tropical cyclone genesis factors in simulations of the last glacial maximum abstractlarge scale environmental factors that favor tropical cyclogenesis are calculated and examined in simulations of the last glacial maximum lgm from the paleoclimate modelling intercomparison project phase 2 pmip2 despite universally colder conditions at the lgm values of tropical cyclone potential intensity which both serves as an upper bound on thermodynamically achievable intensity and indicates regions supportive of the deep convection required are broadly similar in magnitude to those in preindustrial era control simulation some regions including large areas of the central and western north pacific feature higher potential intensities at the lgm than they do in the control runs while other regions including much of the atlantic and indian oceans are lower changes in potential intensity are strongly correlated with the degree of surface cooling during the lgm additionally two thermodynamic parameters one that measures midtropospheric entropy deficits relevant for tropical cyclogen

introduction to the special section geology and geophysics of io io is about the size and density of earth s moon but it has a dramatically different thermal state and geologic history tidal heating leads to intense volcanic and tectonic activity so io is an accelerated experiment in planetary geology and geophysics here we can witness volcanic activity on very large scales and at very high temperatures perhaps providing insights into the early histories of the terrestrial planets io has always been a high priority objective of galileo but her proximity to jupiter s intense radiation belt has meant saving the best for last an io flyby occurred during jupiter orbit insertion in december 1995 but a tape recorder anomaly led to cancellation of remote sensing observations no further close flybys of io were planned until the final two orbits i24 and i25 of the galileo europa mission gem late in 1999 in order to minimize radiation damage to spacecraft and instrument electronics i24 was an exciting encounter with a spacecraft safing event and recovery just hours before io closest approach most of the io data were acquired but not without problems the majority of images from the solid state imager ssi were acquired in a mode that failed due to the cumulative radiation damage producing garbled images although reconstruction has produced some useful pictures keszthelyi et al this issue also the grating of the near infrared mapping spectrometer nims became stuck leading to loss of spectral sampling lopes et al this issue these instrument problems were mitigated by the use of different observation modes or strategies in subsequent orbits the 125 polar pass included another safing event this time eliminating the recording of the highest resolution observations however the medium resolution observations were of excellent quality and provided a surprise look at a new fissure eruption at tvashtar catena gem was followed by the galileo millennium mission gmm including another close io flyby in orbit i27 a fully successful encounter three additional io flybys are anticipated in august 2001 i31 october 2001 i32 and january 2002 i33 the groundtracks for all six io encounters are shown in plate 1

stability analysis of the north eastern slope of daralou copper open pit mine against a secondary toppling failure abstract secondary toppling failures have complicated mechanisms in these instabilities some natural or manmade external factors motivate and overturn a rock mass one of the most common types of secondary toppling failures is slide toe toppling mode when a blocky or layered rock mass is overlaid by a soil or weak rock mass the combination of a toppling failure in the rock at the toe and a circular or non circular sliding in the soil or weak rock in the top leads to this hybrid failure in 2015 such failure occurred in north eastern slope of daralou copper open pit mine during this instability the slope consisted mainly of two 10 m benches and one 4 m semi bench since it was supposed to excavate the slope to the depth of 54 m experts were worried about the project facing a similar larger failure in the future hence a widespread investigation was carried out on the failure firstly the mechanism of this instability was clarified with geological and geotechnical surface and subsurface investigations next existing analytical solution which had been presented for analysis of static slide toe toppling failure was modified and some new equations were obtained for analysis of the failure under dynamic condition then a computer code was developed based on the new equations for evaluation of the instability in the next step the failed slope was analyzed using the code and finite element method and outcomes of these analyses were compared with real conditions the comparison showed that there was satisfactory agreement between the analytical numerical and actual results therefore these methods were used to predict the behavior of the final slope in static and dynamic conditions these evaluations indicated that if displaced materials are completely excavated and removed from the mine and overall dip of the slope is reduced the final slope will be stable against slide toe toppling failure this paper summarizes the results and concludes that both the modified analytical approach and finite element method are able to analyze a slope against the secondary toppling mode furthermore the research proves that re sloping and unloading are two adequate methods which can be used for stabilization of the failure

