north atlantic storm driving of extreme wave heights in the north sea the relationship between storms and extreme ocean waves in the north sea is assessed using a long period wave dataset and storms identified in the interim ecmwf re analysis era interim an ensemble sensitivity analysis is used to provide information on the spatial and temporal forcing from mean sea level pressure and surface wind associated with extreme ocean wave height responses extreme ocean waves in the central north sea arise due to intense extratropical cyclone winds from either the cold conveyor belt northerly wind events or the warm conveyor belt southerly wind events the largest wave heights are associated with northerly wind events which tend to have stronger wind speeds and occur as the cold conveyor belt wraps rearwards round the cyclone to the cold side of the warm front the northerly wind events provide a larger fetch to the central north sea to aid wave growth southerly wind events are associated with the warm conveyor belts of intense extratropical cyclones that develop in the left upper tropospheric jet exit region ensemble sensitivity analysis can provide early warning of extreme wave events by demonstrating a relationship between wave height and high pressure to the west of the british isles for northerly wind events 48 hours prior southerly wind extreme events demonstrate sensitivity to low pressure to the west of the british isles 36 hours prior

structure of a frontal cyclone a diagnostic study of a mid latitude cyclone has been carried out using routinely available numerical weather prediction model products and imagery the cyclone was intense but not exceptionally so and the results are believed to have some generality the detailed description of the cyclone structure just before it began to deepen rapidly integrates concepts from a number of researchers into a common framework a dominant feature of the cyclone close to its centre was the cloud head a region of cloud with a sharp convex outer edge which formed poleward of the main polar front cloud band the cloud head was caused by two flows that entered it from the east ascending and fanning out within it one flow the cold conveyor belt brought low wet bulb potential temperature w air back into the cloud head from low levels ahead of the warm front the other flow was due to high w air that peeled off from the base of the main warm sector airflow i e part of the warm conveyor belt and travelled in the boundary layer back towards the cyclone centre first undercutting dry air that had earlier descended from the upper troposphere called a dry intrusion and then ascending at the upper boundary of the cloud head above the cold conveyor belt the transverse circulation that gave the ascent within the cloud head also led to the cold front fracturing along its length into two separate sharp surface cold fronts with a more diffuse frontal region in between frontal fracture the two sharp surface cold fronts were associated with narrow cold frontal rainbands line convection one of the line convection segments forming the southern edge of the cloud head the overrunning of the dry intrusion in the region of the frontal fracture led to a structure known as a split front in which an upper level humidity front began to run ahead of the position of the surface cold front a feature of the cyclone at this intermediate stage in its evolution was that a large proportion of the precipitation was being generated by ascent of relatively cold air the cold conveyor belt in the cloud head as part of the thermally indirect circulation at the left exit of a developing secondary upper level jet

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

petrology of pumices of april 1993 eruption of lascar atacama chile lascar volcano atacama chile erupted on 18 20 april 1993 several sub plinian explosions occurred and some were mushroom shaped the highest column rose up to 23 km ash clouds crossed south america eastwards dacite pumice falls made of blocks and ashes were deposited on the flanks of the volcano as a result of collapsed columns the pumice contains phenocrysts of plagioclase enstatite augite biotite magnetite and ilmenite and small crystals of apatite the 1992 previous andesite dome inside the crater was destroyed banded blocks resulting from mingling of the dacitic pumice and andesite from the dome are found in the pumice flow both the lava dome and the pumice are representative of the lascar high k magma unit dacitic pumice is a product of crystal fractionation of the andesitic magma

lascar volcano northern chile evidence for steady state disequilibrium lascar volcano located in the central volcanic zone of northern chile is a medium to high k calc alkaline stratovolcano three stages are recognized in the construction of the edifice with activity ranging from andesitic fissure eruptions to a large volume dacitic pumice flow the soncor flow the eruption products are predominantly two pyroxene andesites and dacites with some hornblende dacites occurring in the soncor flow disequilibrium textures resulting from mixing between mafic and acid end members

improved remote sensing estimates of lava flow cooling a case study of the 1991 1993 mount etna eruption infrared radiance data acquired by the landsat thematic mapper tm provide information regarding the thermal state of active lavas which can be used to estimate flow surface temperatures and thus lava cooling saturation of one or both of tm s short wave infrared swir wavebands has meant however that previous studies of lava flow cooling have approximated what is almost certainly an n thermal component flow surface temperature distribution where n 1 with a single pixel integrated temperature pit we show that the high sensitivity of tm s swir wavebands to the small amount of high temperature e g 1000 c material exposed in hot fractures within the flows cooler e g 200 c surface crust results in the calculation of pits that are higher than the temperature of this crust which is usually the dominant radiative component this causes heat loss from such pixels to be overestimated we present adaptations that allow more realistic heat loss estimates to be produced using tm data by assuming that a second high temperature component contributes to the radiance measured from saturated pixels and by defining an appropriate range for the temperature of the lava crust by analyzing a suite of five tm images acquired during the 1991 1993 eruption of mount etna we present more realistic estimates of how this flow cooled as well as results that show how the flow regime of the lava evolved over time the methods we present will continue to be of use as although the next generation of high spatial resolution sensors such as the landsat 7 enhanced thematic mapper plus etm and the terra advanced space borne thermal emission and reflection radiometer aster will be less susceptible to saturation than tm the problem will still persist

