某些测震学指标与地震相关性研究   总被引：3，自引：0，他引：3  

张军  黄显良 《地震》1998,18(2):171-176

通过对１０项测震学指示宾１０ａ的大范围时空扫描得出的有震和无震“预报”进行了与５．０级以上的地震的相关性研究,结果证明这１０项指标当显性水平较低时,均可通过统计检验,表明是有效的提取异常指标。作还依统计检验结果对１０项测震学指标与地震相关性好坏进行了排序,并通过分析得到各指标今后优化方向．  相似文献   

The spatial and temporal changes inV p /V s before strong earthquakes in Kamchatka     

G. A. Sobolev  L. B. Slavina 《Pure and Applied Geophysics》1977,115(4):1047-1060

A method was developed to obtain from a signal station the spatial and temporal distribution ofV _p /V _s ratios before earthquakes of magnitude>6. It was shown thatV _p /V _s values strongly depend upon the relative positions of the stations, the future large earthquake and the foci of the smaller earthquakes used forV _p /V _s determination. The appearance of a zone of anomalousV _p /V _s values with linear dimensions of the order of 100 km was noted at least 4 years before a deep earthquake of magnitude 7. Similar size anomalous zones were detected one year before some magnitude 6 earthquakes. V _p /V _s values decreased by a small but distinct amount during this time. Additionally, local short term minima inV _p /V _s ratios were observed some months before the major event. The epicenters of the large earthquakes were located within the 100 km size zone where the gradients of theV _p /V _s field were largest.  相似文献   

The Dependence of the Geoeffectiveness of Interplanetary Flux Rope on Its Orientation,with Possible Application to Geomagnetic Storm Prediction     

Yuming Wang  Pinzhong Ye  S. Wang 《Solar physics》2007,240(2):373-386

Interplanetary magnetic clouds (MCs) are one of the main sources of large non-recurrent geomagnetic storms. With the aid of a force-free flux rope model, the dependence of the intensity of geomagnetic activity (indicated by Dst index) on the axial orientation (denoted by θ and φ in GSE coordinates) of the magnetic cloud is analyzed theoretically. The distribution of the Dst values in the (θ, φ) plane is calculated by changing the axial orientation for various cases. It is concluded that (i) geomagnetic storms tend to occur in the region of θ<0°, especially in the region of θ≲−45°, where larger geomagnetic activity could be created; (ii) the intensity of geomagnetic activity varies more strongly with θ than with φ; (iii) when the parameters B ₀ (the magnetic field strength at the flux rope axis), R ₀ (the radius of the flux rope), or V (the bulk speed) increase, or |D| (the shortest distance between the flux rope axis and the x-axis in GSE coordinates) decreases, a flux rope not only can increase the intensity of geomagnetic activity, but also is more likely to create a storm, however the variation of n (the density) only has a little effect on the intensity; (iv) the most efficient orientation (MEO) in which a flux rope can cause the largest geomagnetic activity appears at φ∼0° or ∼ 180°, and some value of θ which depends mainly on D; (v) the minimum Dst value that could be caused by a flux rope is the most sensitive to changes in B ₀ and V of the flux rope, and for a stronger and/or faster MC, a wider range of orientations will be geoeffective. Further, through analyzing 20 MC-caused moderate to large geomagnetic storms during 1998 – 2003, a long-term prediction of MC-caused geomagnetic storms on the basis of the flux rope model is proposed and assessed. The comparison between the theoretical results and the observations shows that there is a close linear correlation between the estimated and observed minimum Dst values. This suggests that using the ideal flux rope to predict practical MC-caused geomagnetic storms is applicable. The possibility of the long-term prediction of MC-caused geomagnetic storms is discussed briefly.  相似文献   

Deterministic and ensemble storm surge prediction for Atlantic Canada with lead times of hours to ten days     

