共查询到19条相似文献，搜索用时 250 毫秒
1.
舒曼谐振是由闪电激发的电离层与地面之间的全球电磁震荡,在地球与电离层空腔中传播,由于共振作用,其电磁波能量明显高于其他频率电磁波能量.舒曼谐振具有稳定的频域参数和频谱结构,近几年的研究发现,地震发生前会使这些固有参数发生扰动,因此利用舒曼谐振异常来进行地震短临监测可能是一种行之有效的手段.要判断舒曼谐振地震电磁异常,了解舒曼谐振电磁场背景变化规律是前提.本文利用极低频电磁台站观测的天然电磁场数据,处理和分析了各台站观测的舒曼谐振频率电磁场功率谱随时间的变化,得到了舒曼谐振随季节和纬度的背景变化规律.并提出将舒曼谐振背景变化规律应用到地震短临监测预报中,能够为今后辨别地震监测中的舒曼谐振异常提供物理依据. 相似文献
2.
重力测量中需要扣除大气的影响.大气负荷对重力测量的影响可以分为大气质量变化引起的直接效应和大气负荷引起的地球变形带来的间接效应,大气负荷对重力观测值的直接影响,相对于间接效应量级较大.本文从理论上研究了大气负荷对重力观测的直接影响,仿照Farrell定义的负荷格林函数,引入大气重力格林函数,用来表示大气压变化对于重力观测的直接引力影响.在前人的基础上,本文采用了更为精细的大气模型,考虑大气温度随高程的变化,用离散褶积的方法求得了大气重力格林函数的理论值.实际计算时还要考虑地表温度、台站高程、周围地形等因素的影响,本文讨论了这些因素对大气重力格林函数的影响.考虑地表温度、台站高程、地形改正等各种影响因素以及地球变形引起的间接效应后,对台站周围区域积分即可求得大气变化引起的理论重力信号. 相似文献
3.
利用1951～2000年中国东北地区23个台站资料，对东北夏季气温的时空分布进行了研究，发现其变化除具有整体的一致性外，东北南部和北部的夏季气温在年际和年代际时间尺度都表现出很大不同，其中北部区域的夏季气温在1987～1988年间发生了一次显著的气候突变. 另外，剔除夏季气温全区一致变化的年份后，南北两区夏季气温与大气环流和海表温度的关系表明：突变前，影响北部和南部冷/热夏季的大气环流形势存在显著的不同，关键海域亦有很大差异：影响南部的为中纬度西太平洋和印度洋部分海域，影响北部的主要为ENSO事件；突变后，两区的夏季气温及相应大气环流和关键海区都趋于一致. 在整个分析时段内，北部夏季气温与东亚夏季风存在显著负相关，而南部的关系则不明显. 相似文献
4.
基于标准大气定律和大气圆柱体分布模型,本文引进了大气重力格林函数,用离散格积方法求得了大气对重力场观测的影响,对台站高程、周围地形和地表温度变化等因素的影响问题进行了讨论．结果说明台站近区气压变化是大气重力信号的主要贡献者,考虑大气质量负荷引起的弹性地球形变效应后,对距台站0．5°的区域积分获得的大气重力导纳值为-0．3603μGal／hPa,占全球大气变化引起的总信号的90％以上,这一理论模型结果与超导重力仪实测结果相吻合,并能较有效地用于消除重力观测中的气压干扰成分． 相似文献
5.
地倾斜观测的温度干扰分为太阳照射引起的热倾斜和室温变化影响两部分。木文从热膨胀的角度推导了热倾斜的计算公式。地层的热倾斜除了与地面温度变化幅度、岩石的性质,洞室的覆盖厚度有关以外,地形的坡度也是一个重要因素。但是即使地形坡度很陡的情况下,覆盖厚度达30米以后,热倾斜的年变化幅度可以保证小于0.02秒。我们以张家口台站为例,说明室温变化是山洞内倾斜仪的主要干扰。估算了短周期室温变化引起仪器本身及仪器墩的倾斜量。地倾斜观测的温度干扰有两种方式:一是由大气温度的变化在地层中传导的不均匀性所产生的所谓“热倾斜”,二是仪器洞内室温变化对仪器或墩基的直接影响。本文试图对这两种干扰的量级作一初步探讨。 相似文献
6.
