features such as the mei yu front the climatology also shows fronts to be common features of the south pacific convergence zone in the northern hemisphere fronts shift poleward in summer in the southern hemisphere this and other aspects of seasonal behavior are rather different

rupture process of the 1980 izu hanto toho oki earthquake deduced from strong motion seismograms abstract the 1980 izu hanto toho oki earthquake is studied in detail using near field strong motion seismograms recorded at japan meteorological agency stations a seismogram inversion method is applied to deduce the dislocation distribution and the character of rupture propagation during this earthquake this earthquake involves left lateral strike slip motion on the almost vertical plane with a strike of n10 w the fault plane is shallower than about 12 km in depth and the length is about 20 km the large dislocation large seismic moment occurs near the hypocenter and at the southern end of the fault plane the rupture propagates southward from the central part of the fault plane and spreads to the shallow area of the northern part of the fault plane after a delay of about 5 sec relative to the initiation of this earthquake the total seismic moment is about 7 10 25 dyne cm the aftershocks of magnitude equal to or greater than 4 0 take place in the areas where high stresses are expected to remain after this earthquake the mechanical weakness of small submarine monogenetic volcanoes which are located above the source region seems to affect the rupture process of this earthquake

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

p wave velocity tomography of the venezuelan region from local arrival times arrival times from the local seismological network of venezuela were used to estimate a three dimensional p wave velocity model for the region between longitude 60 74 w and latitude 6 14 n to a depth of more than 80 km the inversion was carried out by damped least squares describing the media by homogeneous velocity blocks the resolved lateral velocity variations in the first layer 0 30 km depth showed a correlation with the main stratigraphic features of the area while second layer 30 50 km depth showed the influence of moho depth variations through the region generating a pattern well correlated to the bouguer anomaly map lithospheric seismic velocities below the moho appear to be influenced by the major crustal fault systems an important low velocity zone is present below the triple junction of the fault systems of oca bocono and moron in northwestern venezuela farther south a similar low velocity zone is present below the junction of the bocono and the santa marta fault systems those are the two continental corners of the triangular maracaibo block below 80 km depth the fourth layer the low velocity zones show a connected pattern that follows or is adjacent to the crustal fault zones the presence of subducted atlantic lithosphere below the eastern venezuelan basin could explain the high velocity zone at this location a similar interpretation emerges from the tectonic wedging model previously proposed to explain the pronounced minimum of the gravity anomaly

a composite study of explosive cyclogenesis in different sectors of the north atlantic part i cyclone structure and evolution general characteristics of the dynamical and thermal structure and evolution of strong explosive cyclones in the northwestern atlantic near north america 18 cases and the extreme northeastern atlantic near iceland 19 cases are compared and contrasted through a composite study twice daily gridded analyses from the european centre for medium range weather forecasts at 2 58 resolution from january 1985 to march 1996 are used in the process of case selection it is found that the frequency of rapid cyclogenesis in the greenland iceland region is higher than previously thought and some of the events can be extremely violent many dynamically consistent differences are found when composite cyclones in the two sectors of the north atlantic are compared the upper level forcing that triggers the development in the northeast atlantic nea is no less intense at the onset of rapid deepening the nea cyclones are also associated with lower static stability and locally concentrated but shallower thermal gradient with less overall environmental baroclinicity these factors lead to rapid depletion of available potential energy and result in a faster evolution and a shorter life cycle therefore low level thermal gradient and upper level forcing components all weaken immediately after rapid deepening the low level incipient low in the nea composite is also stronger with a distinct potential vorticity pv anomaly visible at least 24 h prior to most rapid deepening and the development produces a more pronounced warm core seclusion explosive cyclones in the northwest atlantic on the other hand tend to have a higher stability and a greater amount of environmental baroclinicity with temperature gradients in a broader area and deeper layers these factors correspond to slower evolution and a longer life cycle for cases in the nea near iceland it appears that both upper level forcing and initial system strengths affect the maximum deepening rate the close proximity of this region to the high pv reservoir in the lower stratosphere is helpful in the generation of very strong forcing and a violent development under favorable synoptic conditions when a parent cyclone with appreciable strength exists to the north northeast of the incipient system

regional extent of the s wave reflector beneath the kanto district japan an s wave reflector was found near the upper plane of the double seismic zone associated with the subducting pacific plate beneath the southern kanto district of japan here the areal extent of the reflector is confirmed for a region ranging from 34 5 n to 36 7 n from the analysis of the travel times of the reflected s waves on 8 hz band seismograms a bend of the reflector is found at about 36 n it is coincident with the bend of the upper boundary of the subducting pacific plate obtained from the seismicity analysis in the middle of the kanto district the reflector extends to a depth of 120 km whereas in the northern kanto district it extends just beneath the volcanic front the reflector could not be verified for depths shallower than 60 km depth because the reflected s wave cannot be identified at the eastern most stations of the network

the basic ingredients of the north atlantic storm track part ii sea surface temperatures abstractthe impact of north atlantic sst patterns on the storm track is investigated using a hierarchy of gcm simulations using idealized aquaplanet and semirealistic boundary conditions in the atmospheric component hadam3 of the third climate configuration of the met office unified model hadcm3 this framework enables the mechanisms determining the tropospheric response to north atlantic sst patterns to be examined both in isolation and in combination with continental scale landmasses and orography in isolation a gulf stream sst pattern acts to strengthen the downstream storm track while a north atlantic drift sst pattern weakens it these changes are consistent with changes in the extratropical sst gradient and near surface baroclinicity and each storm track response is associated with a consistent change in the tropospheric jet structure locally enhanced near surface horizontal wind convergence is found over the warm side of strengthened sst gradients associated with ascending air and i

boundary layer friction in midlatitude cyclones results from an idealized three dimensional baroclinic life cycle model are interpreted in a potential vorticity pv framework to identify the physical mechanisms by which frictional processes acting in the atmospheric boundary layer modify and reduce the baroclinic development of a midlatitude storm considering a life cycle where the only non conservative process acting is boundary layer friction the rate of change of depth averaged pv within the boundary layer is governed by frictional generation of pv and the flux of pv into the free troposphere frictional generation of pv has two contributions ekman generation which is directly analogous to the well known ekman pumping mechanism for barotropic vortices and baroclinic generation which depends on the turning of the wind in the boundary layer and low level horizontal temperature gradients it is usually assumed at least implicitly that an ekman process of negative pv generation is the mechanism whereby friction reduces the strength and growth rates of baroclinic systems although there is evidence for this mechanism it is shown that baroclinic generation of pv dominates producing positive pv anomalies downstream of the low centre close to developing warm and cold fronts these pv anomalies are advected by the large scale warm conveyor belt flow upwards and polewards fluxed into the troposphere near the warm front and then advected westwards relative to the system the result is a thin band of positive pv in the lower troposphere above the surface low centre this pv is shown to be associated with a positive static stability anomaly which rossby edge wave theory suggests reduces the strength of the coupling between the upper and lower level pv anomalies thereby reducing the rate of baroclinic development this mechanism which is a result of the baroclinic dynamics in the frontal regions is in marked contrast with simple barotropic spin down ideas finally we note the implications of these frictionally generated pv anomalies for cyclone forecasting

three dimensional fine velocity structure and hypocentral distribution of earthquakes beneath the kanto tokai district japan we determine the three dimensional p wave velocity structure beneath the kanto tokai district central japan and simultaneously relocated by inverting travel time data for 91 events that were observed at 61 stations operated by the national research center for disaster prevention the variance of the travel time data is reduced by 75 as compared to the variance for the routinely used laterally homogeneous model in general our velocity model is consistent with tectonic models of the kanto tokai district our velocity model is also in good agreement with seismic explosion data and bouguer gravity anomalies the uppermost layer from 0 to 16 km depth is characterized by lateral velocity differences of more than 20 we find low velocity zones beneath tokyo bay the middle of the boso peninsula and omae zaki where there are thick sedimentary layers a marked 30 km thick high velocity zone extends to the northeast and the west of the izu peninsula this zone dips gradually from the surface to a depth of 70 km in the eastern region and to a depth of 40 km in the western region and is interpreted as the philippine sea phs plate which is being subducted at the sagami and the suruga troughs the data unquestionably require a high velocity zone beneath mount tsukuba that cannot be explained in terms of present tectonic models we use our three dimensional velocity model to relocate about 23 000 earthquakes that took place from 1983 through 1985 the accuracy of the hypocentral parameters improved considerably as a result the double seismic zone within the subducting pacific plate is more clearly delineated than in previous studies the inclined seismic zone for the subducting phs plate coincides fairly well with the high velocity zone of our three dimensional velocity model

