Orbit computation for transneptunian objects     

Jenni Virtanen  Gonzalo Tancredi  Edward Bowell 《Icarus》2003,161(2):419-430

Using statistical orbital ranging, we systematically study the orbit computation problem for transneptunian objects (TNOs). We have automated orbit computation for large numbers of objects, and, more importantly, we are able to obtain orbits even for the most sparsely observed objects (observational arcs of a few days). For such objects, the resulting orbit distributions include a large number of high-eccentricity orbits, in which TNOs can be perturbed by close encounters with Neptune. The stability of bodies on the computed orbits has therefore been ascertained by performing a study of close encounters with the major planets. We classify TNO orbit distributions statistically, and we study the evolution of their ephemeris uncertainties. We find that the orbital element distributions for the most numerous single-apparition TNOs do not support the existence of a postulated sharp edge to the belt beyond 50 AU. The technique of statistical ranging provides ephemeris predictions more generally than previously possible also for poorly observed TNOs.  相似文献   

Meteorological monitoring of an active volcano: Implications for eruption prediction     

Jenni Barclay  Jade E. Johnstone  Adrian J. Matthews   《Journal of Volcanology and Geothermal Research》2006,150(4):241-358

Rainfall data collected on and around the Soufriere Hills Volcano, Montserrat between 1998 and 2003 were analysed to assess the impact on primary volcanic activity, defined here as pyroclastic flows, dome collapses, and explosions. Fifteen such rainfall-triggered events were identified. If greater than 20 mm of rain fell on a particular day, the probability of a dome collapse occurring on that day increased by a factor of 6.3% to 9.2%, compared to a randomly chosen day. Similarly, the probability of observing pyroclastic flows and explosions on a day with > 20 mm of rainfall increased by factors of 2.6 and 5.4, respectively. These statistically significant links increased as the rainfall threshold was increased. Seventy percent of these rainfall-induced dome collapse episodes occurred on the same calendar day (most within a few hours) as the onset of intense rainfall, but an extra 3 occurred one or two calendar days later. The state of the volcano was important, with the rainfall–volcanic activity link being strongest during periods of unstable dome growth and weakest during periods of no dome growth or after a recent major collapse.Over 50% of the heavy rain days were associated with large-scale weather systems that can potentially be forecast up to a few days ahead. However, the remaining heavy rain days were associated with small-scale, essentially unpredictable weather systems. There was significant variability in the amount of rainfall recorded by different rain gauges, reflecting topographic variations around the volcano but also the inherent small-scale variability within an individual weather system. Hence, any monitoring/warning program is recommended to use a network, rather than just a single gauge. The seasonal cycle in rainfall was pronounced, with nearly all the heavy rain days occurring in the May–December wet season. Hence, the dome was at its most vulnerable at the beginning of the wet season after a period of uninterrupted growth. Interannual variability in rainfall was related to tropical Pacific and Atlantic sea surface temperature anomalies, and holds out the prospect of some limited skill in volcanic hazard forecasts at even longer lead times.  相似文献   

Volcanic hazard communication using maps: an evaluation of their effectiveness   总被引：2，自引：0，他引：2  

Katharine Haynes  Jenni Barclay  Nick Pidgeon 《Bulletin of Volcanology》2007,70(2):123-138

Hazard maps are considered essential tools in the communication of volcanic risk between scientists, the local authorities and the public. This study investigates the efficacy of such maps for the volcanic island of Montserrat in the West Indies using both quantitative and qualitative research techniques. Normal plan view maps, which have been used on the island over the last 10 years of the crisis, are evaluated against specially produced three-dimensional (3D) maps and perspective photographs. Thirty-two demographically representative respondents of mixed backgrounds, sex, education and location were interviewed and asked to complete a range of tasks and identification on the maps and photographs. The overall results show that ordinary people have problems interpreting their environment as a mapped representation. We found respondents’ ability to locate and orientate themselves as well as convey information relating to volcanic hazards was improved when using aerial photographs rather than traditional plan view contour maps. There was a slight improvement in the use of the 3D maps, especially in terms of topographic recognition. However, the most striking increase in effectiveness was found with the perspective photographs, which enabled people to identify features and their orientation much more readily. For Montserrat it appears that well labelled aerial and perspective photographs are the most effective geo-spatial method of communicating volcanic risks.