给定1948～1999年逐月变化的全球观测的海表温度分布，使用全球大气环流模式（CCM3/NCAR）模拟了大气对海表温度变化的响应，利用SVD和合成检验方法，分析了El Nino发展阶段夏季、成熟阶段冬季以及衰亡阶段夏季东亚大气环流的年际异常型.结果表明：El Nino发展阶段夏季，中国东北、朝鲜半岛以及日本海附近为高度负异常中心，西太平洋副高偏弱、偏东，东亚夏季风增强；El Nino成熟阶段冬季，东亚大槽加强，东亚北部冬季风加强；El Nino衰亡阶段夏季，西太平洋副高偏强、偏南、西伸，东亚夏季风减弱；El Nino事件在其衰亡阶段夏季与东亚大气环流异常的关系最紧密，其次是成熟阶段冬季，最后是发展阶段夏季.模拟的El Nino演变不同阶段东亚大气环流年际异常型易于解释以往研究中观测分析揭示的由El Nino造成的我国东部气温和降水异常型. 相似文献
7.
地表温度变化可以引起GPS台站上安装GPS天线的地表水泥墩内部温度变化,还可以通过热传导的方式引起GPS台站基岩温度变化,从而引起GPS台站垂直位移变化.在中国区域,由GPS台站基岩温度变化引起GPS台站垂直位移变化的周年振幅最大可以达到1 mm;在长江以北地区,此周年振幅一般大于0.5 mm.在我国地壳运动观测网络中的23个GPS基准站中,温度变化对GPS台站垂直位移总影响的周年振幅最大值为2.8 mm,其中13个GPS基准站垂直位移的周年振幅变化大于1 mm.因此,温度变化是引起GPS台站垂直位移周年变化的一个不可忽视因素. 相似文献
8.
9.
地电阻率年变化与气象因素及水位的关系 总被引：6，自引：0，他引：6
为了消除ds 观测资料中的年周期变化,对宝坻、塘沽地震台的地电阻率观测资料与台站附近地区的气压、气温、相对湿度、水位及海水水位的同期资料进行了相关处理分析, 并对地电阻率年周期变化产生的原因进行了分析,认为产生地电阻率与气象要素年周期变化的外因是同一源场作用的结果。 而地电阻率变化的内因,则是基于地下咸水层厚度的改变及地壳应力场的变化。 采用最小二乘法由气象参量和水位变化拟合出地电阻率模型值, 并计算出观测值与拟合值的残差,以消除电阻率观测资料中的年周期变化。结果表明, 近年来华北地区发生的 6级左右地震前,在宝坻、塘沽地震台的观测资料中均存在明显的短期前兆异常。 相似文献
10.
绝对地磁测量预报地震 总被引：3，自引：0，他引：3
介绍一种称为地磁等变线预报法的地磁绝对测量预报地震的新的处理方法。该方法既可将全国分散的地磁台站联系起来，使原来不能发挥作用的台站起到应有的作用，也可避免校正长期变差异的麻烦，达到大台距台站之间可直接作差值图的目的。这样，可能为地磁绝对测量预报地震开辟一个新的途径，为该手段在预报地震中起到更大的作用创造一定的条件。 相似文献
11.
舒曼谐振异常现象与地震活动性有较好的相关性,舒曼谐振异常现象可能与地震电离层扰动有关,是岩石层-大气层-电离层耦合的重要体现之一.本文详细介绍了云南舒曼谐振地震前兆观测台的系统结构和仪器参数,以及统计分析和震例分析的结果.永胜台观测数据显示2011年3月10日云南盈江M5.8级地震震前3天By分量出现舒曼异常,2011年1月23日临沧东部M4.0级地震震前2天By分量出现舒曼异常;通海台观测的By分量频谱分析结果显示,2011年5月22日红河州M4.2级地震当日前3阶谐振频率对应谱密度出现强烈扰动.研究表明,舒曼谐振地震前兆监测是一种可行的监测手段. 相似文献
12.
