surface wave mapping of the crust and upper mantle in the arctic region pure path rayleigh wave group velocities for 24 regional grids inside the arctic have been obtained from 74 mixed path measurements the vertical shear wave velocity structures under these 24 grids were then determined according to their pure path group velocity dispersion data this result indicates that the crustal shear wave velocity in the arctic region is generally lower than the worldwide average in addition a typical mid ocean ridge structure was clearly shown under the nansen ridge we also found an abnormally high upper mantle shear wave velocity under the alpha ridge and makarov basin and low velocity beneath the canadian arctic islands in general our inversion result agrees with the known tectonics in the arctic region to further check the validity of our result we have computed synthetic rayleigh waves and a comparison with our observations shows very good agreement

the development of a second circulation center within tropical storm isabel 1985 abstract observations in the boundary layer by the noaa aoc wp 3d aircraft from 8 to 10 october 1985 document the development of a second vortex which evolves into the circulation center for tropical storm isabel the new circulation develops just outside the radius of maximum winds and is associated with intensifying convection 90 km from the original center the original center loses its identity as convection dissipates around it low surface pressure warm dry air and low equivalent potential temperature are found in the new center near its formation time the new center is found beneath the downwind anvil of the intense convection in the rainband and appears to form over a period of 3 6 h although significant changes in the storm scale airflow north of the original center are occurring over the proceeding 24 h the new center moves with a speed and direction similar to that of the original center the observations of isabel are compared to beat bursts subsidence and midlevel mesovortices that h

global marine gravity from retracked geosat and ers 1 altimetry ridge segmentation versus spreading rate 1 three approaches are used to reduce the error in the satellite derived marine gravity anomalies first we have retracked the raw waveforms from the ers 1 and geosat gm missions resulting in improvements in range precision of 40 and 27 respectively second we have used the recently published egm2008 global gravity model as a reference field to provide a seamless gravity transition from land to ocean third we have used a biharmonic spline interpolation method to construct residual vertical deflection grids comparisons between shipboard gravity and the global gravity grid show errors ranging from 2 0 mgal in the gulf of mexico to 4 0 mgal in areas with rugged seafloor topography the largest errors of up to 20 mgal occur on the crests of narrow large seamounts the global spreading ridges are well resolved and show variations in ridge axis morphology and segmentation with spreading rate for rates less than about 60 mm a the typical ridge segment is 50 80 km long while it increases dramatically at higher rates 100 1000 km this transition spreading rate of 60 mm a also marks the transition from axial valley to axial high we speculate that a single mechanism controls both transitions candidates include both lithospheric and asthenospheric processes

structure and evolution of the northern barents kara sea continental margin from integrated analysis of potential fields bathymetry and sparse seismic data summary the northern barents kara sea continental margin is a poorly investigated area because of a permanent ice cover hampering seismic exploration the available geological and geophysical data show that the magma poor margin developed in response to early cenozoic breakup and subsequent opening of the arctic eurasia basin in this study a series of crustalscale geotransects illustrating the architecture of the continental margin are constructed using sparse seismic reflection profiles and a gravity inversion method incorporating a thermal model of rifting the continental side of the northern barents sea margin is underlain by palaeozoic early mesozoic deep sedimentary basins separated from the oceanic side by the marginal uplift a bathymetry analysis complements low resolution seismic data to predict the sedimentary depocenters beyond the shelf break these depocenters are associated with troughs perpendicular to the shelf edge the depocenter in front of the st anna trough may contain a sedimentary section more than 4 km thick the gravity correction for the effect of sedimentary cover was added to the inversion this correction used an exponential density depth function the inversion supports a narrow and steep continent ocean transition cot ca 100 km the conjugate lomonosov ridge margin is modelled using the same technique palaeoreconstructions were made to predict the break up setting the northern barents sea lomonosov ridge rift system can be described as an initially narrow symmetric rift a transitional zone of extreme thinning is assumed between the oldest spreading magnetic anomaly and the stretched continental crust the free air gravity anomaly in the western part ofthemargincanbepredicted bytheupwelling divergentflowmodel implying theexhumation of the lower crust and the continental upper mantle within the cot it is suggested that an episodeofshearorobliqueextensionbeforebreakupisrequiredtoexplaintheobservednarrow symmetric conjugate margins in the eurasia basin

mesoscale air motions associated with a tropical squall line abstract composites of radar and wind observations in a coordinate system attached to a moving tropical squall line confirm that such a squall system is composed of two separate circulation features a convective squall line region and a stratiform anvil region the squall line region is characterized by mesoscale boundary layer convergence which feeds deep convective updrafts and mid to upper level divergence associated with outflow from the cells the anvil region is characterized by mid level convergence which feeds both a mesoscale downdraft below the anvil and a mesoscale updraft within the anvil cloud before this study the mesoscale updraft in the anvil cloud of the tropical squall system had been somewhat speculative and both the anvil updraft and downdraft had been inferred only qualitatively the occurrence of the anvil updraft is now proven and quantitative profiles of the mesoscale anvil updraft and downdraft have been obtained

the relationship between seismic velocity and density in the continental crust a useful constraint summary plots of seismic velocity and density of rock samples show that a range of densities is possible for rocks of each seismic velocity and vice versa although a single linear relationship is often assumed in crustal gravity calculations because of the scatter whenever rocks of known seismic velocity are converted to density using this relationship a reduction is made to the resolving power of the resulting gravity calculation if these rocks reach thicknesses of more than a few kilometres then the uncertainties become significant when compared with the size of commonly observed gravity anomalies examples are considered from the north sea mississippi and carolina trough it is concluded that the use of a seismic velocity measurement as the only indication of rock density does not provide a useful constraint when attempting to reproduce observed gravity variations an appropriate model for isostatic compensation is probably the most important factor for successful predictions of crustal structure on the basis of gravity data

earthquake location genetic algorithms for teleseisms kennen b l n and sambndge m s 1992 earthquake location genetic algorithms for teleselsms phys earth planet inter 75 103 110 the location of earthquakes requires the estimation of the spatial and temporal components of the hypocentre this can he achieved by a direct mmlmtsatlon of a measure of the misfit between observed and calculated travel times and also slownesses and azimuths if array data are available an efficient means of carrying out this optlmlsatlon procedure is to make use of genetic algorithms this technique is based on the use of many estimates of the hypocentre location at once and the properties of the cluster of estimated locations in four dimensions are exploited m the course of the optlmtsatlon process each estimate of the hypocentral location is represented on a local discrete grid by a bit string and successive iterations generate new bit strings and hence location estimates by operations based on biological analogues these operations are the replication of the best fining bit strings the cross over of reformation between pairs of bit strings and the mutation of indwldual bits in a string the non local character of the information on the misfit function carried in the cloud of hypocentral estimates is usually sufficient to prevent the location being trapped in local minima of the misfit surface convergence to the global misfit minimum can be achieved with a very limited sampling of the original spatml and temporal grid no derivatives of the seismic phase information are reqmred and so the technique is easily generahsed to three dimensional velocity models and can be used with any statable measure of the quahty of an earthquake location by the choice of the misfit criterion between observed and calculated quantities

stochastic velocity inversion of seismic reflection refraction traveltime data for rift structure of the southwest barents sea we present results from an active source onshore offshore seismic reflection refraction transect acquired as part of the petrobar project petroleum related studies of the barents sea region the 700 km long profile is oriented nw se coincident with previously published multichannel seismic reflection profiles we utilize layer based raytracing in a markov chain monte carlo mcmc inversion to determine a probabilistic velocity model constraining the sedimentary rocks crystalline crust and uppermost mantle in a complex tectonic regime the profile images a wide range of crustal types and ages fromproterozoic craton to paleozoic to early cenozoic rift basins and volcanics related to eocene continental breakupwith greenland our analyses indicate a complex architecture of the crystalline crust along the profile with crystalline crustal thicknesses ranging from43 kmbeneath the varanger peninsula to 12 kmbeneath the bjornoya basin assuming an original post caledonide crustal thickness of 35 km in the offshore area we calculate the cumulative thinning factors along the entire profile the average factor along the profile is 1 7 0 1 suggesting 211 243 km of extension consistent with the amount of overlap derived from published plate reconstructions local factors approach 3 where bjornoya basin reaches a depth of more than 13 km volcanics carbonates salt diagenesis and metamorphism make deep sedimentary basin fill difficult to distinguish from original pre rift crystalline crust and thus actual stretching may in places exceed our estimates

