monitoring ash emission episodes at mt etna the 16 november 2006 case study abstract mt etna in sicily italy is one of the best monitored basaltic volcanoes in the world due to the frequent eruptions from its summit and flanks routine monitoring carried out by istituto nazionale di geofisica e vulcanologia sezione di catania for surveillance purposes permits following the evolution of volcanic events in this paper a description of the ash monitoring system as occurred during the august december 2006 summit eruption at the southeast crater sec is shown this eruption was characterized by lava flow effusions and vigorous strombolian activity eighteen paroxysmal episodes occurred up to the end of november forming weak ash plumes accompanied by moderate tephra fallout over etna s slopes during these events we applied a multidisciplinary approach to promptly monitor the paroxysmal activity and the associated tephra fallout through analysis from seismic tremor and observation from live cameras sampling operations mapping and analysis of the deposit during the most significant episodes we carried out textural and grain size analysis on tephra samples and evaluated the total grain size deposit and the erupted volume while numerical simulations of tephra dispersal allowed better understanding eruptive dynamics an example of this methodology is applied to the 16 november episode during which seismic tremor furnished important constraints on the chronology this paroxysmal eruption produced light fallout on the north east sector of the volcano for about ten hours and a number of debris avalanches over the slopes of the sec cone the erupted deposit was composed for the most part of lithic components and characterized by a total size distribution centered on 2 2 while its total mass was evaluated 7 10 6 kg on the whole such integrated studies help to obtain information on magma fragmentation and eruptive mechanisms to characterize the explosive styles shown by etna and finally to better approach the monitoring of imminent eruptions

an evaluation of volcanic cloud detection techniques during recent significant eruptions in the western ring of fire we examined recent volcanic cloud events in the western pacific and indonesian area to validate the performance of remote sensing techniques used to support the international airways volcano watch iavw five events were considered during which eruptions from eight volcanoes injected ash into the upper troposphere or lower stratosphere for one of the eruptions at miyakejima japan at least five aircraft encountered volcanic ash clouds and the cost to three operators alone exceeded us 12 000 000 in aircraft repairs diversions and lost operating time we performed reverse absorption and pattern analysis using gms 5 vissr modis and avhrr data and we examined toms so2 and aerosol index data surface based observations pilot reports and dispersion model output our results verify that the introduction of reverse absorption using the geostationary gms 5 platform significantly enhanced our capacity to monitor volcanic ash clouds in the region in one case we tracked an eruption cloud for approximately 80 h the primary impediment to remote monitoring is the presence of overlying cloud or substantial amounts of ice within the volcanic clouds toms data showed success in identifying volcanic clouds during these conditions but was limited by the infrequency of observations more effective future operation of the iavw relies on developing complementary methods of volcanic cloud remote sensing and greatly increasing the amount and quality of available surface and air observations including observations of precursor activity an understanding of the likely future limitations of remote sensing techniques will aid in the refining of iavw procedures

observations of volcanic clouds in their first few days of atmospheric residence the 1992 eruptions of crater peak mount spurr volcano alaska abstract satellite so2 and ash measurements of mount spurr s three 1992 volcanic clouds are compared with ground based observations to develop an understanding of the physical and chemical evolution of volcanic clouds each of the three eruptions with ratings of volcanic explosivity index three reached the lower stratosphere 14 km asl but the clouds were mainly dispersed at the tropopause by moderate to strong 20 40 m s tropospheric winds three stages of cloud evolution were identified first heavy fallout of large 500 m pyroclasts occurred close to the volcano 25 km from the vent during and immediately after the eruptions and the cloud resembled an advected gravity current second a much larger highly elongated region marked by a secondary mass maximum occurred 150 350 km downwind in at least two of the three events this was the result of aggregate fallout of a bimodal size distribution including fine 25 m ash that quickly depleted the solid fraction of the volcanic cloud for the f

hydrometeor enhanced tephra sedimentation constraints from the 18 may 1980 eruption of mount st helens 1 uncertainty remains on the origin of distal mass deposition maxima observed in many recent tephra fall deposits in this study the link between ash aggregation and the formation of distal mass deposition maxima is investigated through reanalysis of tephra fallout from the mount st helens 18 may 1980 msh80 eruption in addition we collate all the data needed to model distal ash sedimentation from the msh80 eruption cloud four particle size subpopulations were present in distal fallout with modes at 2 2 4 2 5 9 and 8 3 settling rates of the coarsest subpopulation closely matched predicted single particle terminal fall velocities sedimentation of particles 100 m was greatly enhanced predominantly through aggregation of a particle subpopulation with modal diameter 5 9 0 2 19 3 m mammatus on the msh80 cloud provided a mechanism to transport very fine ash particles with predicted atmospheric lifetimes of days to weeks from the upper troposphere to the surface in a matter of hours in this mechanism ash particles initiate ice hydrometeor formation high in the troposphere subsequently the volcanic cloud rapidly subsides as mammatus develop from increased particle loading and cloud base sublimation rapid fallout occurs as the cloud passes through the melting level in a process analogous to snowflake aggregation aggregates sediment en masse and form the distal mass deposition maxima observed in many recent volcanic ash fall deposits this work provides a data resource that will facilitate tephra sedimentation modeling and allow model intercomparisons