thickness variation of the descending philippine sea slab and its relationship to volcanism beneath the kanto tokai district central japan 1 we use an iterative nonlinear travel time tomography technique to determine three dimensional p wave and s wave seismic velocity models for the region beneath the kanto tokai district of central japan salient points of the models are the following 1 the subducting philippine sea slab has thickness variation with a stepwise offset east of the izu peninsula the eastern beneath the kanto district and western beneath the area north of izu peninsula and the tokai district regions have respective thicknesses of 60 and 25 km the slab clearly subducts continuously to a depth of 100 km from the sagami trough beneath the kanto district although the tokai slab is indistinct at depths of 50 70 km 2 the oceanic crust at the top of the descending philippine sea slab transforms into eclogite at a depth of about 70 km beneath the kanto district 3 low velocity anomalies are associated with present and past volcanism they are located on the west of a 110 km depth contour of the wadati benioff zone rather than only on the backarc side of the volcanic front deflection of the volcanic front might result from the subducting philippine sea slab which shifts the dehydration reaction deeper as it subducts deeper

low velocity oceanic crust at the top of the philippine sea and pacific plates beneath the kanto region central japan imaged by seismic tomography 1 we construct fine scale three dimensional p and s wave velocity structures beneath the kanto region central japan by seismic tomography with a spatial correlation of velocities the philippine sea and pacific plates subduct beneath the eurasian plate in this area and are imaged with high velocities oceanic crust at the uppermost part of these subducting plates is a low velocity layer low velocity oceanic crust of the philippine sea plate subducts to a depth of approximately 80 km there are also two low velocity bodies with relatively high v p v s ratios of 1 80 1 90 in the mantle wedge above the oceanic crust of the philippine sea plate we speculate that the westernmost of these two low velocity bodies consists of 20 partially serpentinized peridotite continuous with gabbro in the oceanic crust of the uppermost philippine sea plate while the eastern body is composed of 30 partially serpentinized peridotite we trace the subducting oceanic crust of the pacific plate to a depth of 120 km the estimated v p v s ratio of this layer is 1 85 1 90 which indicates a low probability of molten rock the gabbroic oceanic crust may have been metamorphosed to garnet granulite

the formation of new england coastal fronts abstract coastal fronts are a frequent late fall and early winter feature of eastern new england weather data from a mesoscale observing network is used to describe the process of coastal frontogenesis and to determine the causes of formation three distinct types of coastal frontogenesis are found to occur in new england and examples of each are presented using mesoscale surface maps and time series type a coastal fronts form during cold air outbreaks as winds veer from offshore to onshore type b coastal fronts form in the evening as air temperatures over land fall below air temperatures over water both types of fronts represent thermally direct circulations which are created by heating from the warm sea surface often in combination with radiational cooling over land type c coastal fronts are caused by upstream blocking when a stable region of warm advection such as warm front approaches the appalachian mountains from the south type a and type b fronts are described in terms of land and sea bre

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

wave breaking characteristics of northern hemisphere winter blocking a two dimensional approach abstractthis paper generalizes and applies recently developed blocking diagnostics in a two dimensional 2d latitude longitude context which takes into consideration both mid and high latitude blocking these diagnostics identify characteristics of the associated wave breaking as seen in the potential temperature on the dynamical tropopause particularly the cyclonic or anticyclonic direction of wave breaking db index and the relative intensity ri index of the air masses that contribute to blocking formation the methodology is extended to a 2d domain and a cluster technique is deployed to classify mid and high latitude blocking according to the wave breaking characteristics midlatitude blocking is observed over europe and asia where the meridional gradient of is generally weak whereas high latitude blocking is mainly present over the oceans to the north of the jet stream where the meridional gradient of is much stronger they occur on the equatorward and poleward flank of the jet s

life cycle simulations of shallow frontal waves and the impact of deformation strain the life cycle of shallow frontal waves and the impact of deformation strain on their development is investigated using the idealized version of the met office non hydrostatic unified model which includes the same physics and dynamics as the operational forecast model frontal wave development occurs in two stages first a deformation strain is applied to a front and a positive potential vorticity pv strip forms generated by latent heat release in the frontal updraught second as the deformation strain is reduced the pv strip breaks up into individual anomalies the circulations associated with the pv anomalies cause shallow frontal waves to form the structure of the simulated frontal waves is consistent with the conceptual model of a frontal cyclone deeper frontal waves are simulated if the stability of the atmosphere is reduced deformation strain rates of different strengths are applied to the pv strip to determine whether a deformation strain threshold exists above which frontal wave development is suppressed an objective method of frontal wave activity is defined and frontal wave development was found to be suppressed by deformation strain rates 0 4 10 5 s 1 this value compares well with observed deformation strain rate thresholds and the analytical solution for the minimum deformation strain rate needed to suppress barotropic frontal wave development the deformation strain rate threshold is dependent on the strength of the pv strip with strong pv strips able to overcome stronger deformation strain rates leading to frontal wave development than weaker pv strips copyright 2006 royal meteorological society

dynamic adjustment of repeatedly observed levelling networks used in crustal vertical deformation monitoring abstract in order to monitor crustal vertical deformation in certain local areas by means of the geodetic method the levelling nets in these areas are usually observed at regular intervals in order to make a reasonable treatment of the results we have made some adjustments they are 1 a adjustment method of free level nets for a certain period of time 2 b successive condition adjustment of elevation differences and their rate of change 3 c dynamic condition adjustment with rate parameters of bench mark elevations as unknowns 4 d dynamic adjustment of repeatedly observed levelling nets for m periods 5 e dynamic adjustment with nonlinear movement model we have applied these methods to test calculations of levelling nets in several regions in addition we have performed statistical tests on the adjusted results of a certain levelling net and tried to infer the region of anomalous deformation in the area covered by this net

the spatial distribution and evolution characteristics of north atlantic cyclones a climatology of extratropical cyclones is produced using an objective method of identifying cyclones based on gradients of 1 km height wet bulb potential temperature cyclone track and genesis density statistics are analyzed and this method is found to compare well with other cyclone identification methods the north atlantic storm track is reproduced along with the major regions of genesis cyclones are grouped according to their genesis location and the corresponding lysis regions are identified most of the cyclones that cross western europe originate in the east atlantic where the baroclinicity and the sea surface temperature gradients are weak compared to the west atlantic east atlantic cyclones also have higher 1 km height relative vorticity and lower mean sea level pressure at their genesis point than west atlantic cyclones this is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of preexisting parent cyclones the evolution characteristics of composite west and east atlantic cyclones have been compared the ratio of their upper to lower level forcing indicates that type b cyclones are predominant in both the west and east atlantic with strong upper and lower level features among the remaining cyclones there is a higher proportion of type c cyclones in the east atlantic whereas types a and c are equally frequent in the west atlantic

on double rossby wave breaking in the north atlantic we discuss the dynamical features associated with double rossby wave breaking dwb concurrent cyclonic and anticyclonic breakings over the north atlantic with a focus on the north atlantic oscil

pan african subduction collision event evidenced by high p coronas in metanorites from the agou massif southern togo the ultrabasic basic complexes from se ghana and togo to n b enin are generally considered as an unique lithotectonic unit which may decorate the suture zone of the pan african collision belt in the southern region of togo the agou massif is one of these massifs mainly consisting of granulite facies rocks metagabbronorites and metagabbros outcrop in the innermost part of the agou igneous complex aic whereas in the outermost part relict boudins of metagabbronorites are surrounded by related retrogressed rocks such as layered grt bearing amphibolites and amphibolites the latter are intruded by leucocratic to melanocratic veins including dykes of microgabbros post solidus cooling of the metagabbronorites leads to the production of ht mp granulites m1 granulite stage opx1 cpx1 pl1 ilm sil t 850 c p 8kbar following this an evolution toward high pcoronitic granulites is indicated by early cpx and grt coronite developed around opx1 and pl1 granulite 2 stage cpx2 grt2 pl2 qtz sil rt 770 c 10kbar three successive stages of retrogression are then observed from i hornblende granulite facies 700 750 c 9kbar ii to amphibolite facies 700 c 6 7kbar and iii finally greenschist facies conditions 550 500 c 3 4kbar the inferredp tpath defines an unusual anti clockwise loop characterized by a slight pressure increase according to their calc alkaline signature and their metamorphic evolution the granulites of agou are derived from deep seated basic intrusion equilibrated in the lower continental crust under mp ht conditions and never experienced an early eclogite stage this contrasts with granulites derived from eclogites that are also described in sw togo in order to explain the existence of two types of metabasites in togo we propose that the agou massif corresponds to basic magmas emplaced and cooled at the base of an active continental margin western part of the benino nigerian shield whereas the former eclogites reflect subduction of the passive margin of the west african carton during subduction process or at the transition from subduction to collision at c 610ma burial of the edge of the active margin in the subduction zone led to the formation of coronitic granulites during the pan african orogeny at c 580ma the coronitic granulites together with the eclogites were exhumed under amphibolite facies conditions 2004 elsevier b v all rights reserved

