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121.
Roberto Carniel Marta Tárraga Fausto Barazza Alicia García 《Bulletin of Volcanology》2008,70(9):1113-1121
Continuous seismic noise is recorded in the volcanic island of Tenerife (Canary Islands, Spain). The origin of this noise,
strongly augmented by anthropogenic contamination, is still under debate. In this paper, we discuss the relationship between
this noise and the occurrence of local tectonic events in the same area. In particular, transitions are sought in the time
evolution of dynamic parameters computed on the seismic noise, and examples are shown where abrupt transitions may be associated
with the occurrence of tectonic events. These transitions provide further evidence of the existence of a natural origin for
at least part of the seismic noise, which is strongly contaminated—if not dominated—by anthropogenic sources. 相似文献
122.
Marta S.M. Mantovani Wladimir Shukowsky B.B. de Brito Neves André Rugenski 《Geophysical Prospecting》2008,56(5):751-760
A semi-detailed gravity survey was carried out over an area of 650 km2 localized in the Eo-Neoproterozoic coastal zone of Paraiba State where 548 new gravity stations were added to the existing database. Gravity measurements were made with a LaCoste and Romberg model G meter with a precision of 0.04 mGal. The altitude was determined by barometric levelling with a fixed base achieving a 1.2 m measure of uncertainty, corresponding to an overall accuracy of 0.24 mGal for the Bouguer anomaly. The residual Bouguer map for a 7th degree regional polynomial showed a circumscribed negative anomaly coincident with a localized aero-magnetic anomaly and with hydro-thermally altered outcrops, near the city of Itapororoca. The 3D gravity modelling, constrained by geologic mapping was interpreted as a low density, fractured and/or altered material with a most probable volume of approximately 23 km3 , extending to about 8,500 m depth. This result is in accordance with a volcanic body associated with hydrothermal processes accompanied by surface mineralization evidence, which may be of interest to the mining industry. 相似文献
123.
Disturbances produced by geomagnetic storms in the higher regions of the Earth’s atmosphere, such as in the ionospheric F2
region and in the lower ionosphere, are relatively better known than those produced at lower altitudes, where the effects
of geomagnetic storms have been little studied. During magnetically perturbed conditions, some changes in pressure and temperature
at high latitudes have been observed, from the surface level to heights of around 30 km, but there are no morphological studies
and/or patterns of behavior. Moreover, the physical mechanisms are still unknown and what exists is a matter of controversy.
Thus, the aim of this paper is to contribute to the vertical profile of the effects of geomagnetic storms as observed in the
lower sectors of the atmosphere. For that, we study the variations of two atmospheric parameters (temperature and wind speed)
during an intense geomagnetic storm (minimum Dst = −300 nT), at heights between about 6 km and 20 km. The data used were obtained
from weather balloon flights carried out at low, mid and mid-high latitudes in different longitudinal sectors of the northern
hemisphere, which took place twice per day: 00:00 and 12:00 UT. Small, but statistically significant changes in temperature
and in zonal component of the neutral winds are observed at mid-high latitudes, which can be linked to short-term geomagnetic
forcing. However, the results show different atmospheric response to the geomagnetic storm in the different longitudinal sectors
at tropospheric and stratospheric levels, which suggests a regional character of the geomagnetic storms effects at tropospheric
levels. 相似文献
124.
Marta Zossi de Artigas Patricia Fernandez de Campra 《Journal of Atmospheric and Solar》2010,72(7-8):565-569
Trends in total column ozone have been analyzed in terms of the equatorial zonal wind. We used zonal monthly mean total ozone from Total Ozone Mapping Spectrometer (TOMS) and monthly mean zonal wind in the equatorial stratosphere at 30 hPa to define the phases of the quasi-biennial oscillation (QBO). Total column ozone trends have been assessed during the period 1979–2004, for both Hemispheres, and for each month, under three conditions considering, all the ozone dataset, ozone values during easterly phase and ozone values during westerly phase of the QBO. When the whole dataset is considered, negative trends are observed. From low to midlatitudes a zonal pattern is noticed with increasing negative values toward higher latitudes. When the data is filtered according to the QBO phase, statistically significant positive trends appear in the westerly case during January to May at low latitudes .The trend pattern in the case of the easterly phase presents more negative values. 相似文献
125.