analysis of a complex toppling circular slope failure abstract this technical note describes a complex failure that occurred in an open pit mine in valencia spain the failure which was analysed and interpreted in accordance with the local geology occurred in a slope comprised of a limestone rock mass in the upper part and a claystone sandstone sedimentary formation in the lower part the failure mechanism which was interpreted as complex toppling combining toppling and circular failure was back analysed using analytical and numerical techniques

an analytical solution for analysis of toppling slumping failure in rock slopes abstract when a slope consists of a horizontal weak rock or soil overlaid by some vertical strong slender rock columns the slope is prone to a secondary toppling failure which is known as toppling slumping failure in the slope rock columns impose pressure on the lower continuous weak rock or soil mass which leads to a differential settlement at the base of each rock column or a circular shear failure in the continuous mass if the differential settlements reach a special threshold rock column overturn and toppling slumping will happen however the circular shear failure of the soil or weak rock mass which is a well recognized failure mechanism will occur when shear stress in the slope exceeds its shear strength in this paper an attempt has been made to better understanding of the toppling slumping failure mechanism through developing an analytical solution for this purpose first an airy stress function is acquired for the lower continuous soil mass and its stress distribution and displacement are accordingly determined analytically due to the overlaid rock columns loads then differential settlements at the base of all rock columns and shear stresses in the soil or weak rock mass are computed and compared with the toppling and shear failure criteria to assess slope failure finally several design charts are developed that determine the stability of a slope against toppling slumping failure mechanism based on geometric characteristics of the slope and shear strength of its constituent material also a mathematica package code was developed to evaluate the stress distribution within the slope and the safety factor the results show that the vertical stress distribution plays a significant role in the settlement of the rock columns results also manifested that at a certain distance from the slope crest the set of rock columns will act like a single column on a half plane the shear or toppling failure of the slope not only depends on the material s strength but also on the geometry and the normalized column distance

el nino like hydroclimate responses to last millennium volcanic eruptions abstractthe hydroclimate response to volcanic eruptions depends both on volcanically induced changes to the hydrologic cycle and on teleconnections with the el nino southern oscillation enso complicating the interpretation of offsets between proxy reconstructions and model output here these effects are separated using the community earth system model last millennium ensemble cesm lme by examination of ensemble realizations with distinct posteruption enso responses hydroclimate anomalies in monsoon asia and the western united states resemble the el nino teleconnection pattern after tropical and northern eruptions even when enso neutral conditions are present this pattern results from northern hemisphere nh surface cooling which shifts the intertropical convergence zone equatorward intensifies the nh subtropical jet and suppresses the southeast asian monsoon el nino events following an eruption can then intensify the enso neutral hydroclimate signature and el nino probability is enhan

volcanic forcing of climate over the past 1500 years an improved ice core based index for climate models 1 understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate we have investigated one of the most important natural causes of climate change volcanic eruptions by using 54 ice core records from both the arctic and antarctica our recently collected suite of ice core data more than double the number of cores ever used before reduces errors inherent in reconstructions based on a single or small number of cores which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects we extracted volcanic deposition signals from each ice core record by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation we then studied the spatial pattern of volcanic sulfate deposition on greenland and antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month latitude and altitude for the past 1500 years we estimated the uncertainties associated with the choice of volcanic signal extraction criteria ice core sulfate deposition to stratospheric loading calibration factor and the season for the eruptions without a recorded month we forced an energy balance climate model with this new volcanic forcing data set together with solar and anthropogenic forcing to simulate the large scale temperature response the results agree well with instrumental observations for the past 150 years and with proxy records for the entire period through better characterization of the natural causes of climate change this new data set will lead to improved prediction of anthropogenic impacts on climate the new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years as a function of latitude altitude and month is available for download in a format suitable for forcing general circulation models of the climate system

