Long-term fluctuations in volcanic activity: implications for future environmental impact     

Hazel Rymer  Corinne A. Locke  rea Borgia  Maria Martinez  Jorge Brenes  Rodolfo Van der Laat  Glyn Williams-Jones 《地学学报》2009,21(4):304-309

Acidic crater lakes at persistently active volcanoes act as both an index and a moderator of volcanic processes. A catastrophic drop in lake level can therefore lead to serious local environmental damage. In the early 1990s, the crater lake at Poás volcano, Costa Rica diminished, and acid aerosols erupted with devastating consequences for local health, environment and economy. The first indications of this event can be  retrospectively identified to have started from 1985, on the basis of our unique 20-year data time series, which provides evidence for the shallow intrusion of magma. New data presented in this article show similar trends and we conclude that Poás has now entered another active period with renewed intrusion. Severe environmental damage in this region is expected within the next few years if the current trend continues.  相似文献   

Geomorphology of desert sand dunes: A review of recent progress   总被引：2，自引：0，他引：2  

Ian Livingstone  Giles F.S. Wiggs  Corinne M. Weaver 《Earth》2007,80(3-4):239-257

Through the 1980s and 1990s studies of the geomorphology of desert sand dunes were dominated by field studies of wind flow and sand flow over individual dunes. Alongside these there were some attempts numerically to model dune development as well as some wind tunnel studies that investigated wind flow over dunes. As developments with equipment allowed, field measurements became more sophisticated. However, by the mid-1990s it was clear that even these more complex measurements were still unable to explain the mechanisms by which sand is entrained and transported. Most importantly, the attempt to measure the stresses imposed by the wind on the sand surface proved impossible, and the use of shear (or friction) velocity as a surrogate for shear stress also failed to deliver. At the same time it has become apparent that turbulent structures in the flow may be as or more important in explaining sand flux. In a development paralleled in fluvial geomorphology, aeolian geomorphologists have attempted to measure and model turbulent structures over dunes. Progress has recently been made through the use of more complex numerical models based on computational fluid dynamics (CFD). Some of the modelling work has also suggested that notions of dune ‘equilibrium’ form may not be particularly helpful. This range of recent developments has not meant that field studies are now redundant. For linear dunes careful observations of individual dunes have provided important data about how the dunes develop but in this particular field some progress has been made through ground-penetrating radar images of the internal structure of the dunes.

The paradigm for studies of desert dune geomorphology for several decades has been that good quality empirical data about wind flow and sand flux will enable us to understand how dunes are created and maintain their form. At least some of the difficulty in the past arose from the plethora of undirected data generated by largely inductive field studies. More recently, attention has shifted–although not completely–to modelling approaches, and very considerable progress has been made in developing models of dune development. It is clear, however, that the models will continue to require accurate field observations in order for us to be able to develop a clear understanding of desert sand dune geomorphology.  相似文献   

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution   总被引：4，自引：6，他引：4  

Barnier Bernard  Gurvan Madec  Thierry Penduff  Jean-Marc Molines  Anne-Marie Treguier  Julien Le Sommer  Aike Beckmann  Arne Biastoch  Claus Böning  Joachim Dengg  Corine Derval  Edmée Durand  Sergei Gulev  Elizabeth Remy  Claude Talandier  Sébastien Theetten  Mathew Maltrud  Julie McClean  Beverly De Cuevas 《Ocean Dynamics》2006,56(5-6):543-567

