global scatterometer observations of the structure of tropical cyclone wind fields abstracta very large database containing 24 years of scatterometer passes is analyzed to investigate the surface wind fields within tropical cyclones the analysis confirms the left right asymmetry of the wind field with the strongest winds directly to the right of the tropical cyclone center northern hemisphere at values greater than 2 times the radius to maximum winds the asymmetry is approximately equal to the storm velocity of forward movement observed wind inflow angle i e storm motion not subtracted is shown to vary both radially and azimuthally within the tropical cyclone the smallest observed wind inflow angles are found in the left front quadrant with the largest values in the right rear quadrant as the velocity of forward movement increases and the central pressure decreases observed inflow angles ahead of the storm decrease and those behind the storm increase in the right rear quadrant the observed inflow angle increases with radius from the storm center in all other quadrants the observed inflow angle is approximately constant as a function of radial distance

parametric representation of the primary hurricane vortex part i observations and evaluation of the holland 1980 model although numerical models are essential to hurricane forecasting many other applications require only statistical depiction of the wind distribution in holland s 1980 parametric profile radius of maximum wind maximum wind and a measure of the profile width describe the radial variation of the axisymmetric wind variants of the holland profile are used to predict insurance underwriting risk ocean response and storm surge inundation since these calculations guide high stakes financial and emergency managment decisions it is logical to test them against observations the hurricane research division s flight level database archives observations were obtained by noaa and u s air force reserve aircraft the data considered here are winds and geopotential heights observed during 606 lower and midtropospheric flights into atlantic and eastern pacific tropical cyclones during 1977 2000 the 493 profiles that meet quality control criteria are seasonally geographically representative least squares fits of the holland model to these data provide evaluation of the parameters distributions and critical examination of the profile s realism individual fitted profiles differ from the observations in a consistent pattern the areas of strong winds in the eyewall and of nearly calm winds at the vortex center are too wide beyond 2 or 3 times the eye radius the wind decreases too rapidly with distance from the center although the average bias in fitted profiles is 1ms 21 the root mean square error is 4 2 m s 21 5 2 m s21 for independent data maximum winds estimated from the fitted holland profile height wind relation average 2 5 m s 21 too strong with an rms error of 6 5 m s 21 the pattern of too strong wind spread over too much real estate exaggerates the occurrence of winds stronger than 50 m s 21 by 50

formation of si al mg ca rich zoned magnetite in an end permian phreatomagmatic pipe in the tunguska basin east siberia magma sediment interactions in the evaporite rich tunguska basin resulted in the formation of numerous phreatomagmatic pipes during emplacement of the siberian traps the pipes contain magnetite apatite deposits with copper and celestine mineralization we have performed a detailed petrographic and geochemical study of magnetite from long cores drilled through three pipe breccia structures near bratsk east siberia the magnetite samples are zoned and rich in si 5 3 wt sio2 ca al and mg they exhibit four textural types 1 massive ore in veins 2 coating on breccia clasts 3 replacement ore and 4 reworked ore at the crater base the textural types have different chemical characteristics breccia coating magnetite has relatively low mg content relative to si as compared to the other groups and appears to have formed at lower oxygen fugacity time series analyses of mgo variations in microprobe transects across si bearing magnetite in massive ore indicate that oscillatory zoning in the massive ore was controlled by an internal self organized process we suggest that hydrothermal fe rich brines were supplied from basalt sediment interaction zones in the evaporite rich sedimentary basin leading to magnetite ore deposition in the pipes hydrothermal fluid composition appears to be controlled by proximity to dolerite fragments temperature and oxygen fugacity magnetite from the pipes has attributes of iron oxide apatite deposits e g textures oscillatory zoning association with apatite and high si content but has higher mg and ca content and different mineral assemblages these features are similar to magnetite found in skarn deposits we conclude that the siberian traps related pipe magnetite deposit gives insight into the metamorphic and hydrothermal effects following magma emplacement in a sedimentary basin

evidence for tilted toroidal circulations in cumulus intense vortical circulations often organized in counterrotating vortex pairs were detected in midcontinental cumulus congestus over southeast wyoming in july 2003 the sampled clouds developed in dry environments and at cold temperatures and were a few kilometers in depth and width observations were obtained with the wyoming cloud radar from aboard the wyoming king air research aircraft dualdoppler analyses of the data yielded high resolution 30 45 m depictions of the horizontal components of air motions across vigorously growing clouds the vortices found in the horizontal cross sections are interpreted as components of the toroidal circulations in thermals when those are tilted because of the effect of ambient cross flow this configuration also leads to a partial stabilization of the vertical trajectory of the updraft by opposing the drag by the ambient wind additionally dry air intrusions were seen to accompany these features when the vortices developed near the cloud outer boundaries recirculation of hydrometeors occurred when the vortices were adjacent to in cloud downdrafts these features are also evident in the radar reflectivity patterns in general gradients of velocities and vorticity values in horizontal planes are comparable to those found in vertical planes

volcanic coseismic and seasonal changes detected at white island whakaari volcano new zealand using seismic ambient noise ambient noise interferometry is becoming increasingly popular for studying seismic velocity changes such changes contain information on the structural and mechanical properties of earth systems application to monitoring however is complicated by the large number of processes capable of inducing crustal velocity changes we demonstrate this at white island volcano over a 10 year period containing multiple well documented eruptions using individual seismic stations we detect velocity perturbations that we ascribe to volcanic activity large earthquakes and seasonality distant seismic stations capture widespread nonvolcanic changes that are also present at the volcano comparison between velocity changes recorded by distant and local stations then allows us to distinguish volcanic phenomena from seasonality through this we resolve distinct features in ambient noise derived velocity changes that relate to volcanic unrest and a phreatic eruption illustrating the strength of the approach plain language summary detecting small changes in physical properties at volcanoes is important toward effectively forecasting volcanic eruptions one approach is to monitor the speed of seismic waves at the earth s surface which are sensitive to changes in the rock they pass through at volcanoes such changes may manifest through subsurface pressure increases preceding eruptions correctly interpreting these changes however is complicated many other nonvolcanic processes are also capable of producing similar wave speed perturbations at white island volcano new zealand we detect changes associated with volcanic activity large earthquakes and weather related processes using seismometers located on the volcano we demonstrate that volcanic and nonvolcanic features can be distinguished by comparing changes recorded at the volcano with those recorded at large distances where volcanic changes are not expected to be observed through this we resolve distinct differences that can be related to volcanic activity illustrating the strength of this approach

paleoaquifer and deep burial related cements defined by regional cathodoluminescent patterns middle ordovician carbonates virginia middle ordovician ramp carbonates virginia were deposited in a subsiding foreland basin bordered on the southeast by tectonic highlands ramp carbonates were lithified in part by turbid marine cements but major cementation was by nonferroan clear rim and equant cements zoned defined by cathodoluminescence clear cements consist of nonluminescent oldest bright and dull youngest cements the zonation relates to increasingly reducing conditions of pore waters zoned cements in peritidal beds best developed in southeastern belts have complex zonations pendant to pore rimming fabrics and are associated with crystal silt which abuts all cement zones solutional cavities and erosional surfaces which locally truncate dull cement these cements are meteori vadose to shallow phreatic cements in northwestern exposures of peritidal beds are dominated by non zoned dull cement which lacks abundant evidence of early near surface precipitation major cementation of subtidal facies occurred under burial conditions burial cements best developed in southeastern belts have a simple zonation reflecting progressive burial up to 7 5 km 4 5 mi of the carbonate ramp shallow burial nonluminescent cement formed from oxidizing meteoric waters which expelled anoxic connate marine waters these meteoric waters were carried by aquifers from tectonic upland recharge areas on the southeastern basin margin bright cement formed under more reducing conditions following stagnation of the paleoaquifer with burial and possibly was precipitated at depths of 2 to 3 km 1 to 2 mi burial cements in northwestern exposures of subtidal beds are dominated by dull cement initial generations of which precipitated from downdip portions of aquif rs deeper burial dull calcite and ferroan dolomite cements largely formed at burial depths of 2 to 3 km 1 to 2 mi and temperatures of 75 to 135 c 165 to 275 f or more associated with hydrocarbon formation emplacement during the late devonian to mississippian latest clear dull cement fills tectonic fractures and was emplaced during late paleozoic alleghenian deformation probably at temperatures of 200 to 300 c 390 to 575 f and depths of 5 to 7 km 3 to 4 5 mi deeper burial diagenesis appears to be genetically linked to late paleozoic mississippi valley type mineralization in the southern appalachians zoned peritidal and burial cements are confined mainly to southeastern portions of the ramp where cementation was influenced by meteoric waters shed from tectonic uplands on the southeast and carried northwest by paleoaquifers northwestern portions of the ramp were influenced very little by upland sourced meteoric waters and nonzoned dull cements precipitated from relatively reducing waters the distribution of nonluminescent cement in middle ordovician subtidal facies defines the regional distribution of oxidizing portions of the paleoaquifer system such incursion of upland sourced oxidizing meteoric waters into ramp carbonates should be a common feature of foreland basin carbonates deposited adjacent to tectonic uplands furthermore foreland basin carbonates that undergo progressive burial should show a simple nonluminescent to bright to dull sequence of cement zones the close association of zoned cements and regional uplands in the middle ordovician sequence indicates the importance of assessing regional geologic relationships environmental parameters geologic history and tectonics in understanding regional cementation patterns and cementation processes of anci nt carbonate platforms