dynamical aspects of the life cycle of the winter storm lothar 24 26 december 1999 dynamical aspects of the life cycle of the winter storm lothar 24 26 december 1999 are investigated with the aid of the european centre for medium range weather forecasts analysis data and mesoscale model simulations neither of these datasets capture the full amplitude of the observed extreme pressure fall and surface wind speeds but they do help identify a range of key dynamical and physical features that characterize the development of this unusual event the analysis and interpretation is primarily based upon the evolution of the lower and upper level potential vorticity pv field complemented by three dimensional trajectory calculations lothar originated in the western atlantic and travelled as a shallow low level cyclone of moderate intensity towards europe this translation took place below and slightly to the south of a very intense upper level jet and was accompanied by continuous and intense condensational heating that sustained a pronounced positive low level pv anomaly not unlike the concept of a diabatic rossby wave no significant pv anomalies were evident at the tropopause level during this early phase of the life cycle the surface cyclone intensified rapidly when the shallow cyclone approached the jet stream axis the circulation induced by the diabatically produced low tropospheric pv anomaly on steeply sloping isentropic surfaces that transect the intense upper level jet contributed significantly to the rapid formation of a narrow and deep tropopause fold this stratospheric pv anomaly virtually merged with the diabatically produced ephemeral pv feature to form a vertically aligned tower of positive pv at the time of maximum storm intensity a sensitivity study with a dry adiabatic hindcast simulation shows no pv tower configuration and only a very weak surface development and confirms the primary importance of the cloud diabatic heating for the tropopause fold formation and the rapid bottom up intensification of lothar a comparison of the anomalously high atlantic sea surface temperatures in december 1999 with the water vapour source regions for the latent heat release that accompanied the rapid intensification phase of lothar shows a close relationship this is of importance when discussing the possible implications of climate variability and change on the development of north atlantic winter storms copyright 2002 royal meteorological society

the basic ingredients of the north atlantic storm track part i land sea contrast and orography understanding and predicting changes in storm tracks over longer time scales is a challenging problem particularly in the north atlantic this is due in part to the complex range of forcings land sea contrast orography sea surface temperatures etc that combine to produce the structure of the storm track the impact of land sea contrast and midlatitude orography on the north atlantic storm track is investigated through a hierarchy of gcm simulations using idealized and semirealistic boundary conditions in a highresolution version of the hadley centre atmosphere model hadam3 this framework captures the largescale essence of features such as the north and south american continents eurasia and the rocky mountains enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies the physical processes by which the forcing mechanisms impact the large scale flow and the midlatitude storm tracks are discussed the characteristics of the north american continent are found to be very important in generating the structure of the north atlantic storm track in particular the southwest northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the rocky mountains leads to enhanced storm development along an axis close to that of the continent s eastern coastline the approximately triangular shape of north america also enables a cold pool of air to develop in the northeast intensifying the surface temperature contrast across the eastern coastline consistent with further enhancements of baroclinicity and storm growth along the same axis

step wise relocation of isc earthquake hypocenters for linearized tomographic imaging of slab structure a vast volume of seismic phase data computed from routinely determined hypocenter locations is presently available for seismic imaging techniques such as tomographic inversion and residual sphere analysis routinely reported earthquake hypocenters however can be in error by several tens of kilometers these biases in hypocenter location can result in the misidentification of seismic phases and the loss of structural signal in the seismic phase data thus the value of these data in constraining seismic images is significantly reduced furthermore hypocenter mislocations degrade the linearization of the tomographic problem and map into the images produced by tomographic inversion to obtain adequate reference hypocenters for linearized inversion we used iasp91 software and reported arrival times to reprocess isc hypocenters and phase data for northwest pacific earthquakes subsequently we inverted p and pp wave residuals for earth structure and source mis location we describe this step wise relocation of isc hypocenters which underlies the linearization of the tomographic inversion and compare the relocation vectors before and after inversion the hypocenter relocations determined prior to inversion are of the order of 10 km which is significant with regard to both the estimated standard errors and the effect on travel time residuals and systematic with regard to earthquake position in the subducted slab in contrast the spatial components of the relocation vectors determined upon inversion of p and pp residuals are up to an order of magnitude smaller do not reveal a correlation with location in the seismic zone and do not generally exceed the noise level the incorporation of pp data in the relocation was essential to remove the depth bias prior to inversion to retrieve slab signal that might have been absorbed in mislocation and to constrain the focal depth upon seismic inversion non linear inversion schemes will not be efficient in removing the depth bias or in retrieving lost slab signal unless seismic phases that contain additional information about the depth bias like the depth phase pp are used

a classification of fastex cyclones using a height attributable quasi geostrophic vertical motion diagnostic a systematic and objective procedure is developed for applying the simple cyclone classification scheme of petterssen and smebye this method uses a height attributable solution of the quasi geostrophic equation to identify and quantify the relative importance of upper and lower tropospheric forcing and also the time trend in the horizontal spacing of the forcing at these two levels by applying this classification method to a sample of cyclogenesis events during their maximum intensification stage from the fronts and atlantic storm track experiment field experiment the type a and type b scheme of petterssen and smebye is reproduced and extended to include a type c type c consists of upper level dominated cyclones that form at high latitudes and in their initial stages resemble comma cloud type polar lows detailed examples of each of the three types are presented some cyclones can undergo more than one period of development and it is found that each development period can be classified as a different cyclogenesis category a or b these cyclones are classified as hybrid type a b there is some evidence that cyclone forecast accuracy depends on cyclone type thereby suggesting the potential for this method to be used to assign confidence levels for forecasts of cyclogenesis produced by numerical weather prediction models type b cyclones appear more difficult to predict because their development depends initially on the interaction between significant features in the upper and lower troposphere copyright 2002 royal meteorological society t d hewson s contribution is crown copyright

replacement of pyroxene by hornblende isochemically balanced with replacement of plagioclase by garnet in a metagabbro of upper amphibolite grade in a garnet clinopyroxene hornblende metagabbro from the archean basement north of the cape smith wakeham bay belt quebec canada the following major mineral reactions have been observed 1 clinopyroxene hornblende and 2 plagioclase hornblende or fe ti oxides garnet it is argued that these reactions are synchronous and form part of one solid solution reaction system h2o cpx hbl plag fe ti oxides grt cpx hbl plag fe ti oxides qtz a new petrological mixing method is described which starting from the present reaction products estimates the proportions and compositions of the reactants for which the reaction system is completely isochemical the reaction system also explains the observed hornblende quartz symplectic intergrowths and the abundance of ilmeno hematite the isochemical character could also hold for the h2o involved the reaction is probably an adjustment to increasing pressure combined with cooling and can be correlated with the metamorphic peak of the hudsonian metamorphic episode

surface cyclones in the era 40 dataset 1958 2001 part i novel identification method and global climatology abstract a novel method is introduced to generate climatological frequency distributions of meteorological features from gridded datasets the method is used here to derive a climatology of extratropical cyclones from sea level pressure slp fields a simple and classical conception of cyclones is adopted where a cyclone is identified as the finite area that surrounds a local slp minimum and is enclosed by the outermost closed slp contour this cyclone identification procedure can be applied to individual time instants and climatologies of cyclone frequency fc are obtained by simple time averaging therefore unlike most other climatologies the method is not based on the application of a tracking algorithm and considers the size of cyclones in combination with a conventional cyclone center tracking algorithm that allows the determination of cyclone life times and the location of cyclogenesis and cyclolysis additional frequency fields can be obtained for special categories of cyclones that are gener

sequential velocity imaging and microseismic monitoring of mining induced stress change sequential imaging of the temporal changes inp wave velocity offers a practical tool to monitor a rock mass using established correlations between the location of seismic events and velocity structure the temporal seismic potential characteristics of the rock may be monitored furthermore the temporal velocity differences isolate the time dependent factors effecting velocity such as stress while cancelling static factors such as lithology various sequential imaging techniques were compared with respect to accuracy differences between successive velocity images were found to have relatively high associated error estimates however images of velocity differences calculated from measured travel time delays between successive velocity surveys were found to have lower error estimates in particular travel time delays measured using cross correlation techniques resulted in the most accurate sequential image two 3d sequential imaging studies were carried out at strathcona mine in sudbury ontario canada results of the average static images indicated an association between the location of induced microseismicity and a zone of both high velocity and high gradient additional examples are described from the global seismology literature which also show a similar correlation between seismicity and velocity structure we attribute this association to an interrelated stress and strength effect the strathcona mine sequential images show zones of significantly decreased velocity in regions of concentrated microseismic activity which are postulated to be indications of localized destressing and relaxation of the clamping forces resulting in the microseismicity the zones of decreased velocity corresponded to an increase in the velocity gradient one of the case studies also shows an increase in velocity in a zone of high static velocity which is later the site of amn 2 5 mining induced seismic tremor the increase in velocity is believed to correspond to a region of stress concentration resulting in the subsequent seismic tremor

broadening of seismogram envelopes in the randomly inhomogeneous lithosphere based on the parabolic approximation southeastern honshu japan analyzing horizontal component seismograms of small earthquakes with intermediate hypocentral distances in southeastern honshu japan we found that time widths of seismogram envelopes around direct s waves are much longer than source duration times estimated from their magnitudes the time lags of the maximum amplitude and the half maximum after the peak were measured from the onset of the direct s wave arrival from band pass filtered seismograms from 2 to 32 hz even though there is considerable scatter both the time lags are found to increase with increasing hypocentral distance up to 305 km we hypothesize that pulse shape broadens and the maximum amplitude is reduced after propagating through the random structure of the lithosphere the parabolic approximation theoretically predicts that the long wavelength component of velocity inhomogeneities compared with the wavelength of seismic waves produces diffraction fluctuations and makes seismogram envelopes broaden with increasing travel distance in the saturated regime supposing a gaussian autocorrelation function for the randomness and an empirical frequency dependent attenuation we propose a formula for the temporal change in the power spectral density of seismic waves applying this formula to the observed data we statistically evaluated the scale of random inhomogeneities the mean square fractional velocity fluctuation was estimated to be 10 3 times the correlation distance a in kilometers