correlated lightning mapping array and radar observations of the initial stages of three sequentially triggered florida lightning discharges 1 correlated lightning mapping array and vertical scan radar images are presented for three rocket and wire triggered lightning flashes that occurred sequentially within 17 min in the presence of a decaying multicellular convective storm system over north central florida the initial stage is of each flash propagated generally vertically to the altitude of the 0 c melting level about 5 km and then subsequently propagated for many kilometers horizontally along the melting level contour radar images suggest that the propagation paths of the is channels below and above the melting level were heavily influenced by precipitation gradients flash uf 11 24 exhibited a 12 6 km unbranched is channel the longest unbranched channel observed in the study by a factor of three during flash uf 11 25 119 ms following the cessation of the measured is current at ground and prior to the first return stroke a natural cloud to ground discharge perhaps induced by the is initiated between 2 5 and 4 km altitude and struck ground 5 to 7 km from the launching facility the is of flash uf 11 26 propagated upward through a descending precipitation packet and apparently induced a naturally appearing bi level intracloud discharge via an upward negative leader that initiated within the is breakdown region 3 5 km from the launching facility the upward negative leader propagated from 5 6 to 9 3 km altitude in a time of 11 ms the electrical current measured at ground during the is of flash uf 11 26 exhibited a 57 ms polarity reversal transferring 19 c of positive charge to ground

a multidisciplinary effort to assign realistic source parameters to models of volcanic ash cloud transport and dispersion during eruptions during volcanic eruptions volcanic ash transport and dispersion models vatds are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind those models use input parameters called eruption source parameters such as plume height h mass eruption rate duration d and the mass fraction m63 of erupted debris finer than about 4 or 63 m which can remain in the cloud for many hours or days observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected moreover observed plume height may change during an eruption requiring rapid assignment of new parameters this paper reports on a group effort to improve the accuracy of source parameters used by vatds in the early hours of an eruption we do so by first compiling a list of eruptions for which these parameters are well constrained and then using these data to review and update previously studied parameter relationships we find that the existing scatter in plots of h versus yields an uncertainty within the 50 confidence interval of plus or minus a factor of four in eruption rate for a given plume height this scatter is not clearly attributable to biases in measurement techniques or to well recognized processes such as elutriation from pyroclastic flows sparse data on total grain size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions 0 01 and large silicic ones 0 5 we classify eleven eruption types four types each for different sizes of silicic and mafic eruptions submarine eruptions brief or vulcanian eruptions and eruptions that generate co ignimbrite or co pyroclastic flow plumes for each eruption type we assign source parameters we then assign a characteristic eruption type to each of the world s 1500 holocene volcanoes these eruption types and associated parameters can be used for ash cloud modeling in the event of an eruption when no observational constraints on these parameters are available

a parametric and comparative study of different tephra fallout models abstract we perform a parametric and comparative study on three different tephra dispersal models fall3d hazmap and tephra applied to two different scenarios expected for etna volcano these scenarios are similar to the recent 2002 03 and 1990 etna eruptions and correspond respectively to a weak and to a strong plume eruption for each model and scenario we perform a parametric study on several inputs in order to quantify how a variation on a given input parameter i e an uncertainty on the model input affects the results of the model the study considers topographic effects different description for the eruption column column height influence different fits for terminal velocities of particles the effect of particle shape and finally the variation of the modal grain size model differences are quantified by means of a normalized distance that indicates how close in average the results from two different simulations are we also compare predictions from different models to determine under which circumstances the use of a more elaborated model is justified results from our parametric study show that output of the models can be strongly sensitive to the uncertainties and assumptions on input parameters such as mainly mass eruption rate column height distribution of the mass along the column bulk grain size distribution this highlights that for optimal forecasts is urgent to improve the description of these parameters and of some important physical processes like fragmentation and eruption column dynamics further differences between models are often lower than those due to the uncertainties of input parameters although they become more high in simulating weak plumes thus the choice of the model mainly depends on the kind of application such as the need to simulate the evolution of volcanic clouds in the atmosphere finally the use of both a semi analytical hazmap and a fully computational fall3d model for inverting field data of the 2001 etna eruption showed that the best fit parameters are similar for both models and are consistent with values obtained using independent techniques

transport of volcanic aerosol in the troposphere the case study of the 2002 etna plume 1 the transport of aerosol in the troposphere during the 2002 eruption of mount etna was investigated integrating lidar observations and numerical simulations the case study concentrates on the period 30 october to 2 november the lidar observations performed in potenza italy reveal the presence of aerosol layers made up of young sulfate particles and a low soot content characteristic of the volcano s emission downward large scale motion was measured with a velocity larger than that due to gravitational sedimentation forward trajectories from the volcano simulated from 27 october to 4 november show that particles released at the beginning of the period reached potenza after traveling over the southern and western mediterranean basin partially including the sahara region direct northward transport occurred on 31 october and 1 november the main result of this study is to highlight how the integrated use of observations and model simulations leads to understanding the main features of transport in this case study furthermore some specific points are outlined there is fair agreement between the simulated and observed presence of particles over potenza the vertical structure of the aerosol layers and the downward motion are also well evidenced time variations of the particle concentration deduced from measurements and approximately estimated from the numerical simulations also show qualitative agreement

