combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

evaluation of infrasound signals from the shuttle atlantis using a large seismic network inclement weather in florida forced the space shuttle atlantis to land at edwards air force base in southern california on june 22 2007 passing near three infrasound stations and several hundred seismic stations in northern mexico southern california and nevada the high signal to noise ratio broad receiver coverage and atlantis positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model the predictions and observations compare favorably over much of the study area for both atmospheric specifications to the east of the shuttle trajectory there were no detections beyond the primary acoustic carpet infrasound energy was detected hundreds of kilometers to the west and northwest nw of the shuttle trajectory consistent with the predictions of ducting due to the westward summer time stratospheric jet both atmospheric models predict alternating regions of high and low ensonifications to the nw however infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification possibly due to uncertainties in stratospheric wind speeds

seismic precursors to space shuttle shock fronts seismic precursors to space shuttle re entry shock fronts are detected at txar in southwest texas when the ground track of the orbiter vehicle passes within 150 200 km of the observatory these precursors have been termed shuttle quakes because their seismograms superficially mimic the seismograms of small earthquakes from shallow sources analysis of the shuttle quake seismograms however reveals one important difference unlike ordinary earthquakes the propagation azimuths and horizontal phase velocities of the individual phases of the shuttle quakes are functionally related from a theoretical model developed to account for the origin of these precursors it is found that the seismic phases of shuttle quakes are bow waves a bow wave originates at the advancing tip of the shock front trace i e intersection of the re entry shock front with the surface of the earth when the ground speed of the orbiter vehicle exceeds the horizontal phase velocity of a particular seismic phase bow waves are shown to differ in two important respects from the ordinary seismic phases they vanish ahead of the advancing tip of the shock front trace and their propagation azimuths and horizontal phase velocities are functionally related the ground speed of the orbiter vehicle exceeds the horizontal phase velocities of crustal seismic phase over much of the re entry flight profile as a result p s and r g bow waves will be seen as precursors to the re entry shock front at stations located within a few hundred km of its ground track

modelling the diurnal cycle of tropical convection across the grey zone we present the results of simulations carried out with the met office unified model at 12 4 and 1 5 km resolution for a large region centred on west africa using several different representations of the convection processes these span a range of resolutions from much coarser than the size of the convection processes to cloud system resolving and thus encompass the intermediate grey zone the diurnal cycle in the extent of convective regions in the models is tested against observations from the geostationary earth radiation budget instrument on meteosat 8 by this measure the two best performing simulations are a 12 km model without convective parametrization using smagorinsky style subgrid scale mixing in all three dimensions and a 1 5 km simulation with two dimensional smagorinsky mixing of these the 12 km model produces a better match to the magnitude of the total cloud fraction but the 1 5 km one results in better timing for its peak value the results suggest that the previously reported improvement in the representation of the diurnal cycle of convective organization in the 4 km model compared with the standard 12 km configuration is principally a result of the convection scheme employed rather than the improved resolution per se the details of this result and implications for high resolution model simulations are discussed

infrasonic forerunners exceptionally fast acoustic phases 1 a vapor cloud explosion occurred at an oil depot near buncefield in the uk in 2005 three infrasound arrays in the netherlands detected various stratospheric phases some of these phases appeared with celerities i e horizontal propagation velocity in the conventional range of 0 28 to 0 31 km s exceptionally fast arrivals infrasonic forerunners were identified with celerities of 0 31 to 0 36 km s these phases could be explained by head wave like propagation in a high velocity acoustic channel between 40 and 50 km height where stratospheric zonal winds reached values of 120 m s the manifestation of infrasonic forerunners is validated by modeling with raytracing through actual atmospheric models and determining the celerity apparent velocity and back azimuth one phase occurred with a celerity of 0 25 km s hence we propose a new celerity range for fast stratospheric phases of 0 31 to 0 36 km s and to lower the limit of the conventional range to 0 25 km s

finite difference synthesis of infrasound propagation through a windy viscous atmosphere application to a bolide explosion detected by seismic networks summary a finite difference time domain fdtd algorithm has been developed to model linear infrasound propagation through a windy viscous medium the algorithm has been used to model signals from a large bolide that burst above a dense seismic network in the us pacific northwest on 2008 february 19 we compare synthetics that have been computed using a g2s ecmwf atmospheric model to signals recorded at the seismic networks located along an azimuth of 210 from the source the results show that the timing and the range extent of the direct stratospherically ducted and thermospherically ducted acoustic branches are accurately predicted however estimates of absorption obtained from standard attenuation models sutherland bass predict much greater attenuation for thermospheric returns at frequencies greaterthan0 1hzthanisobserved weconcludethateitherthestandardabsorptionmodelfor the thermospheric is incorrect or that thermospheric returns undergo non linear propagation at very high altitude in the former case a better understanding of atmospheric absorption at high altitudes is required in the latter a fully non linear numerical method is needed to test our hypothesis that higher frequency arrivals from the thermosphere result from non linear propagation at thermospheric altitudes

the effects of recharge on flow nonuniformity and macrodispersion the spatial statistical structure of the fluid velocity field in the case of uniformly recharged heterogeneous aquifers is investigated and the spatial covariances of the velocity field are derived this information is necesary for an investigation of flow and macrodispersion using the lagrangian formalism proposed by dagan 1984 the resulting first two moments of the velocity are nonstationary they are functions of a parameter which characterizes the degree of flow nonuniformity and is related to the recharge the displacement variances are computed and tested favorably using numerical simulations simple relations are developed which relate the transport parameters found for the case of uniform in the average flows to nonuniform flows using a simple nonlinear transformation of the travel time based on

evolving infrasound detections from bogoslof volcano alaska insights from atmospheric propagation modeling bogoslof volcano a back arc volcano in alaska s aleutian arc began an eruptive sequence in mid december 2016 that ended in late august 2017 with 70 individual eruptive episodes because there were no local seismic or infrasound stations on the island the alaska volcano observatory avo relied on distant geophysical networks and remote sensing techniques to assess activity during the eruption avo maintains six infrasound arrays to monitor activity along the aleutian arc adak the island of four mountains okmok akutan sand point and dillingham eruption detection at infrasound arrays is subject to local as well as mesoscale meteorological conditions that vary greatly over both short and long timescales infrasound detections from the array nearest to bogoslof okmok with a latency of about 3 min played a crucial role in monitoring activity during the eruption despite the relative proximity of the okmok array to bogoslof 60 km infrasound detections were not uniformly observed with only about two thirds of the events successfully detected the farthest array at dillingham 816 km detected approximately half of the explosive events with all other arrays detecting less than half of the events we compare observations with infrasound propagation model predictions using both normal mode and parabolic equation forward models to interpret the variation in detections of the 70 explosive events across the avo infrasound network the forward models utilize the newly created publicly available avo g2s atmospheric reconstruction using numerical weather predictions data for the lower atmosphere coupled with upper atmosphere empirical models of wind speeds and temperature we find that long range detections 100 km of bogoslof events are largely aligned with seasonal variability in favorable propagation conditions while regional detections 100 km are less consistent with propagation modeling understanding the output of numerical models in comparison to past observations will facilitate their use in future operational settings for avo and other observatories