a comparison of so 2 retrieval techniques using mini uv spectrometers and aster imagery at lascar volcano chile the advanced spaceborne thermal emission and reflection radiometer aster is a useful tool for detecting low quantities of sulfur dioxide at passively degassing volcanoes such as lascar volcano chile two mini uv spectrometers muses were used to make transects of lascar volcano s sulfur dioxide plume on december 7 2004 during a coordinated overpass of aster so2 burdens were retrieved using the thermal infrared channels of the acquired aster image this allowed for a direct comparison between the two methods in order to validate the aster so2 retrieval the results were extremely encouraging with aster deriving so2 fluxes within the range of fluxes obtained by the muse

long term infrared surveillance of lascar volcano contrasting activity cycles and cooling pyroclastics lascar volcano chile erupted on 20 july 2000 generating a 10 km high ash column satellite infrared data have previously indicated that lascar s large vulcanian explosions are preceded by significant cooling within the active crater suggesting that characteristic thermal radiance trends can act as remotely detectable eruption precursors new analyses and data extend the lascar s thermal history to cover all five large vulcanian eruptions occurring over the last 15 years the 2000 eruption follows a formerly undocumented style of infrared radiance variation and indicates that lascar may have modified its activity since 1993 the year of its greatest historical eruption therefore such patterns evident for over a decade at lascar can be unexpectedly modified and this has implications for the way apparent thermal precursors should be treated the largest 1993 eruption produced 8 5 km long pyroclastic flows which the infrared data indicate exhibited exponential cooling over an 8 12 months period

infrared image analysis of volcanic thermal features lascar volcano chile 1984 1992 fifteen landsat thematic mapper tm images of lascar volcano chile recorded between december 1984 and april 1992 document the evolution of a lava dome within the summit crater four of the scenes were acquired at night in every image the two short wavelength infrared bands 5 and 7 have detected thermal radiation from the volcano as a consequence of the planck distribution function the relative response of these two channels depends on the proportions of very hot 600 c surfaces occupying tiny pixel areas and broader regions at moderate temperatures 280 c intercomparison of bands 5 and 7 thereby provides a means for interpreting tm thermal anomalies even in the absence of ground observations pronounced changes in the configuration and intensity of the lascar anomaly suggest that the volcano has experienced at least two cycles of lava dome activity since 1984 the first of these progressed through a cooling period possibly reflecting a reduced flux of magmatic volatiles at the surface and culminated in an explosive eruption on september 16 1986 which appears to have completely destroyed the inferred lava dome the tm data indicate that a new dome had been emplaced by november 1987 more than 15 months before it was first discovered by local observers lascar s style of cyclical effusive and explosive activity is typical of many volcanoes and the remote sensing techniques presented herein could be applied elsewhere

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

evolution of lascar volcano northern chile lascar volcano in the central andes is an ese wnw elongate composite stratocone stage i 3 at 26 45 ka producing the soncor ignimbrite no caldera formed laharic and alluvial fan deposits and a debris avalanche formed from 26 45 to 19 2 ka indicating a humid climatic period the dacitic and andesitic western stratocone stage iii developed over the soncor vent stage iii culminated in the 9 2 ka tumbres eruption which formed andesitic scoria flow fans and a summit collapse crater stage iv activity switched to the east forming an andesite lava three nested summit craters which repeatedly filled with lava and collapsed absence of significant erosion since 9 2 ka is due to the much drier holocene climate activity since 1984 displays cycles of lava dome formation in the summit crater lava dome subsidence with crater collapse vulcanian to plinian explosive eruptions culminating in the major explosive eruption of 19 20 april 1993 the total volume of magma erupted from lascar over a 43 ka period is estimated at 30 to 40 km 3

the magmatic and hydrothermal dominated fumarolic system at the active crater of lascar volcano northern chile low to high temperature fumaroles discharging from the active crater of lascar volcano northern chile have been collected in november 2002 may 2005 and october 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic hydrothermal system of this active volcano chemical and isotopic gas composition shows direct addition of high temperature fluids from magmatic degassing mainly testified by the very high contents of so2 hcl and hf up to 87 800 29 500 and 2 900 mol mol and the high r ra values up to 7 29 contributions from a hydrothermal source mainly in gas discharges of the active crater rim has also been detected significant variations in fluid chemistry mainly consisting of a general decrease of magmatic related compounds i e so2 have affected the fumarolic system during the period of observation indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids the chemical composition of active crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of lascar volcano to be utilized in volcanic surveillance