three dimensional volcanic aerosol dispersal a comparison between multiangle imaging spectroradiometer misr data and numerical simulations 1 the three dimensional reconstruction of volcanic plumes is a central goal to enhance our understanding on dispersal processes in this paper we use data from the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft combined with a stereo matching retrieval procedure we show the potential of misr in capturing important features of volcanic plumes like column height optical depth type and shape of the finest particles of two highly explosive eruptions occurring on mount etna in 2001 and 2002 this work tests how tephra dispersal models reconstruct the 3 d shape of volcanic clouds we compare misr data with fall3d an eulerian model for the transport and deposition of volcanic ash and aerosols coupled with the weather research and forecasting mesoscale meteorological model agreement between simulations and misr data is good regarding both events although it could be improved by increasing the accuracy of the meteorological data a better constraint on volcanological input parameters like the height of the eruptive column and improving our understanding of processes such as aggregation phenomena and volcanic cloud microphysics

a three dimensional eulerian model for transport and deposition of volcanic ashes abstract volcanic ash fallout represents a serious threat to people living near active volcanoes because it can produce several undesirable effects such as collapse of roofs by ash loading respiratory sickness air traffic disruption or damage to agriculture the assessment of such volcanic risk is therefore an issue of vital importance for public safety and its mitigation often requires to evaluate the temporal evolution of the phenomenon through reliable computational models we develop an eulerian model named fall3d for the transport and deposition of volcanic ashes the model is based on the advection diffusion sedimentation equation with a turbulent diffusion given by the gradient transport theory a wind field obtained from a meteorological limited area model lam and the source term derived from by buoyant plume theory it can be used to forecast either ash concentration in the atmosphere or ash loading on the ground model inputs are topography meteorological data given by a lam mass eruption rate and a particle settling velocity distribution a test application to the july 2001 etna eruption is presented

forecasting exposure to volcanic ash based on ash dispersion modeling a technique has been developed that uses puff a volcanic ash transport and dispersion vatd model to forecast the relative exposure of aircraft and ground facilities to ash from a volcanic eruption vatd models couple numerical weather prediction nwp data with physical descriptions of the initial eruptive plume atmospheric dispersion and settling of ash particles three distinct examples of variations on the technique are given using era 40 archived reanalysis nwp data the feb 2000 nasa dc 8 event involving an eruption of hekla volcano iceland is first used for analyzing a single flight results corroborate previous analyses that conclude the aircraft did encounter a diffuse cloud of volcanic origin and indicate exposure within a factor of 10 compared to measurements made on the flight the sensitivity of the technique to dispersion physics is demonstrated the feb 2001 eruption of mt cleveland alaska is used as a second example to demonstrate how this technique can be utilized to quickly assess the potential exposure of a multitude of aircraft during and soon after an event using flight tracking data from over 40 000 routes over three days several flights that may have encountered low concentrations of ash were identified and the exposure calculated relative changes in the quantity of exposure when the eruption duration is varied are discussed and no clear trend is evident as the exposure increased for some flights and decreased for others a third application of this technique is demonstrated by forecasting the near surface airborne concentrations of ash that the cities of yakima washington boise idaho and kelowna british columbia might have experienced from an eruption of mt st helens anytime during the year 2000 results indicate that proximity to the source does not accurately determine the potential hazard although an eruption did not occur during this time the results serve as a demonstration of how existing cities or potential locations of research facilities or military bases can be assessed for susceptibility to hazardous and unhealthy concentrations of ash and other volcanic gases

the vol calpuff model for atmospheric ash dispersal 2 application to the weak mount etna plume of july 2001 1 here the application of the vol calpuff model by barsotti et al to a weak plume erupted from mount etna in july 2001 is presented and discussed the reconstruction of the explosive event was obtained by using high resolution weather forecasts produced by a mesoscale nonhydrostatic model and volcanic source data coming from observations and analytical studies the plume rise and atmospheric dispersal models were investigated over 5 d of eruption mostly in terms of column height aerial ash concentration and ground deposition modeling results are shown as a function of various source conditions and compared to independent observations derived from satellite images and deposit mapping the application of vol calpuff clearly highlights the crucial role played by meteorological conditions in determining dispersal dynamics some of the most important effects described by the model are 1 the large wind field influence on the plume height determination and tilting 2 the contrasting dispersal patterns of ash particles of different sizes 3 the complex and somehow nonintuitive distribution of ash on the ground resulting in preferential directions of dispersal and quite irregular deposit patterns and 4 the impossibility to reproduce both the column height and the deposit accumulation pattern by adopting a steady state vent mass flow rate over the investigated 4 d period due to observed temporal changes in eruption dynamics modeling results also suggest the need for further integration of simulation outcomes with remote sensing and field reconstructions on ash dispersal processes in future