Series of sensitivity tests were performed with a z-coordinate, global eddy-permitting (1/4°) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to carefully evaluate the impact of recent state-of-the-art numerical schemes on model solutions. The combination of an energy–enstrophy conserving (EEN) scheme for momentum advection with a partial step (PS) representation of the bottom topography yields significant improvements in the mean circulation. Well known biases in the representation of western boundary currents, such as in the Atlantic the detachment of the Gulf Stream, the path of the North Atlantic Current, the location of the Confluence, and the strength of the Zapiola Eddy in the south Atlantic, are partly corrected. Similar improvements are found in the Pacific, Indian, and Southern Oceans, and characteristics of the mean flow are generally much closer to observations. Comparisons with other state-of-the-art models show that the ORCA-R025 configuration generally performs better at similar resolution. In addition, the model solution is often comparable to solutions obtained at 1/6 or 1/10° resolution in some aspects concerning mean flow patterns and distribution of eddy kinetic energy. Although the reasons for these improvements are not analyzed in detail in this paper, evidence is shown that the combination of EEN with PS reduces numerical noise near the bottom, which is likely to affect current–topography interactions in a systematic way. We conclude that significant corrections of the mean biases presently seen in general circulation model solutions at eddy-permitting resolution can still be expected from the development of numerical methods, which represent an alternative to increasing resolution.  相似文献   

Speleoseismology: A critical perspective     

Arnfried Becker  Colin A. Davenport  Urs Eichenberger  Eric Gilli  Pierre-Yves Jeannin  Corinne Lacave 《Journal of Seismology》2006,10(3):371-388

Speleoseismology is the investigation of earthquake records in caves. Traces can be seen in broken speleothems, growth anomalies in speleothems, cave sediment deformation structures, displacements along fractures and bedding plane slip, incasion (rock fall) and co-seismic fault displacements. Where earthquake origins can be proven, these traces constitute important archives of local and even regional earthquake activity. However, other processes that can generate the same or very similar deformation features have to be excluded before cave damage can be interpreted as earthquake induced. Most sensitive and therefore most valuable for the tracing of strong earthquake shocks in caves are long and slender speleothems, such as soda straws, and deposits of well-bedded, water-saturated silty sand infillings, particularly in caves close to the earth's surface. Less easily proven is a co-seismic origin of an incasion and other forms of cave damage. The loads and creep movements of sediment and ice fillings in caves can cause severe damage to speleothems which have been frequently misinterpreted as evidence of earthquakes. For the dating of events in geological archives, it is important to demonstrate that such events happened at approximately the same time, i.e. within the error bars of the dating methods. A robust earthquake explanation for cave damage can only be achieved by the adoption of appropriate methods of direct dating of deformation events in cave archives combined with correlation of events in other geological archives outside caves, such as the deformation of lake and flood-plain deposits, locations of rock falls and active fault displacements.  相似文献   

A Modeling System for Studying Climate Controls on Mountain Glaciers with Application to the Patagonian Icefields     

Kerry H. Cook  Xiaosong Yang  Corinne M. Carter  Brian N. Belcher 《Climatic change》2003,56(3):339-367

A modeling system for investigating meteorological controls on glacier mass balance is described and applied to the Southern Patagonian Icefield. Output from a mesoscale atmospheric model is used to drive a glacier mass balance model using model precipitation and turbulent fluxes adjusted to account for the unrealistically low surface elevations of the icefield in the atmospheric model. Simulations of January and July conditionsproduce glacier equilibrium line altitudes (ELAs) that are higher than the observed, but the ELA gradient is realistically simulated. The high ELAs are primarily due to underestimates of vertical temperature gradients in the atmospheric model and uncertainties in the ablation season length. The model shows that both winter and summerprecipitation, as well as summer temperatures, are important determinants of the mass balance of the Southern Patagonia glaciers. The position of the icefield on the continent is also relevant. On the western side of the icefield, precipitation rates are high and dominate the mass balance calculation. In the east, ablation is much more important for determining the mass balance, and this introduces an enhanced sensitivity to atmospheric temperature, wind speed, and atmosphericmoisture levels.  相似文献   

Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data     

Alexei V. Kouraev  Fabrice Papa  Petr I. Buharizin  Anny Cazenave  Jean-Francois Cretaux  Julia Dozortseva  Frederique Remy 《Polar research》2003,22(1):43-50