seismic codas on the earth and the moon a comparison the phenomenon of the seismic coda which is composed of seismic energy delayed by scattering is seen on both the earth and the moon on the moon the scattered coda is very large relative to body wave arrivals with a delay of the time of maximum energy whereas on earth scattered codas are relatively small and show no delay of the energy maximum in both cases the form of the coda is controlled by three distance scales the mean free path l which is the average distance seismic energy travels before it is scattered the attenuation distance x which is the average distance seismic energy travels before it is attenuated and the source receiver distance r two coda models are discussed based on these parameters a strong scattering diffusion model and a weak scattering single scattering model a discussion of the diffusion scattering model indicates that if x l 1 diffusion scattering is an appropriate model but if x l 1 single scattering is the appropriate model within the appropriate range of r a survey of the literature indicates that for the frequency range 0 5 10 hz diffusion scattering is important in lunar codas but for the frequency range 1 25 hz single scattering is important in terrestrial codas another important effect of attenuation is the elimination of scattering paths much longer than x on the moon this means that seismic energy in the coda can only propagate directly in the near surface strong scattering zone between surface sources and the seismometer for source seismometer separations of the order of x l 12 otherwise scattering is limited to regions near the source and the receiver on earth this effect probably prevents multiple scattering

fitting parametric vortices to aliased doppler velocities scanned from hurricanes abstractan alias robust least squares method that produces less errors than established methods is developed to produce reference radial velocities for automatically correcting raw aliased doppler velocities scanned from hurricanes this method estimates the maximum tangential velocity vm and its radial distance rm from the hurricane vortex center by fitting a parametric vortex model directly to raw aliased velocities at and around each selected vertical level in this method aliasing caused zigzag discontinuities in the relationship between the observed and true radial velocities are formulated into the cost function by applying an alias operator to the entire analysis minus observation term to ensure the cost function to be smooth and concave around the global minimum simulated radar velocity observations are used to examine the cost function geometry around the global minimum in the space of control parameters vm rm the results show that the global minimum point can estimate the true vm rm app

on the relative motion of binary tropical cyclones abstract the interaction between spatially proximate binary tropical cyclones is such that relative rotation in the counterclockwise sense and decreasing separation distance between the two storm centers can be expected this is referred to as the fujiwhara effect this study analyzes this effect for 43 binary tropical cyclone systems which occurred over the western north pacific 1949 78 it is shown that most demonstrated mutual interaction according to fujiwhara expectations however there were notable apparent exceptions further analysis of these exceptional cases shows that environmental currents in which the storms were embedded had a significant effect on relative motion and masked the fujiwhara effect additionally it was found that storms exhibiting behavior most in accordance with fujiwhara expectations were located in or near the intertropical convergence zone the main conclusion of the study in confirmation of earlier studies is that forces relative to environmental steering must be de

the boundary layer winds in hurricanes danielle 1998 and isabel 2003 abstract this paper describes the boundary layer wind structure and dynamics of hurricanes danielle 1998 and isabel 2003 based on the analysis of high resolution global positioning system dropwindsonde data and simulation of the flow by a three dimensional boundary layer model produced by kepert and wang the observations show that the hurricane boundary layer has a complex three dimensional structure with large variability over small distances the analysis emphasizes three aspects the degree of gradient wind balance the radially varying depth of the boundary layer and the strength of the near surface wind speed relative to that at a higher level each aspect is compared both with results obtained in a simulation of the individual storm by kepert and wang s model and with theoretical predictions the observations show that the boundary layer depth decreases toward the center of the storm consistent with theoretical arguments the strongest azimuthal winds occur near the top of but still within

the vertical structure of a tornado near happy texas on 5 may 2002 high resolution mobile w band doppler radar observations abstract a mobile w band doppler radar scanned at close range portions of a tornado near happy texas on 5 may 2002 simultaneous boresighted video images were also recorded which facilitated correlating the radar observed features of the tornado with its visual features range height indicators rhis of radar reflectivity and doppler velocity were collected that detail with high spatial resolution aspects of the vertical structure of the tornado near the ground most of the rhis showed a column of a weak echo hole from about 60 m above the ground up to the top of the domain at 800 1000 m above the ground the hole was roughly 40 broader about 100 m above the ground as it was above resulting in a characteristic pear shaped vertical cross section of reflectivity in this tornado the condensation funnel was much narrower than the width of the weak echo hole the visible debris cloud near the ground was approximately just as wide as the hole above 150 m the mean depth of the debris cloud was arou

the spatial distribution of ocean waves in tropical cyclones the spatial structure of both the wind and wave fields within tropical cyclones is investigated using two large databases the first of these was compiled from global overpasses of tropical cyclones by satellite altimeters the second dataset consists of an extensive collection of north american buoy measurements during the passage of tropical cyclones hurricanes the combined datasets confirm the vortex structure of the tropical cyclone wind field with the strongest winds to the right northern hemisphere of the storm the wave field largely mirrors the wind field but with greater right left asymmetry that results from the extended fetch to the right of the translating tropical cyclone the extensive in situ buoy database confirms previous studies indicating that the one dimensional spectra are generally unimodal the directional spectra are however directionally skewed consisting of remotely generated waves radiating out from the center of the storm and locally generated wind sea the one dimensional wave spectra have many similarities to fetch limited cases although for a given peak frequency the spectra contain less energy than for a fetch limited case this result is consistent with the fact that much of the wave field is dominated by remotely generated waves

the retrieval of asymmetric tropical cyclone structures using doppler radar simulations and observations with the extended gbvtd technique abstract the ground based velocity track display gbvtd technique is extended to two doppler radars to retrieve the structure of a tropical cyclone s tc s circulation with this extension it is found that the asymmetric part of the tc radial wind component can be derived up to its angular wavenumber 1 structure and the accuracy of the retrieved tc tangential wind component can be further improved although two radar systems are used a comparison with the traditional dual doppler synthesis indicates that this extended gbvtd egbvtd approach is able to estimate more of the tc circulation when there are missing data previous research along with this study reveals that the existence of strong asymmetric radial flows can degrade the quality of the gbvtd derived wind fields when a tc is observed by one radar it is suggested that the gbvtd method be applied to tcs over a flat surface e g the ocean where the assumption of relatively smaller asymmetric radial winds than asymmetric tangential winds is

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

chemical diagenesis of carbonates in thin sections ion microprobe as a trace element tool abstract ion microprobe is a potential tool for determination of trace element concentrations directly in thin sections such an approach enables direct correlation of chemistry with microtextural features we demonstrate the utility of this instrument for sr mn fe and mg in calcites and dolomites at this stage the sensitivity is 10 ppm and the reproducibility is usually better than 15 relative percent the analyzed spots are 20 we believe that with more homogeneous standards at low concentrtion levels the technique is potentially capable of sensitivity in the ppb ppm ranges fe may prove an exeption from this prediction the technique may also prove suitable for determination of na ion microprobe can serve as a valuable tool for diagenetic and petrological studies of carbonates at this stage its major disadvantage is the poor optical resolution in transmitted light

influence of tropical cyclones on sea surface temperature seasonal cycle and ocean heat transport recent studies suggested that tropical cyclones tcs contribute significantly to the meridional oceanic heat transport by injecting heat into the subsurface through mixing here we estimate the long term oceanic impact of tcs by inserting realistic wind vortices along observed tcs tracks in a 1 2 resolution ocean general circulation model over the 1978 2007 period warming of tcs cold wakes results in a positive heat flux into the ocean oceanic heat uptake ohu of 480 tw consistent with most recent estimates however 2 5 of this ohu only compensates the heat extraction by the tcs winds during their passage another 2 5 of this ohu is injected in the seasonal thermocline and hence released back to the atmosphere during the following winter because of zonal compensations and equatorward transport only one tenth of the ohu is actually exported poleward 46 tw resulting in a marginal maximum contribution of tcs to the poleward ocean heat transport other usually neglected tc related processes however impact the ocean mean state the residual ekman pumping associated with tcs results in a sea level drop rise in the core northern and southern flanks of tc basins that expand westward into the whole basin as a result of planetary wave propagation more importantly tc induced mixing and air sea fluxes cool the surface in tc basins during summer while the re emergence of subsurface warm anomalies warms it during winter this leads to a 10 reduction of the sea surface temperature seasonal cycle within tcs basins which may impact the climate system

high resolution scanning proton microprobe studies of micron scale trace element zoning in a secondary dolomite implications for studies of redox behaviour in dolomites abstract secondary rhomb shaped dolomites from the limestones of the gargano peninsula italy show fine well developed zones when viewed under cathodoluminescence in order to investigate the chemical origin of these zones this material was analyzed using the high resolution scanning proton microprobe the analyses show prominent concentric micrometre scale zones enriched in fe mn and zn at the ppm level the chemical zonations observed are however very much more complex than is shown by the cathodoluminescence image the cathodoluminescent zones correlate with variations in mn concentration but there is little negative quenching effect of fe which can be observed and there is no correlation among the zones of the different elements in contrast to the pronounced and sharp zoning of mn fe and zn observed sr is distributed homogeneously in the dolomite since the activities of fe ii mn ii and zn in solution are all controlled directly or indirectly by redox reactions whereas the behaviour of sr is uninfluenced by changes in oxidation potential these observations strongly suggest that the most important variable controlling the production of zones in these dolomites was eh we believe that the sharp zoning of mn fe and zn and the clear separation of one element from another indicate repeated influxes of pore water of differing eh and possibly ph carrying different amounts of fe ii mn ii and zn in solution

applications of the high resolution scanning proton microprobe in the earth sciences an overview abstract the proton microprobe uses a focused beam of high energy protons to generate x rays in a sample that is to be analyzed the major advantage of the proton microprobe as compared with the electron microprobe lies in its much lower x ray background this makes possible analyses at the 5 10 ppm concentration level with a resolution of 1 m the principles of operation of the proton microprobe are reviewed and the instrument compared with the ion probe and synchrotron x ray microprobe examples of its use in analyzing finely zoned dolomite and in investigating the late stage concentration of elements on grain boundaries in garnet lherzolite xenoliths are reviewed the proton and x ray microprobes are likely to contribute increasing amounts of high quality trace element data in the near future