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

calculation of lava effusion rates from landsat tm data we present a thermal model to calculate the total thermal flux for lava flowing in tubes on the surface or under shallow water once defined we use the total thermal flux to estimate effusion rates for active flows at kilauea hawaii on two dates input parameters were derived from landsat thematic mapper tm field and laboratory measurements using these parameters we obtain effusion rates of 1 76 0 57 and 0 78 0 27 m3 s 1 on 23 july and 11 october 1991 respectively these rates are corroborated by field measurements of 1 36 0 14 and 0 89 0 09 m3 s 1 for the same dates kauahikaua et al 1996 using weather satellite avhrr data of lower spatial resolution we obtain similar effusion rates for an additional 26 dates between the two tm derived measurements we assume that although total effusion rates at the source declined over the period the shut down of the ocean entry meant that effusion rates for the surface flows alone remained stable such synergetic use of remotely sensed data provides measurements that can a contribute to monitoring flow field evolution and b provide reliable numerical data for input into rheological and thermal models we look forward to being able to produce estimates for effusion rates using data from high spatial resolution sensors in the earth observing system eos era such as landsat 7 the hyperspectral imager the advanced spaceborne thermal emission spectrometer and the advanced land imager

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

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

validation and sensitivities of frontal clouds simulated by the ecmwf model abstract clouds simulated by the european centre for medium range weather forecasts ecmwf model are composited to derive the typical organization of clouds surrounding a midlatitude baroclinic system comparison of this composite of about 200 cyclones with that based on satellite data reveals that the ecmwf model quite accurately simulates the general positioning of clouds relative to a low pressure center however the optical depths of the model s high low clouds are too small large relative to the satellite observations and the model lacks the midlevel topped clouds observed to the west of the surface cold front sensitivity studies with the ecmwf model reveal that the error in high cloud optical depths is more sensitive to the assumptions applied to the ice microphysics than to the inclusion of cloud advection or a change of horizontal resolution from 0 5625 to 1 69 lat this reflects the fact that in the ecmwf model gravitational settling is the most rapid process controlling the abundance of ic

magma budgets and steady state activity of vulcano and stromboli we present three models for magma budget during steady state volcanic activity by which non erupted magma is emplaced as dykes or cumulates or crystallises in place using gas and thermal data we apply our models at vulcano to calculate degassing cooling and crystallisation of magma at a rate of 40 375 kg s 1 within a magma body with an upper surface at a 2 km depth at stromboli we calculate a steady magma supply of 300 1300 kg s 1 to shallow 1 km depths

improved identification of volcanic features using landsat 7 etm volcanic eruptions can present unpredictable hazards to populations living within regions containing potentially active volcanoes and for people traveling in jet aircraft that intersect with ash laden eruption clouds methods of monitoring volcanic activity include searching for variations in the thermal signal from active fumaroles lava domes lava lakes flows and other features over many active volcanoes in the western hemisphere low spatial resolution 4 km pixel weather satellite data acquired every 15 min are used to identify changes in eruptive activity but are of insufficient spatial resolution to map active volcanic features the enhanced thematic mapper plus etm on landsat 7 can be used to monitor active volcanoes at a higher spatial resolution 15 to 60 m pixels etm also offers improvements over its predecessor the thematic mapper of landsats 4 and 5 by way of a 15 m panchromatic band and higher spatial resolution 60 m pixel thermal infrared ir band with higher spatial resolution panchromatic data we are able to map lava flow fields trace very high temperature lava channels and at lascar volcano identify an arcuate feature associated with a collapsed crater floor a phenomenon that may precede explosive activity with improved spatial resolution in the thermal ir we are able to map the bifurcation and braiding of underground lava tubes at kilauea identifying tube locations and tracking their extension are important because for a given volumetric lava production effusion rate tube fed flows can extend a much greater distance than surface flows at both kilauea and etna we are able to use the thermal data to estimate effusion rates an important parameter for assessing how far a flow is likely to extend and therefore the hazard it poses an improved etm data collection and distribution system includes a well formulated and executed long term acquisition plan and less expensive data that is available much faster than previously possible

effusion rate trends at etna and krafla and their implications for eruptive mechanisms abstract using effusion rates obtained from ground and satellite based data we build a data set of 381 effusion rate measurements during effusive activity at etna and krafla between 1980 and 1999 this allows us to construct detailed effusion rate curves for six fissure fed eruptions at etna and krafla and four summit fed eruptions at etna these define two trends type i and ii type i trends have effusion rates that rise rapidly to an initial peak before declining more slowly resulting in an exponential decrease in eruption rate and declining growth in cumulative volume type ii trends are characterised by steady effusion and eruption rates and hence a linear increase in cumulative volume the former is typical of fissure eruptions and can be explained by tapping of an enclosed pressurised system the latter are typical of persistent etnean summit eruptions plus one persistent effusive eruption at stromboli 1985 1986 examined here and can be explained by overflow of the time averaged magma supply we use our effusion rate data to assess the magma balance at etna 1980 1995 and krafla 1975 1984 between 1980 and 1995 etna was supplied at a time averaged rate of 6 8 2 3 m 3 s 1 of which 13 was erupted at krafla 817 30 10 6 m 3 was erupted and intruded during 1975 1984 and the ratio of erupted to intruded volume was 0 3 at etna there is evidence for intrusion of the unerupted magma within and beneath the edifice as well as storage in the central magma column at krafla unerupted magma was intruded into a rift zone but an increasing proportion of the supply was erupted from 1980 onwards a result of the rift zone capacity being reached magma intruded prior to an eruptive event may also be entrained and or pushed out during eruption to contribute to the initial high effusion rate phases of type i events the detail in our effusion rate curves was only possible using a thermal approach which estimates effusion rates using satellite data we look forward to analysing satellite derived effusion rate trends in real time using data from current and soon to be launched sensors