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

invariant geodynamical information in geometric geodetic measurements summary repeated geodetic measurements have been used to extract geodynamical quantities such as displacements velocities of movement and crustal strains historical geodetic networks especially those established before the space geodetic era were and still are very important in providing a unique insight into the local or regional historical deformation state of the earth for the geodetic network without a tie to an external reference frame free network adjustment methods have been widely applied to derive geodynamical quantities currently it is commonly accepted that absolute displacements cannot be uniquely determined from triangulation trilateration measurements but relative displacements can be found uniquely if the geodetic network is geometrically overdetermined see e g segall matthews 1988 strain tensors were derived using the coordinate method and were reported to be uniquely determined we have carried out a theoretical analysis of invariant geodynamical information in geometric geodetic observations and concluded 1 that relative displacements are not invariant quantities and thus cannot be uniquely determined from the geodetic network without a tie to an external reference frame and 2 the components of the strain tensors are not all invariant and thus cannot individually be determined uniquely from the network however certain combinations of strain components are indeed invariant and can be uniquely determined from geometric geodetic measurements the theory of invariant information is then applied to the analysis of the tokai first order triangulation trilateration network spanning an interval of more than 100 yr the results show that the normal and principal strains are significantly affected by the unknown scaling biases and orientation differences thus any attempt at geophysical interpretation of these quantities must be exercised with great care if the scaling bias and the orientation difference are small the shear strain is shown to be practically invariant the invariant analysis of the tokai network has also shown that a belt near shizuoka has been significantly deformed in the past 100 yr this has not been seen in any previous analysis of displacements and or strains

seismic transmission survey application to real data from microearthquakes two discontinuities have been discovered which are closely related to the philippine sea phs plate that subducts beneath the kanto district in central honshu japan a seismic transmission survey method is used to image discontinuities in the earth from mode converted transmission mct waves and this method is applied to aftershocks of an event which occurred beneath the southern tokyo bay at a depth of 100 km as a result two predominant interfaces at depths of 24 km and 35 km appear in the section of p sv mct waves this example demonstrates that the seismic transmission survey method proposed by katsumata 1992 should be very useful in studying fine structure in the earth moreover it indicates that even microearthquakes can be used as sources for seismic surveys

izu bonin arc subduction under the honshu island japan evidence from geological and seismological aspect abstract the izu bonin intra oceanic arc with 20 35 km thick continental crust is being subducted under the honshu presumably since 17 ma tomographic image clearly demonstrates that the whole izu bonin arc is subducting under the honshu arc geologic cross section and the thickness of continental crust do not support the accretion of thick crust in spite of the continued subduction over 17 ma

secondary cyclogenesis along an occluded front leading to damaging wind gusts windstorm kyrill january 2007 abstractwindstorm kyrill affected large parts of europe in january 2007 and caused widespread havoc and loss of life in this study the formation of a secondary cyclone kyrill ii along the occluded front of the mature cyclone kyrill and the occurrence of severe wind gusts as kyrill ii passed over germany are investigated with the help of high resolution regional climate model simulations kyrill underwent an explosive cyclogenesis south of greenland as the storm crossed poleward of an intense upper level jet stream later in its life cycle secondary cyclogenesis occurred just west of the british isles the formation of kyrill ii along the occluded front was associated i with frontolytic strain and ii with strong diabatic heating in combination with a developing upper level shortwave trough sensitivity studies with reduced latent heat release feature a similar development but a weaker secondary cyclone revealing the importance of diabatic processes during the formation of kyrill ii kyrill ii moved

seismic waves guided by untransformed oceanic crust subducting into the mantle the case of the kanto district central japan a model of the subduction of oceanic crust is established through an analysis of the upper mantle earthquakes occurring beneath the kanto district central japan a distinct pair of later p and s phases xp and xs commonly observed at specific stations for these events in a depth range of 40 60 km and is considered to take place in association with the subducting motion of the philippine sea plate the xp phase is found from its particle motions to be a longitudinal seismic wave a principal component analysis of wavelets including the initial p and the xp phases shows that the latter arrives at the earth s surface with a slightly shallower angle relative to the former close agreement between the relative arrival time ratio of xs s xp p and the vp vs ratio of crustal or mantle rocks suggests that both xp and xs travel along the same path as longitudinal and tangential waves respectively one can clearly observe these later phases at stations located where the upper surface of the philippine sea plate is apparently in direct contact with the bottom of the crust of the honshu island apparent velocities of the xp and the xs phases are comparable to the seismic velocities of the main layer of the oceanic crust or the lower continental crust which are never expected for an upper mantle earthquake if the velocity structure is laterally homogeneous travel time curves for several earthquakes indicate that these apparent velocities can be directly related to the seismic velocity in the source region the hypocentral distribution of the events related to the subducting motion of the philippine sea plate does not form such a thin seismic zone as observed in southwest japan but extends over the entire thickness of the philippine sea plate the earthquakes from which the later phases are observed occur only in a shallower portion of this thick and contorted seismic zone the deeper portion does not generate such events these characteristics are best explained if these later phases are regarded as the seismic waves guided by the subducted portion of the gabbroic oceanic crust at the top of the philippine sea plate taking the result of our earlier work into account we conclude that the subducting oceanic crust remains in a gabbroic phase without transformation to eclogitic rocks at depths down to about 60 km along the entire northern boundary of the philippine sea plate

three dimensional q structure beneath the kanto tokai district japan the q structure of the upper mantle beneath the kanto tokai district central japan where the eurasian pacific and philippine sea plates are converging is investigated from seismic p and s wave spectral ratios by means of a three dimensional 3 d inversion method it is found that the subducting philippine sea and pacific plates are characterized by high q zones a high q zone also exists between the philippine sea plate and the pacific plate to the east of the volcanic front on the other hand a low q zone in the uppermost mantle extends westward horizontally from the volcanic front under the philippine sea plate and appears to exist over the wedge mantle beneath the western tokai district a very low q value obtained here is roughly equal to the average qvalue in the low velocity layer derived from surface wave and free oscillation data a low q region that suggests a magma chamber under active volcanoes is not detected in the crust

on a threefold classification of extratropical cyclogenesis a recently proposed extension to the twofold extratropical cyclogenesis classification scheme of petterssen and smebye is discussed a third class of extratropical cyclone type c is described in which initial development is controlled by a pre existing upper level potential vorticity pv anomaly in its early stages such a system is indistinguishable from the classical type b cyclone of the petterssen and smebye scheme however subsequent development cannot be understood in terms of a co operative interaction of the upper level feature with a low level baroclinic zone rather the cyclogenetic dynamics of type c systems are dominated by the action of strong midlevel latent heating such heating can generate important anomalies of pv that act to suppress the formation of a low level thermal anomaly and that interact destructively with the pre existing upper level feature candidate type c events are identified using recently developed height attributable quasi geostrophic vertical motion diagnostics the application of one such diagnostic to a climatology of instantaneous cyclonic features suggests that type c events may occur with reasonable frequency the generic behaviour of system types in the proposed threefold classification scheme is compared with the actual dynamics of some cyclones from the fronts and atlantic storm track experiment fastex the analysis is based on piecewise pv inversions and numerical simulations this approach is able to provide a good description of a case of standard type b development consistent with the qualitative description of petterssen and smebye and with the quasi geostrophic diagnostics within the same framework two systems are discussed whose behaviours do not fit the simple a b classification but are consistent with the proposed type c mechanism copyright 2003 royal meteorological society