Katharine HaynesEmail:

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Pre- and syn-eruptive degassing and crystallisation processes of the 2010 and 2006 eruptions of Merapi volcano,Indonesia     

Katie?PreeceEmail author  Ralf?Gertisser  Jenni?Barclay  Kim?Berlo  Richard?A.?Herd  Edinburgh Ion Microprobe Facility 《Contributions to Mineralogy and Petrology》2014,168(4):1061

The 2010 eruption of Merapi (VEI 4) was the volcano’s largest since 1872. In contrast to the prolonged and effusive dome-forming eruptions typical of Merapi’s recent activity, the 2010 eruption began explosively, before a new dome was rapidly emplaced. This new dome was subsequently destroyed by explosions, generating pyroclastic density currents (PDCs), predominantly consisting of dark coloured, dense blocks of basaltic andesite dome lava. A shift towards open-vent conditions in the later stages of the eruption culminated in multiple explosions and the generation of PDCs with conspicuous grey scoria and white pumice clasts resulting from sub-plinian convective column collapse. This paper presents geochemical data for melt inclusions and their clinopyroxene hosts extracted from dense dome lava, grey scoria and white pumice generated during the peak of the 2010 eruption. These are compared with clinopyroxene-hosted melt inclusions from scoriaceous dome fragments from the prolonged dome-forming 2006 eruption, to elucidate any relationship between pre-eruptive degassing and crystallisation processes and eruptive style. Secondary ion mass spectrometry analysis of volatiles (H₂O, CO₂) and light lithophile elements (Li, B, Be) is augmented by electron microprobe analysis of major elements and volatiles (Cl, S, F) in melt inclusions and groundmass glass. Geobarometric analysis shows that the clinopyroxene phenocrysts crystallised at depths of up to 20 km, with the greatest calculated depths associated with phenocrysts from the white pumice. Based on their volatile contents, melt inclusions have re-equilibrated during shallower storage and/or ascent, at depths of ~0.6–9.7 km, where the Merapi magma system is interpreted to be highly interconnected and not formed of discrete magma reservoirs. Melt inclusions enriched in Li show uniform “buffered” Cl concentrations, indicating the presence of an exsolved brine phase. Boron-enriched inclusions also support the presence of a brine phase, which helped to stabilise B in the melt. Calculations based on S concentrations in melt inclusions and groundmass glass require a degassing melt volume of 0.36 km³ in order to produce the mass of SO₂ emitted during the 2010 eruption. This volume is approximately an order of magnitude higher than the erupted magma (DRE) volume. The transition between the contrasting eruptive styles in 2010 and 2006 is linked to changes in magmatic flux and changes in degassing style, with the explosive activity in 2010 driven by an influx of deep magma, which overwhelmed the shallower magma system and ascended rapidly, accompanied by closed-system degassing.  相似文献   

Severe weather affecting European transport systems: the identification,classification and frequencies of events   总被引：1，自引：0，他引：1  

Andrea Vajda  Heikki Tuomenvirta  Ilkka Juga  Pertti Nurmi  Pauli Jokinen  Jenni Rauhala 《Natural Hazards》2014,72(1):169-188