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

a potential vorticity based study of the role of diabatic heating and friction in a numerically simulated baroclinic cyclone abstract a particularly intense case of western atlantic baroclinic cyclogenesis was investigated in this study specifically the roles of latent heat of condensation and surface friction were examined from the potential vorticity or pv thinking perspective the methodology used for this study involves three key components 1 a full physics mesoscale model which provides a continuous and dynamically consistent dataset and provides full user control over physical processes 2 a partitioned pv integration which temporally integrates the accumulation of pv due to various physical processes in the model s eulerian framework and 3 the piecewise inversion method of davis and emanuel which calculates the balanced wind and mass field associated with particular pv anomalies potential vorticity features obtained through the partitioned integration technique were inverted to yield their direct contributions to the total circulation in addition sensitivity studies were carried out to determine the overal

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

geomorphology and structural development of the nested summit crater of lascar volcano studied with terrestrial laser scanner data and analogue modelling abstract many volcano summits host craters that are partially overlapping the formation of such nested craters has been commonly interpreted as vent migration here we present an additional mechanism that may explain the geometry of nested craters at volcanoes lascar volcano the most active volcano of the central volcanic zone in the chilean andes hosts ene wsw trending summit craters that are partially overlapping nested details on the evolution and interaction between the different craters remain unclear to create a robust dataset terrestrial laser scanner tls data were collected at the summit of lascar in 2013 the resulting topographic data set consisting of more than 15 million data points with centimetre sampling allows visualising almost the complete eastern edifice of the volcano s summit from the tls data a digital elevation model dem and a slope map were generated allowing us to create a lineament map and quantify the observed morphological and structural features to further improve our understanding of the processes responsible for the formation of the craters and geomorphology we designed sandbox analogue models results suggest that one of the craters is a parasite crater formed as a consequence of ongoing activity in the adjacent crater our data suggest that the nested craters have all been modified since the last major eruption in 1993 by near surface effects associated with cooling compaction and gravitational sliding of the crater floor infill as the active crater deepens the adjacent inactive crater extends and partially slumps towards the active one understanding the structural development of these nested craters is relevant for assessing potential future eruption sites thus making lascar a dynamic target for a detailed morphology study these findings may similarly be applied to other volcanoes where nested craters have developed

frontal wave cyclogenesis in the north atlantic a climatological characterisation the ambient conditions during cyclogenesis on fronts in the north atlantic na are characterised climatologically in the era interim dataset these secondary cyclones which grow from frontal waves are typically small in scale shallow and deepen rapidly and pose a challenge to forecasters and numerical weather prediction models frontal wave development has been studied intensively in the past based on observations e g fastex real case studies or analytical models in this study frontal wave cyclogenesis is studied from a climatological perspective and is detected by a combination of two automated identification methods for the period between 1979 and 2014 a climatology of frontal wave cyclogenesis is presented horizontal composites provide an estimate of the climatological mean of conditions during frontal wave cyclogenesis which may prove useful in the assessment of the realism of proposed idealized models of frontogenesis the findings are also compared with assumptions made in earlier idealized studies of frontal waves the composites reveal coherent structures of diabatically generated low level pv in the lower troposphere neutral moist static stability at cyclogenesis and an ambient lower troposphere close to saturation the vertical pv structure in the east na is more vertically aligned than in the west na and pv anomalies from the upper and lower levels reach deeper into the mid troposphere which indicates an enhanced phase lock between the two anomalies previous studies suggest the existence of an upper limit of along frontal stretching above which frontal wave development is strongly suppressed the presented multi decadal analysis confirms its existence in a range between 0 6 and 0 8 10 5 s 1 finally a climatology of along frontal stretching for the na is presented and compared to the fraction of cyclogenesis forming on frontal waves

heat and mass flux measurements using landsat images from the 2000 2004 period lascar volcano northern chile a qualitative and quantitative analysis of 13 landsat tm and etm images of lascar volcano for the 2000 2004 period was performed by applying the three bands and three components method to determine heat and mass flux and understand the magma circulation process in a passive degassing volcano related to permanent fumarolic activity the behavior and evolution of spectral radiance during the study period suggest that prior to low to moderate magnitude eruptions these values reach their localized temporal minimum levels corresponding to 1 9 4 38 mw cm2sr m in july 2000 and 4 38 7 11 mw cm2sr m in december 2003 eruptions respectively similar behavior is observed for anomaly area heat and mass fluxes during the 2000 2004 period the heat flux was estimated to vary from 75 46 and 10 527 mw while mass flux ranged between 131 and 18 469 kg s 1 a magma circulation model is proposed to explain these variations where the thermal anomaly is related to the presence of a fumarolic field and fluids movement from a magma chamber located at 10 17 km depth