deep crustal granulites with migmatitic and mylonitic fabrics from the zambezi belt northeastern zimbabwe abstract high p granulites contained in two allochthonous tectonic units were thrust southwards onto the northern margin of the zimbabwe craton during the pan african zambezi orogeny in the lower sheet the masoso metamorphic suite contains mafic garnet granulite assemblages formed during a high p t metamorphic event although the suite as a whole is predominantly granitic the garnet granulites occur as relicts within narrow mafic layers characterized by migmatitic and mylonitic fabrics the annealed mylonites represent surfaces of deep crustal tectonic imbrication that formed immediately before the pan african orogeny gabbros which intruded the granulites after the main phase of migmatization have formed corona textures that document a low p t metamorphic event at mid crustal levels the style of deformation then changed and the masoso suite with its mylonitic layers was folded and thrusted southwards onto the archaean zimbabwe craton

role of the low frequency deformation field on the explosive growth of extratropical cyclones at the jet exit part i barotropic critical region abstract by using new theoretical results on perturbation growth in spatially and temporally complex quasigeostrophic flows this paper investigates the role of the large scale deformation field on extratropical cyclones and especially on their explosive growth in the jet exit region theoretical ideas are tested by decomposing the atmospheric flow into a high and a low frequency part and by analyzing four dimensional variational data assimilation 4dvar reanalysis data of the fronts and atlantic storm track experiment fastex during february 1997 as well as reanalysis data for the end of december 1999 regions where the low frequency deformation magnitude is greater than the absolute value of the low frequency vorticity are shown to correspond to regions where synoptic disturbances at the same level tend to be located these regions in the upper troposphere are intrinsically related to the horizontal inhomogeneities of the low frequency large scale upper tropospheric jet but cannot be detected by look

seismological evidence for metastable olivine inside a subducting slab the nature and location of the olivine spinel phase transition inside subducting slabs differ greatly from the situation in the surrounding mantle due to the different temperature distribution inside the slabs two models have been proposed for this phase transition one in which the location of the phase boundary between olivine and modified phase spinel is determined by equilibrium thermodynamics1 and the other including a metastable olivine phase which persists to a depth of 550 km ref 2 the location of the olivine spinel transition in the slab may be relevant to the generation of deep earthquakes3 5 and to the buoyancy forces driving subduction6 here we use travel time residuals from deep earthquakes recorded by the dense seismograph network in japan to investigate the configuration of the olivine spinel phase boundary inside the subducting pacific plate theoretical travel time residuals for the equilibrium model do not fit the observed residuals whereas those for the metastable model do implying the presence of metastable olivine inside the subducting slab

cause of m 7 intraslab earthquakes beneath the tokyo metropolitan area japan possible evidence for a vertical tear at the easternmost portion of the philippine sea slab 1 we perform travel time tomography beneath kanto japan to obtain detailed structures of the wedge shaped serpentinized mantle previously observed in the philippine sea slab the results suggest that the western boundary of the serpentinized mantle serpentine boundary is subvertical and p and s wave velocities vary by 15 20 across it over the short distance of 10 km two intraslab earthquakes in 1921 m7 0 and 1987 east off chiba earthquake m6 7 are inferred to have occurred along the serpentine boundary accompanied by right lateral movement based on analyses of focal mechanisms and aftershock distribution a subvertical earthquake cluster penetrating the entire philippine sea slab is observed along the serpentine boundary and four earthquakes in the cluster have strike slip focal mechanisms similar to that of the 1987 earthquake focal mechanisms obtained for past large earthquakes and present day microearthquakes suggest a concentration of right lateral deformation along the mechanically weak serpentine boundary the philippine sea slab may have been torn in two along this boundary with the eastern portion being left behind relative to subduction of the western portion assuming that one of the large aftershocks m7 1 of the 1923 kanto earthquake m7 9 which occurred off the boso peninsula ruptured the same asperity as did the 1987 earthquake the slip deficit accumulated along the serpentine boundary during the 64 year interval is consistent with the fault slip of the 1987 earthquake interaction between the seismic slip along the plate interface and the serpentine boundary can explain the series of m7 class earthquakes before and after the 1923 kanto earthquake

3 d spatial variation of b values of magnitude frequency distribution beneath the kanto district japan summary a method is developed for estimation and interpolation of 6 values in space a 3 d spline function is considered for the logarithm of the 6 value at each location in the space since many parameters for the spline coefficients are required to obtain a sensible estimate of the spatial variation of 6 values we consider the penalized log likelihood with the standard roughness penalties for the spline function further the error bands of the b value estimation at each location can be calculated using the current method the spatial distribution of 6 values beneath the kanto district down to the depth of 100km is determined based on hypocentral data of microearthquakes from the kanto tokai observational network of the national research center for disaster prevention the stability of the estimated pattern is checked by comparing with the results using alternative cut off magnitudes this is further ensured by comparison with the result obtained by an alternative model using equally divided blocks on the whole the vertical change in 6 value is greater than the horizontal one it is high in the crust of the eurasian plate especially above the upper boundary of the subducting pacific plate and in the northwest part or the volcanic area in the kanto district a steep decrease of the 6 values is seen to take place in perpendicular direction to the subducting pacific plate boundary also a similar change is seen in the boundary between the eurasian and phillippine sea plates especially beneath the southern part of the kanto plain the 6 value is low in the upper boundary of the subducting plates but high in the lower plane of the double seismic zone in the pacific plate it appears that even within a narrow area of aftershocks the 6 value can change significantly it is also found that the variation of the 6 value estimate is in good agreement with the structure of seismic wave fractional velocity perturbations the regions of high and low 6 values correspond respectively to the lower and higher parts of the p wave velocity the similar relationship is seen with the spatial structure of the seismic wave attenuation

the large scale atmospheric structure accompanying new england coastal frontogenesis and associated north american east coast cyclogenesis an eleven case composite is constructed of the large scale flow configuration accompanying wintertime new england coastal frontogenesis events which are associated with atlantic coast cyclogenesis in the united states the pre coastal front environment is dominated by anticyclonic activity in the lower troposphere over the eastern great lakes the cold anticyclone moves eastward north of new england while slowly strengthening and is eventually responsible for the cold south easterly flow that participates in the developing coastal front circulation coastal frontogenesis commences in an increasingly favourable synoptic scale environment for ascending motion and pressure falls with both the passage of the 500 mb ridge axis and the onset of strong 850 mb warm air advection beneath the entrance region of a broad confluence zone at 500 mb the synoptic scale forcing for ascent over the developing coastal front is maximized from the cyclonic shear side of the jet in the base of the 500 mb trough to the anticyclonic shear side of the jet entrance region in the downstream confluence zone clearly identifiable departures in both the global scale wavenumbers 0 3 and large synoptic scale wavenumbers 4 8 waves from the long term climatological mean 1000 500 mb thickness field are observed during the evolution of the atlantic coast cyclogenesis event the major deviations from climatology in the wavenumbers 0 3 thickness deviation fields are negative anomalies in eastern asia the northern soviet union and the united states and positive anomalies over alaska and greenland the global scale thickness waves show substantial evolution in their transience and amplitude characteristics following the onset of the cyclogenesis event the wavenumbers 4 8 thickness anomaly analyses reveal initially quasi stationary amplification during the onset of cyclogenesis as atlantic coast cyclone development proceeds however a pronounced positive thickness anomaly is generated in the western atlantic and extends into new england similarly wavenumbers 4 8 thickness anomalies from eastern north america to western europe amplify and become more progressive

extratropical fronts in the lower troposphere global perspectives obtained from two automated methods in this study two commonly used automated methods to detect atmospheric fronts in the lower troposphere are compared in various synoptic situations the first method is a thermal approach relying on the gradient of equivalent potential temperature th while the second method is based on temporal changes in the 10 m wind wnd for a comprehensive objective comparison of the outputs of these methods of frontal identification both schemes are firstly applied to an idealised strong baroclinic wave simulation in the absence of topography then two case studies one in the northern hemisphere nh and one in the southern hemisphere sh were conducted to contrast fronts detected by the methods finally we obtain global winter and summer frontal occurrence climatologies derived from era interim for 1979 2012 and compare the structure of these th is able to identify cold and warm fronts in strong baroclinic cases that are in good agreement with manual analyses wnd is particularly suited for the detection of strongly elongated meridionally oriented moving fronts but has very limited ability to identify zonally oriented warm fronts we note that the areas of the main th frontal activity are shifted equatorwards compared to the wnd patterns and are located upstream of regions of main wnd front activity the number of wnd fronts in the nh shows more interseasonal variations than th fronts decreasing by more than 50 from winter to summer in the sh there is a weaker seasonal variation of the number of observed wnd fronts however th front activity reduces from summer djf to winter jja the main motivation is to give an overview of the performance of these methods such that researchers can choose the appropriate one for their particular interest

