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1.
Boteler  D. H. 《Natural Hazards》2001,23(2-3):101-120
This paper presents an assessment ofgeomagnetic hazard on the five largest power systemsin Canada. From east to west these are: Nova ScotiaPower, Hydro-Quebec, Ontario Hydro West System, Manitoba Hydro, and the northern B.C. Hydro system. The aim of this study was to determine howfrequently, and where in a system, largegeomagnetically induced currents (GIC) could beexpected. To do this, an analysis was made of thespectral characteristics of the magnetic fieldvariations that cause GIC, and a review was made ofpublished magnetotelluric soundings in order todetermine conductivity models for different parts ofthe country. The magnetic field spectra and theconductivity information were then used to determinethe electric fields produced during geomagneticdisturbances. A relation was determined betweenelectric field magnitudes and the magnetic activityindex, Kp so that statistics for Kp could be used todetermine the occurrence rates of large electricfields. Power system models were used to determinethe GIC produced by the `1-year' and `10-year'electric fields experienced by each power system.  相似文献   

2.
Geomagnetic storms are a natural hazard tohuman health in the Auroral Belt of the Circumpolar.Geomagnetic disturbances in space, and the associated short-term variations in the atmosphere and the geophysical environment,provoke a disturbance of nervous and cardiovascular systems in the human body. The Heart Rate Variability (HRV) method providesa momentary response of human organisms toshort-term geophysical perturbations related to the Polar Aurora. A pilot project was performed in the Murmansk region in 1997–1999 with a contemporaneous series of records for both HRV in a test group of local inhabitants and the variations of natural geomagnetic fields.A correlation between geomagnetic disturbances and heart rate was calculated and different reactions of people on geophysical impact were shown. The special group of `Aurora Disturbance Sensitive People' (ADSP) was revealed. Aninternational study, aimed atevaluation of the impact on human health due to exposure of northern populations to the geophysical risk factor (GRF) in the Circumpolar areas located under the Aurora Belt, is needed.  相似文献   

3.
In this paper, central elements of the Solar Shield project, launched to design and establish an experimental system capable of forecasting the space weather effects on high-voltage power transmission system, are described. It will be shown how Sun–Earth system data and models hosted at the Community Coordinated Modeling Center (CCMC) are used to generate two-level magnetohydrodynamics-based forecasts providing 1–2 day and 30–60 min lead-times. The Electric Power Research Institute (EPRI) represents the end-user, the power transmission industry, in the project. EPRI integrates the forecast products to an online display tool providing information about space weather conditions to the member power utilities. EPRI also evaluates the economic impacts of severe storms on power transmission systems. The economic analysis will quantify the economic value of the generated forecasting system. The first version of the two-level forecasting system is currently running in real-time at CCMC. An initial analysis of the system’s capabilities has been completed, and further analysis is being carried out to optimize the performance of the system. Although the initial results are encouraging, definite conclusions about system’s performance can be given only after more extensive analysis, and implementation of an automatic evaluation process using forecasted and observed geomagnetically induced currents from different nodes of the North American power transmission system. The final output of the Solar Shield will be a recommendation for an optimal forecasting system that may be transitioned into space weather operations.  相似文献   

4.
We present the Virtual Earth-Sun Observatory (VESO) at the web site http://www.veso.unam.mx. This site shows a real time integrated database obtained from four instruments of the Instituto de Geofisica-UNAM studying Sun-Earth connection phenomena. (1) The Solar Radio Interferometer (RIS, Radio Interferómetro Solar) measures the lower solar atmosphere radiation at 7.5 GHz, revealing microwave bursts associated with solar activity. (2) The Mexican Array Radio Telescope (MEXART, Observatorio de Centelleo Interplanetario de Coeneo) will detect solar wind large-scale disturbances between Sun and Earth (e.g., Interplanetary counterparts of Coronal Mass Ejections (ICMES) and Stream Interaction Regions (SIR)) employing the interplanetary scintillation technique (IPS) operating at 140 MHz. (3) The Cosmic Ray Observatory (RC) detects high energy galactic particles, whose flow is affected by magnetic disturbances in the solar wind, and (4) the Teoloyucan Geomagnetic Observatory (TEO) measures the variations in the Earths magnetic field. The VESO instruments provide data from four different points of the complex chain of the solar terrestrial relations and will allow the study of intense solar events causing geomagnetic activity. The VESO project is part of the celebration of the International Heliophysical Year (IHY) and the Electronic Geophysical Year (EGY) in Mexico.  相似文献   