aircraft observations of ice crystal evolution in an altostratus cloud abstract observations from a lagrangian spiral descent within altostratus cloud associated with a cold front were used to study the evolution of ice particle spectra by following populations of ice crystals as they fell through the cloud the flight track was corrected for wind effects and was divided into distinct regions for spatial comparison of ice particle spectra analysis of size spectra for particles larger than 800 m revealed heterogeneity on horizontal scales of 5 km in average particle diameter and concentration in the temperature range 40 to 20 c the ice crystal evolution was dominated by diffusional growth although observations of the evolution of the bimodal size spectra suggested that aggregation was occurring between 20 and 10 c aggregation dominated evolution

solute transport through the integrated groundwater stream system of a catchment we present a coupled groundwater stream model of catchment scale solute transport using a lagrangian stochastic advective sorptive travel time approach we consider distributed solute input over a

source location of the 19 february 2008 oregon bolide using seismic networks and infrasound arrays 1 on 19 february 2008 a bolide traveled across the sky along a southern trajectory ending in a terminal burst above oregon the event was well recorded by the usarray other seismic networks four infrasound arrays and several video cameras we compare the results of locating the burst using these different sensor networks specifically we reverse time migrate acoustic to seismic coupled signals recorded by the usarray out to 800 km range to image the source in 2 d space and time we also apply a grid search over source altitude and time minimizing the misfit between observed and predicted arrival times using 3 d ray tracing with a high resolution atmospheric velocity model our seismic and video results suggest a point source rather than a line source associated with a hypersonic trajectory we compare the seismic source locations to those obtained by using different combinations of observed infrasound array signal back azimuths and arrival times we find that all locations are consistent however the seismic location is more accurate than the infrasound locations due to the larger number of seismic sensors a more favorable seismic source receiver geometry and shorter ranges to the seismometers for the infrasound array locations correcting for the wind improved the accuracy but implementing arrival times while increasing the precision reduced the accuracy presumably due to limitations of the source location method and or atmospheric velocity model we show that despite known complexities associated with acoustic to seismic coupling aboveground infrasound sources can be located with dense seismic networks with remarkably high accuracy and precision

regional monitoring of infrasound events using multiple arrays application to utah and washington state summary in this paper we present an integrated set of algorithms for the automatic detection association and location of low frequency acoustic events using regional networks of infrasound arrays here low frequency acoustic events are characterized by transient signals which may arise from a range of natural and anthropogenic sources examples of which include but are not limited to earthquakes volcanic eruptions explosions rockets and bolides first we outline a new technique for detecting infrasound signals that works successfully in the presence of correlated noise we use an f statistic sequentially adapted to ambient noise conditions in order to obtain detections at a given statistical significance while accounting for real background noise at each array individual arrivals are then grouped together based on measured delay times and backazimuths each signal is identified as either a first or later arrival first arrivals at spatially separated arrays are then associated using a grid search method to form events preliminary event locations are calculated from the geographic means and spreads of grid nodes associated with each event we apply the technique to regional infrasound networks in utah and washington state in utah over a period of approximately 1 month we obtain a total of 276 events recorded at three arrays in a geographic region of 6 4 for four groundtruth explosions in utah the automatic algorithm detects associates and locates the events within an average offset of 5 4 km to the actual explosion locations in washington state the algorithm locates numerous events that are associated with a large coalmine in centralia washington an example mining explosion from centralia is located within 8 2 km of the mine the methodology and results presented here provide an initial framework for assessing the capability of infrasound networks for regional infrasound monitoring in particular by quantifying detection thresholds and localization errors

solute transport through a heterogeneous coupled vadose saturated zone system with temporally random rainfall the transport of nonreactive solutes through a coupled two dimensional randomly heterogeneous vadose saturated zone system subject to temporally random rainfall is predicted by monte carlo simulation and compared with previously published analytic results for three different rainfall patterns the relative contributions of the uncertain inputs i e rainfall and saturated conductivity to the prediction uncertainty of solute transport are quantified in terms of the statistical moments of the pore water velocity the plume spatial moments and solute flux breakthrough curves at downstream control planes results show that the mean and variance of the saturated zone pore water velocity were approximately equivalent for the cases of uniform and random rainfall and were well predicted by the analytical relationships developed by rubin and bellin 1994 as a result the mean plume displacement estimated by the trajectory of the mean plume center of mass was found to be nearly identical for these cases in the temporally random rainfall case the saturated zone mean plume experienced more spread in the direction of mean flow at early times however the asymptotic rates of spatial spreading of the mean solute plumes were found to be approximately equivalent for the uniform and random rainfall cases and well predicted by the approximate expressions for longitudinal macrodispersivity in nonuniform flow proposed by destouni and graham 1995 random rainfall and random soil properties increased prediction uncertainty of the solute plume behavior in the vadose zone by an order of magnitude when compared with the uniform rain and random soil case this effect was reduced considerably when the solute entered the saturated zone where random rainfall produced only slightly larger prediction uncertainty than the uniform rainfall case the analytic model developed by destouni and graham 1995 accurately predicted the temporal breakthrough of the mean solute plume at saturated zone control planes for all cases if transport through the unsaturated zone accounted for the effects of temporally random rainfall using the methodology developed by foussereau et al 2000a 2000b results of this work indicate that for the humid climates studied here uncertain rainfall patterns dominate transport prediction uncertainty in the shallow unsaturated zone while uncertain solute breakthrough to the saturated zone and uncertain hydraulic conductivity dominate prediction uncertainty in the saturated zone

multiscale solute transport upscaling for a three dimensional hierarchical porous medium a laboratory generated hierarchical fully heterogeneous aquifer model fhm provides a reference for developing and testing an upscaling approach that integrates large scale connectivity mapping with flow and transport modeling based on the fhm three hydrostratigraphic models hsms that capture lithological static connectivity at different resolutions are created each corresponding to a sedimentary hierarchy under increasing system lnk variances 0 1 1 0 4 5 flow upscaling is first conducted to calculate equivalent hydraulic conductivity for individual connectivity or unit of the hsms given the computed flow fields an instantaneous conservative tracer test is simulated by all models for the hsms two upscaling formulations are tested based on the advection dispersion equation ade implementing space versus time dependent macrodispersivity comparing flow and transport predictions of the hsms against those of the reference model hsms capturing connectivity at increasing resolutions are more accurate although upscaling errors increase with system variance results suggest 1 by explicitly modeling connectivity an enhanced degree of freedom in representing dispersion can improve the ade based upscaled models by capturing non fickian transport of the fhm 2 when connectivity is sufficiently resolved the type of data conditioning used to model transport becomes less critical data conditioning however is influenced by the prediction goal 3 when aquifer is weakly to moderately heterogeneous the upscaled models adequately capture the transport simulation of the fhm despite the existence of hierarchical heterogeneity at smaller scales when aquifer is strongly heterogeneous the upscaled models become less accurate because lithological connectivity cannot adequately capture preferential flows 4 three dimensional transport connectivities of the hierarchical aquifer differ quantitatively from those analyzed for two dimensional systems

a study of infrasonic anisotropy and multipathing in the atmosphere using seismic networks we discuss the use of reverse time migration rtm with dense seismic networks for the detection and location of sources of atmospheric infrasound seismometers measure the response of the earth s