《Ocean Modelling》2015

Regional deterministic and ensemble surge prediction systems (RDSPS and RESPS respectively) are used to forecast sea levels off the east of Canada and northeast US. The surge models for the RDSPS and RESPS have grid spacings of 1/30° and 1/12° respectively. The models are driven by surface air pressure and 10 m winds generated by operational global deterministic and ensemble prediction systems that are run operationally by the Canadian Meteorological Centre. Surge forecasts are evaluated for the period 1 March, 2013 to 31 March 2014. Based on traditional statistics (e.g., standard deviation of the difference between observations and predictions) both systems are shown to have skill in forecasting surges six days into the future. It is shown however that skill exists beyond six days if allowance is made for errors in the timing of large surges. The usefulness of the RESPS is demonstrated for two positive surges (important for coastal flooding and erosion) and a negative surge (important for safe navigation in shallow water). It is shown that the RESPS can identify events not forecast by the RDSPS, and can also add useful additional information on the timing of the surge, an important consideration in tidally dominated waters. Several new types of display are used to illustrate the sort of information that can be generated by the RESPS to support the issuers of warnings of unusually high and low total water levels.  相似文献   

论河南“75.8”特大暴雨的研究:回顾与评述   总被引：1，自引：0，他引：1  

丁一汇 《气象学报》2015,73(3):411-424

“75.8”河南特大暴雨的发生已经过去40年了,它在人们的记忆中留下深刻的印象。这场暴雨在1975年8月5—7日3 d之内在河南南部的局部地区降下了1605 mm的总雨量,1、3、6、12 h雨量均破中国降水的历史记录。由于水库垮坝,洪水夺走了该区约2万6千人的生命,经济损失巨大。在这40年间,中国的暴雨研究和预报都取得了重大的进展。其中一个重要原因是中国的气象和水文部门从这场空前强烈的大暴雨和大洪水事件中吸取了宝贵的经验教训,多年来,以这场超级大暴雨洪水为借鉴,不断促进和鼓励中国气象学家向暴雨研究和预报发展的更高目标前进。有感于此,回顾和评述了当年老一辈科学家在比较艰苦的条件下所进行的这次大暴雨的研究活动,以及所获得的卓越科学成果。即使从今天来看,其中不少成果也具有创新性的意义,在中国暴雨研究的发展史上,占有十分重要甚至里程碑式的地位。文中重点对其中的关键科学问题进行了评述,包括:(1)“75.8”特大暴雨的雨情和极值;(2)“75.8”特大暴雨发生的原因;(3)“75.8”特大暴雨的动力诊断;(4)暴雨中尺度分析;(5)地形对暴雨的增幅作用。希望以此纪念河南“75.8”特大暴雨发生40周年,并表达对参与此次研究活动的老一辈科学家深深的怀念和敬意。  相似文献   

Socio-economic drivers of deforestation in Roghani Valley,Hindu-Raj Mountains,Northern Pakistan   总被引：1，自引：1，他引：0  

Fazlur RAHMAN  Fazlul HAQ  Iffat TABASSUM  Ihsan ULLAH 《山地科学学报》2014,11(1):167-179

Deforestation and associated ecological disturbances are the issues of global concern.Researchers have investigated a number of driving forces which accelerate the rate of deforestation at local and regional levels.These include poverty,population growth,market demand and prices,political instability,agricultural expansion and changes in property right and ownership regimes.This paper seeks to explore the impacts of population growth,changing tenure system and other socioeconomic factors on the forest cover of Roghani Valley,located in Hindu Raj Mountains,Northern Pakistan.The present study is mainly based on information collected through participatory observation,selfadministered interviews and questionnaire survey.Geographical Information System（GIS） database is also used for mapping and quantification.The results reveal that in the past three to four decades the study area has been subjected to severe deforestation and about half of the forest area has been converted into barren land.Thus,the area under natural forests decreased from 2099 to 1444 hectares in four decades.This large-scale deforestation is attributed to both proximate and under lying causes particularly traditional land tenure system and demographic development.Consequently,forest resources have been degraded and a number of plant species have disappeared from the forests of the study area while several others are in the process of disappearance.  相似文献   