Severe weather can have serious repercussions in the transport sector as a whole by increasing the number of accidents, injuries and other damage, as well as leading to highly increased travel times. This study, a component of the EU FP7 Project EWENT, delineates a Europe-wide climatology of adverse and extreme weather events that can be expected to affect the transport network. We first define and classify the relevant severe weather events by investigating the effects of hazardous conditions on different transportation modes and the infrastructure. Consideration is given to individual phenomena such as snowfall, heavy precipitation, heat waves, cold spells, wind gusts; a combined phenomenon, the blizzard, is also considered. The frequency of severe weather events, together with the changes in their spatial extension and intensity, is analyzed based on the E-OBS dataset (1971–2000) and the ERA-Interim reanalysis dataset (1989–2010). Northern Europe and the Alpine region are the areas most impacted by winter extremes, such as snowfall, cold spells and winter storms, the frequency of heavy snowfall. The frequency of hot days is highest in Southern Europe. Severe winds and blizzards are the most common over the Atlantic and along its shores. Although heavy rainfall may affect the whole continent on an annual basis, extreme precipitation events are relative sparse, affecting particularly the Alps and the Atlantic coastline. A European regionalization covering similar impacts on the transport network is performed.  相似文献   

Recent observations of meteotsunamis on the Finnish coast     

Hilkka Pellikka  Jenni Rauhala  Kimmo K. Kahma  Tapani Stipa  Hanna Boman  Antti Kangas 《Natural Hazards》2014,74(1):197-215

We present four case studies of exceptional wave events of meteorological origin, observed on the Finnish coast in the summers of 2010 and 2011. Eyewitnesses report unusually rapid and strong sea-level variations (up to 1 m in 5–15 min) and strong oscillating currents during these events. High-resolution sea-level measurements confirm the eyewitness observations, but the oscillations recorded by tide gauges mostly have a considerably smaller amplitude. The oscillations coincide with sudden jumps in surface air pressure at coastal observation stations, related to the passage of squall lines or gust fronts. These fronts propagate above the sea at a resonant speed, allowing efficient energy transfer between the atmospheric disturbance and the sea wave that it generates. Thus, we interpret the observed sea-level oscillations as small meteotsunamis, long tsunami-like waves generated by meteorological processes and resonance effects.  相似文献   

Asteroid orbital ranging using Markov‐Chain Monte Carlo     

Dagmara Oszkiewicz  Karri Muinonen  Jenni Virtanen  Mikael Granvik 《Meteoritics & planetary science》2009,44(12):1897-1904

Abstract— We present a novel Markov‐Chain Monte‐Carlo orbital ranging method (MCMC) for poorly observed single‐apparition asteroids with two or more observations. We examine the Bayesian a posteriori probability density of the orbital elements using methods that map a volume of orbits in the orbital‐element phase space. In particular, we use the MCMC method to sample the phase space in an unbiased way. We study the speed of convergence and also the efficiency of the new method for the initial orbit computation problem. We present the results of the MCMC ranging method applied to three objects from different dynamical groups. We conclude that the method is applicable to initial orbit computation for near‐Earth, main‐belt, and transneptunian objects.  相似文献   

Examining potential genetic links between Jurassic porphyry Cu–Au ± Mo and epithermal Au ± Ag mineralization in the Toodoggone district of North-Central British Columbia,Canada     

Paul Duuring  Stephen M. Rowins  Bradley S. M. McKinley  Jenni M. Dickinson  Larry J. Diakow  Young-Seog Kim  Robert A. Creaser 《Mineralium Deposita》2009,44(4):463-496