using picosatellites for 4 d imaging of volcanic clouds proof of concept using iss photography of the 2009 sarychev peak eruption abstract volcanic ash clouds can present an aviation hazard over distances of thousands of kilometres and to help to mitigate this hazard advanced numerical models are used to forecast ash dispersion in the atmosphere however forecast accuracy is usually limited by uncertainties in initial conditions such as the eruption rate and the vertical distribution of ash injected above the volcano here we demonstrate the potential of the telematics earth observation mission tom picosatellite formation due for launch in 2020 to provide valuable information for constraining ash cloud dispersion models through simultaneous image acquisition from three satellites tom will carry commercial frame cameras using photogrammetric simulations we show that such data should enable ash cloud heights to be determined with a precision 30 140 m depending on configuration comparable to the vertical resolution of lidar observations 30 180 m depending on the cloud height to support these estimates we processed photographs taken from the international space station of the 2009 sarychev peak eruption as a proxy for tom imagery structure from motion photogrammetric software successfully reconstructed the 3 d form of the ascending ash cloud as well as surrounding cloud layers direct estimates of the precision of the ash cloud height measurements as well as comparisons between independently processed image sets indicate that a vertical measurement precision of 200 m was achieved image sets acquired at different times captured the plume dynamics and enabled a mean ascent velocity of 14 m s 1 to be estimated for regions above 7 km in contrast the uppermost regions of the column at a measured cloud top height of 11 km were not ascending significantly enabling us to constrain a 1 d plume ascent model from which estimates for the vent size 50 m and eruption mass flux 2 6 106 kg s 1 could be made thus we demonstrate that nanosatellite imagery has the potential for substantially reducing uncertainties in ash dispersion models by providing valuable information on eruptive conditions

modeling tephra sedimentation from a ruapehu weak plume eruption 1 we present a two dimensional model for sedimentation of well mixed weak plumes accounting for lateral spreading of the cloud downwind advection increase of volumetric flux in the rising stage and particle transport during fallout the 17 june 1996 subplinian eruption of ruapehu produced a bent over plume that rose to a height of 8 5 km in a wind field with an average velocity of 24 m s 1 and generated a narrow deposit on land extending up to 200 km from vent the sedimentation from the ruapehu plume was dominated by coarse ash with all the blocks and most of the lapilli falling while the plume was still rising particles with diameter 125 m show three accumulation maxima one coincident with a secondary maximum in the total tephra deposit about 150 km from the vent numerical modeling shows that the plume started spreading horizontally beyond about 30 km from vent investigations also show that fickian diffusion can be a good approximation to the crosswind spreading of both vigorous and low energy weak plumes but a wide range of diffusion coefficients is to be expected with the largest values necessary to describe the most vigorous weak plumes such as ruapehu one dimensional and two dimensional simulations show that tephra sedimentation must have been subvertical this feature also supported by direct observations can be the result of the turbulence structure of the local wind field and convective instabilities which could also have played an important role in the generation of the pronounced sinuosity shown by the ruapehu deposit

retrieval of microphysical and morphological properties of volcanic ash plumes from satellite data application to mt ruapehu new zealand a quantitative analysis of the properties of several mt ruapehu new zealand ash plumes has been performed using multispectral satellite data from the avhrr 2 and atsr 2 instruments the analysis includes identification of the plume from background clouds using the reverse absorption effect in the thermal channels modelling and retrieval of particle sizes determination of the plume height from cloud shadows stereoscopy and meteorological data and estimates of the mass of fine particles radii less than 10 m a new spectral technique for identifying opaque silica rich ash clouds is demonstrated by utilizing the near infrared 1 6 m and visible 0 67 m channels of the atsr 2 and the optical properties of a simple volcanic cloud are presented for use in radiative transfer studies it is found that the ruapehu eruption cloud contained silica rich ash particles with radii generally less than a few micrometres the distribution of fine particles is monomodal with a dominant mode peak of about 3 m radius mass loadings of fine particles are found to be in the range 1 to 7 mg m 3 and are consistent with estimates of mass loadings of volcanic clouds from eruptions of other volcanoes the height of the plume top derived from radiosonde data and plume top temperatures in the opaque regions was found to be between 7 5 and 8 5 km while the plume thickness was estimated to be between 1 5 and 3 km cloud height derived from atsr 2 stereoscopy on a different plume gave heights in the range 5 to 8 km the results of this study provide important information on the optical properties of nascent volcanic eruption plumes this information may prove useful in determining the potential effects of volcanic clouds on local climate and in assessing any hazard to aviation

weather radar observations of the hekla 2000 eruption cloud iceland the hekla eruption cloud on 26 27 february 2000 was the first volcanic cloud to be continuously and completely monitored advecting above iceland using the c band weather radar near the keflavik international airport real time radar observations of the onset advection and waning of the eruption cloud were studied using time series of ppi plan position indicator radar images including vmi normal echotop and cappi level 2 displays the reflectivity of the entire volcanic cloud ranges from 0 to 60 dbz the eruption column above the vent is essentially characterised by vmi normal and cappi level 2 values 30 dbz due to the dominant influence of lapilli and ash tephra on the overall reflected signal the cloud generated by the column was advected downwind to the north northeast it is characterised by values between 0 and 30 dbz and the persistence of these reflections likely result from continuing water condensation and freezing on ash particles echotop radar images of the eruption onset document a rapid ascent of the plume head with a mean velocity of 30 to 50 m s 1 before it reached an altitude of 11 12 km the evolution of the reflected cloud was studied from the area change in pixels of its highly reflected portions 30 dbz and tied to recorded volcanic tremor amplitudes the synchronous initial variation of both radar and seismic signals documents the abrupt increase in tephra emission and magma discharge rate from 18 20 to 19 00 utc on 26 february from 19 00 the 45 dbz and 30 45 dbz portions of the reflected cloud decrease and disappear at about 7 and 10 5 h respectively after the eruption began indicating the end of the decaying explosive phase the advection and extent of the reflected eruption cloud were compared with eyewitness accounts of tephra fall onset and the measured mass of tephra deposited on the ground during the first 12 h differences in the deposit map and volcanic cloud radar map are due to the fact that the greater part of the deposit originates by fallout off the column margins and from the base of the cloud followed by advection of falling particle in lower level winds