基于EEMD的黄河中上游夏季降水预报方法的研究   总被引：3，自引：0，他引：3  

王文  任冉  李耀辉 《气象科学》2014,34(3):261-266

传统的统计方法难以很好的对气候系统这一集非线性、非平稳性为一身的多层次系统进行处理。因此集层次化处理和平稳化处理的集合正交经验模态分解技术(EEMD)的提出,为解决上述问题提供了有效的途径。本文选取黄河中上游24个气象观测站的逐月降水资料,结合组合预报和集合预报思路,基于EEMD建立了统计预报模型。其中对降水序列中的高频部分进行了二次平稳化处理,实现对2008—2013年6—8月的降水预报,并用预报评分检测预报效果。结果表明:EEMD模型对黄河中上游夏季降水有着较强的预报能力,在该区域与气候模式和传统的统计方法相比具有更高的精度和更好的应用前景。  相似文献   

Introduction to systems approaches in coastal management—The legacy of the SPICOSA project     

《Marine Policy》2014

This Special Issue reflects work developed during and following the execution of the Science and Policy Integration for Coastal System Assessment project. Theoretical and practical outcomes of case studies have been of direct relevance to coastal management not only at local but also at a European scale. Papers included here consider the long term legacy of the project for academics and practitioners involved specifically in integrated coastal zone management. These align to two themes, the first focussing on the generic application of the Systems Approach Framework to coastal management and the second focussing on the specific application of the approach at case study sites.  相似文献   

Relevance of systems approaches for implementing Integrated Coastal Zone Management principles in Europe     

《Marine Policy》2014

Integrated Coastal Zone Management (ICZM) development is described here in the broader context of European coastal management initiatives. The European approach to coastal governance revolves around the principles of ICZM, as enshrined in EC Recommendation 2002/413/EC. This study investigates the extent to which the FP6 funded project SPICOSA (Science Policy Integration for Coastal Systems Assessment) was able to implement these principles. The SPICOSA project aimed to test whether it was possible to develop and implement a systems approach framework via delivery of a structured engagement process between scientists and policymakers. A survey of representatives from 14 European study sites involved in the project revealed that the approach had been effective at implementing some ICZM principles, particularly the “holistic approach”. However, not all principles were fully implemented at all sites and the most challenging to implement was that of “a long term approach”. The paper concludes with a critical consideration of the role of a systems approach framework in progressing the current state of intellectual assent towards practical implementation of ICZM principles. The findings provide evidence of contributions and limitations of systems approaches to sustainability science and good governance.  相似文献   

Decadal modes of sea surface salinity and the water cycle in the tropical Pacific Ocean: The anomalous late 1990s     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Limitations in sea surface salinity (SSS) observations and timescale separation methods have led to an incomplete picture of the mechanisms of SSS decadal variability in the tropical Pacific Ocean, where the El Niño Southern Oscillation (ENSO) dominates. Little is known regarding the roles of the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO) in the large-scale SSS variability over the tropical basin. A self-organizing map (SOM) clustering analysis is performed on the intrinsic mode function (IMF) maps, which are decomposed from SSS and other hydrological fields by ensemble empirical mode decomposition (EEMD), to extract their asymmetric features on decadal timescales over the tropical Pacific. For SSS, an anomalous pattern appeared during 1997 to 2004, a period referred to as the anomalous late 1990s, when strong freshening prevailed in large areas over the southwestern basin and moderate salinization occurred in the western equatorial Pacific. During this period, the precipitation and surface currents were simultaneously subjected to anomalous fluctuations: the precipitation dipole and zonal current divergence along the equator coincided with the SSS increase in the far western equatorial Pacific, while the weak zonal current convergence in the southwestern basin and large-scale southward meridional currents tended to induce SSS decreases there. The dominant decadal modes of SSS and sea surface temperature (SST) in the tropical Pacific both resemble the NPGO but occur predominantly during the negative and positive NPGO phases, respectively. The similarities between the NPGO and Central Pacific ENSO (CP-ENSO) in their power spectra and associated spatial patterns in the tropics imply their dynamical links; the correspondence between the NPGO-like patterns during negative (positive) phases and the CP La Niña (CP El Niño) patterns for SSS is also discussed.  相似文献