The present study is based on simultaneous measurements of the atmospheric electric potential gradient (PG) and Schumann resonances at Nagycenk station (Hungary) from 1993 to 1996. Annual and semiannual variations detected previously in the relative amplitudes of Schumann resonances (SR) in the first three modes are confirmed by the extended data series applied here. The regular annual variation found in the PG (with winter maximum and summer minimum) is in the opposite phase, compared to that of the SR amplitudes. Nevertheless, even the PG (being a parameter of the DC global circuit) occasionally shows a distinct secondary peak in summer as indicated by the results of the present analysis (and corresponding to a recent study on further parameters of the DC global circuit). In spite of the presumed dominance of local influence over the global one, a suitable PG parameter correlates well with SR (representing the AC global circuit) on the annual time scale. It also became evident that a semiannual variation (with spring and autumn maxima and winter and summer minima) is generally present in SR. Certain signatures of a semiannual variation have also been revealed in the PG, however, the phase of this semiannual variation does not fit the pattern shown by SR (and tropical surface air temperature, respectively). The representativeness of the PG data has also been checked by means of a single day’s diurnal variations displaying a phase corresponding to that of the ‘Carnegie Curve’. Additionally, the coincidence of short-term changes (lasting some hours) both in the SR and the PG parameter is also demonstrated on a day disturbed by local factors. The results are discussed in the context of correlations between surface air temperature and parameters of the atmospheric electric global circuit shown by previous studies. 相似文献
13.
The monitoring of global lightning activity and its spatial and temporal variations is known to be very essential for the
study of global warming, the subject of greatest concern to human beings on planet Earth today. As a method of remote sensing
for the global lightning distribution, we have proposed an inverse problem by using the data of natural electromagnetic noise
in the ELF (extremely low frequency) Schumann resonance (SR) band observed simultaneously at a few stations around the world.
The fundamentals of this inversion problem (or ELF tomography) to the SR data have been presented and the first attempt to
deduce the global lightning distribution by means of the real SR data has been performed, which has indicated a possibility
of snapshots of well-known thunderstorm centers on the globe. This ELF tomography consists of two stages. The first stage
is the inversion of the ELF field power spectra to the distribution of lightning intensity by distance relative to an observation
point. The obtained distance profiles of intensity of sources at a few stations are used as tomographic projections for reconstructing
a spatial distribution of sources in the second stage. Maps of the global lightning distributions constructed by the result
of inversions of ELF background field spectra obtained from three stations around the world show that the most active regions
vary meridionally on the diurnal time scale being connected mainly with continental areas in the tropics. We do hope that
this kind of inversion method to multi-stationed ELF data will be of great importance in the future. 相似文献
14.
The time variations in the galactic cosmic ray (GCR) intensity at Apatity stations have been compared to the amplitude of the first Schumann resonance (as an indicator of the global thunderstorm activity power) for 12 cases of Forbush decreases in GCRs. A performed analysis indicated that the amplitude of the first Schumann resonance decreased only once during a Forbush decrease in GCRs as compared to the quiet conditions (during the strongest event in January 2005). In the remaining cases, a statistically significant effect was not observed. 相似文献
15.
Martin J. Jarvis 《Surveys in Geophysics》2001,22(2):155-174
Within the global context, Antarctica has a key role to play in understanding long-term change in the upper atmosphere, both because of its isolation from the rest of the world and because of its unique geophysical attributes. Antarctic upper atmosphere data can provide global change observations regarding the mesosphere, thermosphere, ionosphere, plasmasphere and magnetosphere. It will not only provide trend estimates but, just as importantly, it will define the background variability which exists in the upper atmosphere and against which these trends must be resolved. Upper atmospheric change can be driven both from within the Earth's near environment primarily through changing atmospheric composition, dynamics or geomagnetic field, or it can be driven externally, predominantly by the Sun. Recent observations are discussed in the light of increasing interest in global change issues and sun-weather relationships. 相似文献
16.