theoretical and numerical study on the block flexure toppling failure of rock slopes abstract block flexure toppling failure is frequently encountered in rock slopes in this paper we first proposed two theoretical models to calculate the factor of safety against block flexure toppling namely step by step analysis model lem ssam and overall analysis model lem oam then we developed two special matlab codes for a quick stability estimation based on the proposed methods respectively next the universal distinct element code udec was used to study the failure mechanisms of block flexure toppling in order to realistically simulate the excavation of slope and obtain the detailed damage information of joints we developed two fish functions in udec finally we conducted a comparative analysis of the limit equilibrium method and the numerical simulations through twelve theoretical models the results show that many aspects of block flexure toppling failure have been captured using udec combined with the developed fish functions the lem oam and udec agree well while a larger factor of safety is obtained using the lem ssam it is found that the dip angles and friction angles of the joints dipping steeply into face have a great influence on block flexure toppling failure while the influence of the cross joint spacing is less significant

hydroclimate responses over global monsoon regions following volcanic eruptions at different latitudes abstractunderstanding the influence of volcanic eruptions on the hydroclimate over global monsoon regions is of great scientific and social importance however the link between the latitude of vol

mountains on io high resolution galileo observations initial interpretations and formation models during three close flybys in late 1999 and early 2000 the galileo spacecraft acquired new observations of the mountains that tower above io s surface these images have revealed surprising variety in the mountains morphologies they range from jagged peaks several kilometers high to lower rounded structures some are very smooth others are covered by numerous parallel ridges many mountains have margins that are collapsing outward in large landslides or series of slump blocks but a few have steep scalloped scarps from these observations we can gain insight into the structure and material properties of io s crust as well as into the erosional processes acting on io we have also investigated formation mechanisms proposed for these structures using finite element analysis mountain formation might be initiated by global compression due to the high rate of global subsidence associated with io s high resurfacing rate however our models demonstrate that this hypothesis lacks a mechanism for isolating the mountains the large fraction 40 of mountains that are associated with paterae suggests that in some cases these features are tectonically related therefore we have also simulated the stresses induced in io s crust by a combination of a thermal upwelling in the mantle with global lithospheric compression and have shown that this can focus compressional stresses if this mechanism is responsible for some of io s mountains it could also explain the common association of mountains with paterae

divergent responses of tropical cyclone genesis factors to strong volcanic eruptions at different latitudes to understand the behaviors of tropical cyclones tcs it is very important to explore how tcs respond to anthropogenic greenhouse gases and natural forcings volcanic eruptions are a major natural forcing mechanism because they inject sulphate aerosols into the stratosphere which modulate the global climate by absorbing and scattering solar radiation the number of atlantic hurricanes is thought to be reduced following strong tropical eruptions but whether the response of tcs varies with the locations of the volcanoes and the different ocean basins remains unknown here we use the community earth system model last millennium ensemble to investigate the response of the large scale environmental factors that spawn tcs to strong volcanic eruptions at different latitudes a composite analysis indicates that tropical and northern hemisphere volcanic eruptions lead to significantly unfavorable conditions for tc genesis over the whole pacific basin and the north atlantic during the 3 years post eruption relative to the preceding 3 years southern hemisphere volcanic eruptions result in obviously unfavorable conditions for tc formation over the southwestern pacific but more favorable conditions over the north atlantic the mean response over the indian ocean is generally muted and insignificant it should be noted that volcanic eruptions impact on environmental conditions through both the direct effect i e on radiative forcing and the indirect effect i e on el nino southern oscillation which is not differentiated in this study in addition the spread of the tc genesis response is considerably large for each category of eruptions over each ocean basin which is also seen in the observational proxy based records this large spread is attributed to the differences in stratospheric aerosol distributions initial states and eruption intensities and makes the short term forecast of tc activity following the next large eruption challenging