first paleomagnetic results from mio pliocene series of the hellenic sedimentary arc abstract paleomagnetic measurements have been conducted on the mio pliocene series along the external sedimentary hellenic arc in order to detect the presence or absence of rotational deformations in different sections of the arc in the central eastern part of the arc crete and rhodes paleomagnetic directions are very closely aligned along the north south direction showing that this portion of the arc has not undergone significant rotation since at least 7 m y for crete and 4 m y for rhodes in the western and northwestern parts results from south peloponnesos zakinthos kephallinia and corfu indicate that this section of the arc has undergone a clockwise rotation detailed analysis of the data from the three ionian islands shows that their rotation began about 5 m y b p and has proceeded since then at roughly 5 m y giving a total amplitude of about 26 it is suggested that the beginning of this rotation is related to the lower pliocene compressive phase which most probably initiated the tectonic activity of the present day ionian margin

seismic location calibration of the european arctic a crustal velocity model has been developed for fennoscandia the baltic shield and adjacent areas this model represents a simplified average of various models developed for parts of this region we show that p wave travel times calculated with this model provide an excellent fit to observations at the fennoscandian krsc and iris station networks for a set of seismic events with known or very well constrained locations the station event paths cover large parts of western russia and the barents sea thus indicating that this model which we denote the barents model is appropriate for this entire region we show by examples that significant improvements in event location precision can be achieved compared to using the 1aspei model we finally use the barents model to calculate locations of recent small seismic events in the novaya zemlya region of interest in a ctbt monitoring context

the evolution of hurricane humberto 2001 abstractin 2001 the national oceanic and atmospheric administration and the national aeronautical and space administration marshaled their resources to sample hurricane humberto for 3 successive days during the fourth convection and moisture experiment camex 4 humberto developed from a tropical storm into a category 2 hurricane despite the deep layer vertical shear of the environmental horizontal wind vws increasing markedly on the second and third days of sampling as exhibited in earlier studies the eyewall convection developed an azimuthal wavenumber 1 n 1 asymmetry as the vws increased horizontal divergence and vertical stability within 100 km of the eye exhibited persistent relationships to the vws vector the warm core evolved in an unexpected way the warm anomaly was initially located in the lower troposphere and built upward as the storm intensified the maximum temperature anomaly remained in the lower troposphere on all 3 days while the development of the upper tropospheric warm anom

the role of vortical hot towers in the formation of tropical cyclone diana 1984 abstract a high resolution 3 km horizontal grid spacing near cloud resolving numerical simulation of the formation of hurricane diana 1984 is used to examine the contribution of deep convective processes to tropical cyclone formation this study is focused on the 3 km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle the numerical simulation reveals the presence of vortical hot towers or cores of deep cumulonimbus convection possessing strong vertical vorticity that arise from buoyancy induced stretching of local absolute vertical vorticity in a vorticity rich prehurricane environment at near cloud resolving scales these vortical hot towers are the preferred mode of convection they are demonstrated to be the most important influence to the formation of the tropical storm via a two stage evolutionary process i preconditioning of the local environment via diabatic production of mul

a numerical study of the genesis of extratropical convective mesovortices part i evolution and dynamics abstract the purpose of this study is to understand the genesis of extratropical convective mesovortices and the large scale environmental features that influence the vortex formation a hypothesis is proposed that mesovortices form in the stratiform rain regions of mesoscale convective systems mcss due to the reduction of static stability that reduces the effective local rossby radius in such regions a conceptual model of the mesoscale convective cyclogenesis is introduced which describes the three stages of the mesovortex formation a modified version of the pennsylvania state university national center for atmospheric research three dimensional hydrostatic mesoscale model is used to simulate mesovortex genesis in analytically generated pre mcs large scale environments the model simultaneously incorporates parameterized convection and a grid resolvable convective scheme containing the effects of hydrostatic water loading condensation evaporation freezing melting and sublimation a control si

mesoscale interactions in tropical cyclone genesis with the multitude of cloud clusters over tropical oceans it has been perplexing that so few develop into tropical cyclones the authors postulate that a major obstacle has been the complexity of scale interactions particularly those on the mesoscale which have only recently been observable while there are well known climatological requirements these are by no means sufficient a major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development observations exist for only a few forming cases in these the moist convection in the preformation environment is organized into mesoscale convective systems each of which have associated mesoscale potential vortices in the midlevels interactions between these systems may lead to merger growth to the surface and development of both the nascent eye and inner rainbands of a tropical cyclone the process is essentially stochastic but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences for example a monsoon trough provides a region of reduced deformation radius which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices further a strong monsoon trough provides a vertical wind shear that enables long lived midlevel mesoscale vortices that are able to maintain or even redevelop the associated convective system the authors develop this hypothesis by use of a detailed case study of the formation of tropical cyclone oliver observed during toga coare 1993 in this case two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband the eye developed on the edge of the major convective system and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere the importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western north pacific

the 11 october 2010 novaya zemlya earthquake implications for velocity models and regional event location characterizing the seismicity of novaya zemlya and the surrounding arctic seas requires accurate event location estimates low magnitude events in this region are currently observed only by a small number of stations in the european arctic with a large azimuthal gap making the accuracy of regional velocity models all the more important regional travel time calibration is difficult given the scarcity of sufficiently well constrained events on 11 october 2010 a magnitude 4 5 event occurred close to the northern tip of novaya zemlya this event is significant in that it is the first event in this region to have been recorded both on the relatively recent regional networks and arrays and also teleseismically with good azimuthal coverage we examine how well we can constrain the location and origin time using only teleseismic phases using only first teleseismic p arrivals we constrain the epicenter to approximately 76 25 n and 64 75 e but with no depth resolution clear depth phases notably on stations in the southern united states indicate a depth between 9 and 15 km this independent hypocenter and origin time estimate allow evaluation of regional phase travel time prediction using different models the predicted sn travel time appears to cause the greatest variability in regional location estimates the 3d regional seismic travel times models provide excellent pn travel time estimates for barents sea paths but may slightly overestimate sn travel times from this source region a modified regional 1d velocity model is defined which best predicts pn and sn observations at multiple stations up to 15 the significance of the regional travel time models for estimating location is demonstrated for a low magnitude event on or close to the northern island of novaya zemlya in march 2014 recorded with a satisfactory signal to noise ratio at only four stations

objective determination of hurricane tracks from aircraft observations abstract an algorithm for location of hurricane centers by least squares using aircraft data has been developed as the aircraft traverses the eye lines of position normal to the wind are constructed each 100 m along its track an additional line of position is constructed normal to the track at the closest point of approach to the center the center coordinates are then chosen such that the sum of the squares of the normal distances from the center to the lines of position is minimized a cubic spline storm track is first constructed using centers based on winds in a coordinate system fixed to the earth a track based upon winds in moving storm centered coordinates may be obtained by transformation of the winds into such a coordinate system and iterative redetermination of the centers for intense hurricanes the centers can be located with an accuracy of 3 km and the mean motion over a period of four to six hours determined to within 4 of direction and 0 5 m s 1 of speed the details of the track osc

the johnstown flood of july 1977 a long lived convective system abstract the heavy rains responsible for the disastrous flash floods new johnstown pennsylvania on the night of 19 20 july 1977 are shown to be part of a large quasi circular mesoscale convective complex this complex can be traced back to an origin in south dakota nearly 96 h earlier the complex tends to become more compact and intense during the night with a radius of 150 km and to expand in response to new and peripheral convection during the day on the small synoptic scale the system is characterized by a pool of cool air at the surface and throughout the lower troposphere just north of the centroid of the rainstorm by a cyclonic circulation of substantial intensity in the lower and middle troposphere and by anticyclonic circulation in the upper troposphere airflow relative to the moving storm is southeasterly at the surface veering rapidly to southwesterly in the boundary layer and then to westerly in the upper troposphere substantial convective instability is present throughout the env