the evolution of an mcs over southern england part 2 model simulations and sensitivity to microphysics simulations using the met office unified model at 1 km horizontal grid spacing of a mesoscale convective system mcs with a cold pool which propagated across southern england on 25 august 2005 are validated using detailed observations from the convective storm initiation project csip early organisation of the system is not especially well treated but the model goes on to form a system which developed qualitative and quantitative features remarkably similar to the observations a sensitivity study suggests that the initial linear system is driven by the position of a low level lid and upper level instability the linear organisation being promoted by a weak rear inflow jet forced by the upper level warm anomaly in the cloud anvil a weak cold pool develops in the absence of ice phase processes but this does not promote system propagation strengthening and descent of the rear inflow jet and acceleration of the system is promoted by the additional heating through glaciation and cooling through snow evaporation the surface cold pool and gust front are further strengthened by snow melting and rainfall evaporation with ice phase processes present the cold pool strengthens as a result of the system development and its strength is broadly correlated with system propagation speed during the middle phase of the system s lifetime propagation enables the convective band to sweep up any convective cells which trigger ahead of the system the differing scales of microphysical processes means that it is difficult to form a steady state system the observed transition phase corresponds to an increase in the slantwise nature of the flow in the storm and in the low level cooling by rainfall evaporation near the gust front combined with a change in ambient conditions advection over the sea which eventually enable the cold pool to propagate ahead of the system

infrasonic crackle and supersonic jet noise from the eruption of nabro volcano eritrea the lowermost portion of an explosive volcanic eruption column is considered a momentum driven jet understanding volcanic jets is critical for determining eruption column dynamics and mitigating volcanic hazards however volcanic jets are inherently difficult to observe due to their violence and opacity infrasound from the 2011 eruption of nabro volcano eritrea has waveform features highly similar to the crackle phenomenon uniquely produced by man made supersonic jet engines and rockets and is characterized by repeated asymmetric compressions followed by weaker gradual rarefactions this infrasonic crackle indicates that infrasound source mechanisms in sustained volcanic eruptions are strikingly similar to jet noise sources from heated supersonic jet engines and rockets suggesting that volcanologists can utilize the modeling and physical understandings of man made jets to understand volcanic jets the unique distinctive infrasonic crackle from nabro highlights the use of infrasound to remotely detect and characterize hazardous eruptions and its potential to determine volcanic jet parameters key points nabro volcano produced sound similar to supersonic jet engines and rockets volcanic and man made jets have similar sound source mechanisms infrasound can remotely detect and characterize volcanic eruptions and jets 2013 american geophysical union all rights reserved

infrasound detection of large mining blasts in kazakstan we describe infrasonic observations recorded since october 1997 at the kurchatov observatory in kazakstan from large mining blasts in kazakstan and siberia seismic signals are regularly recorded on a 21 element cross array from events located at the ekibastuz mine 250 km nw of kurchatov however associated infrasonic detections are infrequent and appear to be seasonal with maximum numbers of detections occurring during november to january raytracing through model atmosphere temperature and wind profiles predicts enhanced infrasound reception during the winter months when the prevailing stratospheric winds blow towards kurchatov in addition raytracing confirms that the first infrasound arrivals at kurchatov propagate through the troposphere and are followed some 50 70 s later by a stratospheric arrival

temporal scaling of hydraulic head and river base flow and its implication for groundwater recharge 1 spectral analyses were conducted for hourly hydraulic head h data observed over a 4 year period at seven monitoring wells in the walnut creek watershed iowa the log power spectral density of the hydraulic head fluctuations versus log frequency f at all seven wells is shown to have a distinct slope or fractal dimension d indicating temporal scaling in the time series of water level fluctuations the fractal dimension of the time series varies from well to well and the spectrum for the average h over all seven wells has a fractal dimension of 1 46 and hurst coefficient of 0 54 the log power spectral density of estimated base flow in the walnut creek and four other watersheds versus log f is shown to have two distinct slopes with a break in scaling at about 30 days it is shown that the groundwater recharge process in a basin can be estimated from a head spectrum based on existing theoretical results hydraulic head in an aquifer may fluctuate as a fractal in time in response to either a white noise or fractal recharge process depending on physical parameters i e transmissivity and specific yield of the aquifer the recharge process at the walnut creek watershed is shown to have a white noise spectrum based on the observed head spectrum

long range acoustic observations of the eyjafjallajokull eruption iceland april may 2010 1 the april may 2010 summit eruption of eyjafjallajokull iceland was recorded by 14 atmospheric infrasound sensor arrays at ranges between 1 700 and 3 700 km indicating that infrasound from modest size eruptions can propagate for thousands of kilometers in atmospheric waveguides although variations in both atmospheric propagation conditions and background noise levels at the sensors generate fluctuations in signal to noise ratios and signal detectability array processing techniques successfully discriminate between volcanic infrasound and ambient coherent and incoherent noise the current global infrasound network is significantly more dense and sensitive than any previously operated network and signals from large volcanic explosions are routinely recorded because volcanic infrasound is generated during the explosive release of fluid into the atmosphere it is a strong indicator that an eruption has occurred therefore long range infrasonic monitoring may aid volcanic explosion detection by complementing other monitoring technologies especially in remote regions with sparse ground based instrument networks

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

pressure drag for shallow cumulus clouds from thermals to the cloud ensemble this study takes the first step to bridge the gap between the pressure drag of a shallow cloud ensemble and that of an individual cloud composed of rising thermals it is found that the pressure drag for a cloud ensemble is primarily controlled by the dynamical component the dominance of dynamical pressure drag and its increased magnitude with height are independent of cloud lifetime and are common features of individual clouds except that the total drag of a single cloud over life cycle presents vertical oscillations these oscillations are associated with successive rising thermals but are further complicated by the evaporation driven downdrafts outside the cloud the horizontal vorticity associated with the vortical structure is amplified as the thermals rise to higher altitudes due to continuous baroclinic vorticity generation this leads to the increased magnitude of local minima of dynamical pressure perturbation with height and consequently to increased dynamical pressure drag

the source of infrasound associated with long period events at mount st helens 1 during the early stages of the 2004 2008 mount st helens eruption the source process that produced a sustained sequence of repetitive long period lp seismic events also produced impulsive broadband infrasonic signals in the atmosphere to assess whether the signals could be generated simply by seismic acoustic coupling from the shallow lp events we perform finite difference simulation of the seismo acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere the effects of topography velocity structure wind and source configuration are considered the simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of p sv and rayleigh wave energy converted locally along the propagation path and acoustic energy originating from the source epicenter although the horizontal acoustic velocity of the latter is consistent with our data the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source the observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic lp events the observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated highly permeable material heating by magmatic activity causes pressure to rise periodically reaching the pressure threshold for rupture of the valve sealing the crack sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack initiating resonance of the remaining fluid subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13 4 km to the nw of the volcano are attributed primarily to atmospheric boundary layer propagation effects superimposed upon amplitude changes at the source

analysis of nonlinear effects on tracer migration in heterogeneous aquifers using lagrangian travel time statistics advective transport in a heterogeneous two dimensional aquifer is simulated and quantified by the statistical moments of tracer travel time and transverse displacement these moments depend on the