stability analysis of slopes against combined circular toppling failure abstract circular failure is one of the most probable instabilities on slopes with severely crushed rock or soil slopes another type of instability is block flexural toppling which is the most common type of toppling failure in this type of failure some rock blocks are broken by bending and other topples due to their weight in some slopes a soil mass has direct contact with the rock mass with the potential of block flexural failure if so the total slope failure potential is the combination of circular toppling failure this instability can be called secondary toppling failure for which there is no solution available in the literature studies on circular and toppling failure are reviewed then the interaction between soil mass and rock blocks is studied considering the interaction between soil and rock this study proposes a theoretical model for stability analysis for the combination of circular toppling failure and the required equations are developed solving these equations manually is time consuming thus a special computer code is programmed to analyze the combination failure the code receives slope s information from the user and calculates the factor of safety subject to combination failure circumstances finally a real case instability of a slope in vana village along haraz road in northern iran is analyzed with this code and results are compared with the observed data

silicate volcanism on io io is currently emitting 1 1 5 w m 2 of tidal energy as a result of its volcanic activity if the lithosphere is more than 20 km thick as appears probable from the surface relief only a fraction of the tidal energy can be dissipated within the lithosphere otherwise it will become thinner the rest of the tidal energy must be dissipated below the lithosphere io is likely to be highly differentiated as a result of the volcanic activity with a low melting temperature fraction such as basalt near the surface and a high melting temperature fraction such as peridotite at depth if solidus temperatures are reached at depths shallower than the thickness of the basalt layer a partial melt zone will separate an all basalt lithosphere above from a peridotite mantle below and part of the tidal energy will be dissipated by viscous deformation within the melt zone most of the energy dissipated below the lithosphere will be transported upward through the lithosphere as silicate magma which is generated in quantities sufficient to resurface the satellite at a rate of a few tenths of a centimeter a year depending on the lithosphere thickness many of the characteristics of the ionian surface have been explained in terms of sulfur volcanism however most of the features observed can be as readily explained by silicate volcanism and silicates are more consistent with the apparent strength of the surface as implied by the relief simulations of basaltic eruptions indicate that the surface temperatures that would result from basaltic eruptions are similar to those measured by the voyager infrared interferometer spectrometer experiment the high rates of emission by the ionian hot spots imply eruption rates that are high compared with typical terrestrial eruptions an eruption rate of 4000 m3 s 1 may be required to explain loki which is currently emitting 1013 w although the near surface materials are mainly silicate they may contain several percent of volatile components rich in s na and k remobilization of these components by the ongoing silicate eruptions causes the plumes provides material to the torus and gives the satellite its characteristic reflectivity

high temperature silicate volcanism on jupiter s moon io infrared wavelength observations of io by the galileo spacecraft show that at least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on earth today in at least one case the eruption near pillan patera two independent instruments on galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin the most likely explanation is that these lavas are ultramafic magnesium rich silicates and this idea is supported by the tentative identification of magnesium rich orthopyroxene in lava flows associated with these high temperature hot spots

io s thermal emission from the galileo photopolarimeter radiometer galileo s photopolarimeter radiometer instrument mapped io s thermal emission during the i24 i25 and i27 flybys with a spatial resolution of 2 2 to 300 kilometers mapping of loki in i24 shows uniform temperatures for most of loki patera and high temperatures in the southwest corner probably resulting from an eruption that began 1 month before the observation most of loki patera was resurfaced before i27 pele s caldera floor has a low temperature of 160 kelvin whereas flows at pillan and zamama have temperatures of up to 200 kelvin global maps of nighttime temperatures provide a means for estimating global heat flow

consistent decrease in north atlantic tropical cyclone frequency following major volcanic eruptions in the last three centuries injection of sulphate aerosols into the stratosphere following major volcanic eruptions alters global climate through the absorption and scattering of solar radiation one proposed consequence is a decrease in north atlantic tropical cyclone tc activity as was observed following the el chichon 1982 and mount pinatubo 1991 eruptions we test this relationship using documentary and proxy reconstructions of major volcanic eruptions and tc frequency in the north atlantic basin over the last three centuries we find a consistent reduction in the number of tcs formed during the 3 years following major eruptions compared to the preceding 3 years including after eruptions located at northern high latitudes our findings suggest that low latitude eruptions reduce atlantic tc frequency by decreasing local sea surface temperatures whereas the mechanisms for the decrease in tc frequency following high latitude eruptions are less clear and attribution is hampered by poor identification of these events