The paper discusses time and space variations of ice extent in the Caspian and Aral seas during the last decade (1992-2002). It uses synergy of data from active (radar altimeter) and passive (radiometer) microwave nadir-looking instruments onboard the TOPEX/Poseidon satellite. The proposed approach is substantiated and validated using both in situ and satellite imagery data for the Caspian Sea. The results indicate significant spatial and temporal variability of ice conditions, with a significant decrease of both the duration of ice season and ice extent during the last four winters (1998-2002). The TOPEX/Poseidon-derived time series of sea ice extent are very valuable in view of the fragmentary and mostly unpublished data on ice conditions on the Caspian and Aral seas since the mid-1980s.  相似文献   

Subsurface structure across the axis of the Tongariro Volcanic Centre,New Zealand     

John Cassidy  Malcolm Ingham  Corinne A. Locke  Hugh Bibby 《Journal of Volcanology and Geothermal Research》2009,179(3-4):233-240

The relationship between structure and volcanism in the Tongariro Volcanic Centre, New Zealand, is largely masked by a mantle of young volcanic deposits. Here we report the results of an integrated geophysical investigation (using gravity, multi-level aeromagnetic and magnetotelluric methods) of subsurface deposits and structures in the upper 1–2 km across the axis of the Tongariro Volcanic Centre. Modelling of these data across the Tama Lakes saddle shows that the outcropping volcanic deposits are up to 800 m thick, underlain by Tertiary sediments (of a few 10's to a few 100 m in thickness) and in turn lying above a basement of probable Mesozoic greywacke. Basement faulting is shown to be concentrated in the centre of the rift, which is 18 km wide at this location, but no vertical offset is resolved at the rift axis. Vertical displacements on basement faults of 250–300 m are modelled giving a minimum total basement subsidence of 650 m. A 5 km-wide, deep low resistivity zone occurs at the axis of the rift which is interpreted as either resulting from extensive fracturing and/or hydrothermal alteration within the basement. Steep-sided volcanic bodies with a high proportion of lavas/dykes coincide with the Waihi fault and the rift axis. Coincidence with the Waihi Fault suggests that this fault system may have provided magma pathways to the surface and a focus for dyke emplacement, which could have contributed to rift extension. The lack of offset at the rift axis may reflect the juvenile nature of faulting at this location, which is consistent with the notion of a migration of faulting towards the centre of the graben, alternatively, rifting may have been entirely accommodated by dyke emplacement.  相似文献   

Small-scale variability of the current in the Strait of Bonifacio   总被引：1，自引：1，他引：0  

Olivia Gérigny  Sylvain Coudray  Chiara Lapucci  Corinne Tomasino  Paul-Antoine Bisgambiglia  François Galgani 《Ocean Dynamics》2015,65(8):1165-1182

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A Simple Tiered Methodology for the Determination of Ambient Air Quality Guidelines          下载免费PDF全文

Catherine Pirard  Jean‐Marc Brouhon  Annick Fourmeaux  Corinne Charlier 《洁净——土壤、空气、水》2016,44(5):464-473

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Use of a Sodar to Improve the Forecast of Fogs and Low Clouds on Airports     

Alain Dabas  Samuel Remy  Thierry Bergot 《Pure and Applied Geophysics》2012,169(5-6):769-781

A sodar was deployed at Roissy–Charles de Gaulle airport near Paris, France, in 2008 with the aim of improving the forecast of low visibility conditions there. During the winter of 2008–2009, an experiment was conducted that showed that the sodar can effectively detect and locate the top of fog layers which is signaled by a strong peak of acoustic reflectivity. The peak is generated by turbulence activity in the inversion layer that contrasts sharply with the low reflectivity recorded in the fog layer below. A specific version of the 1D-forecast model deployed at Roissy for low visibility conditions (COBEL-ISBA) was developed in which fogs’ thicknesses are initialized by the sodar measurements rather than the information derived from the down-welling IR fluxes observed on the site. It was tested on data archived during the winters of 2008–2009 and 2009–2010 and compared to the version of the model presently operational. The results show a significant improvement—dissipation times of fogs are better predicted.  相似文献