the four cumulus cloud modes and their progression during rainfall events a c band polarimetric radar perspective 1 there is no objective definition to separate cumulus congestus clouds from the shallow cumulus and deep clouds this has generated misinterpretation about the role of congestus clouds to promote deep convection through the potential of moistening the middle troposphere in this study an objective identification for the different tropical cumulus modes is found by examining the occurrence frequency of the cloud cell top heights cths and near ground at 2 5 km height rainfall properties of these cells using a three season database of the darwin c band polarimetric radar four cumulus modes were identified namely a shallow cumulus mode with cth in the trade inversion layer 1 3 km a congestus mode with tops in the highly stable middle troposphere 3 6 5 km a deep convective mode with tops in the region of free convection 6 5 15 km and an overshooting convection mode with tops in the tropical tropopause layer cth 15 km the study also investigates the connections between these cumulus modes during heavy rainfall events the congestus mode occurs predominantly from 10 h prior to the peak rainfall event to 2 h past the event the deep cloud populations modes 3 and 4 have their maxima at and shortly after the time of the rainfall peak with maximum occurrence just below the tropical tropopause layer a comparison of the heavy rainfall events occurring in morning oceanic conditions against the afternoon continental conditions revealed a higher ratio of the shallow to the deep cloud population and a shorter transition time from the shallow to the onset of deep population in the morning oceanic conditions than the afternoon land conditions it is also found through the analysis of the large scale moisture budget data set that for both the morning and afternoon events the moistening peaked before the peak in the congestus populations

volcanic tremor and plume height hysteresis from pavlof volcano alaska the march 2016 eruption of pavlof volcano alaska produced an ash plume that caused the cancellation of more than 100 flights in north america the eruption generated strong tremor that was recorded by seismic and remote low frequency acoustic infrasound stations including the earthscope transportable array the relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption similar hysteresis has been observed between seismic river noise and discharge during storms suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data we propose that the time varying relationship at pavlof arose from changes in the tremor source related to volcanic vent erosion this relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity

detecting hidden volcanic explosions from mt cleveland volcano alaska with infrasound and ground coupled airwaves 1 in alaska where many active volcanoes exist without ground based instrumentation the use of techniques suitable for distant monitoring is pivotal in this study we report regional scale seismic and infrasound observations of volcanic activity at mt cleveland between december 2011 and august 2012 during this period twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent and ground coupled acoustic waves were recorded at seismic stations across the aleutian arc several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data however many explosions eluded initial automated analyses of satellite data due to poor weather conditions infrasound and seismic monitoring provided effective means for detecting these hidden events we present results from the implementation of automatic infrasound and seismo acoustic eruption detection algorithms and review the challenges of real time volcano monitoring operations in remote regions we also model acoustic propagation in the northern pacific showing how tropospheric ducting effects allow infrasound to travel long distances across the aleutian arc the successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at mt cleveland

evidence for a meteoritic origin of the september 15 2007 carancas crater on september 15th 2007 around 11 45 local time in peru near the bolivian border the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations soon after a crater was discovered south of lake titicaca these events have been detected by the bolivian seismic network and two infrasound arrays operating for the comprehensive nuclear test ban treaty organization situated at about 80 and 1620 km from the crater the localization and origin time computed with the seismic records are consistent with the reported impact the entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and backazimuths from the crater diameter and the airwave amplitudes the kinetic energy mass and explosive energy are calculated using the estimated velocity of the meteoroid and similarity criteria between orbital elements an association with possible parent asteroids is attempted the favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded

a joint seismic and acoustic study of the washington state bolide observations and modeling 1 on 3 june 2004 a bolide was observed over british columbia washington oregon and idaho in addition to eyewitness accounts the event was recorded on videotape and at 100 seismometers located in washington state and southern british columbia seismic records are consistent with a terminal burst rather than the hypersonic shock of the meteors passage through the atmosphere arrival times from seismic waveform data are used to obtain an accurate source location for this terminal burst the source location can effectively be considered to be ground truth for assessing current atmospheric models and infrasound propagation algorithms we observe clear infrasonic signals associated with the terminal burst of the fireball at infrasound stations i56us and i57us in washington state and california respectively at i56us we observe at least four distinct acoustic arrivals for which we are able to model three using a state of the art atmospheric model the ground to space g2s model and both ray tracing and parabolic equation propagation algorithms to our knowledge this is the first study in which a complex sequence of arrival packets at an individual station has been successfully modeled by range dependent ducting and specular reflection off terrain gradients at i57us a single coherent acoustic signal was observed which we are unable to satisfactorily model this could be due to errors in the specification of the background atmosphere incorrect assumptions and approximations inherent to the acoustic propagation algorithms and the greater range of propagation which amplifies the effect of errors in source location and the atmospheric specifications

stochastic analysis of solute transport in heterogeneous aquifers subject to spatially random recharge this paper derives and solves approximate unconditional moment equations for a concentration plume in a two dimensional spatially random transmissivity field subject to spatially random recharge and non uniform linear trending velocity closed form expressions are derived for the unconditional non stationary auto covariances for head and velocity and the cross covariances between velocity head recharge and log transmissivity based on a system of coupled first order partial differential moment equations and assumed hole type input covariance functions for log transmissivity and recharge the unconditional flow related moment equations are incorporated into a system of solute transport moment equations which is solved using a galerkin finite element algorithm a constant positive mean recharge yields a mean velocity gradient which enhances the ensemble mean plume spreading in the longitudinal direction similar to results found by rubin and bellin 1994 water resour res 30 4 939 948 spatial variability in recharge further enhances the spreading of the ensemble mean plume especially in the lateral direction uncertainty in the spatial distribution of recharge also increases the extent of the ensemble standard deviation plume particularly in the lateral direction and increases the coefficient of variation of solute concentration the uncertainty in the prediction of solute transport increases with increasing recharge variance and spatial correlation scale

a new boundary layer mixing scheme part i scheme description and single column model tests a new boundary layer turbulent mixing scheme has been developed for use in the ukmo weather forecasting and climate prediction models this includes a representation of nonlocal mixing driven by both surface fluxes and cloud top processes in unstable layers either coupled to or decoupled from the surface and an explicit entrainment parameterization the scheme is formulated in moist conserved variables so that it can treat both dry and cloudy layers details of the scheme and examples of its performance in single column model tests are presented

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

global morphology of infrasound propagation i atmospheric sound waves in the 0 02 10 hz region also known as infrasound exhibit long range global propagation characteristics measurable infrasound is produced around the globe on a daily basis by a variety of natural and man made sources as a result of weak classical attenuation 0 01 db km 1 at 0 1 hz these acoustic signals can propagate thousands of kilometers in tropospheric stratospheric and lower thermospheric ducts to model this propagation accurately detailed knowledge of the background atmospheric state variables the global winds and temperature fields from the ground to 170 km is required for infrasound propagation calculations we have developed a unique atmospheric specification system g2s that is capable of providing this information using acoustic ray tracing methods and detailed g2s atmospheric specifications we investigate the major aspects of the spatiotemporal variability of infrasound propagation characteristics

acoustic propagation and atmosphere characteristics derived from infrasonic waves generated by the concorde infrasonic signals generated by daily supersonic concorde flights between north america and europe have been consistently recorded by an array of microbarographs in france these signals are used to investigate the effects of atmospheric variability on long range sound propagation statistical analysis of wave parameters shows seasonal and daily variations associated with changes in the wind structure of the atmosphere the measurements are compared to the predictions obtained by tracing rays through realistic atmospheric models theoretical ray paths allow a consistent interpretation of the observed wave parameters variations in the reflection level travel time azimuth deviation and propagation range are explained by the source and propagation models the angular deviation of a ray s azimuth direction due to the seasonal and diurnal fluctuations of the transverse wind component is found to be 5 from the initial launch direction one application of the seasonal and diurnal variations of the observed phase parameters is the use of ground measurements to estimate fluctuations in the wind velocity at the reflection heights the simulations point out that care must be taken when ascribing a phase velocity to a turning height ray path simulations which allow the correct computation of reflection heights are essential for accurate phase identifications