5.
杨合群 《西北地质》2002,35(3):126-130
地球磁场极性在地质历史中发生过相当频繁的倒转。作者将地球内部划分为岩石圈-软流圈-中圈-液圈-固核等5个动力学圈层,认为中圈与固核间可异步旋转;地球偶极磁场由中圈与固核异步旋转时所驱动的液圈中的封闭涡流与系磁场作用产生;该偶极子场极性由地球所通过的银道面上侧或下侧磁场方向及液圈涡流的方向共同决定,二者之一反向,极性发生倒转。  相似文献   

6.
The voltage stability problem in long-distance transmission systems can be exacerbated by geomagnetic disturbance (GMD) even in middle and low latitude areas where the effects of GMDs are considered to be mild compared to auroral areas. With the high voltage and the long-distance transmission lines, power system in China has to face the voltage instability risk. To clarify and measure the risk from GMD represented by geoelectric field, method for analysis of relationship between voltage stability of the long-distance transmission system and the size and direction of geoelectric field is provided. On the basis of calculation for geomagnetically induced currents (GICs) of power system and the additional reactive power losses of transformer due to GIC, the model of long-distance transmission line affected by geoelectric field is established. To measure the impact on the voltage stability of power system and the sensitivity of voltage to geoelectric field, the voltage stability index and the set of voltage limit violation nodes are proposed and calculated considering different geoelectric field and different initial operation conditions of power system. By taking the Northwest 750 kV power system in China as an example, voltage stability with geoelectric field magnitude from 1 V/km to 10 V/km, direction (0°) from north to south (180°) is analyzed and the voltage stability index is calculated, and the set of voltage limit violation nodes are summarized as well. The results show that the method is feasible and the index can reflect actually the relationship between the long-distance transmission system voltage stability and the geoelectric field, and the set of the voltage limit violation nodes can indicate which nodes are most susceptible to GMD.  相似文献   

7.
国际地磁参考场的计算   总被引:1,自引:0,他引:1  
毛玉仙 《铀矿地质》1992,8(1):48-52
  相似文献   

8.
As the regions around active volcanoes succumb to large increases in population, particularly in the developing world where most of the high-risk volcanoes are located, the threat posed by eruptions becomes increasingly serious. Improvements in eruption forecasting are critical to combat this situation, for reducing injury and loss of life, and for minimizing the detrimental effects to local economies and to the fabric of society. Better-constrained forecasts are strongly dependent on geophysical and other data gathered during a program of volcano surveillance, and we reveal how, if interpreted in terms of static rock fracturing, analysis of changes in volcanic seismicity and ground deformation may be used to forecast more accurately the onset of eruptive activity. As illustrated by recent events at several volcanoes, studies of previous activity, increased levels of monitoring, and improved training of scientists are also all crucial to improving forecasts of impending eruptions.  相似文献   

9.
The method of rectangular harmonic analysis is applied to the geomagnetic field data from central India to isolate long wavelength magnetic anomalies associated with largescale crustal structures. The long-wavelength anomalies have accounted for approximately 20 % of the spatial variability of the residual magnetic field over the International Geomagnetic Reference Field. On the magnetic anomaly map, reflecting the surface expression of longwavelength anomalies, the Tapi-Narmada-Son zone is characterized by a feeble positive anomaly bounded by a strong negative anomaly. The anomaly pattern is believed to be caused by the large-scale undulation in Moho and related variations in the thickness of the lower (basaltic) crust. The other two prominent anomalies, the magnetic low striking northwest and the magnetic high trending east-northeast, appear to be related to the deep structural feature of the Godavari graben and the eastern Rajasthan lineament respectively.  相似文献   

10.
泥石流成因机理的非饱和土力学理论研究   总被引:4,自引:2,他引:4  
泥石流是一种具有较强破坏力的自然山地灾害。对于它的预报研究历来为人们所重视,并建立了很多雨量预报模型。然而,这些雨量预报模型的预报时间很短,往往只能在灾害发生前几十分钟作出预报。论文应用非饱和土强度理论对降雨型泥石漉的成园机理进行了研究,提出降雨型泥石流的形成过程可以划分为2个阶段:第一个阶段与前期实效降雨量有关;第二个阶段与短历时强降雨有关。并对各个阶段降雨作用机理以及固体松散物质的力学性质变化特征进行探讨。为预先判断在降雨条件下,会不会发生泥石流以及所需要的降雨量和雨型提供依据。  相似文献   