epicentre accuracy based on seismic network criteria summary we establish reliable and conservative estimates for epicentre location accuracy using data that are readily available in published seismic bulletins a large variety of seismic studies rely on catalogues of event locations making proper assessment of location uncertainty critical event location and uncertainty parameters in most global regional and national earthquake catalogues are obtained from traditional linearized inversion methods using a 1 d earth model to predict traveltimes reported catalogue uncertainties are based on the assumption that error processes are gaussian zero mean and uncorrelated unfortunately these assumptions are commonly violated leading to the underestimation of true location uncertainty especially at high confidence levels we find that catalogue location accuracy is most reliably estimated by station geometry we make use of two explosions with exactly known epicentres to develop local network location 0 2 5 accuracy criteria using monte carlo simulations of network geometry we find that local network locations are accurate to within 5 km with a 95 per cent confidence level when the network meets the following criteria 1 there are 10 or more stations all within 250 km 2 an azimuthal gap of less than 110 3 a secondary azimuthal gap of less than 160 and 4 at least one station within 30 km to derive location accuracy criteria for near regional 2 5 10 regional 2 5 20 and teleseismic 28 91 networks we use a large data set of exceptionally well located earthquakes and nuclear explosions beyond local distances we find that the secondary azimuthal gap is sufficient to constrain epicentre accuracy and location error increases when the secondary azimuthal gap exceeds 120 when station coverage meets the criterion of a secondary azimuth gap of less than 120 near regional networks provide 20 km accuracy at the 90 per cent confidence level while regional and teleseismic networks provide 25 km accuracy at the 90 per cent confidence level

geological structures on the south cretan continental margin and hellenic trench eastern mediterranean abstract combination of recent seismic profiles obtained along the south cretan continental margin with previously published data has provided a basis for mapping the overall structure of this portion of the active hellenic margin two sectors are distinguished from western crete to 25 east the continental slope is crossed by post late miocene extensional features creating a series of sedimental marginal troughs and steep basement ridges the lower slope the trench and parts of its outer slope are areas of little sedimentation most of the sediments are trapped on the margin and of active deformation this area represents the eastern prolongation of the ionian branch matapan trench of the hellenic subduction zone and is interpreted in the light of ne directed compression from 25 e to eastern crete the geological structures of both the continental margin and the adjacent trenches differ from those to the west this difference possibly relates to interferences between the present day structural directions interpreted in relation to a left lateral transform motion and previous trends inherited from a preceding ns compression

mesoscale and convective scale characteristics of mature hurricanes part i general observations by research aircraft abstract the analysis of instrumented aircraft data from four recent mature hurricanes reveals common mesoscale and convective scale features the structure and organization of the convection precipitation and wind flow are studied by combining the airborne observations using basic instrumentation with quantitative radar measurements three predominant precipitation features seen are 1 the eyewall 2 a stratiform rain region adjacent to and outside the eyewall and 3 rainbands that contain both convective and stratiform regions the eyewall is so named because it surrounds the rain free eye but several additional features distinguish it from other convective bands in the hurricane in particular the updraft tangential wind maximum and highest rainfall have preferred locations relative to each other with the updraft being radially inward from the rain and wind maxima the 10 dbz radar reflectivity contour indicative of the inner edge slopes substantially outward with height and there is evide

evolution of the structure of precipitation in hurricane allen 1980 abstract reflectivity data from the airborne radar systems on board the three noaa aircraft were gathered during six consecutive days in hurricane allen of 1980 the data have been used to specify the horizontal and vertical precipitation distribution within 111 km radius of the hurricane center the evolution of the structure and intensity of the precipitation in the storm is described from representative time composite radar maps for seven research flights made during the 6 day period the eyewall was characterized by a narrow ring 12 15 km wide of intense reflectivity 42 47 dbz surrounding the center of the storm at a radius that varied in time from 12 40 km the eyewall had steep radial gradients of reflectivity 4 5 db km 1 and tilted radially outward in height the rainbands were characterized by areas of enhanced reflectivity embedded in a region of stratiform rainfall that contained a distinct bright band at the height of the 0 c isotherm the most striking changes in structure during the 6 d

structural sketch of the hellenic continental margin between the western peloponnesus and eastern crete a structural sketch of the hellenic continental margin and adjacent areas based on numerous seismic profiles obtained in the past few years shows two distinct structural domains an inner extensional domain characterizes most of the continental margin the offshore regions as well as the cretan sea an outer compressional domain extends over the trenches and part of their outer slope we believe that this perplexing pattern is related to the presence of an underlying evaporitic series progressively deformed and piling up against a resistant continental margin the completion of subduction and subsequent continental collision are also involved in this structural framework

the hellenic margin from eastern crete to rhodes preliminary results abstract complementary data on previously surveyed areas have been obtained and more than 3000 km of continuous seismic profiles along the eastern hellenic continental margin between eastern crete and rhodes have been made among the important preliminary observations we note the relatively great thickness due to probable coarse rapid fill of the margin sedimentary cover which is also intensively affected by extensional faulting the presence of a well defined sedimentary basin lying between the strabo and pliny trench where evaporitic strata exist but where the acoustic facies also suggest coarse fill is probably derived from surrounding topographical highs exposed to erosion during the messinian finally we observe a progressive and perplexing change of the strabo trench structural pattern from west to east which indicates a more complex tectonic regime than we expected we speculate that at the southern margin of the rhodes basin northward thrusting may now be occurring

extensional compressional tectonics associated with the aegean arc comparison with the andean cordillera of south peru north bolivia extensional compressional tectonics are analysed along the convergent boundaries of the aegean arc and of the andean cordillera of south peru and north bolivia this paper deals only with deformations of miocene pliocene and pleistocene ages the prevailing regime in the aegean basin is extensional yet two compressional tectonic phases of u miocene l pliocene and of l pleistocene age have been recorded they are also known in many places all around the mediterranean thus forces that induce compressional tectonics in the aegean seem to have their origin outside the region they seem to be linked with changes in the conditions of convergence change in rate between the arabo african and eurasian plates beneath the andean cordillera of south peru north bolivia the subduction zone plunges at an angle of 25 30 as it does under the aegean arc there as in the aegean sea tectonics are predominantly extensional and several short lived compressional phases break up this extensional regime the latter may also be induced by changes of the conditions of convergence here between the nazca and south american plates beneath central peru north of the nazca ridge the subduction zone plunges at a small angle about 10 there neotectonic deformations are different in the recent they are essentially compressional or expressed by strike slip faulting geological data from the aegean and andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries

a three dimensional geophysical model of the crust in the barents sea region model construction and basement characterization summary barents50 a new 3 d geophysical model of the crust in the barents sea region has been developed by the university of oslo norsar and the u s geological survey the target region comprises northern norway and finland parts of the kola peninsula and the east european lowlands novaya zemlya the kara sea and franz josef land terminate the region to the east while the norwegian greenland sea marks the western boundary in total 680 1 d seismic velocity profiles were compiled mostly by sampling 2 d seismic velocity transects from seismic refraction profiles seismic reflection data in the western barents sea were further used for density modelling and subsequent density to velocity conversion velocities from these profiles were binned into two sedimentary and three crystalline crustal layers the first step of the compilation comprised the layer wise interpolation of the velocities and thicknesses within the different geological provinces of the study region linear relationships between the thickness of the sedimentary rocks and the thickness of the remaining crystalline crust are observed we therefore used the separately compiled area wide sediment thickness data to adjust the total crystalline crustal thickness according to the total sedimentary thickness where no constraints from 1 d velocity profiles existed the barents50 model is based on an equidistant hexagonal grid with a node spacing of 50 km the p wave velocity model was used for gravity modelling to obtain 3 d density structure a better fit to the observed gravity was achieved using a grid search algorithm which focussed on the density contrast of the sediment basement interface an improvement compared to older geophysical models is the high resolution of 50 km velocity transects through the 3 d model illustrate geological features of the european arctic the possible petrology of the crystalline basement in western and eastern barents sea is discussed on the basis of the observed seismic velocity structure the barents50 model is available at http www norsar no seismology barents3d