in situ characterization of dolomite crystals evaluation of dolomitization process and its effect on zoning dolomitization is a dissolution re precipitation process which proceeds via micrometre scale interface reaction horizons however the effect of this fundamental local medium of replacement process on precipitated dolomite crystals is rarely investigated for this purpose dolomite samples of ordovician boat harbour formation carbonates newfoundland canada from main brook and daniel s harbour about 150 km apart were studied the investigation used high resolution approaches to carry out imaging and elemental analyses of individual dolomite crystals including scanning electron microscopy scanning electron microscopy based cathodoluminescence secondary ion mass spectrometry and electron microprobe analysis the purpose was to better understand geochemical variations across the crystal traverses and their association with dolomite replacement processes and conditions the scanning electron microscopy based cathodoluminescence zoning character reveals three major crystal facies distinctly planar boundaries zoned core and indistinctly zoned core are zoned dolomite crystal facies in burial dolomite from main brook relatively unzoned crystal facies was identified in that of daniel s harbour compositionally zoned dolomite crystals are characterized by decreasing sr na y and ree but increasing mn and fe from core to rim sections core to rim zoning was not found for major mg and ca elements the zoning exhibited by the replacive dolomite crystals is interpreted to be principally a result of limited exchange between solutes of the bulk pore fluid and those of dissolving precursor marine carbonate in tandem with petrographic features the systematic compositional zoning character demonstrates that the effectiveness of the dolomitization process grades from indistinctly zoned core to relatively unzoned crystal facies via interface reaction horizons homogenization of major elements of core and rim sections seen in distinctly zoned core crystal facies and to a much greater extent in relatively unzoned crystal facies via a secondary reaction interface is the first recognized stage of the maturation process followed by homogenization of the trace elements seen largely in relatively unzoned crystal facies

the energy partitioning and the diffusive character of the seismic coda following recent theoretical developments of the radiative transfer the ory of elastic waves we propose to use the ratio r of energies of curl and divergence part of the ground displacement to distinguish between the different possible domi nant scattering regimes in the lithosphere a consequence of the diffusion regime is the partitioning of the energy between different vibrational modes which is inde pendent of time it results in the stabilization of r this behavior is not expected if low order diffraction such as single scattering is dominant we apply our technique to seismograms recorded by a small aperture seismic array operated during june august 1997 in guerrero mexico we estimate the energy ratio r in the coda of 13 earthquakes recorded by the array we find it to be very stable in the coda window while the energy level itself changes by several orders of magnitude the value of r is 7 1 independent of the earthquake location and the magnitude the observed stabilization of r is a strong indication of the diffusive regime of the seismic coda

real time monitoring of relative velocity changes using ambient seismic noise at the piton de la fournaise volcano la reunion from january 2006 to june 2007 we present the results of a real time method based on coda wave interferometry from seismic noise cross correlation functions for relative seismic velocity variations monitoring on a volcanic edifice the ambient seismic noise at the piton de la fournaise volcano on la reunion island is analyzed from january 2006 to june 2007 during this period five eruptions occurred showing a great diversity in eruption duration intensity and eruptive fissure location two different methods are used to compute the velocity variations in order to compare their stability in quasi real time routine we compare the obtained velocity variations with the surface deformation observed by gps and extensometers networks this allows us to identify and quantify three major processes at the origin of seismic wave velocity variations in the edifice firstly the observed pre eruptive summit inflation is accompanied by a decrease in seismic velocity secondly the edifice deflation following the opening of an eruptive fissure is characterized by an increase of the velocity finally the summit caldera collapse generates a strong velocity drop coda wave interferometry from seismic noise cross correlation functions in quasi real time may allow us to forecast eruption and constrain the processes taking place in the volcanic plumbing system

how does the boundary layer contribute to eyewall replacement cycles in axisymmetric tropical cyclones abstractthree diagnostic models of the axisymmetric tropical cyclone boundary layer with different levels of approximation are applied to the problem of tropical cyclones with concentric eyewalls the outer eyewall is shown to have an inherently stronger frictional updraft than the inner because it is in an environment of lower vorticity similarly a relatively weak local enhancement of the radial vorticity gradient outside the primary radius of maximum winds can produce a significant frictional updraft even if there is no outer wind maximum based on these results it is proposed that the boundary layer contributes to the formation of outer eyewalls through a positive feedback among the local enhancement of the radial vorticity gradient the frictional updraft and convection the friction induced secondary circulation associated with the inner eyewall is shown to weaken as the outer wind maximum strengthens and or contracts so boundary layer processes will contribute along with the heating induced

mars orbiter camera observations of martian dust devils and their tracks september 1997 to january 2006 and evaluation of theoretical vortex models 1 a multiyear planet wide survey of martian dust devils was conducted using observations from mars global surveyor mars orbiter camera acquired through 21 january 2006 a total of 223 350 images were surveyed and 11 456 dust devils were seen in 0 4 of the images 11 5 in the southern and 88 5 in the northern hemisphere dust devils were observed at latitudes from 71 9 s to 62 2 n over a range of surface albedos am 0 11 0 22 and elevations from hellas 8750 m to arsia mons 17 250 m the light and dark toned streaks created by dust devils were observed from 80 s to 80 n and changed on timescales as short as 1 month at mid to high latitudes seasonal changes in streak patterns contribute to the seasonal wave of darkening observed telescopically from earth dust devils were observed in all seasons in both hemispheres with the exception of ls 202 8 281 5 in the north peak activity occurred during midsummer in each hemisphere five regions in amazonis syria claritas meridiani and gusev were monitored regularly amazonis had the largest dust devils and was the most active planet wide with annual activity occurring from ls 8 5 197 interannual variability resulted from dust storms and planet encircling dust hazes which were observed to initiate and abate dust devil activity there was no evidence suggesting dust devils cause or lead to initiation of dust storms model derived tangential wind speeds of large vortices were 20 m s 1 at 20 m above the surface dust flux calculations suggest that dust devils are a contributor to the background dust opacity observed through northern spring and summer

on the warm core of a tropical cyclone formed near the tropopause abstracton the basis of numerical results of a three dimensional model diagnosed using balance dynamics a mechanism by which the upper level warm core of tropical cyclones tcs forms is proposed the numerical results reveal that an upper level warm core develops when tcs intensify just prior to reaching the mature stage potential temperature budget analysis reveals that for the tendency of potential temperature the azimuthal mean component of advection is dominant at the upper level of the eye at the mature stage sawyer eliassen diagnosis shows that tendencies due to forced flow by diabatic heating and diffusion of tangential wind are dominant in the eye and are negatively correlated to each other the distributions of the diabatic heating in the simulated tc are not peculiar therefore it is unlikely that the heating distribution itself is the primary cause of the flow from the lower stratosphere the analyses of forced circulations of idealized vortices show that the upper level subsidence is enh

centrifuging of hydrometeors and debris in tornadoes radar reflectivity patterns and wind measurement errors high resolution doppler radar observations of tornadoes reveal a distinctive tornado scale signature with the following properties a reflectivity minimum aloft inside the tornado core described previously as an eye a high reflectivity tube aloft that is slightly wider than the tornado core and a tapering of this high reflectivity tube near the ground the results of simple one dimensional and two dimensional models demonstrate how these characteristics develop important processes in the models include centrifugal ejection of hydrometeors and or debris by the rotating flow and recycling of some objects by the nearsurface inflow and updraft doppler radars sample the motion of objects within the tornado rather than the actual airflow since objects move at different speeds and along different trajectories than the air error is introduced into kinematic analyses of tornadoes based on radar observations in a steady axisymmetric tornado objects move outward relative to the air and move more slowly than the air in the tangential direction in addition the vertical air relative speed of an object is less than it is in still air the differences between air motion and object motion are greater for objects with greater characteristic fall speeds i e larger denser objects and can have magnitudes of tens of meters per second estimates of these differences for specified object and tornado characteristics can be obtained from an approximation of the one dimensional model doppler on wheels observations of the 30 may 1998 spencer south dakota tornado demonstrate how the apparent tornado structure can change when the radar scatterer type changes when the spencer tornado entered the town and started lofting debris changes occurred in the doppler velocity and reflectivity fields that are consistent with an increase in mean scatterer size

nakhlak carbonate hosted pb ag deposit isfahan province iran a geological mineralogical geochemical fluid inclusion and sulfur isotope study abstract the upper cretaceous nakhlak epigenetic vein type pb ag deposit is located 55 km northeast of the town of anarak in isfahan province iran the deposit contains 7 mt of galena barite ore with an average grade of 8 33 pb 0 38 zn and 72 ppm ag the ore mineralization occurs as stratabound epigenetic steeply dipping east west trending veins in faulted or fracture controlled upper cretaceous sadar carbonates galena and barite are the primary minerals minor sphalerite tennantite tetrahedrite pyrite and chalcopyrite occur as inclusions in galena cerussite with minor amounts of anglesite and plattnerite formed in the oxidized supergene zone the ore and ore related minerals were deposited in the hydrothermally dolomitized carbonate host rock containing saddle shaped dolomite geochemically the dolomitized carbonate host rocks are enriched in mgo fe 2 o 3 mno pb zn and ba but depleted in cao the galena concentrate contains high values of ag 932 ppm sb 342 ppm cu 422 ppm as 91 ppm and zn 296 ppm the presence of these trace elements indicates a low temperature type of galena mineralization this interpretation is corroborated by fluid inclusions containing 12 98 wt nacl equivalent salinity the inclusions homogenize at the low temperature of about 152 1 c the similarity between 34 s v cdt values in nakhlak barite and permian triassic 34 s marine sulfate values indicates that the nakhlak sulfur was probably provided from evaporates of permian triassic age the 34 s v cdt values of galena and barite samples occupy the ranges of 1 04 to 8 62 and 10 95 to 13 71 respectively and are similar to mississippi valley type mvt deposits the low temperature basinal fluids evaporate originated sulfur and fault or fracture controlled galena rich veins in the nakhlak deposit resemble the type of geological features documented in pb rich mvt deposits