the role of the environmental flow in the development of secondary frontal cyclones the impact of the environmental flow on the development of secondary frontal cyclones is investigated several case studies are examined as examples of secondary frontal cyclone events observed in the north atlantic western europe sector a simple measure of growth is defined to chart their development the vorticity attribution technique of bishop is utilized to calculate the action of the large scale environmental flow on the fronts in particular the environmental along front stretching shown to be important in theoretical models of frontal instabilities is calculated the role of the environmental deformation appears to be crucial as part of a baroclinic life cycle stretching deformation acts to build up a front but suppress along front waves if the stretching rate diminishes barotropic instabilities may then break out diagnostics are examined to try to ascertain the growth mechanisms at work in each frontal cyclone case a range of values for the commonly prescribed deformation frontogenesis and shearing frontogenesis parameters are calculated

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

temporal trends in lava dome extrusion at santiaguito 1922 2000 we present a means of extracting lava dome extrusion rates from data provided by the thematic mapper and enhanced thematic mapper plus instruments flown on the landsat satellites extrusion rates derived from the landsat data for santiaguito dome complex guatemala during november 1987 and january 2000 of 0 72 0 08 and 0 48 0 09 m3 s 1 compare favorably with ground based estimates of 0 63 0 28 and 0 48 0 17 m3 s 1 a satellite data derived set of 18 extrusion rate estimates between 1987 and 2000 along with ground based volume estimates prior to 1987 allow us to infer volumes of magma erupted since 1922 these data reveal cyclic extrusion at santiaguito each cycle begins with a 3 6 year long phase of high extrusion rate 0 5 2 1 m3 s 1 followed by a longer 3 11 years phase of low extrusion rate 0 2 m3 s 1 the 8th cycle began in 1996 and was still in its high extrusion rate phase during january 2000 with time however the durations of the low extrusion rate phases have increased peak extrusion and time averaged extrusion rates for each cycle have decreased and the difference between extrusion rates during the high and low extrusion rate phases of each cycle has decreased these trends may be the result of depressurization and exhaustion of the source in this case the current eruption may be expected to end around 2020 alternatively santiaguito may be entering a period of persistent activity maintained by a stable magma supply in this case we may expect extrusion to become less cyclic and to stabilize at 0 2 0 4 m3 s 1 however a 2 wt decrease in sio2 content of erupted products since 1970 appears to be consistent with chamber exhaustion as well as an increase in block lava flow lengths during 1970 2000

the 16 september 1986 eruption of lascar volcano north chile satellite investigations landsat thematic mapper tm images acquired in 1984 and 1985 revealed a pronounced thermal anomaly on lascar volcano north chile subsequent images showed that the anomaly was persistent but variable and that after a significant eruption on 16 september 1986 it was weaker and divided into several sources tm studies and other observations of lascar indicate that the persistent thermal anomaly may be due to high temperature fumaroles within the summit crater goes weather satellite images and field investigations confirm that the 16 september event was a short lived vulcanian type eruption which produced an ash column that reached 15 km altitude the ash cloud can be tracked on geos images to about 400 km downwind and covered an area 112 000 km2 transport occurred in the upper troposphere at speeds up to 180 km h ash fall from the plume was well sorted and moderately fine grained md 200 m formation and fallout of ash as aggregates was unimportant in the deposition of the ash layer although small the lascar 16 september eruption is significant because few historic eruptions have been recorded in the central andes little would have been known of the eruption in the absence of remote sensed data

life cycle study of a diabatic rossby wave as a precursor to rapid cyclogenesis in the north atlantic dynamics and forecast performance abstractthe life cycle of a north atlantic cyclone in december 2005 that included a rapid propagation phase as a diabatic rossby wave drw is investigated by means of operational analyses and deterministic forecasts from the ecmwf a quasigeostrophic omega diagnostic has been applied to assess the impact of upper level forcing during the genesis propagation and intensification phase respectively the system was generated in the gulf of mexico as a mesoscale convective vortex mcv influenced by vertical motion forcing from a nearby upper level trough the drw propagation phase was characterized by a shallow low level diabatically produced potential vorticity pv anomaly that rapidly propagated along the southern border of an intense baroclinic zone no significant upper level forcing could be identified during this phase of the development eventually explosive intensification occurred as the region of vertical motion forced by an approaching upper level trough reached the position of the drw the