the role of a convective burst in the genesis of typhoon hagupit 2008 1 this study explores the effects of the mesoscale descent associated with a convective burst during the genesis of typhoon hagupit 2008 based on a high resolution cloud resolving numerical simulation the simulation result captures the synoptic scale circulation surrounding the pre hagupit depression and the evolution of the storm a burst of intense deep convection occurs about 1 day before the genesis of hagupit after the convective burst temperature deviation near the center of the depression increases in the lower troposphere this warming contributes to a drop in the central pressure of the depression and hence to the beginning of the so called system scale intensification in addition the low level warming tends to inhibit vertical motion by acting as a lid horizontal flow is therefore dominant in the boundary layer thereby the air can efficiently gain energy from the sea surface increased energy in the boundary layer air feeds intense deep convection near the center of the depression just before the genesis time these results are consistent with a previous observational study tangential momentum budget analysis demonstrates that just before the genesis time actual tendency of tangential velocity has larger values throughout the depth of the troposphere indicating the importance of the deep layer spin up of the depression these large values are attributed to the upward transport of tangential momentum by intense deep convection in contrast when the convective burst occurs about 1 day before the genesis time positive actual tendency is confined to the lower troposphere because of smaller upward transport of tangential momentum

evidence for northward thrusting south west of the rhodes basin models of convergence between the major african and european plates involve a stretching aegean plate whose present motion relative to africa is south west1 3 this motion has resulted in subduction of eastern mediterranean sea floor as shown by seismicity volcanism and morphology the southern boundary of the aegean plate is formed by the hellenic trench intensive study culminating in the use of submersibles and multibeam echo sounding as part of the hellenic arc and trench program4 has outlined the complexity of this boundary detailed reflection profiling which we carried out in autumn 1980 of the eastern portion of the hellenic trench system shows arcward verging thrusting south west of the rhodes basin we conclude that collision of the african continental margin with the hellenic arc is now in progress causing overriding by the mediterranean ridge along the southeastern branch of the hellenic trench system

hyposat an enhanced routine to locate seismic events a program package called hyposat has been under development that attempts to use the maximum information possible to estimate the hypocenter of a seismic source the standard input parameters can be used arrival times of first and later onsets with backazimuths and ray parameters or apparent velocities in addition travel time differences between different phases observed at the same station can be optionally used the observed standard deviations are used to weight all input parameters and the inversion is done with a generalized matrix inversion code

the structure and regional significance of the talea ori crete abstract on the basis of detailed geological mapping in the talea ori of crete metamorphic rocks previously interpreted as basement to the plattenkalk series are re interpreted as down faulted parts of the overlying phyllite quartzite series nappe a supposed unconformity separating these two units is shown to be a high angle fault the phyllite quartzite series and overlying nappes were affected by two major deformational phases whereas the plattenkalk series has a simpler structural history and was folded and imbricated by southwards directed overthrusting which emplaced the phyllite quartzite series nappe and other overlying nappes in the oligocene we reject previous models of a huge inversion of the plattenkalk series and we also consider that considerable local inversion by tight to isoclinal folding and thrusting means that the stratigraphic thickness is much less than previously appreciated the differences between the structural and sedimentological histories of the plattenkalk series and the overlying nappes implies that they were separated by a major crustal discontinuity such as a transform or transcurrent fault before the oligocene overthrusting

fish tanks of eastern crete greece as indicators of the roman sea level abstract the ancient fish tanks and fish traps of crete are relics of the roman domination of the island they were usually constructed near the major urban centers of that period the direct relationship of their various functional characteristics with past sea levels and the relatively accurate determination of their construction dates establish them as sensitive indicators of sea level change through space and time the fish tanks presented in detail in this study namely those of matala chersonissos mochlos and sitia and the fish trap in the gulf of zakros have all been reported recorded and or interpreted in regard to their operation by previous researchers in the absence of a comprehensive interdisciplinary approach to the issue uneven methodologies inaccurate data and wrong measurements have led to erroneous conclusions about sea level during their operation and about the size and direction of vertical tectonic movements in eastern crete during the upper holocene the present study is based on a new underwater survey in the course of which the architectural and functional features of the ancient constructions were reexamined precisely their depth from modern sea level was measured and their relationship with coastal landforms indicative of a past sea levels was investigated a review of their manner of operation and their modern submerged position allowed the definition of a roman mean sea level 1 24 m 0 09 m below the present one the submersion of the central and eastern parts of crete included in the same tectonic block with a total length of at least 150 km at an average tectonic rate of 0 65 mm year during the last 1900 100 years occurred as is shown by historical evidence during a paroxysmal tectonic event probably related to the strong earthquake of 1604

a mesoscale convective complex generated inertially stable warm core vortex abstract a long lived mesoscale convectively generated vortex mcv associated with a mesoscale convective complex mcc is documented the mcv with a rossby number of approximately 0 5 is investigated as a feature intrinsic to the organization of the mcc on 6 7 july 1982 a particularly large and intense mcc developed in a region of high convective available potential energy cape but weak vertical wind shear bulk richardson number 150 and weak advection of temperature and vorticity convection initially was organized in a narrow line with elements propagating relative to the mean environmental flow these elements subsequently developed a large semicircular area of stratiform precipitation and a surface mesolow to the rear heavy rain fell over a broad area amounts as great as 10 9 cm accompanied by flooding were reported in central oklahoma as the large semicircular rain area dissipated a three layered structure became evident a large upper tropospheric anticyclone a rain cooled mesoscale h

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction

continent ocean transition across a trans tensional margin segment off bear island barents sea a 410 km long ocean bottom seismometer profile spanning from the bear island barents sea to oceanic crust formed along the mohns ridge has been modelled by use of ray tracing with regard to observed p waves the northeastern part of the model represents typical continental crust thinned from ca 30 km thickness beneath the bear island to ca 13 km within the continent ocean transition between the hornsund fz and the knolegga fault a 3 4 km thick sedimentary basin dominantly of permian carboniferous age is modelled beneath the ca 1 5 km thick layer of volcanics vestbakken volcanic province the p wave velocity in the 3 4 km thick lowermost continental crust is significantly higher than normal ca 7 5 km s 1 we interpret this layer as a mixture of mafic intrusions and continental crystalline blocks dominantly related to the paleocene early eocene rifting event the crystalline portion of the crust within the south western part of the cot consists of a ca 30 km wide and ca 6 km thick high velocity 7 3 km s 1 body we interpret the body as a ridge of serpentinized peridotites the magmatic portion of the ocean crust accreted along the knipovich ridge from continental break up at ca 35 ma until ca 20 ma is 3 5 km thicker than normal we interpret the increased magmatism as a passive response to the bending of this southernmost part of the knipovich ridge the thickness of the magmatic portion of the crust formed along the mohns ridge at ca 20 ma decreases to ca 3 km which is normal for ultra slow spreading ridges

miocene detachment in crete and exhumation p t t paths of high pressure metamorphic rocks a major problem posed by the geology of crete is the horizontal contact of an upper unit without miocene metamorphism onto a metamorphosed lower one with early miocene high pressure low temperature hp lt parageneses this very sharp contact is roughly parallel to the major oligo miocene thrust planes which were reactivated as a large scale detachment which allowed exhumation of high pressure units we describe the extensional deformation and the metamorphic evolution of the lower plate most first order deformation features relate to the retrogression from high pressure to low pressure conditions a n s pervasive stretching is observed everywhere often associated with a top to the north sense of shear the extreme variation of thickness of the phyllite quartzite nappe upper part of the lower plate is probably the result of large scale boudinage similar to the one seen in large outcrops the most important observation is the systematic occurrence of fresh carpholite immediately below the base of the tripolitza nappe except in northwestern crete where a late extensional shear zone is present deeper in the nappe pile carpholite is systematically retrograded this observation reveals a drastically different pt history for the upper part of the phyllite quartzite nappe it also suggests that the late extensional shear zone found along the northern side of crete cuts inside the metamorphic structure and brings the nonmetamorphosed tripolitza nappe directly in contact with the deeper parts of the phyllite quartzite nappe pt t paths suggest a fast temperature decrease in the top of the phyllite quartzite during retrogression and hence during the top to the north shear the deeper part of the phyllite quartzite nappe shows a low temperature regime throughout but its pt path includes an isothermal decompression in the first stage we produce a tentative map of domains having experienced similar pt trajectories during decompression the overall cool regime is related to the continuous underthrusting of cola continental units during exhumation isothermal decompression observed in the core of the phyllite quartzite nappe implies fast exhumation during extension and the faster cooling of the upper part is related to a continuous displacement toward the north of a cooler unit during exhumation single grain 39ar 40ar ages obtained on phengites 15 25 ma in various structural sites are in good agreement with these conclusions and with the geological context suggesting that underthrusting of cold units at the front the accretionnary complex occurred contemporaneously with unroofing below a north dipping detachment near the top of the wedge the age of this detachment is bracketed between the end of the high pressure event 20 ma and the deposition of the breccia early to middle miocene in the neogene basins

joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath utah united states abstract we present a method for using any combination of body wave arrival time measurements surface wave dispersion observations and gravity data to simultaneously invert for three dimensional p and s wave velocity models the simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type resulting in a comprehensive and higher resolution three dimensional geophysical model in a case study for utah we combine body wave first arrivals mainly from the usarray transportable array rayleigh wave group and phase velocity dispersion data and bouguer gravity anomalies to invert for crustal and upper mantle structure of the region results show clear delineations visible in both p and s wave velocities between the three main tectonic provinces in the region without the inclusion of the surface wave and gravity constraints these delineations are less clear particularly for s wave velocities indeed checkerboard tests confirm that the inclusion of the additional datasets dramatically improves s wave velocity recovery with more subtle improvements to p wave velocity recovery demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints

origin and tectonic setting of some melange units in turkey a geologic study of three different melange belts in turkey revealed that the melange units in these belts were formed by gravity sliding in basins underlain by continental basement rather than by tectonic crushing in trenches mafic volcanic activity is a characteristic feature of such basins which are located on continental margins adjacent to tectonically active belts the peridotite and gabbro blocks of the melange units were transported but some of the basalts radiolarites and mudstones originated within the basins and hence are not part of an ophiolite suite

eo alpine metamorphism in the uppermost unit of the cretan nappe system petrology and geochronology the uppermost unit of the cretan nappe system consists of ophiolites on the top and an ophiolitic melange at the base

insights into the lithospheric structure and tectonic setting of the barents sea region from isostatic considerations summary we study the tectonic setting and lithospheric structure of the greater barents sea region by investigating its isostatic state and its gravity field 3 d forward density modelling utilizing available information from seismic data and boreholes shows an apparent shift between the level of observed and modelled gravity anomalies this difference cannot be solely explained by changes in crustal density furthermore isostatic calculations show that the present crustal thickness of 35 37 km in the eastern barents sea is greater than required to isostatically balance the deep basins of the area 19 km to isostatically compensate the missing masses from the thick crust and deep basins and to adequately explain the gravity field high density material 3300 3350 kg m 3 in the lithospheric mantle below the eastern barents sea is needed the distribution of mantle densities shows a regional division between the western and eastern barents and kara seas in addition a band of high densities is observed in the lower crust along the transition zone from the eastern to western barents sea the distribution of high density material in the crust and mantle suggests a connection to the neoproterozoic timanide orogen and argues against the presence of a caledonian suture in the eastern barents sea furthermore the results indicate that the basins of the western barents sea are mainly affected by rifting while the eastern barents sea basins are located on a stable continental platform

travel times and attenuation relations for regional phases in the barents sea region a database containing 45 events in the barents sea region has been compiled and analyzed with the aim of evaluating crustal models travel times and attenuation relations in the context of performing regional detection threshold monitoring of this region the 45 events are mostly located around the circumference of the study area due to the virtually aseismic nature of the barents sea itself regional p n and s n phases were observable for most events in the database while p g and l g phases were only observable for events with raypaths that do not cross the tectonic structures in the barents sea this corroborates a number of previous observations of l g wave blockage within the barents sea three existing velocity models were evaluated with a model having slightly lower s velocities than earlier assumed in the upper mantle giving the overall best fit to the observed arrivals in order to estimate magnitudes short term average sta and spectral amplitude values were calculated in several frequency bands for all phase arrivals in the database there were no significant differences between spectral and sta amplitudes so the latter were used as this parameter is more efficient to calculate in real time processing an inversion was performed in order to determine an attenuation relation specific for this region the resulting magnitudes based on p n p g s n and l g phases gave an internally consistent reasonably stable set of values which can be calibrated towards any existing global or regional scale

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

the prina complex in eastern crete and its relationship to possible miocene strike slip tectonics abstract the basal neogene formations in the ierapetra region eastern crete are strongly influenced by a late serravallian tectonic phase which resulted in the breakup of pre existing palaeogeographic patterns important vertical movements caused the southward emplacement of neogene sediments together with parts of the underlying pre neogene nappe pile the resulting chaotic association of exotic blocks and sediments known as the prina complex has the properties of a sedimentary melange it can be traced for more than 15 km from north to south in the north a relatively coherent accumulation of large slide masses overlies deformed neogene coarse clastics and pre neogene rocks distally it comprises a poorly stratified sequence of breccias and intermixed finer grained sediments which locally contains olistostromes and debris flows and interfingers to the south with submarine fan deposits the intricate relation of faulting and gravity sliding in a rapidly subsiding basin can be explained by generation in a strike slip setting it is suggested that the ierapetra basin and its offshore extension the south cretan trough were initiated by sinistral movements along a ne sw oriented fault zone implications of this model for the geodynamic evolution of the south aegean area are discussed

thermodynamic and kinematic influences on precipitation symmetry in sheared tropical cyclones bertha and cristobal 2014 abstractprior studies have shown an association between symmetrically distributed precipitation and tropical cyclone tc intensification although environmental vertical wind shear typically forces an asymmetric precipitation distribution in tcs the magnitude of this asymmetry can exhibit considerable variability even among tcs that experience similar shear magnitudes this observational study examines the thermodynamic and kinematic influences on precipitation symmetry in two such cases bertha and cristobal 2014 consistent with the impact of the shear both tcs exhibited a tilted vortex as well as a pronounced azimuthal asymmetry with the maximum precipitation occurring in the downshear left quadrant however bertha was characterized by more symmetrically distributed precipitation and relatively modest vertical motions while cristobal was characterized by more azimuthally confined precipitation and much more vigorous vertical motions observations showed three potential hindrances to precipitat

extension and exhumation of the hp lt rocks in the hellenic forearc ridge localized intensive ductile and ductile brittle extension of along the arc orientation is prominent in phyllite quartzite unit pqu rocks in kythera and the adjacent southeastern peloponnese but declines in prominence to the north and to the south along the cretan peloponnese ridge using zircon and apatite fission track dating we find that this structural characteristic is correlated with the youngest zircon fission track cooling ages of 14 to 9 ma and with the highest pressure temperature condition recorded in the metamorphic rocks below the structural detachment the cooling ages of the high pressure phyllite quartzite unit pqu rocks along the hellenic forearc ridge show that exhumation migrated from both crete and from the peloponnese to the area with the youngest ages in kythera and the southeastern peloponnese starting in the early miocene and continuing to the present trench rollback and slab retreat expanded the hellenic arc and this bending of the arc from an initial more rectilinear geometry increased areas of oblique convergence and we suggest this localized the subsequent arc parallel extension and local enhanced exhumation of hp rocks the zircon fit exhumation ages from the arc parallel stretching episode restrict the ductile part of this episode in exposed rocks to between about 14 and 9 ma apatite ft ages suggest brittle along arc extension continued to about 7 ma this episode is proposed to be the result of a temporary higher rate of rollback and slab retreat younger normal faults including those which define the margins of the present hellenic arc show return to arc normal extension