diagenesis of carbonate cements in permo triassic sandstones from the iberian range spain evidence from chemical composition and stable isotopes petrographic chemical and stable isotope investigations have been made on calcite dolomite and fe dolomite ankerite from permian triassic clastic sequences from the iberian range spain calcite and dolomite cements have precipitated before the fe dolomite ankerite calcite however has also formed by calcitization of dolomite due to uplift the negative 13cpdb values 9 51 to 2 13 in these carbonates suggest derivation of carbon from oxidation of organic matter in the early carbonates and from decarboxylation of organic matter in the late fe dolomite ankerite early diagenetic dolomitic cements have heavier 13c 3 54 higher mn mn fe and mn mn mg and lower fe fe mg ratios than later diagenetic dolomitic cements the latters are also characterized by lighter 18opdb 10 64 than the early cements due to increase in temperature and to pore water mineral reactions

fine scale doppler radar observations of tornadoes observations obtained with a mobile pencil beam doppler radar revealed many previously unresolved structures within tornadic storms and tornadoes and helped verify various aspects of conceptual models radar data from the parent circulations indicate the existence of spiral reflectivity bands intense radial wind shear zones and multiple larger scale velocity maxima tornado structures observed include debris shields clear axial eye regions multiple reflectivity bands surrounding the center of the eye and occasional reflectivity protrusions into the eye velocity and reflectivity data from tornado scale circulations show evidence of axial downdrafts

high resolution 3d shallow crustal structure in long beach california application of ambient noise tomography on a dense seismic array ambient noise tomography has proven to be effective in resolving shallow earth structure we applied ambient noise tomography on a dense seismic array in long beach california the array was composed of more than 5200 stations with an average spacing close to 100 m three weeks of passive ambient noise were crosscorrelated between each station pair which resulted in more than 13 5 million crosscorrelations within the area clear fundamental mode rayleigh waves were observed between 0 5 and 4 hz which were most sensitive to structure above 1 km depth for each station pair we applied frequency time analysis to determine the phase traveltime dispersion and for each frequency we applied eikonal tomography to determine the rayleigh wave phase velocity map the eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis the compilation of phase velocity maps was then used to invert for 3d shear velocity structure the inverted model showed clear correlation with the known geologic features such as the shallow south north velocity dichotomy and a deeper fast anomaly associated with the newport inglewood fault zone our results can potentially be used to complement traditional active source studies

ion microprobe analysis of trace elements in calcite with an application to the cathodoluminescence zonation of limestone cements from the lower carboniferous of south wales u k ion microprobe analysis offers high spatial resolution 10 m and low detection limits for many elements in calcite detection limits are likely to be instrument dependent the values given here are specific to the instrument used a modified aei im 20 and more recent instrument designs should give lower detection limits li na and k signals have been observed and detection limits are estimated to be 10 ppm the detection limit for pb is in the range 10 50 ppm zn and ba suffer from significant molecular interferences which impose higher detection limits mg fe mn and sr were standardised against three chemically analysed calcites detection limits in the range 1 5 ppm were obtained for mg mn and sr but fe is subject to interference by a hydride species so that the detection limit is determined by vacuum conditions calcite cements in sections cut from a lower carboniferous limestone from south wales can be divided texturally into four zones analyses were made for mg fe mn and sr only sr differs among the zones mn is the main activator of cathodoluminescence cl in these cements when the fe content is up to 1600 ppm there is a positive relationship between cl intensity and mn content fe acts as a suppressor of cl intensity for a given mn concentration the cl intensity decreases as the fe content increases for fe contents 1600 ppm the cl intensity may be negatively related to the mn concentration when the mn content is below 125 150 ppm the fe content has little discernible effect on the cl intensity in these cements non luminescence can only be predicted with confidence if the mn concentration is below 25 ppm there is no critical concentration of fe up to 7000 ppm or critical fe mn ratio in the range 0 26 which always causes mn bearing locations to become extinct with respect to cl the present data are compared with those from the literature and a diagram is constructed which represents the region of fe mn composition space where luminescence can occur conflicting evidence regarding the relative importance of fe mn ratio and absolute fe and mn concentrations can be reconciled both concentrations and fe mn ratio are involved in controlling luminescence

chemical controls of cathodoluminescence of natural dolomites and calcites new data and review calcites and dolomites from the late precambrian bonahaven formation of scotland exhibit luminescence when mnco3 0 03 wt dolomite or 0 06 wt calcite and feco3 2 2 5 wt dolomite comparison with other published data shows close similarity in the position of fe quenching in dolomite but more variability in the position of mn activation in calcites and dolomites and the onset of fe quenching in calcites these anomalies are thought to relate to chemical controls subsidiary to the dominant factors of fe and mn concentration it is not practical to make a useful comparison between operating conditions of different luminescence instruments because of differences in design and an inability to measure routinely the current actually on the specimen surface

the control of cathodoluminescence in dolomite by iron and manganese variations in the cathodoluminescent properties of carbonates are usually attributed to differing proportions of manganese mn2 as the most important activator and iron fe2 as the main inhibitor of luminescence interactions between manganese and iron concentrations and the luminescent properties of dolomite are demonstrated by petrographic and chemical analyses of 86 samples of dolomite representing a range of depositional environments and ages cambrian to cretaceous and a wide geographical distribution north america and europe iron and manganese are positively correlated in the dolomites with the former showing a greater range of variation very small amounts of manganese are sufficient to activate the luminescence and as little as 100 ppm mn2 is present in highly luminescing samples the intensity of luminescence is not proportional to the manganese concentration iron begins to quench luminescence as its concentration reaches 10 000 ppm above that level luminescence is rapidly lost and total extinction occurs among samples containing more than 15 000 ppm fe2 regardless of the manganese concentration

trace element and isotopic zonation in vein calcite from the mendip hills uk with spatial process correlation analysis abstract high resolution scanning proton microprobe spm analyses of fissure filling calcite from the mendip hills uk show fine scale chemical zonation patterns in fe and mn concentrations from fissure centre to wall these fluctuations are sharp and steep peaks of 0 01 0 1 mm width with concentrations changing by as much as 8000 ppm zonation in pb and zn is similar to that obtained for mn and fe and maxima in the concentrations of these two elements are correlated with maxima in mn concentration longer wavelength fluctuations 1 0 3 0 mm are evident in data obtained for sr for which changes in concentration are gradual and fluctuate by at most 500 ppm auto correlation calculations show that oscillations in the mn and fe data have a wavelength of 0 9 1 3 mm in contrast to auto correlations and cross correlations with zn and pb which indicate wavelengths of 0 4 mm strontium correlations indicate a peak to trough distance of 4 2 mm which implies a much longer wavelength fluctuation in the sr data cross correlations also clearly show that pb and zn concentrations co vary strongly cross correlation function value of 0 7 at lag 0 but all other cross correlations are weak these computations demonstrate that intrinsic controls on trace element partitioning cannot alone account for the observed patterns long period fluctuations are interpreted to result from a sustained change in the starting composition of the aqueous phase while the high frequency oscillations are interpreted to be caused by mixing reactions among fluids that have reacted with different portions of country rock prior to calcite precipitation analyses of the carbon oxygen and strontium isotopes from these vein calcites have also been completed 18o plotted as a function of 13c results in an inverted triangular array we interpret this along with the trace element data as resulting from three distinct fluids participating in the formation of these fissure fills a low mn fe high sr marine fluid apex at 18o 0 13c 4 both relative to pdb a high mn fe low sr hydrothermal fluid 2 9 5 and a low mn fe low sr meteoric fluid 12 5 the trace element and isotopic compositions of this zoned calcite thus document the following processes in detail 1 the formation of a meteoric fissure system triassic 2 reactions with hotter and more reduced circulating fluids and 3 the subsequent flooding of the system with seawater during transgression of the area rhaetian early jurassic strontium isotopic data from a belemnite located within one of the fissures gives an early jurassic age of approximately 198 ma hot reduced fluids with high metal concentrations were probably forced up into these fissures by seismic pumping during movement on associated regional faults

reexamining the near core radial structure of the tropical cyclone primary circulation implications for vortex resiliency abstract recent theoretical studies based on vortex rossby wave vrw dynamics have established the importance of the radial structure of the primary circulation in the response of tropical cyclone tc like vortices to ambient vertical wind shear linear vrw theory suggests in particular that the degree of broadness of the primary circulation in the near core region beyond the radius of maximum wind strongly influences whether a tilted tc vortex will realign and resist vertical shear or tilt over and shear apart fully nonlinear numerical simulations have verified that the vortex resiliency is indeed sensitive to the initial radial structure of the idealized vortex this raises the question of how well the true nature of a tc s primary circulation is represented by idealized vortices that are commonly used in some theoretical studies in this paper the swirling wind structure of tcs is reexamined by utilizing flight level observations collected from atlantic and eastern pacific storms during 1977 2