11.
The recent improvement of numerical weather prediction (NWP) models has a strong potential for extending the lead time of precipitation and subsequent flooding. However, uncertainties inherent in precipitation outputs from NWP models are propagated into hydrological forecasts and can also be magnified by the scaling process, contributing considerable uncertainties to flood forecasts. In order to address uncertainties in flood forecasting based on single-model precipitation forecasting, a coupled atmospheric-hydrological modeling system based on multi-model ensemble precipitation forecasting is implemented in a configuration for two episodes of intense precipitation affecting the Wangjiaba sub-region in Huaihe River Basin, China. The present study aimed at comparing high-resolution limited-area meteorological model Canadian regional mesoscale compressible community model (MC2) with the multiple linear regression integrated forecast (MLRF), covering short and medium range. The former is a single-model approach; while the latter one is based on NWP models [(MC2, global environmental multiscale model (GEM), T213L31 global spectral model (T213)] integrating by a multiple linear regression method. Both MC2 and MLRF are coupled with Chinese National Flood Forecasting System (NFFS), MC2-NFFS and MLRF-NFFS, to simulate the discharge of the Wangjiaba sub-basin. The evaluation of the flood forecasts is performed both from a meteorological perspective and in terms of discharge prediction. The encouraging results obtained in this study demonstrate that the coupled system based on multi-model ensemble precipitation forecasting has a promising potential of increasing discharge accuracy and modeling stability in terms of precipitation amount and timing, along with reducing uncertainties in flood forecasts and models. Moreover, the precipitation distribution of MC2 is more problematic in finer temporal and spatial scales, even for the high resolution simulation, which requests further research on storm-scale data assimilation, sub-grid-scale parameterization of clouds and other small-scale atmospheric dynamics.  相似文献   

12.
Herein we document and interpret an absolute chronological dating attempt using geomagnetic paleointensity data from a post-glacial sediment drape on the western Antarctic Peninsula continental shelf. Our results demonstrate that absolute dating can be established in Holocene Antarctic shelf sediments that lack suitable material for radiocarbon dating. Two jumbo piston cores of 10-m length were collected in the Western Bransfield Basin. The cores preserve a strong, stable remanent magnetization and meet the magnetic mineral assemblage criteria recommended for reliable paleointensity analyses. The relative paleomagnetic intensity records were tuned to published absolute and relative paleomagnetic stacks, which yielded a record of the last ∼8500 years for the post-glacial drape. Four tephra layers associated with documented eruptions of nearby Deception Island have been dated at 3.31, 3.73, 4.44, and 6.86 ± 0.07 ka using the geomagnetic paleointensity method. This study establishes the dual role of geomagnetic paleointensity and tephrochronology in marine sediments across both sides of the northern Antarctic Peninsula.  相似文献   

13.
Published and new data on the Earth’s past magnetic field have been interpreted in terms of its links with the frequency of magnetic polarity reversals and with tectonic events such as plume-related eruptions and rifting. The paleointensity and reversal frequency variations show an antiphase correlation between 0 and 160 Ma, and the same tendency likely holds for the past 400 Myr. The geomagnetic field intensity averaged over geological ages (stages) appears to evolve in a linearly increasing trend while its variations increase proportionally in amplitude and change in structure. Both paleointensity and reversal frequency patterns correlate with rifting and eruption events. In periods of high rifting activity, the geomagnetic field increases (15 to 30%) and the reversals become about 40% less frequent. Large eruption events between 0 and 150 Ma have been preceded by notable changes in magnetic intensity which decreases and then increases, the lead being most often within a few million years.  相似文献   

14.
地磁场数据处理涉及的内容颇多。实际工作中,应该针对地磁场异常特点和需要解决的地质问题,必须抓住数据处理的关键技术。本文通过对已知矿区地磁场数据的曲化平、向下延拓、局部场和背景场的分离等关键技术的应用,结果表明,经三种地磁场数据处理关键技术的应用,取得了良好的地质效果。  相似文献   