observed winter cyclone tracks in the northern hemisphere in re analysed ecmwf data the observed cyclone activity in the northern hemisphere winter djf is investigated in 1979 97 european centre for medium range weather forecasts re analyses the cyclone trajectories are determined automatically by a next neighbour search of minima identified in the 1000 hpa geopotential height field z1000 these are compared with the traditional storm track defined by the root mean square of the band pass filtered 500 hpa geopotential height anomaly the analysis covers the north atlantic and north pacific basins the trend of the cyclone density distribution is similar to that of the storm track in the north atlantic but opposite in the north pacific in the atlantic the total number of cyclones with low central z1000 increases due to the northward shift towards lower regional climatological pressure whereas the number of cyclones with large gradients decreases in the pacific the number of intense weak cyclones with large low gradients increases decreases the cyclone track variability is investigated by a cluster analysts of the relative cyclone trajectories the three centroids corresponding to north eastward and zonally propagating cyclones and nearly stationary ones are very similar in both ocean basins the winter mean cluster occupation numbers of the two propagating cyclone clusters are positively correlated with one another in the atlantic and negatively in the pacific the three atlantic cyclone clusters can be linked to particular aspects of the central european climate the cyclonic activity can be related to teleconnection patterns which are dominant during northern hemisphere winter during high north atlantic oscillation index winters deeper icelandic lows the atlantic cyclone density shifts northward and is associated with more stationary cyclones during el nino warm event winters the pacific cyclone density is shifted northward and their propagation is oriented more zonally as in high pacific north american index phases deeper aleutian lows in the north atlantic propagating cyclones occur less and stationary ones more frequently in el nino winters the correlations between the north east ward propagating cyclones in the pacific and the north eastward and zonally propagating ones in the atlantic suggest an interaction between the two storm tracks

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

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

statistical analysis and updated climatology of explosive cyclones abstract a statistical analysis of 12 and 24 hour deepening rates for all surface lows analyzed on at least two successive nmc 12 hourly front half hemispheric surface charts was performed for one year of data both 12 and 24 hour deepening distributions showed statistically significant at the 5 level departures from normality with the largest deviations occurring along the tail of the distribution associated with most rapid deepening the sum of two normal curves of different means and standard deviations was successfully fitted to the deepening distributions suggesting that most cases of explosive cyclogenesis are the result of some additional physical mechanism distinct from ordinary baroclinic instability the climatology of explosive cyclones sanders and gyakum was updated to include the 1979 82 cold seasons and compared to the previous three year sample in addition a climatology of formation positions maximum deepening positions and dissipation positions for all cyclones in a one year d

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

thermal radiance observations of an active lava flow during the june 1984 eruption of mount etna the thermal budget of an active lava flow observed on 20 june 1984 from the southeast crater of mount etna sicily italy was analyzed from data taken by the landsat thematic mapper the thematic mapper images constitute one of the few satellite data sets of sufficient spatial and spectral resolution to allow calibrated measurements on the distribution and intensity of thermal radiation from active lava flows using radiance data from two reflective infrared channels we can estimate the temperature and areas of the hottest parts of the active flow which correspond to hot 500 c fractures or zones at the flow surface using this technique we estimate that only 10 20 of the total radiated thermal power output is emitted by hot zones or fractures which constitute less than 1 of the observed surface area generally it seems that only where hot fractures or zones constitute greater than about 1 of the surface area of the flow will losses from such features significantly reduce internal flow temperatures using our radiance observations as boundary conditions for a multicomponent thermal model of flow interior temperature we infer that for the parts of this flow subject to analysis the boundary layer and flow thickness effects dominate over radiant zones in controlling the depression of core temperature

volcano monitoring using short wavelength infrared data from satellites data from remote sensing satellites operating in the short wavelength infrared can be used to measure temperatures of about 150 c and above the gain settings of the landsat thematic mapper tm sensors are such that to record pixel integrated temperatures from 150 c to over 1000 c requires the use of several spectral bands if the radiant source occupies less than a whole pixel as is the case for fumaroles or a crusted lava surface with incandescent cracks then the pixel integrated temperature is less than the actual surface temperature of the hot areas and appears to be different at each wavelength by determining pixel integrated temperature in two spectral bands we can estimate both the temperature and size of hot areas which occupy less than a complete pixel in some cases our observations provide the only available data on the state of activity of a particular volcano in others they support and refine field observations our landsat tm data reveal otherwise unobserved precursor and subsequent activity related to the september 1986 eruption of lascar volcano chile and supplement other data on the march 1986 eruption of augustine volcano alaska they also indicate the continued presence of lava lakes at erta ale ethiopia in the absence of any ground based observations and document minor eruptive activity at mount erebus antarctica landsat multispectral scanner data have been used to measure the variation in temperature along a lava flow on sierra negra galapagos islands which occurred in 1979