hurricane sea surface inflow angle and an observation based parametric model abstractthis study presents an analysis of near surface 10 m inflow angles using wind vector data from over 1600 quality controlled global positioning system dropwindsondes deployed by aircraft on 187 flights into 18 hurricanes the mean inflow angle in hurricanes is found to be 22 6 2 2 95 confidence composite analysis results indicate little dependence of storm relative axisymmetric inflow angle on local surface wind speed and a weak but statistically significant dependence on the radial distance from the storm center a small but statistically significant dependence of the axisymmetric inflow angle on storm intensity is also found especially well outside the eyewall by compositing observations according to radial and azimuthal location relative to storm motion direction significant inflow angle asymmetries are found to depend on storm motion speed although a large amount of unexplained variability remains generally the largest storm relative inflow angles 50 are found in the fas

coda wave interferometry for estimating nonlinear behavior in seismic velocity in coda wave interferometry one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time with this technique we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions this technique can be used in warning mode to detect the presence of temporal changes in the medium or in diagnostic mode where the temporal change in the medium is quantified

reexamining the vertical structure of tangential winds in tropical cyclones observations and theory a few commonly held beliefs regarding the vertical structure of tropical cyclones drawn from prior studies bothobservationalandtheoretical areexaminedinthisstudy oneofthesebeliefsisthattheoutwardslopeof the radius of maximumwinds rmw is a function of the size of the rmw another belief is that the outward slope of the rmw is also a function of the intensity of the storm specifically shea and gray found that the rmw becomes increasingly vertical with increasing intensity and decreasing radius the third belief evaluated here is that the rmw is a surface of constant absolute angular momentum m these three conventional wisdoms of vertical structure are revisited with a dataset of three dimensional doppler wind analyses comprising seven hurricanes on 17 different days azimuthal mean tangential winds are calculated for each storm andtheslopesofthermwandmsurfacesareobjectivelydetermined theoutwardslopeofthermw is shown to increase with radius which supports prior studies in contrast to prior results no relationship is found between the slope of the rmw and intensity it is shown that the rmw is indeed closely approximated by an m surface for the majority of storms however there is a small but systematic tendency for m to decrease upward along the rmw utilizing emanuel s analytical hurricane model a new equation is derived for the slope of the rmw in radius pressure space this predicts a linear increase of slope with radius and essentiallyno dependence of slope on intensity an exactly analogous equationcan be derivedin log pressure height coordinates and a numerical solution yields the same conclusions in geometric height coordinates these conclusions are further supported by the results of simulations utilizing emanuel s simple timedependent axisymmetric hurricane model as both the model and the analytical theory are governed by the dual constraints of thermal wind balance and slantwise moist neutrality it is demonstrated that it is these two assumptionsthat requirethe slope of the rmw to be a functionof its size but not of the intensityof the storm finally it is shown that within the context of emanuel s theory the rmw must very closely approximate an m surface through most of the depth of the vortex

a high resolution simulation of asymmetries in severe southern hemisphere tropical cyclone larry 2006 abstract advances in observations theory and modeling have revealed that inner core asymmetries are a common feature of tropical cyclones tcs in this study the inner core asymmetries of a severe southern hemisphere tropical cyclone tc larry 2006 are investigated using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model mm5 and the kepert wang boundary layer model the mm5 simulated tc exhibited significant asymmetries in the inner core region including rainfall distribution surface convergence and low level vertical motion the near core environment was characterized by very low environmental vertical shear and consequently the tc vortex had almost no vertical tilt it was found that prior to landfall the rainfall asymmetry was very pronounced with precipitation maxima consistently to the right of the westward direction of motion persistent maxima in low level convergence and vertical motion formed ahead of the translating tc resul

intensity and structure changes during hurricane eyewall replacement cycles abstracta flight level aircraft dataset consisting of 79 atlantic basin hurricanes from 1977 to 2007 was used to develop an unprecedented climatology of inner core intensity and structure changes associated with eyewall replacement cycles ercs during an erc the inner core structure was found to undergo dramatic changes that result in an intensity oscillation and rapid broadening of the wind field concentrated temporal sampling by reconnaissance aircraft in 14 of the 79 hurricanes captured virtually the entire evolution of 24 erc events the analysis of this large dataset extends the phenomenological paradigm of ercs described in previous observational case studies by identifying and exploring three distinct phases of ercs intensification weakening and reintensification in general hurricanes intensify sometimes rapidly when outer wind maxima are first encountered by aircraft the mean locations of the inner and outer wind maximum at the start of an erc are 35 and 106 km from storm center respe

seismic noise correlations to image structural and mechanical changes associated with the mw 7 9 2008 wenchuan earthquake we locate temporal changes of seismic wave speed and scattering properties of the crust associated with the 2008 mw7 9 wenchuan earthquake to that end we analyze ambient seismic noise records from 2007 until the end of 2008 in the 1 3 s period band and in the 12 20 s period band measured in a region that covers the southern two thirds of the fault activated during the earthquake to locate the changes we use a refined imaging procedure based on the sensitivity of scattered waves to weak perturbations this inverse method uses the radiative transfer approximation to describe the intensity of the noise correlation coda our results show that the largest structural changes are observed northeast of the wenchuan epicenter around the fault zone where aftershocks are distributed the spatial and temporal characteristics of the behavior of the crust at depth around the wenchuan earthquake suggest a postseismic and geology dependent signature of the middle crust we also observe a clear seasonal signature within the sichuan basin at depth that we relate to the heavy rainfalls during the monsoon season this seasonality can also be observed at the surface in form of a waveform decoherence our study highlights that seismic velocity changes and waveform decoherence are independent measurements that are sensitive to different parameters and can thus give complementary information in our study we also point out the value of studying the evolution of the changes at different times in the coda

finescale radar observations of the dimmitt texas 2 june 1995 tornado abstract the mature and dissipating stages of a strong tornado were observed from close range by the prototype doppler on wheels mobile radar volumetric observations repeated eight times over an 840 s period with resolution volumes at the center of the tornado as low as 61 m 61 m 75 m 2 8 105 m3 revealed new details about three dimensional tornado vortex structure and evolution observed structures included a conical debris envelope a low reflectivity eye multiple windfield maxima and multiple semiconcentric bands of reflectivity surrounding the eye the three dimensional structure of the debris and single doppler wind field were well characterized as well as more rapid dissipation of the tornado aloft compared to near the ground volumetric measures of tornado strength are introduced a downdraft exhibiting w 30 m s 1 indicative of a partial two cell vortex was observed only during the earliest radar scans when the tornado was near maximum intensity comparisons with simple conceptual m

scattering behaviour at merapi volcano java revealed from an active seismic experiment summary the seismic structure of the stratovolcano merapi java indonesia was studied using an active seismic experiment three 3 km long seismic profiles each consisting of up to 30 three component seismometers with an interstation distance of 100 m were built up in an altitude range between 1000 and 2000 m above sea level the detailed study of the seismic properties of the propagation media in active volcanic regions is important to understand the natural seismic signals used for eruption forecasting the seismic experiment at merapi therefore concentrates on the heterogeneous structure within a radius of 5 km from the active dome where the sources of most of the natural volcanic seismic events are located the cone of merapi volcano consists of different materials changing on a small scale due to the layering of eruptive material additionally the topography of the erosion valleys leads to an irregular deposition which cannot be described by a simple 1 d layering these inhomogeneities have a strong influence on seismic signals the direct p and s waves are attenuated quickly and show only small amplitudes on seismograms the energy lost from the direct waves however is not changed into heat but scattered and can be observed as seismic coda following the direct waves the observed seismograms show a spindle like amplitude increase after the direct p phase this shape of the envelope can be explained by the diffusion model according to this model there are so many strong inhomogeneities that the direct wave can be neglected and all energy is concentrated in multiple scattered waves besides the envelope the coherence and polarization properties of the wavefield also indicate strong scattering only the first onset shows coherence over a station spacing of 100 m whereas the late phases carrying the major part of the energy are mainly incoherent the horizontal components of the seismograms have larger amplitudes than the vertical component but within the horizontal plane the polarization is almost arbitrary corresponding to waves arriving from scatterers located arbitrarily in space as a result of the inversion using the diffusion model we obtain values of the s wave scattering attenuation coefficient gs and the s wave intrinsic absorption coefficient gi in the frequency range of 4 20 hz used in this study the scattering attenuation is at least one order of magnitude larger than the intrinsic absorption gs gi the mean free path of s waves is as low as 100 m gs1 100 m the scattering coefficient is independent of frequency gsyf 0 0 whereas the coefficient of intrinsic attenuation increases with increasing frequency giyf 1 6 the natural seismic signals at merapi volcano show similar characteristics to the artificial shots the first onsets have only small amplitudes and the energy maximum arrives delayed compared to the direct waves therefore these signals appear to be strongly affected by multiple scattering also

long term observation of in situ seismic velocity and attenuation 1 we conducted 1 year continuous measurements of in situ compressional wave velocity and attenuation across a distance of 12 m in a vault at the coast of miura bay japan using a piezoelectric transducer as the ultrasonic wave source we detected for the first time periodic variations in both velocity and attenuation with amplitudes of 0 3 and of 4 respectively corresponding to the diurnal and semidiurnal lunar and solar tides these variations correlate well with the in situ areal strain change due to tidal ocean loading estimated from the strain records about 100 m away from the observational site relative minimum velocity and relative maximum attenuation occur at every time of relative maximum areal strain expansion suggesting that opening closure of pores or cracks of in situ rocks is responsible for these periodic variations the velocity variation shows a remarkable 14 day periodicity corresponding to the spring and neap tides arising from a nonlinear response of the velocity change to tidal strain change such that the velocity change depends on how slowly the tidal dilatation departs from its peak value