rossby wave breaking the upper level jet and serial clustering of extratropical cyclones in western europe winter 2013 14 was the stormiest on record for the uk and was characterized by recurrent clustering of extratropical cyclones this clustering was associated with a strong straight and persistent north atlantic jet and was also associated with rossby wave breaking rwb on both flanks pinning the jet in place the occurrence of rwb and cyclone clustering is further studied in 36 years of the era interim reanalysis clustering at 55 n is associated with an extended and anomalously strong eddy driven jet flanked on both sides by rwb however clustering at 65 45 n has a dominance of rwb to the south north of the jet deflecting the jet northward southward a positive correlation was found between clustering and rwb occurrence to the north and south of the jet however there is considerable spread in these relationships

the upper boundary of the philippine sea plate beneath the western kanto region estimated from s p converted wave abstract in the kanto tokai district of central japan the configuration of the subducting philippine sea plate has been estimated using three dimensional velocity inversions of the seismic wave velocity structure and the distribution of microearthquakes however it is difficult to show the configuration of the philippine sea plate from the distribution of microearthquakes beneath the western kanto region i e the yamanashi and nagano prefectures because seismic activity is quite low there a clear x phase between p and s phases on seismograms from an earthquake is observed at temporary seismological stations located in this area this x phase is identified as the s to p converted wave at the upper boundary of the subducting philippine sea plate thus we have been able to deduce the shape of the philippine sea plate and to show that it dips northwest

frontal wave stability during moist deformation frontogenesis part i linear wave dynamics abstract it has been shown that lower tropospheric potential vorticity zones formed during moist deformation frontogenesis will support growing waves if at some time the frontogenesis ceases in this paper the ways in which these waves are affected by the frontogenetic process are identified observations show that fronts in the eastern atlantic commonly feature saturated ascent regions characterized by zero moist potential vorticity furthermore in many cases the horizontal temperature gradient in the lowest one to two kilometers of the atmosphere is rather weak these features are incorporated in an analytical archetype the dynamical implications of saturated ascent in conditions of zero moist potential vorticity are represented in the model by assuming that adiabatic temperature changes are precisely balanced by diabatic tendencies the observed small temperature gradient at low levels is represented in the model by taking it to be zero in the lowest two kilometers consequently the forcing of the

the south fossa magna japan revealed by high resolution p and s wave travel time tomography abstract detailed tomographic images of the collision zone between the northern edge of the philippine sea and the eurasian plates reveal a high correlation between tectonic features inferred from seismicity and p and s wave velocity structures the linear tomographic inversion covered a 150 150 60 km region in the south fossa magna centered on the northern izu peninsula thirty three three component stations were located in the target region and 3823 high quality earthquakes were selected from the catalogues of the nriesdp giving rise to 53 593 p and 50 059 s wave phase arrivals used in the inversion the model was parameterized by 60 60 10 rectilinear blocks measuring 2 5 km per side horizontally and 5 10 km varying thicknesses in depth three dimensional perturbations from the one dimensional nriesdp layered model were derived by minimizing the squared misfit of the travel time residuals regularization was employed to reduce the effects of noisy data by constraining the two dimensional laplacian of the model within horizontal layers to be small the large sparse matrix was solved using the conjugate gradient algorithm lsqr reduction of misfit was 50 for the p wave inversion and 57 for the s wave inversion there is a high correlation between the p and s wave inversions between 5 15 km depth both 3d images indicate low velocity anomalies trending northward in the west along the fujikawa from suruga bay to northwest of mt fuji north of izu peninsula there is a broad high velocity zone these results correlate with bouguer gravity anomalies previously observed starting at 5 km depth a high velocity northeast dipping anomaly beneath sagami bay is inferred to be the shallow subducting phs plate to the north a high velocity zone in the vicinity of the east yamanashi seismic swarm 15 32 km depth is clearly observed on the p wave inversion and to a lesser extent on the s wave inversion because of the high seismicity in this region we speculate this is the zone where the phs plate is grazing the eur plate to the northwest and the high velocity anomaly represents a large scale asperity to the west below thmt fuji area a broad low velocity is observed between 15 and 32 km depth we interpret the deep low velocity structure which exhibits little seismicity to be either the subduction of the volcanic arc or a region of elevated temperature associated with hot rising magma near the swarm area on the eastern edge of izu peninsula low velocity anomalies are observed near the surface on both p and s wave inversions along the eastern part of izu peninsula a prominent low velocity anomaly is observed between 10 and 20 km on the s wave image but is less pronounced on the p wave inversion

secondary frontal waves in the north atlantic region a dynamical perspective of current ideas the current understanding of the dynamics of secondary cyclogenesis on frontal systems in the north atlantic region is reviewed these secondary cyclones are often poorly forecast and in extreme cases can have damaging consequences but because of their small scales and potential for rapid growth detailed observations and analyses are limited in this paper recent work is described and compared it is argued that on the synoptic scale the development of primary baroclinic waves is well understood but on the subscales of these systems where the secondaries develop there is a wider variety of mechanisms which may cause or modify cyclone growth this variety may be reflected in a wider range of resulting systems various dynamical models have been postulated secondary frontal waves are seen as the instability of a low level potential vorticity strip or warm band at a front with possible finite amplitude triggering by upper level features latent heating is thought to provide a suitable unstable potential vorticity strip but the degree to which the latent heating contributes to the instability itself is a matter of dissent secondary systems are often shallow so boundary layer processes are important but the influence of these is not well understood laboratory experiments have suggested that the boundary layer will act to suppress instability in general frontogenetic strain flow while acting to intensify the basic state front suppresses wave development in contrast recent work suggests that a frontolytic strain flow may be important in enhancing the development of one class of waves the fastex experiment an international field study of north atlantic secondary cyclogensis has recently attempted to observe these systems in detail it is hoped that the data which have been obtained will help to resolve some of the outstanding issues in this field

secondary cyclogenesis the initiation phase of a frontal wave observed over the eastern atlantic the initiation phase of a secondary frontal wave in the wake of a primary cyclogenesis event over the atlantic is documented north of the trailing surface cold front and south west of the primary cyclone an intense upper level jet generates a direct and transverse ageostrophic circulation in its entrance region evidence is shown for two conflicting roles of this circulation first stabilization of the front through frontogenetic cross frontal low level convergence and second an increase of the potential for instability of the front through diabatic e g latent heat release potential vorticity pv redistribution in the upward branch of the circulation following saturation of the primary cyclogenesis and the associated along front north eastwards shift of the upper level jet the low level branch of the ageostrophic circulation behaves like a zipper closing on the front while in the upward branch an anomalous strip of pv builds along the cold front isentropic pv maps show that parcles of stratospheric origin embedded in the downward branch of the ageostrophic circulation a tropopause fold may have ended in the vicinity of the strip of anomalous low level pv perhaps contributing to an increase in the potential for instability of the surface front using the domain independent attribution method of bishop it is shown that the frontal wave forms on a part of the cold front where first the along front stretching rate due to the environmental flow decays below the critical threshold value 0 6 10 5 s 1 prescribed by theoretical studies and second the across front frontogenetic component due to the ageostrophic circulation decays this is consistent with semi geostrophic theory where the cross frontal convergence and the stretching deformation are linked through the sawyer eliassen equation results add to other recent observational findings that the potential for instability the evolving environmental flow and the induced ageostrophic convergence each have a crucial role in differentiating between frontal waves that will grow and those that will be suppressed

amplitude distribution of seismic waves for laterally heterogeneous structures including a subducting slab summary we demonstrate the effects that the subducting plate 3 d velocity and q structures of the upper mantle beneath japan can have on the amplitudes of seismic waves observed above the inhomogeneous structure and we explore the possibility of finding the fine velocity and q structures by means of the amplitude distribution the methods used for the computation of the seismograms are the ray tracing and also gaussian beams which give more accurate amplitudes at caustics and shadow zones first we construct a slab velocity model by calculating the temperature distribution within and around the subducting slab and investigate the effects of relative source location within the slab possible detachment of shallow and deep parts of the slab and elevation and depression of the 400 km discontinuity within the slab the possibility of detecting the location of the leading edge of the subducted slab is also examined by calculating the amplitude distribution of incident plane waves the distribution of the ray amplitudes is also calculated for a velocity model including the pacific plate subducting beneath japan we finally adopt a 3 d velocity and q structure model including the subducting pacific plate and philippine sea plate in the uppermost mantle beneath japan obtained from previous studies the calculations for incident plane waves reveal that there may be large variations of the amplitudes on the surface it is found that the maximum amplitude distribution of waveforms calculated by the gaussian beam method for most of the above cases gives a smoothed pattern of the corresponding ray amplitudes and that the amplitudes for low frequency waves are smoother than those of high frequencies from all these calculations we find that the amplitude distributions are very sensitive to the velocity heterogeneities suggesting that the amplitude distribution may be used to obtain the source location within the slab and fine velocity and q structures of the upper mantle near the subduction zone