a statistical approach to evaluate the tephra deposit and ash concentration from puff model forecasts abstract in this paper we present a new statistical approach which provides tephra deposit load and ash concentration using puff a lagrangian model widely used to forecast volcanic ash dispersal during volcanic crisis we perform a parametric study in order to analyze the influence of each input parameter on model outputs for this test we simulate two eruptive scenarios similar to the 2001 scenario 1 and 1998 scenario 2 etna eruptions using high resolution weather data and a domain of 170 170 km results show that for both scenarios we are able to calculate the tephra deposit load and ash concentration but the use of millions of particles is required specifically up to 33 and 220 millions of particles were necessary to accurately predict the tephra deposit and ash concentration in air respectively this is approximately two orders of magnitude larger than the values typically considered running puff the parametric study shows that the horizontal diffusion coefficient the time step of the simulations the topography and the standard deviation of the particle distribution greatly affect the model outputs we also validate the model by best fit procedures results show a good comparison between field data of the 2001 etna eruption and puff simulations being inside 5 and 1 5 times the observed data comparable with results of eulerian models this work will allow to reliably outline the areas of contaminated airspace using puff or any other lagrangian model in order to define the no fly zone and ensure the safety aviation operations as required after the eyjafjallajokull eruption

volcanic ash plume identification using polarization lidar augustine eruption alaska 1 during mid january to early february 2006 a series of explosive eruptions occurred at the augustine volcanic island off the southern coast of alaska by early february a plume of volcanic ash was transported northward into the interior of alaska satellite imagery and puff volcanic ash transport model predictions confirm that the aerosol plume passed over a polarization lidar 0 694 m wavelength site at the arctic facility for atmospheric remote sensing at the university of alaska fairbanks for the first time lidar linear depolarization ratios of 0 10 0 15 were measured in a fresh tropospheric volcanic plume demonstrating that the nonspherical glass and mineral particles typical of volcanic eruptions generate strong laser depolarization thus polarization lidars can identify the volcanic ash plumes that pose a threat to jet air traffic from the ground aircraft or potentially from earth orbit

misr observations of etna volcanic plumes 1 in the last twelve years mt etna located in eastern sicily has produced a great number of explosive eruptions volcanic plumes have risen to several km above sea level and created problems for aviation and the communities living near the volcano a reduction of hazards may be accomplished using remote sensing techniques to evaluate important features of volcanic plumes since 2000 the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft has been extensively used to study aerosol dispersal and to extract the three dimensional structure of plumes coming from anthropogenic or natural sources including volcanoes in the present work misr data from several explosive events occurring at etna are analyzed using a program named minx misr interactive explorer minx uses stereo matching techniques to evaluate the height of the volcanic aerosol with a precision of a few hundred meters and extracts aerosol properties from the misr standard products we analyzed twenty volcanic plumes produced during the 2000 2001 2002 03 2006 and 2008 etna eruptions finding that volcanic aerosol dispersal and column height obtained by this analysis is in good agreement with ground based observations misr aerosol type retrievals 1 clearly distinguish volcanic plumes that are sulphate and or water vapor dominated from ash dominated ones 2 detect even low concentrations of volcanic ash in the atmosphere 3 demonstrate that sulphate and or water vapor dominated plumes consist of smaller sized particles compared to ash plumes this work highlights the potential of misr to detect important volcanic plume characteristics that can be used to constrain the eruption source parameters in volcanic ash dispersion models further the possibility of discriminating sulphate and or water vapor dominated plumes from ash dominated ones is important to better understand the atmospheric impact of these plumes

effect of wind on the rise height of volcanic plumes a theoretical model of a volcanic plume based on applying the equations of motion in a plume centered coordinate system suggests that the interaction between a volcanic plume and wind causes enhanced entrainment of air and horizontal momentum plume bending and a decrease in plume rise height at constant eruption rate because of rapid dilution in the high windspeeds of the polar jet plumes that vary over more than one order of magnitude in mass eruption rate 106 to 107 108 kg s if injected into the polar jet may all attain rise heights only slightly different from that of the core of the jet 10 km as opposed to 17 33 km in a still atmosphere

a multi sensor plume height analysis of the 2009 redoubt eruption abstract during an explosive volcanic eruption accurately determining the height of a volcanic plume or cloud is essential to accurately forecast its motion because volcanic ash transport and dispersion models require the initial plume height as an input parameter the direct use of satellite infrared temperatures for height determination one of the most commonly employed methods at the alaska volcano observatory often does not yield unique solutions for height this result is documented here for the 2009 eruption of redoubt volcano satellite temperature heights consistently underestimated the height of ash plumes in comparison to other methods such as ground based radar and multi angle imaging spectroradiometer misr stereo heights for ash plumes below the tropopause increasing transparency of a plume begins to affect the accuracy of simple temperature height retrievals soon after eruption with decreasing opacity plume temperature heights become increasingly inaccurate comparison with dispersion models and aircraft gas flight data confirms that radar and misr stereo heights are more accurate than basic satellite temperature heights even in the cases in which satellite temperature results appeared to be relatively accurate e g for plumes below the tropopause a mixed signal of plume and ground radiation still presented an issue for almost every event studied this was true regardless of the fact that a band differencing method was used to remove presumably translucent pixels the data presented here make a strong case for the use of data fusion in volcano monitoring as there is a need to confirm satellite temperature heights with other height data if only basic satellite temperature heights are available for a given eruption then these heights must be considered with a significant margin of error