tropical cyclone kinematic structure retrieved from single doppler radar observations part i interpretation of doppler velocity patterns and the gbvtd technique abstract deducing the three dimensional primary circulation of landfalling tropical cyclones tcs from single ground based doppler radar data remains a difficult task the evolution and structure of landfalling tcs and their interactions with terrain are left uncharted due to the lack of dual doppler radar observations existing ground based single doppler radar tc algorithms provide only qualitative information on axisymmetric tc center location and intensity in order to improve understanding of the wind structures of landfalling tcs using the widely available wsr 88d data along the u s coastal region a single ground based radar tc wind retrieval technique the ground based velocity track display gbvtd technique is developed part i of this paper presents 1 single doppler velocity patterns of analytic asymmetric tcs 2 derivation of the gbvtd technique and 3 evaluation of the gbvtd retrieved winds using analytic tcs the doppler velocity patterns of asymmetric tcs display more complex structu

body wave reconstruction from ambient seismic noise correlations in an underground mine abstractthe reconstruction of seismic green s functions from correlations of ambient seismic noise has recently developed as a promising approach for exploring the earth s interiors without the requirement of costly active seismic sources this approach is widely used for imaging the crust at a kilometer scale however few studies report noise based green s function reconstruction at smaller scales in industrial environments we have investigated the possibility of constructing seismic green s functions between sensors in an active underground mine garpenberg sweden by crosscorrelating seismic noise generated by mining activities we have determined with realistic numerical simulations that the mining excavations in an underground mine lead to a regime of strong scattering which is favorable for constructing seismic green s functions by crosscorrelating seismic noise one month of continuous data was recorded by 18 seismic sensors located more than 1 km below surface a variety of broadband 10 3000

mobile doppler radar observations of a tornado in a supercell near bassett nebraska on 5 june 1999 part ii tornado vortex structure abstract this is part ii of a paper detailing an analysis of high resolution wind and reflectivity data collected by a mobile w band doppler radar the analysis depicts the near surface life history of a tornado in a supercell in north central nebraska on 5 june 1999 the structure of the tornado vortex near the ground is described from a sequence of sector scans at 10 15 s intervals during much of the lifetime of the tornado the formation of the tornado vortex near the ground is described in part i the wind and reflectivity features in the tornado evolved on timescales of 10 s or less a time history of the azimuthally averaged azimuthal and radial wind profiles and the asymmetric components of the azimuthal and radial wind fields in the tornado were estimated by applying the ground based velocity track display gbvtd technique to the doppler wind data if the magnitude of the asymmetric part of the radial wind component were indeed much less than that of the azimuthal wind component a necessary req

seismic tomography of the southern california plate boundary region from noise based rayleigh and love waves we use cross correlations of ambient seismic noise between pairs of 158 broadband and short period sensors to investigate velocity structure over the top 5 10 km of the crust in the southern california plate boundary region around the san jacinto fault zone sjfz from the 9 component correlation tensors associated with all station pairs we derive dispersion curves of rayleigh and love wave group velocities the dispersion results are inverted first for rayleigh and love waves group velocity maps on a 1 5 1 5 km2 grid that includes portions of the sjfz the san andreas fault saf and the elsinore fault we then invert these maps to 3d shear wave velocities in the top 7 km of the crust the distributions of the rayleigh and love group velocities exhibit 2 azimuthal anisotropy with fast directions parallel to the main faults and rotations in complex areas the reconstructed 3d shear velocity model reveals complex shallow structures correlated with the main geological units and strong velocity contrasts across various fault sections along with low velocity damage zones and basins the sjfz is marked by a clear velocity contrast with higher v s values on the ne block for the section se of the san jacinto basin and a reversed contrast across the section between the san jacinto basin and the saf velocity contrasts are also observed along the southern parts on the saf and the elsinore fault with a faster southwest block in both cases the region around the salton trough is associated with a significant low velocity zone strong velocity reductions following flower shape with depth are observed extensively around both the sjfz and the saf and are especially prominent in areas of geometrical complexity in particular the area between the sjfz and the saf is associated with an extensive low velocity zone correlated with diffuse seismicity at depth and a similar pattern including correlation with deep diffuse seismicity is observed on a smaller scale in the trifurcation area of the sjfz these results augment local earthquake tomography images that have low resolution in the top few km of the crust and provide important constraints for studies concerned with behavior of earthquake ruptures generation of rock damage and seismic shaking hazard in the region

the multiple vortex structure of the el reno oklahoma tornado on 31 may 2013 abstractthis study documents the formation and evolution of secondary vortices associated within a large violent tornado in oklahoma based on data from a close range mobile polarimetric rapid s

traveltime measurements from noise correlation stability and detection of instrumental time shifts we test the feasibility of using green s functions extracted from records of ambient seismic noise to monitor temporal changes in the earth crust properties by repeated measurements at regional distances we use about 11 yr of continuous recordings to extract surface waves between three pairs of stations in california the correlations are computed in a moving 1 month window and we analyse the temporal evolution of measured interstation traveltimes the comparison of the arrival times in the positive and negative correlation time of rayleigh and love waves allows us to separate time shifts associated with any form of physical change in the medium those resulting from clock drift or other instrumental errors and those due to change in the localization of the noise sources this separation is based on the principle of time symmetry when possible we perform our analysis in two different period bands 5 10 and 10 20 s the results indicate that significant instrumental time errors 0 5 s are present in the data these time shifts can be measured and tested by closure relation and finally corrected independently of any velocity model the traveltime series show a periodic oscillation that we interpret as the signature of the seasonal variation of the region of origin of the seismic noise between 1999 and 2005 the final arrival time fluctuations have a variance of the order of 0 01 s this allows us to measure interstation traveltimes with errors smaller than 0 3 per cent of the interstation traveltime and smaller than 1 per cent of the used wave period this level of accuracy was not sufficient to detect clear physical variation of crustal velocity during the considered 11 yr between the three stations in california such changes may be more easily detectable when considering pairs of stations more closely located to each other and in the vicinity of tectonically active faults or volcanoes

assessment of resolution and accuracy of the moving window cross spectral technique for monitoring crustal temporal variations using ambient seismic noise summary temporal variations in the elastic behaviour of the earth s crust can be monitored through the analysis of the earth s seismic response and its evolution with time this kind of analysis is particularly interesting when combined with the reconstruction of seismic green s functions from the cross correlation of ambient seismic noise which circumvents the limitations imposed by a dependence on the occurrence of seismic events in fact because seismic noise is recorded continuously and does not depend on earthquake sources these cross correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station and can be used to extract observations of variations in seismic velocities these variations however are typically very small of the order of 0 1 per cent such accuracy can be only achieved through the analysis of the full reconstructed waveforms including later scattered arrivals we focus on the method known as moving window cross spectral analysis that has the advantage of operating in the frequency domain where the bandwidth of coherent signal in the correlation function can be clearly defined we investigate the sensitivity of this method by applying it to microseismic noise cross correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated we propose threshold signal to noise ratios above which these perturbations can be reliably observed such values are a proxy for cross correlation convergence and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving window cross spectral technique

doppler radar observations of dust devils in texas abstract analyses of a dust devil dataset collected in northwest texas are presented the data were collected just above the ground at close range with a mobile w band 3 mm wavelength doppler radar having an azimuthal radial resolution of 3 5 m 30 m at the range of the dust devils most dust devils appeared as quasi circular rings of relatively high radar reflectivity four dust devil vortices were probed three of which were cyclonic and one anticyclonic documentation was obtained of a pair of adjacent cyclonic vortices rotating cyclonically around each other approximate radial profiles of azimuthal and radial wind components and of radar reflectivity are detailed and discussed the diameters of the core of the dust devils ranged from 30 to 130 m the latter diameters are much wider than that of typical dust devils in a homogeneous environment the widest vortex was cyclonic and exhibited evidence of a two cell structure i e sinking motion near the center and rising motion just outside the ra

residence time of diffuse waves in the crust as a physical interpretation of coda q application to seismograms recorded in mexico summary we consider a simple model for elastic wave propagation in the earth s litho sphere consisting of a heterogeneous and scattering crust overlying a homogeneous mantle that is we neglect backscattering from the upper mantle this rough condition is not strictly valid everywhere but this model allows us to investigate the effects of variations of diffracting properties between crust and mantle on the coda decay the free parameters describing the wave propagation are the mean free path of the waves and the intrinsic absorption in the crust in the framework of the radiative transfer theory we treat accurately jumps in s wave speed and the mean free path at the moho without intrinsic absorption this configuration yields a synthetic coda decay 1 texp 2 ft qc a form similar to that proposed by aki chouet 1975 to parametrize the observations the exponential decay in our purely elastic model is due to the partial leakage of diffuse energy into the mantle in order to test the applicability of our model we have determined the coda q parameter qc in the 1 15 hz frequency band from data recorded at four stations in mexico in the low frequency regime around 1 hz we suggest that the energy leakage significantly affects coda q whilst at higher frequencies around 10 hz the anelastic attenuation dominates a weak intrinsic absorption expressed by a frequency independent parameter qi of about 1000 accounts satisfactorily for the observed qc values in the whole frequency range our very simple model has only two free parameters and offers an attractive alternative physical interpretation of coda q in mexico this model is sufficient to interpret the coda observations according to our model in regions where the mean free path is much larger than the crustal thickness weakly heterogeneous crust the leakage effect should be small and the observed qc will mainly be due to the intrinsic absorption on the other hand when the mean free path is of the order of the crustal thickness strongly heterogeneous crust we predict a strong sensitivity of the decay rate of the coda to the crustal thickness this dependence may be important for the interpretation of the regional variations of coda q we propose introducing a new parameter d the residence time of diffuse energy in the crust which is physically more meaningful than a quality factor to quantify the leakage effect