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128.
Radon anomalies and volcanic eruptions 总被引:1,自引:0,他引:1
Paolo Gasparini Marta Silvia Maria Mantovani 《Journal of Volcanology and Geothermal Research》1978,3(3-4)
A well-documented case of 222Rn anomaly preceding the eruptive activity of Karymsky volcano (Kamchatka) was recently reported in the literature. Stimulated by this example, we have attempted to utilize the available data on radon emanation from rocks, its solubility, and its circulation in waters to discuss how a 222Rn anomaly can be produced by magma approaching the surface. It is shown that the most likely process of radon release is the flushing of gases through pore fluids. Heating of extensive fracture surfaces by high-temperature gases may also be important. In order to survive in detectable amounts after moving distances greater than a few meters, radon must be transported by fast-moving fluids, such as those rising toward the surface through a fracture or in the ascending limbs of fluids convecting in very porous rocks under high temperature gradients. The pattern observed at Karymsky volcano is interpreted on the basis of these relations. 相似文献
129.
Present and future climatologies in the phase I CREMA experiment 总被引:1,自引:0,他引:1
Erika Coppola Filippo Giorgi Francesca Raffaele Ramon Fuentes-Franco Graziano Giuliani Marta LLopart-Pereira Ashu Mamgain Laura Mariotti Gulilat Tefera Diro Csaba Torma 《Climatic change》2014,125(1):23-38
We provide an overall assessment of the surface air temperature and precipitation present day (1976–2005) and future (2070–2099) ensemble climatologies in the Phase I CREMA experiment. This consists of simulations performed with different configurations (physics schemes) of the ICTP regional model RegCM4 over five CORDEX domains (Africa, Mediterranean, Central America, South America, South Asia), driven by different combinations of three global climate models (GCMs) and two greenhouse gas (GHG) representative concentration pathways (RCP8.5 and RCP4.5). The biases (1976–2005) in the driving and nested model ensembles compared to observations show a high degree of spatial variability and, when comparing GCMs and RegCM4, similar magnitudes and more similarity for precipitation than for temperature. The large scale patterns of change (2070–2099 minus 1976–2005) are broadly consistent across the GCM and RegCM4 ensembles and with previous analyses of GCM projections, indicating that the GCMs selected in the CREMA experiment are representative of the more general behavior of current GCMs. The RegCM4, however, shows a lower climate sensitivity (reduced warming) than the driving GCMs, especially when using the CLM land surface scheme. While the broad patterns of precipitation change are consistent across the GCM and RegCM4 ensembles, greater differences are found at sub-regional scales over the various domains, evidently tied to the representation of local processes. This paper serves to provide a reference view of the behavior of the CREMA ensemble, while more detailed and process-based analysis of individual domains is left to companion papers of this special issue. 相似文献
130.
The influence of the Arctic atmosphere on Northern Hemisphere midlatitude tropospheric weather and climate is explored by comparing the skill of two sets of 14-day weather forecast experiments using the ECMWF model with and without relaxation of the Arctic atmosphere towards ERA-Interim reanalysis data during the integration. Two pathways are identified along which the Arctic influences midlatitude weather: a pronounced one over Asia and Eastern Europe, and a secondary one over North America. In general, linkages are found to be strongest(weakest) during boreal winter(summer) when the amplitude of stationary planetary waves over the Northern Hemisphere is strongest(weakest). No discernible Arctic impact is found over the North Atlantic and North Pacific region, which is consistent with predominantly southwesterly flow. An analysis of the flow-dependence of the linkages shows that anomalous northerly flow conditions increase the Arctic influence on midlatitude weather over the continents. Specifically, an anomalous northerly flow from the Kara Sea towards West Asia leads to cold surface temperature anomalies not only over West Asia but also over Eastern and Central Europe. Finally, the results of this study are discussed in the light of potential midlatitude benefits of improved Arctic prediction capabilities. 相似文献