volcanic eruption plume top topography and heights as determined from photoclinometric analysis of satellite data photoclinometry a shape from shading technique is applied to satellite data to determine the three dimensional height and morphology of the upper optical surface of a plume from the eruption of redoubt volcano alaska the technique can be applied to visible images of volcanic plumes that have uniform scattering properties and is most effective on images with moderate incident sun angles and plume transport perpendicular to the azimuth of the sun the two most significant sources of error are the finite resolution of the image data and the choice of image data number dn value for a flat plume element provided the plume spans at least 10 image pixels useful results can be obtained for the central portion of the plume the closest approximation to a flat plume element is found to be the visible dn value corresponding to the coldest pixel along a transect errors in the element altitude due to uncertainty in the dn value for a flat pixel amount to 10 20 m per pixel and are cumulative along the plume transect for redoubt this results in an uncertainty of approximately 300 m at the highest points the method indicates that the redoubt plume rose to an altitude of approximately 3 km while traveling a distance of 150 km from the vent and that the surface topography of the plume exhibits influences of the ambient wind through simple wave structures this technique will have a tremendous impact on studies of plume spreading dynamics and the time integrated evolution of plumes

fallout and distribution of volcanic ash over argentina following the may 2008 explosive eruption of chaiten chile 1 the major explosive eruption of chaiten volcano chile in may 2008 provided a rare opportunity to track the long range dispersal and deposition of fine volcanic ash the eruption followed 10 000 years of quiescence was the largest explosive eruption globally since hudson chile in 1991 and was the first explosive rhyolitic eruption since novarupta alaska in 1912 field examination of distal ashfall indicates that 1 6 1011 kg of ash dense rock equivalent volume of 0 07 km3 was deposited over 2 105 km2 of argentina during the first week of eruption the minimum eruption magnitude estimated from the mass of the tephra deposit is 4 2 several discrete ashfall units are identifiable from their distribution and grain size characteristics with more energetic phases showing a bimodal size distribution and evidence of cloud aggregation processes ash chemistry was uniform throughout the early stages of eruption and is consistent with magma storage prior to eruption at depths of 3 6 km deposition of ash over a continental region allowed the tracking of eruption development and demonstrates the potential complexity of tephra dispersal from a single eruption which in this case comprised several phases over a week long period of intense activity

influence of convective sedimentation on the formation of widespread tephra fall layers in the deep sea the formation of widespread volcanic ash fall layers in deep sea sediments was investigated experimentally to examine the settling behavior of tephra 20 180 m diameter as it travels from the atmosphere into water using a fallout mass flux rate that was constrained by measurements of distal fallout from the 1980 eruption of mount st helens 0 2 g cm 2 hr the experiments show that particle settling in the water column is dramatically accelerated by the formation of diffuse vertical gravity currents the currents form as a result of convective instabilities that develop in a surface boundary layer when the local particle concentration becomes large at the air water interface the settling velocity of particles drops abruptly and the concentration of particles increases because of the differential in mass flux above and below the fluid surface the implication of the experiments is that deposition of distal tephra fall layers in deep sea sediments may be dominantly controlled by diffuse vertical gravity currents as opposed to passive settling of individual particles through the water column this process greatly reduces the residence time of fine ash in the ocean and diminishes the role of ocean currents in influencing the distribution patterns of individual tephra layers support for this mechanism comes from observations of greatly accelerated tephra settling rates in the south china sea following the 1991 eruption of mount pinatubo in the philippines

total grain size distribution and volume of tephra fall deposits on 17 june 1996 ruapehu volcano new zealand produced a sustained andesitic sub plinian eruption which generated a narrow tephra fall deposit extending more than 200 km from the volcano the extremely detailed data set from this eruption allowed methods for the determination of total grain size distribution and volume of tephra fall deposits to be critically investigated calculated total grain size distributions of tephra fall deposits depend strongly on the method used and on the availability of data across the entire dispersal area the voronoi tessellation method was tested for the ruapehu deposit and gave the best results when applied to a data set extending out to isomass values of 1 g m 2 the total grain size distribution of a deposit is also strongly influenced by the very proximal samples and this can be shown by artificially constructing subsets from the ruapehu database unless the available data set is large all existing techniques for calculations of total grain size distribution give only apparent distributions the tephra fall deposit from ruapehu does not show a simple exponential thinning but can be approximated well by at least three straight line segments or by a power law fit on semi log plots of thickness vs area 1 2 integrations of both fits give similar volumes of about 4 106 m3 integration of at least three exponential segments and of a power law fit with at least ten isopach contours available can be considered as a good estimate of the actual volume of tephra fall integrations of smaller data sets are more problematic