the dynamic response of the hurricane wind field to spiral rainband heating abstract the response of the hurricane wind field to spiral rainband heating is examined by using a three dimensional nonhydrostatic linear model of the vortex anelastic equations diabatic heat sources which are designed in accordance with previous observations of spiral rainbands are made to rotate with the flow around the hurricane like wind field of a balanced axisymmetric vortex common kinematic features are recovered such as the overturning secondary circulation descending midlevel radial inflow and cyclonically accelerated tangential flow on the radially outward side of spiral rainbands comparison of the responses to the purely convective and stratiform rainbands indicates that the overturning secondary circulation is mostly due to the convective part of the rainband and is stronger in the upwind region while midlevel radial inflow descending to the surface is due to the stratiform characteristics of the rainband and is stronger in the downwind region the secondary horizontal wind maxim

depth sensitivity of seismic coda waves to velocity perturbations in an elastic heterogeneous medium summary numerous monitoring applications make use of seismic coda waves to evaluate velocity changes in the earth this raises the question of the spatial sensitivity of coda wave based measurements here we investigate the depth sensitivity of coda waves to local velocity perturbations using 2 d numerical wavefield simulations we calculate the impulse response at the surface before and after a slight perturbation of the velocity within a thin layer at depth is introduced we perform a parametric analysis of the observed apparent relative velocity changes e obs versus the depth of the thin perturbed layer through the analysis of the decay of e obs we can discriminate two different regimes one for a shallow perturbation and the other for a deep perturbation we interpret the first regime as the footprint of the 1 d depth sensitivity of the fundamental surface wave mode to interpret the second regime we need to model the sensitivity of the multiply scattered body waves in the bulk we show that the depth sensitivity of coda waves can be modelled as a combination of bulk wave sensitivity and surface wave sensitivity the transition between these two regimes is governed by mode conversions due to scattering we indicate the importance of surface waves for the sensitivity of coda waves at shallow depths and at early times in the coda at later times bulk waves clearly dominate the depth sensitivity and offer the possibility of monitoring changes at depths below the sensitivity of the surface waves based on the transition between the two regimes we can discriminate a change that occurs at the surface from a change that occurs at depth this is illustrated for shallow depth perturbations through an example from lunar data

parametric representation of the primary hurricane vortex part ii a new family of sectionally continuous profiles abstract for applications such as windstorm underwriting or storm surge forecasting hurricane wind profiles are often approximated by continuous functions that are zero at the vortex center increase to a maximum in the eyewall and then decrease asymptotically to zero far from the center comparisons between the most commonly used functions and aircraft observations reveal systematic errors although winds near the peak are too strong they decrease too rapidly with distance away from the peak pressure wind relations for these profiles typically overestimate maximum winds a promising alternative is a family of sectionally continuous profiles in which the wind increases as a power of radius inside the eye and decays exponentially outside the eye after a smooth polynomial transition across the eyewall based upon a sample of 493 observed profiles the mean exponent for the power law is 0 79 and the mean decay length is 243 km the database actually contains 606 aircraft sorties but 113 of these failed

two distinct regimes in the kinematic and thermodynamic structure of the hurricane eye and eyewall abstract using aircraft flight level data the present work demonstrates that the kinematic and thermodynamic distributions within the eye and eyewall of strong hurricanes are observed to evolve between two distinct regimes in the first regime angular velocity is greatest within the eyewall and relatively depressed within the eye in the second regime radial profiles of angular velocity are nearly monotonic with maxima found at the eye center considering sequential profiles within individual hurricanes the authors find that the evolution of the kinematic distribution is often marked by a transition from the first regime to the second the transition can occur in less than 1 h also noted during the transition are dramatic changes in the thermodynamic structure of the hurricane prior to the transition regime 1 the eye is typically very warm and dry and the equivalent potential temperature is often elevated within the eyewall and relatively depressed within the eye after the transition regime 2

observed boundary layer wind structure and balance in the hurricane core part i hurricane georges abstract the gps dropsonde allows observations at unprecedentedly high horizontal and vertical resolution and of very high accuracy within the tropical cyclone boundary layer these data are used to document the boundary layer wind field of the core of hurricane georges 1998 when it was close to its maximum intensity the spatial variability of the boundary layer wind structure is found to agree very well with the theoretical predictions in the works of kepert and wang in particular the ratio of the near surface wind speed to that above the boundary layer is found to increase inward toward the radius of maximum winds and to be larger to the left of the track than to the right while the low level wind maximum is both more marked and at lower altitude on the left of the storm track than on the right however the expected supergradient flow in the upper boundary layer is not found with the winds being diagnosed as close to gradient balance the tropical cyclone boundary layer model of kepert and wan

the structure of tornadoes near attica kansas on 12 may 2004 high resolution mobile doppler radar observations abstract the university of massachusetts w and x band mobile doppler radars scanned several tornadoes at close range in south central kansas on 12 may 2004 the detailed vertical structure of the doppler wind and radar reflectivity fields of one of the tornadoes is described with the aid of boresighted video the inside wall of a weak echo hole inside the tornado was terminated at the bottom as a bowl shaped boundary within several tens of meters of the ground doppler signatures of horizontal vortices were noted along one edge in the lowest 500 m of the tornado the vertical structure of doppler velocity displayed significant variations on the 100 m scale near the center of the tornado a quasi horizontal radial bulge of the weak echo hole at 500 600 m agl dropped to about 400 m above the ground and was evident as a weak echo band to the south of the tornado it is suggested that this feature represents echo weak material transported radially outward by a vertical circulation significant vertical

a revised model for radial profiles of hurricane winds abstract a revision to the holland parametric approach to modeling the radial profile of winds in hurricanes is presented the approach adopted uses information readily available from hurricane archives or in hurricane warning information and the profile can be readily incorporated into existing parametric models of the hurricane surface wind field the original model utilized central and environmental surface pressures maximum winds and radius of maximum winds in the revision a capacity to incorporate additional wind observations at some radius within the hurricane circulation was included if surface observations are used then a surface wind profile will result obviating the need for deriving a boundary layer reduction from the gradient wind level the model has considerably less sensitivity to data errors compared to the original and is shown to reproduce hurricane reconnaissance and surface wind profiles with high accuracy

multiple doppler radar observations of the evolution of vorticity extrema in a convective boundary layer abstract overdetermined dual doppler wind syntheses are used to document the evolution structure and dynamics of vertical vorticity extrema observed in a convective boundary layer during the 12 june 2002 international h2o project ihop mission discrete vertical vorticity extrema having horizontal scales of 1 2 km can be observed continuously for periods exceeding an hour the evolution of the vorticity field is characterized by complex interactions among vorticity extrema and between the vertical vorticity and vertical velocity fields the most prominent vorticity maxima have amplitudes of approximately 0 01 s 1 and are associated with retrieved pressure deficits of order 0 1 mb the vorticity extrema weaken with height and tilt in the presence of vertical wind shear advection and propagation both contribute substantially to the motion of the vorticity extrema amplifications of vertical vorticity are closely linked to the intensification of updrafts both stretching and tilting can contribute signi

the 30 may 1998 spencer south dakota storm part ii comparison of observed damage and radar derived winds in the tornadoes abstract a violent supercell tornado passed through the town of spencer south dakota on the evening of 30 may 1998 producing large gradients in damage severity the tornado was rated at f4 intensity by damage survey teams a doppler on wheels dow mobile radar followed this tornado and observed the tornado at ranges between 1 7 and 8 0 km during various stages of the tornado s life the dow was deployed less than 4 0 km from the town of spencer between 0134 and 0145 utc and during this time period the tornado passed through spencer and peak doppler velocity measurements exceeded 100 m s 1 data gathered from the dow during this time period contained high spatial resolution sample volumes of approximately 34 m 34 m 37 m along with frequent volume updates every 45 50 s the high resolution doppler velocity data gathered from low level elevation scans when sample volumes are between 20 and 40 m agl are compared to extensive ground and aerial damage surveys performed by the national weather servic

trace element zoning in dolomite proton microprobe data and thermodynamic constraints on fluid compositions abstract lower cretaceous euhedral dolomite crystals from the gargano peninsula italy have been analyzed by scanning proton microprobe spm for the trace elements sr zn fe mn cu ni y and rb intricate decoupled zoning patterns for fe mn and zn are a ubiquitous feature of the outer 55 microns of the dolomite crystals differences between peak and baseline concentrations are on the order of several hundred parts per million in contrast sr concentrations are nearly constant at 110 ppm the concentrations of the other cations are all low cu 20 ppm y 10 ppm and ni and rb 5 ppm in order to investigate the origin of the gargano dolomite we have used the method of tardy and garrels to estimate equilibrium partition coefficients for divalent cations between aqueous fluids and the dolomite structure 18o measurements on gargano dolomites show that they formed at a maximum temperature of 75 c 7 c estimated equilibrium constants for substitution of the cation m into dolomite calculated baseline molar cation ratios for fluids in equilibrium with gargano dolomite and measured cation ratios for seawater and marine sediment pore fluids at 75 c are as follows m n k eq log10 calculated ratio log10m n measured ratio in seawater log10m n measured ratio marine pore fluids mn mg 1 27 4 62 7 17 2 75 fe mg 12 66 4 77 6 57 3 81 zn mg 6 85 5 27 6 72 4 84 sr ca 0 17 2 94 1 92 1 83 cation ratios of fluids in equilibrium with the baseline concentrations of mn fe and zn in the gargano dolomite samples are bracketed by the cation ratios measured in seawater and in marine sediment pore fluids the factor often discrepancy for sr in the predicted fluid compared with seawater is probably due to nonideal mixing of sr on the ca site the decoupled fluctuations of the mn and fe concentrations in these samples can be explained by eh fluctuations in the reactant fluid zn fluctuations may be a product of ph dependent oxide surface reactions to test this hypothesis of origin unzoned tertiary dolomites from enewetak atoll and from the bahama bank have also been analyzed the homogeneous sr concentration in the gargano dolomite is similar to the sr concentrations measured in the enewetak atoll 175 ppm and bahama bank 150 ppm dolomites samples which in both cases almost certainly grew in equilibrium with seawater gargano baseline mn 20 ppm and fe 80 ppm concentrations are also much the same as the bahama bank dolomite mn 15 ppm and fe 140 ppm concentrations the lack of sr zoning in the gargano samples and the similarity of their sr mn and fe content to dolomite that formed in equilibrium with seawater indicates that the dolomitizing fluid was most likely seawater or a seawater type brine low sr concentrations 12 ppm in pore filling calcite from the gargano suggests that in contrast to the dolomite the calcite precipitated from meteoric fluids