surface cyclogenesis from convectively driven amplification of midlevel mesoscale convective vortices mesoscale convective vortices mcvs are midtropospheric warm core cyclonic circulations that often develop in the stratiform region of mesoscale convective systems typically divergent anticyclonically circulating mesoscale cold anomalies appear both above and below the mcv the upper level cold anomaly is usually found near the tropopause while the low level anomaly is surface based and exhibits locally higher pressure one aspect of mcvs that has received much attention recently is the role that they may play in tropical cyclogenesis of special interest is how an mcv amplifies when deep convection redevelops within the borders of its midlevel cyclonic circulation and how the amplified mcv transforms the divergent surface based cold pool with anomalously high surface pressure into a convergent cyclonic circulation with anomalously low pressure the pennsylvania state university national center for atmospheric research fifth generation mesoscale model is used to simulate an mcv that was instrumental in initiating within the borders of the midlevel vortex s circulation several successive cycles of convective development and decay over a 2 day period after each cycle of convection both the horizontal size of the cyclonic circulation and the magnitude of the potential vorticity associated with the vortex were observed to increase the simulation reproduces the development and evolution of the mcv and associated convective cycles mesoscale features responsible for the initiation of convection within the circulation of the vortex and the impact of this convection on the structure and evolution of the vortex are investigated a conceptual model is presented to explain how convective redevelopment within the mcv causes low level heights to fall and cyclonic vorticity to grow downward to the surface applying this conceptual model to a tropical marine environment is also considered

crustal and uppermost mantle structure in the middle east assessing constraints provided by jointly modelling ps and sp receiver functions and rayleigh wave group velocity dispersion curves

the inflow to tropical cyclone humberto 2001 as viewed with azimuth height surfaces over three days abstractthe deployment of 228 global positioning system dropwindsondes gps sondes over three consecutive days in tropical cyclone humberto 2001 allows for the creation of azimuth height z surfaces from sea level to 3 km altitude at 0 25 and 0 5 latitude distance from the storm center the authors estimate the radial flow along these z surfaces to diagnose the mass flux through said surfaces as humberto deepens from 1000 to 983 hpa from the first to the second day then fills to 992 hpa by the third day as the tropical cyclone tc intensifies the width depth and rate of inflow increase the inflow remains a wavenumber 1 pattern throughout the three days the center of the inflow rotates clockwise over this period following the expected forcing due to both the tropical cyclone motion and deep layer shear vectors net vertical mass flux based on continuity within a given volume is correlated with tc intensity only for the inner 0 25 z surface slightly farther from the center at 0 5

monte carlo approach to assess the uncertainty of wide angle layered models application to the santos basin brazil abstract in the santos basin brazil two parallel wide angle refraction profiles show different crustal structures one shows moderate crustal velocity gradient and a clear moho with topography the other has an anomalous velocity zone and no clear moho reflections this has large implications on the geological and geodynamical interpretation of the basin model uncertainties must be excluded as a source of these differences we developed vmontecarlo a tool to assess model uncertainty of layered velocity models using a monte carlo approach and simultaneous parameter perturbation using all picked refracted and reflected arrivals it gives insights into the acceptable geological interpretations allowed by data and model uncertainty through velocity depth plots that provide a the velocity depth profile range that is consistent with the travel times b the random model that provides the best fit keeping most of the observations covered by ray tracing c insight into valid models dispersion d main model features unequivocally required by the travel times e g first order versus second order discontinuities and velocity gradient magnitudes e parameter value probability distribution histograms vmontecarlo is seamlessly integrated into a rayinvr based modelling work flow and can be used to assess final models or sound the solution space for alternate models and is also capable of evaluating forward models without the need for inversion thus avoiding local minima that may trap the inversion algorithms and providing information for models still not well parametrised results for the brazilian models show that the imaged structures are indeed geologically different and are not due to different interpretations of the same features within the model uncertainty bounds these differences highlight the strong heterogeneity of the crust in the middle of the santos basin where the rift is supposed to have failed

genesis of pre hurricane felix 2007 part i the role of the easterly wave critical layer abstract the formation of pre hurricane felix 2007 in a tropical easterly wave is examined in a two part study using the weather research and forecasting wrf model with a high resolution nested grid configuration that permits the representation of cloud system processes the simulation commences during the wave stage of the precursor african easterly wave disturbance here the simulated and observed developments are compared while in part ii of the study various large scale analyses physical parameterizations and initialization times are explored to document model sensitivities in this first part the authors focus on the wave vortex morphology its interaction with the adjacent intertropical convergence zone complex and the vorticity balance in the neighborhood of the developing storm analysis of the model simulation points to a bottom up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by dunkerton montgome

mesoscale observations of the genesis of hurricane dolly 1996 abstract recent numerical studies of tropical cyclone genesis suggest a new paradigm for how the surface vortex is established based on a highly nonaxisymmetric mechanism involving the interaction of low level cyclonic circulations generated by deep cumulonimbus convection a reexamination of mesoscale observations during the genesis of hurricane guillermo 1991 confirms the presence of multiple cyclonic circulations more recently airborne doppler radar wind observations during the genesis of atlantic hurricane dolly 1996 also reveal multiple lower to middle tropospheric mesoscale cyclonic circulations during sequential 15 20 min compositing periods a particularly well organized but initially weak mean tangential wind of 7 m s 1 low level cyclonic vortex embedded within the pre dolly tropical disturbance is observed coincident with deep vertically penetrating cumulonimbus convection the earliest observations of this vortex show the peak circulation near 2 km height with a mean diameter of 30 4

atypical thermodynamic profiles in hurricanes the global positioning system dropwindsondes deployed in hurricane bonnie on 26 august 1998 with supporting deployments in hurricanes mitch 1998 and humberto 2001 are used to identify three unusual thermodynamic structures in the lower cloud and subcloud layers two of these structures impact the energy content of the inflow and therefore the intensity of the hurricane first positive lapse rates of equivalent potential temperature are found near the top of the inflow these layers insulate the inflow from the negative impacts of entrainment mixing and promote rapid energy increases especially near the eyewall the second structure is a rapid decrease of equivalent potential temperature adjacent to the sea surface this is essentially a prominent surface layer that owes its existence to both higher moisture content and a superadiabatic lapse rate the steep lapse rate most often occurs under and near the eyewall where wind speeds at the surface exceed hurricane force the author speculates that water loading from spray increases the residence time of air parcels in the surface layer contributing to the creation of this structure the third feature is a moist absolutely unstable layer previously identified by bryan and fritsch for the midlatitudes these layers are found adjacent to the eyewall in rainbands and in the hub cloud within the eye and are evidence of mesoscale or vortex scale convergence and the very modest instabilities often found in the core of a hurricane

the life cycle and internal structure of a mesoscale convective complex abstract this paper describes the life cycle and precipitation structure of a mesoscale convective complex mcc that passed through the data collecting network of the texas portion of the high plains cooperative program hiplex on 8 june 1980 the mcc was the third in a sequence of five mesoscale convective systems that formed in association with a low level frontal zone short wave perturbations in the 500 mb flow outflow from previous convection and upslope forcing quantitative radar data together with surface upper air and satellite data were used to determine the three dimensional structure of the mcc isolated echoes formed over the davis mountains of far western texas and merged as they moved eastward to form a mesoscale convective system with a lifetime of 24 h and a low level precipitation pattern 500 km across the leading edge of the low level precipitation pattern was a north south line of intense convective cells possessing the echo structure and low level kinematic and thermodynamic

observed tropical cyclone eye thermal anomaly profiles extending above 300 hpa abstractas recently pointed out by stern and nolan much of our knowledge of the warm core structure of the tropical cyclone eye has come from composites of in situ data taken from multiple aircraft studies of three storms in the late 1950s and 1960s further observational confirmation of eye thermal structure has been lacking since much of the dropsonde data analyzed to date have been limited to pressure levels of 500 hpa or lower however there exist a number of dropsonde eye profiles extending to near 250 hpa these profiles were acquired from nasa aircraft during various field campaigns here the author uses these data to calculate eye temperature anomaly profiles these data are supplemented by several surface based radiosonde releases in tropical cyclone eyes over the period 1944 2003 the author finds that the pressure altitude of the maximum anomaly varies between 760 and 250 hpa the author also finds positive correlations between the maximum anomaly level and storm intensity size upper leve