15.
Geomagnetic effects related to the stresses induced by the water load of the Chiotas reservoir (NW Italy) were studied, with measurements of the geomagnetic field at different stages of filling. The highest effect, mean 7 nT, was recorded at three-quarters full; subsequently, as the volume of water increased, the anomalous variations fell to about 2 nT.  相似文献   

16.
Particle-laden turbulent flows, called dilute pyroclastic density currents, can be generated during explosive volcanic eruptions. They are the most hazardous events of interaction with buildings and human environments in volcanic areas. A qualitative comparison with the dusty turbulent shear currents generated after the Twin Towers collapse on September 11, 2001 shows that turbulent, multiphase flow-building interaction causes flow separation and recirculation around the buildings. This simple idea could be applied to dilute pyroclastic density currents, and improved in future by adhoc numerical simulations of flow-building interaction.  相似文献   

17.
Between 1973 and 1986 a group at the University of Wisconsin worked on the use of the periodic portion of climatic time series with the aim of exploring the potential for year-or-more in advance forecasting. This paper reports on the real time verification of the last sets of forecasts made by the group. From spectra of temperature and cube-rooted precipitation the dominant frequencies were chosen. These were usually related to tidal frequencies. A Fourier series of these dominant terms was then fitted to the dependent data set and future values calculated. These were analyzed for forecast skill, and the skillful Fourier series retained. Real time forecasts were then made. Verification shows a low probability that the forecast skills were obtained by chance. It is suggested that the periodic term might be a useful addition to more standard approaches to long range forecasting.  相似文献   

18.
The magnetic measurements of declination (D), horizontal (H) and vertical (Z) components of earth’s magnetic field, collected from ground surveys between 1962 and 1966, are used to develop an analytical model of geomagnetic field variations over Indian region for the epoch 1965. In order to reflect spatial features with wavelengths of approximately 1000 km, sixth degree polynomial as a function of differential latitude and longitude is calculated by the method of least squares. The root mean square fit of the model to the input data is better than that accounted by the International Geomagnetic Reference Field for 1965.0. Isomagnetic charts drawn forD, H, Z and total force (F) reflect more details than that shown on world magnetic charts. Further, the values of the field at common repeat stations recorded between 1962 and 1974, after eliminating the field values for the epoch 1965.0, are used to get the secular variation as well as its spatial dependence again by means of polynomial which now includes coefficients which are functions of time and of geographical locations. The accuracy of coefficients is tested against the behaviour of secular variation at permanent magnetic observatories. The merits and limitations of the model are discussed.  相似文献   

19.
Palaeomagnetic and palynological studies have been made of the sediments of two Finnish lakes. Geomagnetic field changes in Finland can be traced since lake sediments record the ambient geomagnetic field at, or close to, the time they are deposited. Pollen analyses provided a useful method of dating these changes since 14C dates proved to be misleading.  相似文献   

20.
Western Canada lies in a zone of active tectonics and volcanism, but thedispersed population has witnessed few eruptions due to the remoteness of the volcanoes and their low level ofactivity. This has created a false perception that Canada's volcanoes are extinct.There are more than 200 potentially-active volcanoes in Canada, 49of which have erupted in the past 10,000 years. They occur in five belts, with origins related totectonic environment. The minimum annual probability of a Canadian volcanic eruption is approximately 1/200;for an effusive (lava) eruption the probability is about 1/220, and for a significant explosive eruptionit is about 1/3333. In-progress studies show that there have been earthquakes associated with at least 9 ofthe youngest Canadian volcanoes since 1975. A scenario of an eruption of Mt. Cayley (50.1°N,123.3°W) shows how western Canada is vulnerable to an eruption. The scenario is basedon past activity in the Garibaldi volcanic belt and involves both explosive and effusive activity.The scenario impact is largely a result of the concentration of vulnerable infrastructure in valleys.Canadian volcanoes are monitored only by a regional seismic network,that is capable of detecting a M > 2 event in all potentially-active areas.This level of monitoring is probably sufficient to alert scientistsat or near eruption onset, but probably insufficient to allow a timelyforecast of activity. Similarly the level of geological knowledge about the volcanoes is insufficient to createhazard maps. This will improve slightly in 2002 when additional monitoring is implemented in theGaribaldi volcanic belt. The eruption probabilities, possible impacts, monitoring limitations and knowledgegaps suggest that there is a need to increment the volcanic risk mitigation efforts.  相似文献   

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