a study of acoustic propagation from a large bolide in the atmosphere with a dense seismic network 1 a large meteor entered the atmosphere above northeastern oregon on 19 february 2008 at 530 pst several hundreds of broadband seismic stations in the u s pacific northwest recorded acoustic to seismic coupled signals from this event the travel times of the first arriving energy are consistent with a terminal explosion source model suggesting that the large size of the explosion masked any signals associated with a continuous line source along its supersonic trajectory several infrasound arrays in north america also recorded this event both the seismic and infrasound data have been used to locate the explosion in 3 d space and time climatological atmospheric velocity models predict that infrasound signals from sources that occur at mid northern latitudes in winter are usually ducted to the east due to eastward zonal winds in this paper we analyze travel time picks and use 3 d ray tracing to generate synthetic travel times based on various atmospheric models to show that the seismic network data instead reveal a predominant westward propagation direction a sudden stratospheric warming event that reversed the zonal wind flow explains this westward propagation the seismic data illuminate in unprecedented spatial detail the range and azimuthal definition of shadow zones out to a range of 500 km suggesting that dense seismic networks can be used to study infrasound propagation at spatial resolutions that exceed that which can be done with only a handful of globally distributed infrasound arrays

application of an updated atmospheric model to explore volcano infrasound propagation and detection in alaska abstract winds and temperature gradients greatly affect the long range propagation of infrasound the spatio temporal variability of these parameters must therefore be accurately characterized to correctly interpret recorded infrasound at long distances specifically to differentiate between source and propagation effects here we present the first results of an open source reanalysis model termed alaska volcano observatory ground to space avo g2s constructed to accurately characterize the atmosphere and model long range infrasound propagation from volcanic eruptions in alaska we select a number of case studies to examine recent eruptions of alaskan volcanoes whose ash emissions posed a threat to air traffic including the two most recent eruptions of pavlof volcano and two typical explosions from cleveland volcano strong tropospheric ducting and low noise at the station during the 21 july 2015 explosion of cleveland volcano led to an automated detection of the explosion at an infrasound array 992 km away whereas low signal to noise ratio for the 6 november 2014 cleveland volcano explosion helps explain the non detection in real time of a predicted strong stratospheric arrival for the november 2014 pavlof eruption discrepancies between local seismic data and a distal infrasound array 460 km away cannot be solely explained by changes in atmospheric conditions though some features of the complex propagation predictions follow the trends in long range infrasound signals the most recent eruption of pavlof volcano in march 2016 shows minimal changes in propagation conditions throughout the eruption and therefore indicates that the signals detected at long range primarily reflect source processes these results show how detailed examination of the acoustic propagation conditions provides insight into detection capability and eruption dynamics future work will implement avo g2s and high resolution long range infrasound propagation modeling in real time for alaskan volcanoes of interest

the estimation of upper atmospheric wind model updates from infrasound data 1 in our recent paper the sensitivity of infrasound to the upper atmosphere is investigated using impulsive signals from the tungurahua volcano in ecuador we reported on the coherent variability of thermospheric travel times with periods equal to those of the tidal harmonics moreover it was shown that the error in predicted thermospheric travel time is in accord with typical uncertainties in the upper atmospheric wind speed models given the observed response of the infrasound celerities to upper atmospheric tidal variability it was suggested that infrasound observations may be used to reduce uncertainty in the knowledge of the atmospheric specifications in the upper atmosphere in this paper we discuss the estimation of upper atmospheric wind model updates from the infrasound data described in the aforementioned paper the parameterization of the model space by empirical orthogonal functions is described it is found that the wind model in the upper mesosphere and lower thermosphere can be described by a four parameter model due to the small dimensionality of the model space a grid search method can be used to solve the inverse problem a bayesian method is used to assess the uncertainty in the inverse solution given the a priori uncertainty in the data and model spaces and the nonlinearity of the inverse problem at hand we believe that this is the first study in which such methods are applied to real infrasound data allowing for a rigorous analysis of this inverse problem it is found that the complexity of the a posteriori model distribution increases for a larger dimensional model space and larger uncertainties in the data a case study is presented in which the nonlinear propagation from source to receiver is simulated using an updated wind model and nonlinear ray theory as nonlinear propagation effects further constrain the propagation path this is a way to check the physical self consistency of the travel time inversion approach we obtain excellent agreement between the simulated and observed waveforms

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

stochastic analysis of transport in a combined heterogeneous vadose zone groundwater flow system 1 first order analysis was used to investigate the effect of a few characteristics of the vadose zone and the solute source at the soil surface on the expected breakthrough curves btcs of tracer solutes in a combined unsaturated saturated spatially heterogeneous formation with a three dimensional statistically anisotropic structure the analysis is based on a stochastic continuum representation of the stationary and nonstationary eulerian velocity vectors in the unsaturated and saturated domains respectively and a general lagrangian description of the solute mass flux in steady state flow results of the present analysis suggest that the length scales and the flow characteristics of the spatially heterogeneous unsaturated zone that affect the travel time probability density function between the soil surface and the water table also affect the expected solute btc at a control plane located downstream in the groundwater the flow in the unsaturated zone might enhance the early arrival time and the spreading of the expected solute btc in the groundwater especially when the vertical extent of the unsaturated zone is relatively large when the unsaturated zone consists of relatively dry coarse textured stratified soil material and when the horizontal extent of the solute source in the direction of the mean groundwater flow is relatively large the effect of the characteristics of the vadose zone and the solute source at the soil surface on the expected solute btc in the groundwater decreases as the distance to the control plane increases and as the process of the solute breakthrough is more advanced the relatively good agreement between the results of the presentfirst order stochasticanalysiswiththeresultsofdetailed numericalanalysesofflow and transport in a three dimensional heterogeneous combined vadose zone groundwater flow domain suggests that the first order stochastic analyses may be sufficiently reliable to showappropriatetrendswhichmightoccurinrealisticcombinedvadosezone groundwater flow systems citation russo d and a fiori 2009 stochastic analysis of transport in a combined heterogeneous vadose zone groundwater flow system water resour res 45 w03426 doi 10 1029 2008wr007157

using the nonstationary spectral method to analyze asymptotic macrodispersion in uniformly recharged heterogeneous aquifers summary this paper describes an investigation of the influence of uniformly distributed groundwater recharge on asymptotic macrodispersion in two dimensional heterogeneous media this is performed using a nonstationary spectral approach li s g mclaughlin d 1991 a nonstationary spectral method for solving stochastic groundwater problems unconditional analysis water resour res 27 7 1589 1605 li s g mclaughlin d 1995 using the nonstationary spectral method to analyze flow through heterogeneous trending media water resour res 31 3 541 551 based on fourier stieltjes representations for the perturbed quantities to solve the problem analytically focus is placed on the case where the local longitudinal dispersivity l is much smaller than the integral scale of log transmissivity i e l 1 the closed form expressions are obtained for describing the spectrum of flow velocity the variability of flow velocity and asymptotic macrodispersion in terms of the statistical properties and the integral scale of log transmissivity local transport parameters and a parameter rubin y bellin a 1994 the effects of recharge on flow nonuniformity and macrodispersion water resour res 30 4 939 948 used to characterize the degree of flow nonuniformity due to the groundwater recharge the impact of on these results is examined