loop current mixed layer energy response to hurricane lili 2002 part ii idealized numerical simulations abstractin this second part of a two part study details of the upper ocean response within an idealized baroclinic current to a translating tropical cyclone are examined in a series of nonlinear reduced gravity numerical simulations based on observations obtained as part of a joint noaa national science foundation nsf experiment in hurricane lili 2002 the preexisting ocean mass and momentum fields are initialized with a gulf of mexico loop current like jet which is subsequently forced by a vortex whose wind stress field approximates that observed in the lili experiments because of 1 favorable coupling between the wind stress and preexisting current vectors and 2 wind driven currents flowing across the large horizontal pressure gradient wind energy transfer to the mixed layer can be more efficient in such a regime as compared to the case of an initially horizontally homogeneous ocean however nearly all energy is removed by advection and wave flux by two local inertial periods after storm pa

cathodoluminescence in calcite cements new insights on pb and zn sensitizing mn activation and fe quenching at low trace element concentrations abstract the role of pb and zn as sensitizers of cathodolumines cl in sedimentary carbonates is still speculative as is the relationship between mn fe and cl intensity at low concentrations of mn and fe we address these questions using calcite cements from the lower oligocene suwannee formation of florida which have mean mn pb zn and fe concentrations less than 45 ppm only a small fraction of these cements exhibit visible cl but when present the luminescence is orange to reddish orange trace element contents were measured using a synchrotron x ray fluorescence microprobe and cl intensity was approximated by spot metered photomicrograph exposure times based on mn and fe contents four cement populations can be defined group i is luminescent calcite with mn 25 ppm and molar mn fe 1 8 group ii contains both luminescent and nonluminescent cements all with mn 25 ppm molar mn fe 25 ppm molar mn fe 100 ppm group iv is nonluminescent calcite with mn 25 ppm and variable fe these groupings and statistical analyses of the data mann whitney tests and factor analyses confirm that 25 ppm mn is necessary to initiate visible cl and that mn is the sole control on cl intensity when mn and fe contents are very low 100 ppm the data also establish 100 ppm fe as a new minimum for the quenching of cl when mn is below 200 ppm there is no evidence in our data that pb or zn concentrations in tens of parts per million either activate or sensitize cl the mann whitney test shows that there is no statistical evidence at the 95 confidence level to indicate that luminescent and nonluminescent cements reflect different populations of pb and zn except for group ii cements that have more pb in nonluminescent cements than in otherwise chemically equivalent luminescent cements factor analysis shows that cl intensity in all luminescent cements is unrelated to pb or zn concentrations given that pb or zn sensitizing is lacking in low mn calcites like the suwannee cements it is hard to imagine how these elements could play a significant role in calcites containing even more mn as is typical of most sedimentary carbonates

ambient seismic noise monitoring of a clay landslide toward failure prediction given that clay rich landslides may become mobilized leading to rapid mass movements earthflows and debris flows they pose critical problems in risk management worldwide the most widely proposed mechanism leading to such flow like movements is the increase in water pore pressure in the sliding mass generating partial or complete liquefaction this solid to liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones which could be detected by monitoring shear wave velocity variations with this purpose in mind the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the pont bourquin landslide swiss alps this small but active composite earthslide earthflow was equipped with continuously recording seismic sensors during spring and summer 2010 an earthslide of a few thousand cubic meters was triggered in mid august 2010 after a rainy period this article shows that the seismic velocity of the sliding material measured from daily noise correlograms decreased continuously and rapidly for several days prior to the catastrophic event from a spectral analysis of the velocity decrease it was possible to determine the location of the change at the base of the sliding layer these results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides

a new parametric tropical cyclone tangential wind profile model abstracta new parametric tropical cyclone tc wind profile model is presented for depicting representative surface pressure profiles corresponding to multiple maxima wind profiles that exhibit single dual and triple maximum concentric eyewall wind peaks associated with the primary inner secondary first outer and tertiary second outer complete rings of enhanced radar reflectivity one profile employs five key parameters tangential velocity maximum radius of the maximum and three different shape velocity parameters related to the shape of the profile after tailoring the model for tc applications a gradient wind is computed from a cyclostrophic wind formulated in terms of the cyclostrophic rossby number a pressure via cyclostrophic balance was partitioned into separate pressure components that corresponded to multiple maxima cyclostrophic wind profiles in order to quantitatively evaluate the significant fluctuations in central pressure deficits the model tc intensity in terms of varying

direct determination of strontium enrichment on grain boundaries in a garnet lherzolite xenolith by proton microprobe analysis the mechanisms by which trace and radiogenic elements are held and transported in the earth s mantle are of prime importance in studies of basalt petrogenesis and the chemical processing of the mantle while such mechanics include the migration of melts and the convective physical admixture of differentiated material1 the role of fluids as transport agents has attracted much interest especially in regions affected by kimberlitic activity2 4 continental basaltic volcanism5 6 and in areas of subduction related magmatic activity7 8 the observation that many incompatible elements are readily leached from garnet lherzolites by dilute acid treatment3 has led to the assumption that a proportion of these elements is located on grain boundaries rather than in solution in the various minerals present this indirect evidence is reinforced by comparison of the compositions of mineral separates with their bulk parental material4 8 11 although careful electron microprobe analyses have made it possible to detect minor and trace elements within grains12 the low concentrations involved together with the high x ray background of the electron microprobe have made it impossible to investigate the supposed distribution of incompatible trace elements on grain boundaries we have measured directly using a high resolution proton microprobe9 10 the distribution of sr and other elements in a garnet lherzolite xenolith the analyses demonstrate that in this sample sr is preferentially concentrated along grain boundaries

polygonal eyewalls asymmetric eye contraction and potential vorticity mixing in hurricanes hurricane eyewalls are often observed to be nearly circular structures but they are occasionally observed to take on distinctly polygonal shapes the shapes range from triangles to hexagons and while they are often incomplete straight line segments can be identified other observations implicate the existence of intense mesovortices within or near the eye region is there a relation between polygonal eyewalls and hurricane mesovortices are these phenomena just curiosities of the hurricane s inner core circulation or are they snapshots of an intrinsic mixing process within or near the eye that serves to determine the circulation and thermal structure of the eye as a first step toward understanding the asymmetric vorticity dynamics of the hurricane s eye and eyewall region these issues are examined within the framework of an unforced barotropic nondivergent model polygonal eyewalls are shown to form as a result of barotropic instability near the radius of maximum winds after reviewing linear theory simulations with a high resolution pseudospectral numerical model are presented to follow the instabilities into their nonlinear regime when the instabilities grow to finite amplitude the vorticity of the eyewall region pools into discrete areas creating the appearance of polygonal eyewalls the circulations associated with these pools of vorticity suggest a connection to hurricane mesovortices at later times the vorticity is ultimately rearranged into a nearly monopolar circular vortex while the evolution of the finescale vorticity field is sensitive to the initial condition the macroscopic end states are found to be similar in fact the gross characteristics of the numerically simulated end states are predicted analytically using a generalization of the minimum enstrophy hypothesis in an effort to remove some of the weaknesses of the minimum enstrophy approach a maximum entropy argument developed previously for rectilinear shear flows is extended to the vortex problem and end state solutions in the limiting case of tertiary mixing are obtained implications of these ideas for real hurricanes are discussed

a method for retrieving mean horizontal wind profiles from single doppler radar observations contaminated by aliasing the velocity azimuth display vad technique was designed to estimate the areal mean vertical profile of the horizontal wind above a ground based doppler radar the method uses radial velocity observations under the assumption of a linear wind field though it encounters difficulty when the observations are contaminated by velocity ambiguities large noise and when viable data exist only over a restricted azimuthal range the method suggested in this paper uses gradients of radial velocity rather than only the velocity itself to derive wind profiles and thus is termed the gradient velocity azimuth display gvad technique both the vad and gvad methods are tested first on simulated data to examine their sensitivity to different type of errors in radial velocity the retrieved mean wind profiles are shown to be insensitive to random errors in radial velocity even at large amplitude however the vad method is very sensitive to systematic errors caused by velocity ambiguities the experiments indicate t

finescale doppler radar observation of a tornado and low level misocyclones within a winter storm in the japan sea coastal region abstract life histories of low level misocyclones one of which corresponded to a tornado vortex within a winter storm in the japan sea coastal region on 1 december 2007 were observed from close range by x band doppler radar of the east japan railway company continuous plan position indicator ppi observations at 30 s intervals at the low elevation angle revealed at least four cyclonic misocyclones within the head of the comma shaped echo of the vortical disturbance under winter monsoon conditions the meso scale vortical disturbance developed within the weak frontal zone at the leading edge of cold air outbreaks high resolution observation of misocyclones revealed the detailed structures of these misocyclones and their temporal evolution as the parent storm evolved a low level convergence line was observed at the edge of the easternmost misocyclone this convergence line was considered to be important for the initiation and development of the misocyclones and the tornado through vortex stretching