reducing discrepancies in ground and satellite observed eruption heights abstract the plume height represents a crucial piece of evidence about an eruption feeding later assessment of its size character and potential impact and feeding real time warnings for aviation and ground based populations there have been many observed discrepancies between different observations of maximum plume height for the same eruption a comparison of maximum daily height estimates of volcanic clouds over indonesia and papua new guinea during 1982 2005 shows marked differences between ground and satellite estimates and a general tendency towards lower height estimates from the ground without improvements in the quality of these estimates reconciled among all available methods warning systems will be less effective than they should be and the world s record of global volcanism will remain hard to quantify examination of particular cases suggests many possible reasons for the discrepancies consideration of the satellite and radar cloud observations for the 1991 pinatubo eruptions shows that marked differences can exist even with apparently good observations the problem can be understood largely as a sampling issue as the most widely reported parameter the maximum cloud height is highly sensitive to the frequency of observation satellite and radar cloud heights also show a pronounced clumping near the height of the tropopause and relative lack of eruptions reaching only the mid troposphere reinforcing the importance of the tropopause in determining the eruption height in convectively unstable environments to reduce the discrepancies between ground and satellite estimates a number of formal collaboration measures between vulcanological meteorological and aviation agencies are suggested

satellite observations and interpretation of the 1991 mount pinatubo eruption plumes we demonstrate the use of hourly geostationary meteorological satellite gms and noaa polar orbiting advanced very high resolution radiometer avhrr satellite images of the june 1991 mount pinatubo volcanic eruption plumes in providing details of the timing changing eruptive style and umbrella plume movement and dynamics a chronology of explosive events which culminated in a 9 hour long climactic phase on june 15 has been determined from satellite data and favorably compared to ground based and other ancillary information maximum eruption column altitudes of 40 km and column top undercooling in excess of 55 c below the ambient atmosphere occurred during the climactic phase phases dominated by plinian versus coignimbrite eruptive plumes can be distinguished on the images analysis of the spreading umbrella plume during the climactic phase suggests that over the first 4 5 hours the plume spread laterally as a gravitational intrusion before becoming advected in the ambient winds we compare the rate of plume growth to a model of a radially symmetric continuously fed intrusion to describe the motion the rate of plume growth shows good agreement with this simple model for the first 4 5 hours from column top heights we determine eruption rates and obtain an independent estimate of the total volume of magma erupted from june 12 16 of 5 5 km3 dense rock equivalent dre in good agreement with an independent estimate of the total eruptive volume made from deposits on land and submarine ash fall of up to 5 3 km3 dre we also show that secondary explosions in the pinatubo ignimbrite deposits produced ash plumes reaching altitudes as high as 19 km in september 1991 this study indicates that realistic interpretation and monitoring of major eruption plumes can be accomplished by analysis of high temporal resolution satellite data

assessing the altitude and dispersion of volcanic plumes using misr multi angle imaging from space sixteen years of volcanic activity in the kamchatka peninsula russia abstract volcanic eruptions represent a significant source of atmospheric aerosols and can display local regional and global effects impacting earth systems and human populations in order to assess the relative impacts of these events accurate plume injection altitude measurements are needed in this work volcanic plumes generated from seven kamchatka peninsula volcanoes shiveluch kliuchevskoi bezymianny tolbachik kizimen karymsky and zhupanovsky were identified using over 16 years of multi angle imaging spectroradiometer misr measurements eighty eight volcanic plumes were observed by misr capturing 3 25 of reported events at individual volcanoes retrievals were most successful where eruptive events persisted over a period of weeks to months compared with existing ground and airborne observations and alternative satellite based reports compiled by the global volcanism program gvp misr plume height retrievals show general consistency the comparison reports appear to be skewed towards the region of highest concentration observed in misr constrained plume vertical extent the report observations display less discrepancy with misr toward the end of the analysis period 2013 2016 with improvements in the suborbital data likely the result of the deployment of new instrumentation conversely the general consistency of misr plume heights with conventionally reported observations supports the use of misr in the ongoing assessment of volcanic activity globally especially where ground based observations are unavailable differences between the northern shiveluch kliuchevskoi bezymianny and tolbachik and southern kizimen karymsky and zhupanovsky volcanoes broadly corresponding to the central kamchatka depression ckd and eastern volcanic front evf geological sub regions of kamchatka respectively are distinguished by varying magma composition for example by comparison with reanalysis model simulations of local meteorological conditions ckd plumes were generally less constrained by mid tropospheric

tectonic control on the eruptive dynamics at mt etna volcano sicily during the 2001 and 2002 2003 eruptions abstract the eruptive events of the july august 2001 and october 2002 january 2003 at mt etna provide new insights for reconstructing the complex geometry of the feeding system and their relationship to regional tectonics the 2001 eruption took place mainly on the upper southern sector of the volcano the eruption was preceded by a large earthquake swarm for a few days before its onset and accompanied by ground deformation and fracturing the development of surface cracking along with the seismic pattern has allowed us to recognize three distinct eruptive systems the sw ne nnw sse and n s systems which have been simultaneously active such eruptive systems are only the upper portions of a complex feeding system that was fed at the same time by two distinct magmas the sw ne and nnw sse systems connected with the se crater conduit were fed by magma coming from depth whereas the n s system served instead as an ascending pathway for an amphibole bearing magma residing in a shallow reservoir the eruptive activity started again on october 2002 on the ne rift zone where about 20 eruptive vents were aligned between 2500 and 1900 m a s l and on the southern flank from the central crater to the montagnola the onset of eruptive activity was accompanied by a seismic swarm as in the 2001 eruptive event two independent feeding systems formed characterized by distinct magmas the sw ne system controlled the feeding of the northeast rift and was accommodated by left lateral displacement along the wnw ese trending pernicana fault the n s system fed the eruptions on the southern flank moreover the associated crustal deformation triggered seismic reactivation of tectonic structures in the eastern flank of the volcano and offshore these two last eruptions indicate that at mt etna the ascent of magma as well as the accommodation of deformation is strongly dominated by local extensional structures that are connected to a regional tectonic regime