tropical cyclogenesis via convectively forced vortex rossby waves in a shallow water primitive equation model abstract this work examines further the problem of tropical cyclogenesis by convective generation of vertical vorticity within a preexisting cyclonic circulation whose initial maximum tangential wind is approximately 5 m s 1 this paper validates and extends recent work examining the suggested upscale cascade mechanism in a three dimensional quasigeostrophic framework using a simple shallow water primitive equation swpe numerical model and helps clarify certain aspects of the rossby adjustment problem on a nonresting basic state for finite amplitude nonaxisymmetric disturbances the swpe approach serves as a meaningful intermediate step between the quasigeostrophic and full physics frameworks and allows a simple investigation of the effects of unbalanced dynamics contributions of gravity waves and rossby numbers of order unity the authors compare quantitative results of the two models on the storm spinup time and magnitude for asymmetric initial conditions whose mass and wind field are out of balanc

a probabilistic seismic model for the european arctic 1 the development of three dimensional seismic models for the crust and upper mantle has traditionally focused on finding one model that provides the best fit to the data while observing some regularization constraints in contrast to this the inversion employed here fits the data in a probabilistic sense and thus provides a quantitative measure of model uncertainty our probabilistic model is based on two sources of information 1 prior information which is independent from the data and 2 different geophysical data sets including thickness constraints velocity profiles gravity data surface wave group velocities and regional body wave traveltimes we use a markov chain monte carlo mcmc algorithm to sample models from the prior distribution the set of plausible models and test them against the data to generate the posterior distribution the ensemble of models that fit the data with assigned uncertainties while being computationally more expensive such a probabilistic inversion provides a more complete picture of solution space and allows us to combine various data sets the complex geology of the european arctic encompassing oceanic crust continental shelf regions rift basins and old cratonic crust as well as the nonuniform coverage of the region by data with varying degrees of uncertainty makes it a challenging setting for any imaging technique and therefore an ideal environment for demonstrating the practical advantages of a probabilistic approach maps of depth to basement and depth to moho derived from the posterior distribution are in good agreement with previously published maps and interpretations of the regional tectonic setting the predicted uncertainties which are as important as the absolute values correlate well with the variations in data coverage and quality in the region a practical advantage of our probabilistic model is that it can provide estimates for the uncertainties of observables due to model uncertainties we will demonstrate how this can be used for the formulation of earthquake location algorithms that take model uncertainties into account when estimating location uncertainties

the neotectonics of the aegean an alternative view minor reverse faults in widely dispersed neogene outcrops in the central aegean have led several people to suggest that the regional extension which started in the lower pliocene or earlier was interrupted by short periods of compression the durations of these postulated compressional episodes are short compared to the time scale on which convective forces acting on the base of the lithosphere can change thus possible mechanisms for driving such motions are limited in this paper we offer alternative explanations for these observations and in particular show that these apparently compressional episodes are probably not regional in extent and may not be truly compressional in origin in some places they are more likely to be a consequence of the considerable rotation that is found in extensional terranes the plio quaternary paleogeography of the central aegean is satisfactorily explained by uplift in the footwall blocks of normal faults and does not require regional compression studies of the faulting associated with recent large earthquakes suggest that the sort of microtectonic analysis which is typically carried out on small faults in surficial sediments is more likely to reflect the internal deformation of blocks bounded by major fault structures than be a reliable indicator of regional stress patterns

tectonics of the hellenic trench a synthesis of sea beam and submersible observations abstract detailed bathymetric investigations were performed in four zones of the hellenic trench system in 1978 using the multi narrow beam echo sounder sea beam on r v jean charcot in 1979 a field study using the 3000 m submersible cyana was conducted in three of the four sites covered by sea beam we summarize here the principal tectonic results of these studies and publish the corresponding sea beam maps it is shown that compressional structures affect the sedimentary cover of the outer wall and trench whereas extensional tectonics is present on the inner wall in addition there is evidence that most of the upper sedimentary cover is not subducted but rather piles up in front of the trench to form the mediterranean ridge we suggest that the surface limit of the zone of mechanical decoupling occurs near the base of the inner wall we show that the gross structure of the trench as well as the strain pattern observed is controlled by the kinematics of subduction and we discuss its evolution since its initiation about 13 m y ago

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

crustal structure of the fennoscandian shield a traveltime interpretation of the long range fennolora seismic refraction profile abstract the 1979 fennoscandian long range project fennolora was aimed at the determination of the detailed structure in the earth s mantle down to a depth of about 400 km observation distances reached almost 2000 km within scandinavia between shotpoints off the north cape and the southern coast of sweden to achieve an unbiased regarding the upper mantle structure a careful crustal survey was carried out along the entire profile at the same time beneath the fennoscandian shield i e the central section of the profile the crust is characterized by quite a smooth increase in p wave velocity down to the moho which lies at a depth of about 50 km in the southern half of the shield and at about 45 km further north the mean crustal velocity is 6 6 6 7 km s at the base of the crust the velocity increases gradually from about 7 km s to 8 0 8 4 km s in a 5 10 km thick crust mantle transition zone both in the south and in the north the relatively homogeneous crust of the baltic shield borders on areas with a more differentiated velocity structure first order discontinuities at shallower depth characterize the crust mantle boundary near the southeastern tip of sweden 38 km and under the caledonides in the north 43 km

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

environmental conditions prior to formation of a midget tropical cyclone during tcm 93 abstract during a 10 day period in the tropical cyclone motion tcm 93 field experiment over the tropical western north pacific tropical cyclone formation occurred in association with persistent deep convection that was observed over low level north oriented confluent flow between a large monsoon gyre to the west of a strong subtropical ridge the convection was also modulated by a strong diurnal cycle with a convective maximum just before dawn and a convective minimum during the late afternoon observations from two aircraft observing periods a0ps during two consecutive daytime periods identified three distinct mesoscale convective vortices mcvs in the persistent deep convection during the initial aop aop 1a a well defined mesoscale circulation at 500 mb was located directly above the strong low level south southwesterly confluent flow however reduction in convection and associated midlevel forcing during the convective minimum period contributed to the decay of the mcv before it could pene

tropical cyclone formation in a sheared environment a case study abstract the development of hurricane danny 1997 from depression to hurricane was examined using cloud to ground lightning data reconnaissance aircraft data and satellite imagery vertical wind shear between 850 and 200 hpa of 5 11 m s 1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development early in the period the storm intensified steadily in the presence of this downshear convection during the last and most intense outbreak a second vortex appeared to develop within the convection evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original based on these events it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process equivalent potential temperature fields within 500 m of the surface were examined only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of eq

comparison of location procedures the kara sea event of 16 august 1997 various location procedures and velocity models are compared for the ml 3 3 kara sea event of 16 august 1997 this event has been the subject of considerable discussion because of its geographical position and the difficulty in obtaining a reliable focal depth estimate a comprehensive data set was extracted by re reading the records from all available stations these readings have then been used in a sequence of location experiments to examine the effect of using different velocity models to describe the travel times of the phases and also to compare the use of a fully nonlinear scheme shakena sambridge and kennett 2001 and a linearized location algorithm hyposat schweitzer 2001 2002 a standard least squares misfit criterion has been used for direct comparisons between the two methods the results confirm both the importance of s wave information in assessing the depth of regional events and the need to apply a reliable velocity model to place the strongest constraints on the location of the event even with only a limited data set but an adequate velocity model it is possible to find the position of the kara sea event close to the most probable locations however there is then no depth resolution reported error ellipses from standard data centers tend to have relatively small error ellipses with the commonly made assumption that the reading errors and the a posteriori residuals have an unbiased normal distribution such inversion results may indicate an unreasonably high resolution and accuracy of the solution the epicenter estimates for the whole data set using the range of different tech niques agree quite well with some overlap of the estimated confidence regions the observed seismic source was most likely an earthquake in the middle or lower crust at about 10 30 km depth

deep seismic reflection profiles across the western barents sea summary the continental crust beneath the western barents sea has been acoustically imaged down to moho depths in a large scale deep seismic reflection experiment a first order pattern of crustal reflectivity has been established and the thickness of the crust determined a number of features with important implications for the tectonics of the area have been discovered the results are presented in the form of two transects