stability analysis of slopes with a potential of slide head toppling failure abstract toppling is a mode of slope instability that may occur in a wide range of layered or blocky rock masses if this instability is caused by some natural or man made external factors it is termed a secondary toppling failure one of the important modes of toppling instability is the slide head toppling failure when a layer of soil or weak rock is overlaid by a blocky or layered rock mass the combination of a toppling failure in the rock at the top and a circular sliding in the soil or weak rock in the bottom leads to this hybrid failure the mechanism of this hybrid failure is extremely complicated and it may occur in some special geological conditions in civil engineering and mining projects in this paper the mechanisms of toppling failures in general and the mechanism of slide head toppling failure in particular are presented and described then the outcomes of seven physical models which were constructed with base friction materials and conducted under static loading conditions by a tilting table apparatus are summarized to investigate this hybrid failure mechanism subsequently a new step by step theoretical approach is proposed for assessment of this failure mode and a typical example is analyzed to better demonstrate the results finally the results of the physical modeling are compared with the outcomes of the proposed theoretical method and an existing analytical approach this comparison shows that there are acceptable agreements between the physical and analytical results hence both proposed and existing analytical approaches can be used for the analysis of the slide head toppling slope failure

modelling and back analysing failures in steep limestone cliffs abstract the observation of 12 rock fall scars in steep limestone cliffs has shown that the fallen masses were stable as a result of relatively small rock bridges these results demonstrate that consideration of rock bridges is necessary for a realistic evaluation of stability limit equilibrium methods of analysis are presented for sliding and toppling for both isostatic and hyperstatic conditions these methods are illustrated with four case histories the results of nine back analyses of rock falls with volumes between 24 and 3500 m 3 are presented the rock cohesion obtained from back analysis appears to be significantly lower than the cohesion obtained from classical laboratory tests this discrepancy can be attributed to several factors including a spatial and temporal scale effect the oversimplified modelling two dimensional limit equilibrium and some uncertainties affecting the geometrical data when analysing the stability of a cliff with a limit equilibrium method the authors suggest dividing the cohesion by a scale and method factor of 3

variation of the summer asian westerly jet over the last millennium based on the pmip3 simulations investigation of the evolution of summer asian westerly jet awj in earth history may deepen our understanding of the behavior of awj in the present and future here the variation of summer weste

prometheus io s wandering plume unlike any volcanic behavior ever observed on earth the plume from prometheus on io has wandered 75 to 95 kilometers west over the last 20 years since it was first discovered by voyager and more recently observed by galileo despite the source motion the geometric and optical properties of the plume have remained constant we propose that this can be explained by vaporization of a sulfur dioxide and or sulfur snowfield over which a lava flow is moving eruption of a boundary layer slurry through a rootless conduit with sonic conditions at the intake of the melted snow can account for the constancy of plume properties

atlantic hurricane activity following two major volcanic eruptions 1 in 1982 and 1991 two major volcanic eruptions loaded the stratosphere with long lived sulfate aerosols altering the global climate by redistributing longwave and shortwave radiation at the surface and throughout the atmosphere cooling the surface and subsurface waters of the tropical oceans theory and observations demonstrate through direct and indirect mechanisms a causal relationship between tropical north atlantic sea surface temperatures and seasonal atlantic hurricane frequency duration and intensity therefore it is plausible that hurricane activity in the seasons immediately following these eruptions is diminished however to date such a theory remains untested here i use observations reanalysis data and output from a numerical model to suggest that the number duration and intensity of hurricanes in the years following the eruptions of el chichon 1982 and mount pinatubo 1991 decreased via the aerosol direct effect determining the effects of each eruption on seasonal cyclone activity is complicated by simultaneous positive enso events thus further study of the relationship between atlantic tropical cyclones and major volcanic eruptions is warranted