stochastic determination of well capture zones a stochastic approach is adopted for characterizing the uncertainty in well capture zones in heterogeneous formations transmissivity is modeled as a random space function and a monte carlo approach is used to infer the probability distribution of the resulting stochastic capture zones through several numerical experiments the influence of the statistical parameters of transmissivity variation on the extent of uncertainty in the location of the capture zone is investigated two aquifer models are considered a fully confined aquifer and a leaky confined aquifer receiving recharge from above a connection is made with previous work on transport theory and the statistical parameters of the capture zone probability distribution are compared with those of a solute concentration plume

stochastic determination of three dimensional capture zones for a fully penetrating well 1 a stochastic methodology is used to investigate transport of a conservative solute by steady flow to a fully penetrating pumping well in a three dimensional heterogeneous formation the spatially variable hydraulic conductivity is modeled as a stationary random function of anisotropic two point covariance although mean transport is radial heterogeneity produces three dimensional velocity fluctuations which are shown to affect solute recovery and the capture zone distribution expressions accurate to the first order in log conductivity variance y2 are derived for travel time variance capture zone extent and solute recovery under the following simplifying assumptions 1 the vertical integral scale of conductivity is much less than the horizontal integral scale 2 the depth of the formation is much greater than the vertical integral scale of conductivity 3 the well bore diameter is much smaller than the horizontal scale of conductivity 4 longitudinal and lateral local dispersion are negligible while the effect of transverse dispersion is examined travel time variance 2 for transport in convergent flow in a three dimensional aquifer is shown to be greater than 2 in either constant mean flow in a three dimensional formation or radially convergent flow in a heterogeneous two dimensional medium transverse dispersion between layers in a sedimentary formation is found to increase mixing between flow paths leading to a marginal reduction in travel time variance because of negative correlation between mass flux and travel time solute retrieval at the well occurs earlier from a constant flux solute source than from an instantaneous plume the relationship between initial plume length and relative plume spreading is illustrated for simple plume geometries

improving simulations of convective systems from trmm lba easterly and westerly regimes abstract the 3d goddard cumulus ensemble model is used to simulate two convective events observed during the tropical rainfall measuring mission large scale biosphere atmosphere trmm lba experiment in brazil these two events epitomized the type of convective systems that formed in two distinctly different environments observed during trmm lba the 26 january 1999 squall line formed within a sheared low level easterly wind flow on 23 february 1999 convection developed in weak low level westerly flow resulting in weakly organized less intense convection initial simulations captured the basic organization and intensity of each event however improvements to the model resolution and microphysics produced better simulations as compared to observations more realistic diurnal convective growth was achieved by lowering the horizontal grid spacing from 1000 to 250 m this produced a gradual transition from shallow to deep convection that occurred over a span of hours as opposed to an abrupt appearance of

efficient approximate spectral method to delineate stochastic well capture zones in nonstationary groundwater flow systems summary this study presents an unconditional approximate spectral method asm to delineate well capture zones in nonstationary groundwater systems taking advantages of spectral theories in solving unmodeled small scale variability in hydraulic conductivity k the proposed spectral method can efficiently estimate flow uncertainties such velocity uncertainties associated with the concept of particle tracking can delineate well capture zones for groundwater systems with practical complexities and scales in this study the developed asm is assessed to quantify the accuracy of delineated well capture zones under a variety of conditions including bounded flow domains flow systems with multiple wells multiple hydraulic conductivity scales and nonstationary flows caused by complex sources and sinks in the modeling areas the asm solutions are systematically compared with the corresponding numerical solutions of nonstationary spectral method nsm and monte carlo simulation mcs simulation results reveal that the proposed asm is computationally efficient and the solutions of velocity variances agree well with the corresponding numerical solutions of nsm and mcs based on the simple and efficient approximations the developed asm can delineate accurately the mean and variance dynamics of capture zones in complex large scale groundwater flow systems

infrasonic precursors to a vulcanian eruption at sakurajima volcano japan the may 1998 eruption sequence of sakurajima volcano was monitored by ten infrasonic stations ten seismometers and a video camera during this seismo acoustic experiment we recorded hundreds of infrasonic tremor and long period events associated with seismic signals and observed a progression from relative quiescence to a vulcanian eruption the number of infrasonic events increased with escalating volcanic activity and the dominant character of the infrasonic signals changed from impulsive to emergent at 22 17 of may 19 sakurajima released ash and gases to a height of 2 km above the vent an event that was recorded continuously by one infrasonic and two seismic stations we present the experimental setup as well as a procedure through which infrasonic signals may be incorporated into future eruption monitoring and forecasting algorithms for open vent volcanic systems in addition our recordings suggest that infrasonic signals are more representative of processes occurring within the volcanic interior than are seismic signals which are strongly altered by diffraction and scattering in the volcanic edifice

nonstationary stochastic analysis of flow in a heterogeneous unconfined aquifer subject to spatially random periodic recharge summary the problem of two dimensional groundwater flow in a heterogeneous unconfined aquifer under periodic random forcing in time is analyzed from a stochastic point of view it is assumed that the periodic random forcing namely random recharge can be represented by a sinusoidal function in time analytical solutions are developed through the nonstationary spectral approach in conjunction with the principle of superposition the results namely the variances of hydraulic head and specific discharge are expressed in terms of statistical properties of hydraulic parameters and recharge field it can be concluded from the analytical results that the mean recharge rate and integral scale of spatially random recharge fluctuations play essential roles in enhancing the variability of hydraulic head and specific discharges

efficient sensitivity analysis for flow and transport in the earth s crust and mantle summary this paper focuses on the role of sensitivity analysis in studies of water transport in the environmental and geophysical sciences sensitivity analysis is useful in model development to determine how changes in parameter input will affect a model s response it is also used in data assimilation to incorporate observations into a model the adjoint method allows an efficient calculation of a model s sensitivity when the number of parameters exceeds the number of observations in this paper we present studies demonstrating the use of the adjoint method for modelling water transport in both the earth s crust and mantle

modelling precipitation in frontal rainbands the main aim of this study is to establish the ability of a simple parametrization to represent adequately the microphysical processes acting in frontal rainbands in order to do this we compare it with a more detailed parametrization in conditions typical of warm frontal and narrow cold frontal rainbands simulations using a 2 dimensional diagnostic model indicate that a mixed phase parametrization is required in dynamical models of high resolution

listening to sounds from an exploding meteor and oceanic waves low frequency sound infrasound measurements have been selected within the comprehensive nuclear test ban treaty ctbt as a technique to detect and identify possible nuclear explosions the seismology division of the royal netherlands meteorological institute knmi operates since 1999 an experimental infrasound array of 16 micro barometers here we show the rare detection and identification of an exploding meteor above northern germany on november 8th 1999 with data from the deelen infrasound array dia at the same time sound was radiated from the atlantic ocean south of iceland due to the atmospheric coupling of standing ocean waves called microbaroms occurring with only 0 04 hz difference in dominant frequency dia proved to be able to discriminate between the physically different sources of infrasound through its unique lay out and instruments the explosive power of the meteor being 1 5 kt tnt is in the range of nuclear explosions and therefore relevant to the ctbt