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

erosion transport and segregation of pumice and lithic clasts in pyroclastic flows inferred from ignimbrite at lascar volcano chile abstract investigations have been made on the distribution of pumice and lithic clasts in the lithic rich soncor ignimbrite 26 5 ka and the 1993 pumice flow deposits of lascar volcano chile the soncor ignimbrite shows three main lithofacies which grade into one another coarse lithic breccias range from matrix poor stratified varieties irregular shaped sheets and elongate hummocks in proximal environments to breccia lenses with pumiceous ignimbrite matrix massive lithic rich facies comprise the bulk of the ignimbrite pumice rich facies are bimodal with abundant large pumice clasts often with reverse grading rare lithic clasts and occur distally and on high ground adjacent to deep proximal valleys in the 1993 pyroclastic flow deposits lithic rich facies are deposited on slopes up to 14 whereas pumice rich facies are deposited only on slopes

remote sensing of active volcanoes the synoptic coverage offered by satellites provides unparalleled opportunities for monitoring active volcanoes and opens new avenues of scientific inquiry thermal infrared radiation can be used to monitor levels of activity which is useful for automated eruption detection and for studying the emplacement of lava flows satellite radars can observe volcanoes through clouds or at night and provide high resolution topographic data in favorable conditions radar inteferometery can be used to measure ground deformation associated with eruptive activity on a centimetric scale clouds from explosive eruptions present a pressing hazard to aviation therefore techniques are being developed to assess eruption cloud height and to discriminate between ash and meterological clouds the multitude of sensors to be launched on future generations of space platforms promises to greatly enhance volcanological studies but a satellite dedicated to volcanology is needed to meet requirements of aviation safety and volca

using the landsat thematic mapper to detect and monitor active volcanoes an example from lascar volcano northern chile the landsat thematic mapper tm offers a means of detecting and monitoring thermal features of active volcanoes using the tm we have discovered a prominent thermal anomaly on lascar volcano northern chile data from two short wavelength infrared channels of the tm show that material within a 300 m diameter pit crater was at a temperature of at least 380 c on two dates in 1985 the thermal anomaly closely resembles in size and radiant temperature the anomaly over the active lava lake at erta ale in ethiopia an eruption took place at lascar on september 16 1986 tm data acquired on october 27 1986 revealed significant changes within the crater area we find that lascar is in a much more active state than any other volcano in the central andes and for this reason it merits further careful monitoring our studies show that the tm is capable of confidently identifying thermal anomalies less than 100 m in size at temperatures of above 150 c and thus it offers a valuable means of monitoring the conditions of active or potentially active volcanoes particularly those in remote regions

structure of a warm front helsinki testbed observations and model simulation abstractthe purpose of this study is to document the structure of a warm front in northeast europe identify the effects that the finnish coastline has on the evolution of the front and investigate factors that influence the speed that the warm front moves at within and above the boundary layer the warm front formed over estonia traveled northward across the gulf of finland and then crossed the southern coastline of finland surface based measurements from the helsinki testbed are analyzed together with output from a high resolution numerical weather prediction model application of research to operations at mesoscale arome during the early stages of development the warm front interacted with a stationary baroclinic zone and consequently evolved into an s shape as the front approached the southern coast of finland the temperature gradient at 1000 hpa increased as it merged with a diabatically generated temperature gradient at 1000 hpa the front stalled at the coastline due to friction enh

rossby wave initiation by recurving tropical cyclones in the western north pacific abstractthe interaction of recurving tropical cyclones tcs with midlatitude rossby waves during extratropical transition et can significantly alter the midlatitude flow configuration this study provides a climatological investigation of rossby wave initiation rwi by transitioning tcs in the specific configuration of an initially zonal midlatitude waveguide and elucidates physical processes governing ab initio flow amplification during et recurving tcs interacting with a zonally oriented waveguide in the western north pacific wnp basin from 1979 to 2013 are categorized into cases initiating rossby waves tc rwi or not tc norwi interactions with a zonally oriented waveguide occurred for 22 7 of the recurving tcs and one third of these resulted in tc rwi in the presence of a tc the probability of rwi on a zonally oriented waveguide is 3 times larger than in situations without a tc the occurrence of tc rwi exhibits a seasonality and is relatively more common during boreal summer than in aut