numerical simulations of the genesis of hurricane diana 1984 part i control simulation abstract the complete transformation of a weak baroclinic disturbance into hurricane diana is reproduced by numerical simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model three distinct phases of the evolution are evident first baroclinic and barotropic development strongly modified by the effects of latent heating occurs during the latter part of this phase the low level circulation is strengthened through the axisymmetrization of remote potential vorticity anomalies that are generated by condensational heating and then advected toward the incipient storm the axisymmetrization process evinces properties of both nonlinear discrete vortex merger and vortex rossby wave dynamics the transformation from cold core to warm core vortex occurs in this development stage in the second phase lasting 10 12 h little deepening occurs spiral bands of convection begin to form and the core of the storm moistens eventually reaching 95

early pliocene sedimentation in the cretan region implications for the timing and amount of vertical motion along the south hellenic arc eastern mediterranean abstract a boxcore taken from the top of a seamount south of crete on the outer south side of the hellenic trench contains allochtonous coarse clastics consisting mainly of rock fragments of alpine basement brecciated early middle pliocene marls and reworked older neogene sediments this mixture of lithologies is interpreted as an early middle pliocene mass flow deposit which can be correlated with similar deposits from adjoining on and offshore areas the wide distribution of these sediments may be related to a period of increased tectonic activity which caused substantial vertical movements in the south hellenic arc it is concluded that at the time of the formation of the mass flow deposits this part of the hellenic trench had not yet evolved

evolution and structure of the 6 7 may 1985 mesoscale convective system and associated vortex abstract observations collected during the oklahoma kansas pre storm experiment are used to document the evolution and structure of the mesoscale convective system mcs that occurred on 6 7 may 1985 the storm began when a short squall line developed in an area of preexisting thunderstorm activity thunderstorm updrafts along the squall line lifted warm moist air with its southerly momentum to the upper troposphere a broad region of convective outflow and a meso scale updraft region with a mean vertical velocity in excess of 15 10 3 mb s 1 were created a stratiform rain area with an embedded mesovortex formed behind the squall line the vortex resided beneath the deepest upper level outflow the mesovortex altered the wind field and consequently became the principal organizational feature within the mcs a descending current from the storm s rear that depending on location extended from 1 km to the upper troposphere was intensified and focused by the vortex the descending rear inflow had a peak

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

tectonic subsidence of the lomonosov ridge the cenozoic sedimentary record revealed by the integrated ocean drilling program s arctic coring expedition acex to the lomonosov ridge microcontinent in 2004 is characterized by an unconformity attributed to the period 44 18 ma according to conventional thermal kinematic models the microcontinent should have subsided to 1 km depth owing to rifting and subsequent separation from the barents kara sea margin at 56 ma we propose an alternative model incorporating a simple pressure temperature p t relation for mantle density using this model we can explain the missing stratigraphic section by post breakup uplift and erosion the pattern of linear magnetic anomalies and the spreading geometry imply that the generation of oceanic crust in the central eurasia basin could have been restricted and confined by non volcanic thinning of the mantle lithosphere at an early stage ca 56 40 ma in response to a rise in temperature the mantle mineral composition may have changed through breakdown of spinel peridotite and formation of less dense plagioclase peridotite the consequence of lithosphere heating and related mineral phase transitions would be post breakup uplift followed by rapid subsidence to the deep water environment observed on the lomonosov ridge today

the casanova complex of the northern apennines a melange formed on a distal passive continental margin abstract the cretaceous palaeocene casanova complex occurs in two thrust sheets of the eugeosynclinal ligurids of the northern apennines it is a sedimentary melange with ophiolitic and quartzose turbidites or limestone shale olistostrome submarine debris flows as matrix exotic blocks of ophiolite and granite serpentinite breccias and lenticular ophiolitic breccias and olistostromes contribute to the melange character of the complex deformational structures include soft sediment slump folds indicating a sw dipping palaeoslope and boudins a gradational slumped top to the melange small scale faults in chert blocks and deformation associated with the emplacement of the exotic slide blocks the blocks were shed as rotational slides from submarine fault scarps and are surrounded by haloes of debris created by submarine weathering the stacking pattern of the blocks with the originally stratigraphically highest ophiolite lithologies lowest in the pile of blocks is explained by a diverticulation model with progressively deeper erosion mechanical analysis shows that the blocks were stable when partly exposed resting on a soft sediment substratum criteria which distinguish the casanova complex from a tectonic melange and which may be of value in other melanges are discussed previous interpretations of the complex as a precursor olistostrome to northeastward nappe emplacement the bracco ridge model are rejected the melange is believed to have formed on ocean crust as a result of turbidite and debris flow sedimentation soft sediment deformation block faulting gravity sliding and submarine erosion at the distal edge of a uniformly sw dipping continental margin

warm core formation in tropical storm humberto 2001 at 0600 utc 22 september 2001 humberto was a tropical depression with a minimum central pressure of 1010 hpa twelve hours later when the first global positioning system dropwindsondes gps sondes were jettisoned humberto s minimum central pressure was 1000 hpa and it had attained tropical storm strength thirty gps sondes radar from the wp 3d and in situ aircraft measurements are utilized to observe thermodynamic structures in humberto and their relationship to stratiform and convective elements during the early stage of the formation of an eye the analysis of tropical storm humberto offers a new view of the pre wind induced surface heat exchange pre wishe stageoftropicalcycloneevolution humbertocontainedamesoscaleconvectivevortex mcv similar to observations of other developing tropical systems the mcv advects the exhaust from deep convection in the form of an anvil cyclonically over the low level circulation center on the trailing edge of the anvilanareaofmesoscaledescentinducesdryadiabaticwarmingin thelowertroposphere thenascentwarm core at low levels causes the initial drop in pressure at the surface and acts to cap the boundary layer bl as bl air flows into the nascent eye the energy content increases until the energy is released from under the cap on the down shear side of the warm core in the form of vigorous cumulonimbi which become the nascent eyewall this series of events show one possible path in which a mesoscale convective system may evolve into a warm cored structure and intensify into a hurricane

interpretation of depth to the magnetic basement in the northern barents sea south of svalbard abstract aeromagnetic data covering some 135 000 km2 with 34 000 km of profiles in the northern barents sea south of svalbard have been interpreted the survey area is situated between 74 30 and 78 n and 15 and 32 e the main result of the study is a contour map of the depth to the top of the magnetic basement indicating the thickness of the sedimentary rocks in the area three different graphical techniques and the autocorrelation method have been applied to determine the depths to magnetic sources from the profile data the different methods yield errors which generally vary between 5 and 15 systematic errors will add to the spread shown by the different methods therefore the inaccuracy of individual point estimates can sometimes be as large as 30 the interpreted depths to the magnetic basement exceed 10 km in the sorkapp basin in parts of storfjorden and towards the olga basin the basement is located at depths of less than 2 to 3 km on the bjornoya sorkapp high and the hopen high and at depths of about 6 km on the gardar banken high depths in the area of the central platform vary smoothly and gradually from 6 to 9 km it is suggested that in some areas pre permian sediments may constitute more than half of the total sedimentary column the location of the continent ocean transition zone has been interpreted from the aeromagnetic data strong gradients in the contour map of depth to magnetic basement coincide with the well known bjornoya sorkapp fault zone the strongest gradients seen elsewhere in the depth to basement map may therefore reveal major basement faults and or flexures which define the margins of structural highs and troughs in the tertiary the continental crust in the western part of the study area was deformed along nnw sse trending fault zones these faults are sub parallel to linear positive magnetic anomalies observed in the same area which reflect trends within the basement and sub parallel to major tectonic lines including basement faults mapped by geologists further to the north on spitsbergen it is therefore inferred that precambrian basement fault or fracture zones have been reactivated in phanerozoic times east of a major tectonic line running n s to nw se through the central part of the area the basement map and the aeromagnetic map show variable trends with ne sw trends dominating comparison with deep seismic reflection data suggests that the interpreted discontinuity may represent a major caledonian compressional structure perhaps the iapetus suture which separates two different crustal terranes

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t