a comprehensive study of infrasound signals detected from the ingolstadt germany explosion of 1 september 2018 the explosion at the ingolstadt oil refinery was widely recorded at seismic and infrasound stations deployed throughout central europe to distances of several hundred to a thousand kilometres this study focuses on the wealth of data recorded at infrasound stations in central and eastern europe while from the many detecting seismic stations within 400 km range only seismic and seismo acoustic arrivals at the close in grafenberg array are considered here most of the infrasound stations are acoustic arrays enabling us to apply array processing techniques to determine relevant wave field parameters such as backazimuth and slowness resp trace velocity these parameters not only confirm the source direction but also put constraints on the observed arrivals propagation modes wave field parameters suggest that we observe tropospheric arrivals to about 150 km and stratospheric and or thermospheric returns for longer distances 1d 2d and 3d ray tracing predict tropospheric arrivals to westerly directions up to distances of 100 km beyond which only thermospheric returns are obtained azimuth independent beyond 250 300 km stratospheric returns do not follow from any of the increasingly complex ray tracing models parabolic equation propagation modeling however suggests that in a number of cases stratospheric ducting may be possible however neither the tropospheric seismo acoustic arrivals at the grafenberg array nor the various arrivals at ims station is26 could be modeled therefore the ingolstadt explosion along with the observed infrasonic phases provide an excellent test bed to investigate our ability in realistically forecasting atmospheric wave propagation with existing algorithms and available atmospheric models

determination of a well head protection zone by stochastic inverse modelling abstract capture zones of wells play an important role in the protection of groundwater against pollution by persistent chemical compounds groundwater flow models can be used to delineate capture zones as however the accuracy and uniqueness of such models may be poor the outcome of a deterministic modelling exercise is likely to be unreliable in such a case stochastic modelling presents an alternative for the delineation of capture zones in this paper two methods are compared the unconditional and conditional monte carlo simulation in each method realizations of the aquifer characterized by a combination of recharge rates and transmissivity values are produced for each realization the capture zone of the well is determined by particle tracking by superposition of all capture zones produced a probability distribution is obtained that describes the probability of a point on the ground surface to belong to the capture zone this probability is given by the fraction of catchments among all realizations which contain the point conditioning the calculation with measured heads usually implies a zoning or spatial resolution of the transmissivity distribution the need for identification of large scale features for a meaningful zonation is stressed for a given zoned aquifer the influence of successively adding measured heads used to condition the stochasticsis studied with an increasing number of conditioning heads the probability distribution of the capture zone is shown to narrow this method allows the quantification of the value of measured head data

convective updraught evaluation in high resolution nwp simulations using single doppler radar measurements this study presents an evaluation of the size and strength of convective updraughts in high resolution simulations by the uk met office unified model um updraught velocities have been estimated from range height indicator rhi doppler velocity measurements using the chilbolton advanced meteorological radar as part of the dynamical and microphysical evolution of convective storms dymecs project based on mass continuity and the vertical integration of the observed radial convergence vertical velocities tend to be underestimated for convective clouds due to the undetected cross radial convergence velocity fields from the um at a resolution corresponding to the radar observations are used to scale such estimates to mitigate the inherent biases the analysis of more than 100 observed and simulated storms indicates that the horizontal scale of updraughts in simulations tend to decrease with grid length the 200 m grid length agreed most closely with the observations typical updraught mass fluxes in the 500 m grid length simulations were up to an order of magnitude greater than observed and greater still in the 1 5 km grid length simulations the effect of increasing the mixing length in the sub grid turbulence scheme depends on the grid length for the 1 5 km simulations updraughts were weakened though their horizontal scale remained largely unchanged progressively more so for the sub kilometre grid lengths updraughts were broadened and intensified horizontal scale was now determined by the mixing length rather than the grid length in general simulated updraughts were found to weaken too quickly with height the findings were supported by the analysis of the widths of reflectivity patterns in both the simulations and observations

uncertainty estimation of well catchments in heterogeneous aquifers 1 the uncertainty in the boundary of two dimensional steady state well catchments due to the uncertainty of the spatially variable hydraulic conductivity field is investigated the well discharge rate and the areal recharge rate are assumed constant the catchment boundary is traced by backward particle tracking in the velocity field the uncertainty bandwidth of the catchment boundary is approximated in first order by formulating the time dependent longitudinal and transversal second moments of the particle displacements along and normal to the mean particle trajectory applications of the approach are presented for a set of simple configurations the results are compared with the results from unconditional numerical monte carlo simulations the comparison allows an assessment of the accuracy the applicability and the limits of the method the approximation corresponds quite well with the monte carlo simulations provided that the distance to the domain boundary is sufficiently large

equivalent vadose zone steady state flow an assessment of its capability to predict transport in a realistic combined vadose zone groundwater flow system 1 the applicability of an equivalent steady state vadose zone flow model to a realistic transient three dimensional heterogeneous combined vadose zone groundwater flow system was tested here two cases pertinent to semiarid regions and the presence or absence of an irrigated crop were analyzed and are presented in detail using the hydraulic properties from the bet dagan trench in addition the case of a more humid region characterized by additional summer precipitation and soils of different textures was analyzed and is discussed briefly results of the analyses suggested that when the water table is located at sufficiently large distance from the soil surface the vadose zone can be divided conceptually into two distinct zones a highly transient near surface zone and a deeper quasi steady state zone under these conditions an equivalent steady state influx obtained by averaging the cumulative flux of the net applied water over the relevant time period may provide a relatively good approximation of the cumulative water flux that crossed the water table as for solute transport in all cases examined the trajectories of the centroid of the solute plume and the mean and the standard deviation of the solute breakthrough curves at a given horizontal control plane cp expressed as functions of the cumulative flux crossing the pertinent horizontal cp associated with the transient flows were in relatively good agreement with their counterparts associated with the equivalent steady state flows particularly under noncropped conditions and when the soil texture is coarser the main finding of this study is that for the case in which the water table is located at sufficiently large distance from the soil surface equivalent steady state vadose zone flow may reconstruct the true solute btc or the solute travel time pdf at a horizontal cp located in the vicinity of the water table depth the latter finding applies to heterogeneous soils of different textures and to different atmospheric forcing conditions at the soil surface and in the presence or absence of vegetation and despite the fact that features of the transport unique to vadose zone transient flow induced by the temporal fluctuations in the water table depth cannot be reproduced by the equivalent steady state vadose zone flow

time reversal for localization of sources of infrasound signals in a windy stratified atmosphere time reversal is used for localizing sources of recorded infrasound signals propagating in a windy stratified atmosphere due to the convective effect of the background flow the back azimuths of the recorded signals can be substantially different from the source back azimuth posing a significant difficulty in source localization the back propagated signals are characterized by negative group velocities from which the source back azimuth and source to receiver str distance can be estimated using the apparent back azimuths and trace velocities of the signals the method is applied to several distinct infrasound arrivals recorded by two arrays in the netherlands the infrasound signals were generated by the buncefield oil depot explosion in the u k in december 2005 analyses show that the method can be used to substantially enhance estimates of the source back azimuth and the str distance in one of the arrays for instance the deviations between the measured back azimuths of the signals and the know