thermal monitoring of lascar volcano chile using infrared data from the along track scanning radiometer a 1992 1995 time series lascar volcano 22 22 s 67 44 w is the most active volcano of the central andes of northern chile activity since 1984 has been characterised by periods of lava dome growth and decay within the active crater punctuated by explosive eruptions we present herein a technique for monitoring the high temperature activity within the active crater using frequent measurements of emitted shortwave infrared swir radiation made by the spaceborne along track scanning radiometer atsr the atsr is an instrument of low spatial resolution pixels 1 km across that shares certain characteristics with the modis instrument planned for use as a volcano monitoring tool in the nasa eos volcanology project we present a comprehensive time series of over 60 cloud and plume free nighttime atsr observations for 1992 1995 a period during which lascar experienced its largest historical eruption variations in short wavelength infrared flux relate directly to changes in high temperature surfaces within the active crater from these data interpretations can be made that supplement published field reports and that can document the presence and status of the lava dome during periods where direct ground based observations are lacking our data agree with less frequent information collected from sensors with high spatial resolution such as the landsat thematic mapper oppenheimer et al 1993 and are consistent with field observations and models that relate subsidence of the dome to subsequent explosive eruptions matthews et al 1997 most obviously lascar s major april 1993 eruption follows a period in which the magnitude of emitted shortwave infrared radiation fell by 90 at this time subsidence of the 1991 1992 lava dome was reported by field observers and this subsidence is believed to have impeded the escape of hot volatiles and ultimately triggered the eruption smithsonian institution 1993a extrapolating beyond the period for which field observations of the summit are available our data show that the vulcanian eruption of 20 july 1995 occurred after a period of gradual increase in short wavelength infrared flux throughout 1994 and a more rapid flux decline during 1995 we attribute this additional otherwise undocumented cycle of increasing and decreasing swir radiance as most likely representing variations in degassing through fumaroles contained within the summit crater alternatively it may reflect a cycle of dome growth and decay the explosive eruption of 17 december 1993 appears to have followed a similar but shorter variation in swir flux and we conclude that large explosive eruptions are more likely when the 1 6 m signal has fallen from a high to a low level the atsr instrument offers low cost data at high temporal resolution despite the low spatial detail of the measurements atsr type instruments can provide data that relate directly to the status of lascar s lava dome and other high temperature surfaces we suggest that such data can therefore assist with predictions of eruptive behaviour deduced from application of physical models of lava dome development at this and similar volcanoes

insight into ground deformations at lascar volcano chile from sar interferometry photogrammetry and gps data implications on volcano dynamics and future space monitoring abstract we present a detailed study of lascar volcano chile based on the combination of satellite aerial and ground based data in order i to better characterize the deformation style of andean explosive volcanoes and ii to provide new insights on the potential of space techniques to monitor active volcanic deformations on such edifices lascar is one of the most active volcanoes in central andes characterized by a recent cyclic activity additionally it is located in favourable conditions for radar imaging lascar thus offers very good conditions for studying large to small scale ground deformations associated with volcano dynamics the analysis of insar synthetic aperture radar interferometry time series data from the european and japanese satellites ers jers acquired between 1993 and 2000 encompassing three eruptive events confirmed the absence of broad far field deformation signal thus during the recent activity of lascar we discard significant magmatic input at depth the following approaches were used to improve the insar signal noise ratio in order to detect possible local deformation we carried out a quantitative evaluation of the potential tropospheric contribution in insar interferograms for the salar de atacama lascar area using radar asar envisat and spectrometer modis data we also used an accurate aerial photogrammetric and gps constrained dem in our insar data reprocessing we find a co eruptive ground deformation confined into the summit crater for the 1995 eruption this deformation has spatial dimension of 500 by 400 m and relates to a subsidence of crater floor up to 17 mm we interpret it as pressure or volume decrease at subsurface levels below the active crater our study made it possible to image a new near field volcanic deformation confined within the summit crater of the lascar volcano it also demonstrates that the combination of precise photogrammetry dem and insar data can significantly improve our ability to remotely sense subtle surface deformation on these explosive volcanoes this methodology might contribute to better understand volcano dynamics and to complement their monitoring in remote areas

interpretation of volcanic gas data from tholeiitic and alkaline mafic lavas the analyses of approximately 100 high temperature gas samples from erupting lavas of surtsey erta ale ardoukoba kilauea mount etna and nyiragongo exhibit erratic compositions resulting from analytical errors condensation effects reactions with sampling devices and contamination by atmospheric gases meteoric water and organic material computational techniques have been devised to restore reported analyses to compositions representative of the erupted gases the restored analyses show little evidence of short term variations the principal species are h2o co2 so2 h2 co h2s s2 and hcl the o2 fugacities range from nickel nickel oxide to a half order of magnitude below quartz magnetite fayalite there is no evidence for a unique magmatic gas composition instead the erupted gases show regular compositional trends characterized by decreasing co2 with progressive outgassing the gases from more alkaline lavas etna nyiragongo are distinctly richer in co2 while those from less alkaline surtsey or tholeiitic lavas erta ale ardoukoba tend to be richer in h2o kilauean gases range from co2 rich to h2o rich the total sulfur contents of the erupted gases show an excellent positive correlation with lava o2 fugacity all restored analyses are significantly lower in h2o and enriched in sulfur and co2 compared to the excess volatiles

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

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

low cost volcano surveillance from space case studies from etna krafla cerro negro fogo lascar and erebus satellite data offer a means of supplementing ground based monitoring during volcanic eruptions especially at times or locations where ground based monitoring is difficult being directly and freely available several times a day data from the advanced very high resolution radiometer avhrr offers great potential for near real time monitoring of all volcanoes across large 3000 3000 km areas herein we describe techniques to detect and locate activity estimate lava area thermal flux effusion rates and cumulative volume and distinguish types of activity application is demonstrated using data for active lavas at krafla etna fogo cerro negro and erebus a pyroclastic flow at lascar and open vent systems at etna and stromboli automated near real time analysis of avhrr data could be achieved at existing or cheap to install receiving stations offering a supplement to conventional monitoring methods