identification and climatology of southern hemisphere mobile fronts in a modern reanalysis abstractpresented here is an objective approach to identify characterize and track southern hemisphere mobile fronts in hemispheric analyses of relatively modest resolution such as reanalyses among the principles in its design were that it should be based on broadscale synoptic considerations and be as simple and easily understood as possible the resulting eulerian scheme has been applied to the european centre for medium range weather forecasts ecmwf re analysis era interim and a climatology of frontal characteristics at both the 10 m and 850 hpa levels derived for the period 1 january 1989 28 february 2009 the knowledge of the character of these features is central to understanding weather and climate over the hemisphere in both summer and winter the latitude belt 40 60 s hosts the highest frequency of frontal points but there are significant zonal asymmetries within this band the climatology reveals that the longest fronts are in the indian ocean where mean lengths exceed 2000 km the me

the role of secondary cyclones and cyclone families for the north atlantic storm track and clustering over western europe secondary cyclones are those that form in association with a pre existing primary cyclone typically along a trailing cold front in previously studied cases they have been shown to cause extreme damage across europe particularly when multiple cyclones track over the same location in rapid succession known as cyclone clustering to determine the dynamical relationship between primary and secondary cyclones over the north atlantic a frontal identification algorithm is partnered with a cyclone identification method to objectively identify secondary cyclones in 35 extended winter periods using reanalysis data cyclones are grouped into cyclone families consisting of a single primary cyclone and one or more secondary cyclones this paper aims to quantify the differences between secondary and primary cyclones over the north atlantic and how cyclone families contribute to episodes of cyclone clustering across western europe secondary cyclones are shown to occur most frequently in the central and eastern north atlantic whereas primary cyclones are commonly found over the western north atlantic cyclone families have their strongest presence over the north atlantic ocean and contribute more than 50 of cyclones over the main north atlantic storm track a final category solo cyclones which are not associated with cyclogenesis on any connected fronts are most commonly identified over continental regions as well as the mediterranean sea primary cyclones are associated with the development of an environment that is favourable for secondary cyclone growth enhanced rossby wave breaking following primary cyclone development leads to an increase in the upper level jet speed and a decrease in low level stability secondary cyclogenesis commonly occurs in this region of anomalously low stability close to the european continent during periods of cyclone clustering secondary cyclones are responsible for approximately 50 of the total number of cyclones the increase in jet speed and decrease in static stability initiated by the primary cyclones acts to concentrate the genesis region of secondary cyclones and direct the cyclones that form along a similar track while there is an increase in the secondary cyclogenesis rate near western europe during periods of european clustering the basin wide secondary cyclogenesis rate decreases during these periods thus the large scale environment redistributes secondary cyclones during periods of clustering rather than increasing the total number of secondary cyclones

detection of the subducting crust of oceanic plates beneath the kanto district japan abstract low velocity crustal layers on the top of the subducting slabs beneath the kanto district central japan were detected by a travel time inversion using 40 763 p wave arrival times from 3038 local earthquakes recorded by a local network of 41 seismic stations the inversion covered 188 228 110 km volume of the target region and the model was parameterized by 47 57 18 rectilinear blocks measuring 4 0 km per side horizontally and 4 10 km varying thickness in depth a prominent e w directed low velocity band of about 25 km width appeared in the central kanto region at a depth of 30 km moving north or northwestward gradually with depth this band can be traced to the depth of about 60 km at a depth of 60 km a slightly lower amplitude nearly n s directed low velocity band was observed at the east coast of the kanto region moving westward with depth these low velocity bands are thin layers attached to the top of the inclined thick layers with relatively high velocity in the kanto district the philippine sea phs plate subducts under the eurasian eur plate and the pacific pac plate also underthrusts beneath both the eur and phs plates some authors already suggested low velocity anomalies near the surface of those descending plates in this region mainly from the analyses of later phases and focal mechanisms of local earthquakes the shapes of the low velocity bands are similar to the depth distribution of the upper boundary of the phs and pac plates proposed by other authors the thrust earthquakes that occur at the boundaries between the eur and phs plates and between the phs and pac plates are almost located in the low velocity layers described above we conclude that these low velocity layers are the crusts that exist at the top of the subducting phs and pac plates while high velocity layers are subducting slabs themselves for the phs plate low density crust of the izu bonin arc is probably stacking at the range from 139 25 e to 139 55 e at 35 55 n which is observed as a thick low velocity region to the south of the range and in a steep inclination to the north of it this is also recognized from the gravity anomaly

vertical crustal movement in the boso peninsula south kanto japan as deduced from the adjustment of a geodetic network with signals abstract in the adjustment of a leveling network that is frequently resurveyed we introduce corrections not only to the approximated heights of the stations but also to their rates of vertical movement which are linear over time as an unknown thus we can apply least squares collocation to the problem and have some cases corresponding to the rank deficiency of the design matrix in the observation equation we have applied this method to the study of the vertical crustal deformation in the kanto district particularly to the boso peninsula honshu japan rates of vertical crustal movement and their covariance matrices are deduced for two periods for the kanto district 1 1965 1978 and 2 1978 1989 and for three periods for the boso peninsula 1 1965 1972 2 1973 1976 and 3 1976 1988 the deduced rates range from 10 mm yr to 10 mm yr and their standard deviations amount to 11 mm yr for the kanto district for the boso peninsula they range from 22 mm yr to 6 mm yr and amount to 5 mm yr this peninsula is very close to the convergent plate boundary between the philippine sea plate and south kanto and the results of this analysis reveal the typical fluctuating behavior of the crustal movements associated with the subduction process during the interseismic period the author interprets this episodic crustal movement as being due to intermittent creep dislocation along the deeper part of the interface between the kanto district and the philippine sea plate

the role of large scale atmospheric flow and rossby wave breaking in the evolution of extreme windstorms over europe we investigate the relationship between large scale atmospheric flow and the evolution of the most extreme windstorms affecting western continental europe the 25 most destructive western continent

amphibolitization of metagabbros in the scottish highlands compositions of actinolite hornblende and cummingtonite together with pyroxene and plagioclase are studied in basic intrusions in the dalradian of north east scotland and the glen scaddle complex in the west moine amphibolitization is due to influx of water from the country rocks pyroxene compositions are found to have adjusted to the regional metamorphic environment owing to the difficulty of diffusion of al and si calcic amphiboles are zoned and commonly contain quartz blebs discontinuities in zoning give rise to actinolite hornblende pairs compared with north east scotland disequilibrium is less strong in the glen scaddle area in the latter plagioclase compositions have been greatly changed na partition between hornblende and plagioclase is close to equilibrium the maximum al content of hornblende is lower and zoning patterns are more consistent the fe mg ratio in calcic amphiboles varies with al content while approaching equilibrium partition with other minerals both zoning patterns and fe mg partition with cummingtonite suggest that fe mg of the calcic amphiboles increases more strongly with increasing alvi fe3 than can be explained simply by substitution of al fe3 for mg on m2 model reactions for amphibole formation are constructed cummingtonite formed at lower chemical potential of cao than actinolite ca was exchanged for mg fe between orthopyroxene derived and clinopyroxene derived local systems both cummingtonite and actinolite were formed because of kinetic constraints as intermediate reaction products actinolite hornblende pairs represent disequilibrium this work suggests that many occurrences of actinolite with hornblende where the minerals are zoned may also be due to diffusion kinetics

subducting oceanic crusts of the philippine sea and pacific plates and weak zone normal compression in the kanto district japan summary oceanic crusts subducting into the mantle were detected by analyses of mantle earthquakes in the kanto district central japan earthquakes in a depth range of 30 80 km in the southwestern ibaraki prefecture were relocated by a modified method of joint hypocentre determination we obtained a good distribution map of hypocentres and focal mechanisms a boundary layer between the eurasian and philippine sea plates was found where thrust earthquakes with p axes in the nw se direction and of which low angle nodal planes dip northward occurred in a layer with a thickness of about 4 km the p wave velocity in this layer is estimated to be less than about 7 0kms l another boundary layer between the philippine sea and pacific plates exists about 15 km beneath the above boundary layer thrust earthquakes with p axes in the ew direction and of which low angle nodal planes dip westward occurred in this layer that also has a thickness of about 4km furthermore normal faulting earthquakes of which the p axes are almost perpendicular to the boundary layers were found immediately outside the boundary layers combining these results we can conclude that the boundary layers are oceanic crusts that exist at the top of the subducting philippine sea and pacific plates weak zone normal compression was proposed to result from the existence of low velocity oceanic crusts at plate boundaries this hypothesis can be explained because only stress caused by relative motion of the two plates is consumed inside the weak oceanic crust the remnant stress after subtracting the above stress from the tectonic one applied at the plate boundary is the stress of which the p axis is normal to the plate boundary