distinguishing remobilized ash from erupted volcanic plumes using space borne multiangle imaging volcanic systems are comprised of a complex combination of ongoing eruptive activity and secondary hazards such as remobilized ash plumes similarities in the visual characteristics of remobilized and erupted plumes as imaged by satellite based remote sensing complicate the accurate classification of these events the stereo imaging capabilities of the multi angle imaging spectroradiometer misr were used to determine the altitude and distribution of suspended particles remobilized ash shows distinct dispersion with particles distributed within 1 5 km of the surface particle transport is consistently constrained by local topography limiting dispersion pathways downwind the misr research aerosol ra retrieval algorithm was used to assess plume particle microphysical properties remobilized ash plumes displayed a dominance of large particles with consistent absorption and angularity properties distinct from emitted plumes the combination of vertical distribution topographic control and particle microphysical properties makes it possible to distinguish remobilized ash flows from eruptive plumes globally

failures in detecting volcanic ash from a satellite based technique abstract immediate and accurate detection of airborne volcanic ash is an operational imperative of the aviation industry especially jet aircraft ash encounters place passengers aboard these aircraft at severe risk and significantly impact via forced rerouting both the safety and profit margins of freight carriers due to their limited fuel supply moreover the airlines can suffer high economic costs for repair and replacement of equipment operational detection and tracking of volcanic ash by most national weather services has relied heavily on a split window differencing technique of thermal longwave infrared channels on currently operational satellites unfortunately prior work on volcanic ash detection has not emphasized the dynamical interaction between the erupting volcano and the effects of overlying atmospheric water vapor phreatic and phreatomagmatic water sources six volcanic ash eruptions from around the globe were chosen for study because they have wide variation in ambient atmospheric water vapor available ground and surface water and different magma types results show that the present differencing technique is not uniformly effective in properly classifying volcanic ash pixels in the satellite scene and often falsely interprets meteorological clouds as volcanic ash clouds and conversely moreover it is not always a robust early detector an operational aviation requirement seasonal variability in global integrated atmospheric water vapor coupled with the geographical distribution of currently active volcanoes suggests the concerns discussed herein with regard to six specific eruptions have applicability to the global aviation industry operational implications are discussed and a strategic proposal is presented on necessary steps to improve detection

sedimentation from strong volcanic plumes 1 we develop descriptions of the key processes influencing tephra dispersal from strong volcanic plumes these are characterized by the development of a subvertical eruption column in the atmosphere that forms a spreading current at a level of neutral buoyancy we describe the propagation of the spreading current due to both gravity and wind advection using scaling arguments and a simplified geometry to model particle sedimentation in a windy as well as a wind free environment new parameterizations are used to describe the wind field below the spreading current particle aggregation and particle density variations we conducted a broad study to investigate the effects of these processes and made comparisons with field observations the greatest variations resulted from wind advection below the spreading current which shifts the plume corner mass accumulation and the position of transitions in fallout regimes downwind particle aggregation strongly depends on the initial grain size distribution and significantly affects deposit thinning depending on the aggregate size and density and on the relative amount of aggregating particles small aggregates can reproduce secondary maxima of mass accumulation when sedimenting in a wind field variation of particle density also affects the resulting thinning trend the model provides acceptable reproduction of observations of the propagation of the spreading current tested with the plinian phase of the 18 may 1980 eruption of mount st helens and of observed thinning of tephra fallout deposits tested with deposits from mount st helens 1980 askja d 1875 quizapu 1932 minoan eruption 3 6 ka b p novarupta a 1912 and hudson 1991

an automatic procedure to forecast tephra fallout tephra fallout constitutes a serious threat to communities around active volcanoes reliable short term forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the surrounding areas during an episode of crisis we present a platform independent automatic procedure with the aim to daily forecast transport and deposition of volcanic particles the procedure builds on a series of programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout models firstly the procedure downloads regional meteorological forecasts for the area and time interval of interest filters and converts data from its native format and runs the calmet diagnostic model to obtain the wind field and other micro meteorological variables on a finer local scale 3 d grid defined by the user secondly it assesses the distribution of mass along the eruptive column commonly by means of the radial averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent granulometry mass eruption rate etc all these data serve as input for the fallout models the initial version of the procedure includes only two eulerian models hazmap and fall3d the latter available as serial and parallel implementations however the procedure is designed to incorporate easily other models in a near future with minor modifications on the model source code the last step is to postprocess the outcomes of models to obtain maps written in standard file formats these maps contain plots of relevant quantities such as predicted ground load expected deposit thickness and for the case of or 3 d models concentration on air or flight safety concentration thresholds