The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary rocks, which unconformably overlie submarine island-arc volcanic and sedimentary rocks of the Lower Permian Asitka Group and Middle Triassic Takla Group, some of which are intruded by Upper Triassic to Lower Jurassic plutons and dikes of the Black Lake suite. Although plutonism occurred episodically from ca. 218 to 191 Ma, the largest porphyry Cu–Au ± Mo systems formed from ca. 202 to 197 Ma, with minor mineralization occurring from ca. 197 to 194 Ma. Porphyry-style mineralization is hosted by small-volume (<1 km³), single-phase, porphyritic igneous stocks or dikes that have high-K calc-alkaline compositions and are comparable with volcanic-arc granites. The Fin porphyry Cu–Au–Mo deposit is anomalous in that it is 16 m.y. older than any other porphyry Cu–Au ± Mo occurrence in the district and has lower REEs. All porphyry systems are spatially restricted to exposed Asitka and Takla Group basement rocks, and rarely, the lowest member of the Hazelton Group (i.e., the ca. 201 Ma Duncan Member). The basement rocks to intrusions are best exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential exposure. In contrast, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district, where the overlying Hazelton Group rocks dominate exposures. Cogenetic porphyry systems might also exist in the northern areas; however, if they are present, they are likely to be buried deeply beneath Hazelton Group rocks. High-sulfidation epithermal systems formed at ca. 201 to 182 Ma, whereas low-sulfidation systems were active at ca. 192 to 162 Ma. Amongst the studied epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic fluids; fluid inclusion studies demonstrate that its ore fluids were hot (>468°C), saline, and deposited metals at deep crustal depths (>2 km). Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid, but also suggest that the ore fluid interacted with Asitka and Takla Group country rocks prior to metal deposition. In contrast, in the Shasta, Lawyers, and Griz-Sickle low-sulfidation epithermal systems, there is no clear association with magmatic fluids. Instead, their fluid inclusion data indicate the involvement of low-temperature (175 to 335°C), low-salinity (1 to 11 equiv. wt.% NaCl) fluids that deposited metals at shallow depths (<850 m). Their isotope (i.e., O, H, Pb) data suggest interaction between meteoric and/or metamorphic ore fluids with basement country rocks.  相似文献   

American Trappist Monasteries and the Changing Spiritual Landscape     

Thomas Barclay Larsen 《Geographical review》2019,109(1):47-66

Spiritual landscapes arise from a dynamic relationship of spiritual beliefs, ritual practices, and embodied encounters in place. They can contain multiple spiritual and non‐spiritual elements that change over time. This paper offers an appreciation of the diverse, overlapping, and ambivalent meanings emerging from Trappist monasteries in the United States. With origins tracing back to eleventh‐century France, Trappist monasteries are Roman Catholic intentional communities belonging to the Order of Cistercians of the Strict Observance. Attempts to establish monasteries in the American scene began around the turn of the nineteenth century. Contemplation, a receptive state of interior spiritual silence, represents one significant component of Trappist spirituality. Like other aspects of the spiritual landscape, contemplation has been reprioritized as Trappist monks and nuns confront situations like political conflict, changes in monastic leadership, and economic problems. These places continue to address challenges and possibilities for reinvention as they become open to shifting social contexts.  相似文献   

Geographical information system approaches for hazard mapping of dilute lahars on Montserrat, West Indies     

A. R. Darnell  J. Barclay  R. A. Herd  J. C. Phillips  A. A. Lovett  P. Cole 《Bulletin of Volcanology》2012,74(6):1337-1353

Many research tools for lahar hazard assessment have proved wholly unsuitable for practical application to an active volcanic system where field measurements are challenging to obtain. Two simple routing models, with minimal data demands and implemented in a geographical information system (GIS), were applied to dilute lahars originating from Soufrière Hills Volcano, Montserrat. Single-direction flow routing by path of steepest descent, commonly used for simulating normal stream-flow, was tested against LAHARZ, an established lahar model calibrated for debris flows, for ability to replicate the main flow routes. Comparing the ways in which these models capture observed changes, and how the different modelled paths deviate can also provide an indication of where dilute lahars, do not follow behaviour expected from single-phase flow models. Data were collected over two field seasons and provide (1) an overview of gross morphological change after one rainy season, (2) details of dominant channels at the time of measurement, and (3) order of magnitude estimates of individual flow volumes. Modelling results suggested both GIS-based predictive tools had associated benefits. Dominant flow routes observed in the field were generally well-predicted using the hydrological approach with a consideration of elevation error, while LAHARZ was comparatively more successful at mapping lahar dispersion and was better suited to long-term hazard assessment. This research suggests that end-member models can have utility for first-order dilute lahar hazard mapping.  相似文献