frontal instability generated by tropospheric potential vorticity anomalies the development of secondary disturbances on a two dimensional front is described using a linear stability analysis a two stage process is envisaged in which first strong frontogenesis produces condensation at the front this leads to the generation of a lower tropospheric zone of high potential vorticity pv lying along the front as frontogenesis weakens the second stage is entered in which an essentially steady front is susceptible to the growth of linear normal modes along the front owing to the existence of the pv anomaly or equivalently the frontal rainband thus for a typical band of width 160 km a frontal wave of some 800 km is produced with a growth rate of about 1 day 1 the dynamics of these modes is examined by considering both the realistic frontal flow as well as idealized strips of pv anomalies the idealized case is potentially applicable to a variety of meteorological situations such as upper jet streaks useful insight is gained from an analysis of the energetics of the modes this shows that for narrow frontal pv anomalies the waves main energy source is the basic kinetic energy and further they have a negative vertical heat flux recent observations suggest that frontal waves are indeed characterized by such a heat flux as most frontal zones involve significant condensation and therefore are likely to exhibit a lower tropospheric pv maximum it is stressed that studies of frontal waves need to include this aspect of the frontal structure

imaging the subducting slabs and mantle upwelling under the japan islands summary a high resolution p wave tomography of the crust and mantle down to 700 km depth beneath the japan islands is determined using a large number of high quality arrival time data from local earthquakes and teleseismic events simultaneously the tomography shows that the philippine sea slab is subducting aseismically down to 430 km depth under southwest japan though the seismicity within the slab ends at 180 km depth a low velocity low v zone in the mantle wedge under tohoku and kyushu is found to extend westward from the volcanic front to the backarc under the japan sea and east china sea significant low v anomalies are revealed in the deep portion of the mantle wedge 400 500 km depth above the pacific slab under southwest japan which may reflect hot mantle upwelling associated with fluids from the deep dehydration of the pacific slab low v anomalies appear at 420 700 km depths beneath the pacific slab under eastern japan which may reflect hot mantle upwelling associated with the deep subduction of the pacific slab and its collapsing down to the lower mantle

contemporary crustal deformations in the izu peninsula honshu japan and acceleration of plate bending in the northernmost part of the philippine sea plate since the beginning of the anomalous vertical crustal movement in the izu peninsul honshu japan many repeated precise levellings have been carried out by the geographical survey institute trilaterations covering the entire izu peninsula have also been carried out by the geographical survey institute a new technique is developed to adjust the results of levellings because they had been carried out for different epochs along each levelling route and because of rapid vertical crustal movements in conventional least squares adjustment of levelling network only corrections to the approximate height are assumed to be unknown while in the present analysis a special model in which rates of vertical deformation at any bench marks are also assumed to be unknown is adopted in addition tidal stations along the coast of the izu peninsula yield the rate of vertical crustal movement from analysis of tidal data independent of levelling data we select several special bench marks in which rates of vertical movement are determined by tidal analysis thereafter special adjustment is applied according to the type of network

classifying dynamical forcing mechanisms using a climatology of extratropical cyclones summary a climatology of almost 700 extratropical cyclones is compiled by applying an automated feature tracking algorithm to a database of objectively identified cyclonic features cyclones are classified according to the relative contributions to the midlevel vertical motion of the forcing from upper and lower levels averaged over the cyclone intensification period average u lratio and also by the horizontal separation between their upper level trough and low level cyclone tilt the frequency distribution of the average u lratio of the cyclones contains two significant peaks and a long tail at high u lratio although discrete categories of cyclones have not been identified the cyclones comprising the peaks and tail have characteristics that have been shown to be consistent with the type a b and c cyclones of the threefold classification scheme using the thresholds in average u lratio determined from the frequency distribution type a b and c cyclones account for 30 38 and 32 of the total number of cyclones respectively cyclones with small average u l ratio are more likely to be developing cyclones attain a relative vorticity 1 2 10 4 s 1 whereas cyclones with large average u lratio are more likely to be non developing cyclones 60 of type a cyclones develop whereas 31 of type c cyclones develop type a cyclogenesis dominates in the development region east of the rockies and over the gulf stream type b cyclogenesis dominates in the region off the east coast of the usa and type c cyclogenesis is more common over the oceans in regions of weaker low level baroclinicity

role of moist processes in the tracks of idealized midlatitude surface cyclones abstractthe effects of moist processes on the tracks of midlatitude surface cyclones are studied by performing idealized mesoscale simulations in each simulation a finite amplitude surface cyclone is initialized on the warm air side of a zonal baroclinic jet for some simulations an upper level cyclonic anomaly upstream of the surface cyclone is also added initially sensitivities to the upper level perturbation and moist processes are analyzed by both performing a relative vorticity budget analysis and adopting a potential vorticity pv perspective whatever the simulation there is a systematic crossing of the zonal jet by the surface cyclone occurring after roughly 30 h a pv inversion tool shows that it is the nonlinear advection of the surface cyclone by the upper level pv dipole which explains the cross jet motion of the surface cyclone the simulation with an initial upper level cyclonic anomaly creates a stronger surface cyclone and a more intense upper level pv dipole than the simulation with

structure of the benioff zone beneath the shumagin islands alaska relocation of local earthquakes using three dimensional ray tracing seismic rays are traced through a prescribed three dimensional inhomogeneity that simulates the subducted slab below the shumagin islands region to calculate local station delays for a given hypocenter and a slab model hypocenters determined by the shumagin seismic network are then relocated using the station delays a flat layered velocity structure and a standard earthquake location computer program station delays are calculated for 12 hypocenters with respect to six different slab models to identify the slab model that is most consistent with the available arrival time and waveform data a set of path corrections that is calculated for each grid point station pair on a preliminary grid of 36 points in the depth range from 60 to 300 km is used to recalculate the hypocenters for all of the 1982 earthquakes with depths greater than 50 km application of this method to data from 1982 for the digitally recording shumagin seismic network shows the following results 1 a previously observed apparent increase in dip of the subducted slab at depths of 100 km disappears 2 the subducted slab can be modeled as a dipping structure that dips at a constant angle of 45 toward north northwest at depths between 80 and 250 300 km and has a 7 higher velocity than the surrounding mantle 3 hypocenters determined from shumagin network data are located only 10 20 km south of high quality hypocenters determined from teleseismic data alone 4 qualitative comparison of digitally recorded seismograms with calculated ray paths shows enrichment of high frequency coda possible converted phases and low amplitudes of first p arrivals for rays that travel mostly along the slab conversely for rays that travel almost vertically through the upper plate the seismograms show a high amplitude of first p arrivals that are followed by an insignificant coda and low amplitude s waves

characteristics of the atlantic storm track eddy activity and its relation with the north atlantic oscillation abstract this study focuses on feedbacks of the high frequency eddy activity onto the quasi stationary circulation particularly with regard to the north atlantic oscillation nao the methodology consists of analyzing ncep ncar reanalysis data and sensitivity runs from a high resolution nonhydrostatic regional model consistent with recent studies results show that the jet displacement characteristic of the nao phenomenon depends strongly on the dynamics of the synoptic scale waves and the way they break positive and negative phases of the nao are closely related to anticyclonic and cyclonic wave breaking respectively indeed the high frequency momentum flux whose sign is directly related to the type of wave breaking is correlated with the nao index over the atlantic the peak of the momentum flux signal precedes that of the nao by a few days suggesting that wave breaking is triggering nao events two examples illustrate the significant impact of single storms in particular those occurring in the e

a pv perspective on the vertical structure of mature midlatitude cyclones in the northern hemisphere development of extratropical cyclones can be seen as an interplay of three positive potential vorticity anomalies an upper level stratospheric intrusion low tropospheric diabatically produced potential vorticity pv and a warm anomaly at the surface acting as a surrogate pv anomaly this study based on the interim ecmwf re analysis era interim dataset quantifies the amplitude of the pv anomalies of mature extratropical cyclones in different regions in the northern hemisphere on a climatological basis a tracking algorithm is applied to sea level pressure slp fields to identify cyclone tracks surface potential temperatureanomalies duandverticalprofilesofpvanomalies dpvarecalculatedatthetimeofthecyclones minimumslpinaverticalcylinderaroundthesurfacecyclonecenter tocomparethecyclones characteristics they are grouped according to their location and intensity composite dpv profiles are calculated for each region and intensity class at the time of minimum slp and during the cyclone intensification phase in the maturestage allthree anomaliesare on averagelargerfor intense thanforweak wintercyclones e g 0 6 versus 0 2 potential vorticity units pvu 1 pvu 510 26 kk g 21 m 2 s 21 at lower levels and 1 5 versus 0 5 pvu at upper levels the regional variability of the cyclones vertical structure and the profile evolution is prominent cyclones in some regionsare moresensitiveto the amplitude ofa particularanomalythanin other regions values of du and low level dpv are on average larger in the western parts of the oceans than in the eastern parts results for summer are qualitatively similar except for distinctively weaker surface du values