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

the 12 december 2017 baumgarten gas hub explosion a case study on understanding the occurrence of a large infrasound azimuth residual and a lack of seismic observations the baumgarten explosion occurred on 12 december 2017 at a gas storage site about 30 km east of vienna austria acoustic arrivals from this accidental surface explosion were detected at dozens of stations of the alparray seismic network to distances up to 150 km mainly in easterly directions thus it was expected that the hungarian infrasound array pszi located about 230 km to the east southeast of baumgarten would detect this acoustic wave as well standard progressive multichannel correlation processing and frequency wavenumber analysis identified a signal emerging at 7 57 55 utc from an azimuth of 296 300 and with trace velocity 400 m s the extraordinarily high trace velocity and excessive backazimuth residual relative to the explosion site direction of 282 however cast strong doubts on the arrival s connection to the baumgarten event accounting for the effect of non planar geometry of the infrasound array results in a reduction of the azimuth residual by half additionally 2d and 3d raytracing methods are used including the european centre for medium range weather forecasts ecmwf atmospheric model to further explain the remaining azimuth residual as well as to elucidate the large trace velocity estimates the prevailing stratospheric winds in excess of 150 m s are identified as the underlying cause including both factors the initial azimuth residual of up to 18 decreases to 4 allowing to associate the infrasound signal at pszi with the baumgarten event finally the data from a seismic station at 30 km range is re investigated for magnitude estimation the local magnitude of ml 1 0 explains well the scarcity of seismic observations within 50 km range where three or four stations show signals mainly consisting of rg type surface waves but no body waves

transport upscaling in highly heterogeneous aquifers and the prediction of tracer dispersion at the made site we thank daniel fernandez garcia for sharing the data for the two concentration snapshots of the made 2 experiment and alraune zech and aldo fiori for sharing the made 1 data with us the authors acknowledge the financial support of the european research council through the project mhetscale grant agreement no 617511 and the spanish ministry of science and innovation through a severo ochoa project no cex2018 000794 s and the project hydropore pid2019 106887gb c31 juan j hidalgo acknowledges the support of the spanish ministry of science and innovation through a ramon y cajal fellowship no ryc 2017 22300 alessandro comolli acknowledges support through the prodex grant chypi

stochastic analysis of transport in hillslopes travel time distribution and source zone dispersion 1 a stochastic model is developed for the analysis of the traveltime distribution f in a hillslope the latter is described as made up from a surficial soil underlain by a less permeable subsoil or bedrock the heterogeneous hydraulic conductivity k is described as a stationary random space function and the model is based on the lagrangian representation of transport a first order approach in the log conductivity variance is adopted in order to get closed form solutions for the principal statistical moments of the traveltime our analysis indicates that the soil is mainly responsible for the early branch of f i e the rapid release of solute which preferentially moves through the upper soil the early branch of f is a power law with exponent variable between 1 and 0 5 the behavior is mainly determined by unsaturated transport the subsoil response is slower than that of the soil the subsoil is mainly responsible for the tail of f which in many cases resembles the classic linear reservoir model the resulting shape for f is similar to the gamma distribution analysis of the f moments indicates that the mean traveltime is weakly dependent on the hillslope size the traveltime variance is ruled by the distribution of distances of the injected solute from the river the effect is coined as source zone dispersion the spreading due to the k heterogeneity is less important and obscured by source zone dispersion the model is tested against the numerical simulation of fiori and russo 2008 with reasonably good agreement with no fitting procedure

ground coupled acoustic airwaves from mount st helens provide constraints on the may 18 1980 eruption abstract the may 18 1980 mount st helens eruption perturbed the atmosphere and generated atmosphere to ground coupled airwaves which were recorded on at least 35 seismometers operated by the pacific northwest seismograph network pnsn from 102 distinct travel time picks we identify coherent airwaves crossing washington state primarily to the north and east of the volcano the travel time curves provide evidence for both stratospheric refractions at 200 to 300 km from the volcano as well as probable thermospheric refractions at 100 to 350 km the very few first hand reports of audible volcano sounds within about 80 km of the volcano coincide with a general absence of ground coupled acoustic arrivals registered within about 100 km and are attributed to upward refraction of sound waves from the coherent refracted airwave arrivals we identify at least four distinct sources which we infer to originate 10 s 114 s 180 s and 319 s after the onset of an 8 32 11 pdt landslide the first of these sources is attributed to resultant depressurization and explosion of the cryptodome most of the subsequent arrivals also appear to be coincident with a source located at or near the presumed volcanic conduit but at least one of the later arrivals suggests an epicenter displaced about 9 km to the northwest of the vent this dislocation is compatible with the direction of the sector collapse and lateral blast we speculate that this concussion corresponds to a northern explosion event associated with hot cryptodome entering the toutle river valley

the three dimensional morphology of simulated and observed convective storms over southern england abstracta set of high resolution radar observations of convective storms has been collected to evaluate such storms in the met office unified model during the dynamical and microphysical evolution of convective storms dymecs project the 3 ghz chilbolton advanced meteorological radar was set up with a scan scheduling algorithm to automatically track convective storms identified in real time from the operational rainfall radar network more than 1000 storm observations gathered over 15 days in 2011 and 2012 are used to evaluate the model under various synoptic conditions supporting convection in terms of the detailed three dimensional morphology storms in the 1500 m grid length simulations are shown to produce horizontal structures a factor of 1 5 2 wider compared to radar observations a set of nested model runs at grid lengths down to 100 m show that the models converge in terms of storm width but the storm structures in the simulations with the smallest grid lengths are too narrow and too intense c

radar characteristics of storms in the sydney area abstract the characteristics of radar echoes for 12 thunderstorm days in the vicinity of sydney australia in the summer of 1995 96 have been examined using an objective methodology for storm identification and tracking the spatial distribution of identified storms shows a maximum in frequency and intensity along the east side of the mountains that lie inland from the coast characteristics such as storm volume area and height are shown to have a lognormal frequency distribution reflectivity also has a skewed frequency distribution with a prevalence of lower reflectivity storms both the maximum reflectivity and storm height are shown to be correlated with the logarithm of storm volume although small storms predominate the bulk of precipitation flux comes from the relatively few large scale storms it is also shown that storms generally move or propagate in a direction slightly to the left of the mass weighted mean wind for the surface to 300 hpa layer at a speed slightly less than the mean speed

normal modes modelling of post seismic ionospheric oscillations since 1960 several experiments have shown strong perturbations of the ionosphere after earthquakes for the biggest quakes doppler ionospheric soundings have revealed displacements of several tens of meter of the ionized layers e and f an accurate modelling of these phenomena was however never described we present here synthetic displacements of such oscillations and compare it with experimental data realistic models of the atmosphere including viscosity are used as well as realistic earth and seismic source model these ionospheric oscillations are computed by normal modes summation taking explicitly into account the coupling between the solid earth and the open atmosphere they are associated to the rayleigh fundamental surface waves we obtain a good agreement between synthetics and observations so it should be possible to use this method to study the ionospheric post seismic perturbations and possibly the high altitude profile of the density and the viscosity of the atmosphere

modeling propagation of infrasound signals observed by a dense seismic network the long range propagation of infrasound from a surface explosion with an explosive yield of about 17 6 t tnt that occurred on june 16 2008 at the utah test and training range uttr in the western united states is simulated using an atmospheric model that includes fine scale layered structure of the wind velocity and temperature fields synthetic signal parameters waveforms amplitudes and travel times are calculated using parabolic equation and ray tracing methods for a number of ranges between 100 and 800 km from the source the simulation shows the evolution of several branches of stratospheric and thermospheric signals with increasing range from the source infrasound signals calculated using a g2s ground to space atmospheric model perturbed by small scale layered wind velocity and temperature fluctuations are shown to agree well with recordings made by the dense high lava plains seismic network located at an azimuth of 300 from uttr the waveforms of calculated infrasound arrivals are compared with those of seismic recordings this study illustrates the utility of dense seismic networks for mapping an infrasound field with high spatial resolution the parabolic equation calculations capture both the effect of scattering of infrasound into geometric acoustic shadow zones and significant temporal broadening of the arrivals