Marek Gołkowski Marek Kubicki Morris Cohen Andrzej Kułak Umran S. Inan 《Acta Geophysica》2011,59(1):183-204
Variations in the global atmospheric electric circuit are investigated using a wide range of globally spaced instruments observing
VLF (∼10 kHz) waves, ELF (∼300 Hz) waves, Schumann resonances (4–60 Hz), and the atmospheric fair weather electric field.
For the ELF/VLF observations, propagation effects are accounted for in a novel approach using established monthly averages
of lightning location provided by the Lightning Image Sensor (LIS) and applying known frequency specific attenuation parameters
for daytime/nighttime ELF/VLF propagation. Schumann resonances are analyzed using decomposition into propagating and standing
waves in the Earth-ionosphere waveguide. Derived lightning activity is compared to existing global lightning detection networks
and fair weather field observations. The results suggest that characteristics of lightning discharges vary by region and may
have diverse effects upon the ionospheric potential. 相似文献
17.
Daniel Labendz 《Journal of Atmospheric and Solar》1998,60(18):1779-1789
The Earth–ionosphere cavity is characterized by a number of disturbances which cause departures from the behaviour expected for the spherical symmetric case usually applied in model calculations. The main effects are the inhomogeneity of the upper atmosphere which is characterised by different conductivity profiles during day and night, and the conductivity anisotropy introduced by the Earths magnetic field. Standing waves, excited by the global thunderstorm activity, with an eigenfrequency of ≈8 Hz develop in this cavity. This phenomenon, which is called Schumann resonance, suffers a frequency splitting due to the removal of the spherical symmetry.At the Institut für Geophysik we measured the electromagnetic field components for a whole year at frequencies up to 20 Hz. We present the results of the analysis of the polarization of individual events of the horizontal magnetic field components. With the help of the polarization parameters as indicators, we show the existence of the aforementioned splitting. A frequency difference of 0.1–0.2 Hz between the two elliptical modes has been estimated. 相似文献
18.
V. V. Pchelkin M. I. Beloglazov A. N. Vasiliev A. I. Voronin 《Geomagnetism and Aeronomy》2010,50(5):623-631
The observation results of Q-type bursts in the measurements of the horizontal component of the noise magnetic field in the range of the first Schumann
resonance in polar regions (Lovozero high-latitude observatory) are presented. Automatic selection of Q-type bursts from the experimental data series is implemented on the basis of a waveform recognition algorithm. The resonant
nature of Q-bursts is shown. The possibility of selecting such events in magnetic excitation conditions is highlighted. The global resonator
quality upon decreasing the selected waveform amplitudes is estimated. The data obtained by this method are compared with
estimates on the basis of Fourier analysis and values known from the world literature. The possible reasons for disagreements
of the estimates are analyzed, including the problem of selecting the function approximating the spectrum, the problem of
accounting for the background, and the possible irregularity of the spectrum. It is shown that Q-type bursts, besides the quality, allow estimating the resonant frequency of the first oscillation mode; however, the accuracy
of such estimation is lower as compared to the results of Fourier analysis methods. 相似文献
19.
通过功率谱分析和波阻抗函数计算,本文证实了Aureol 3卫星在电离层高度上(>600km)观测到的极低频(ELF)波场扰动是和舒曼共振相关的电磁振荡.与舒曼共振地面观测相比较,Aureol 3观测到的舒曼共振电场分量具有很好的谐振谱结构,峰值频率和各阶舒曼共振本征频率对应;磁场分量的高阶峰值频率偏离14, 20, 26Hz等舒曼共振本征频率;随着卫星高度的改变,电场与磁场谐振的一阶最大能量峰值并不会发生在同一频率,结合本文分析的数据,分别位于78Hz和10Hz;水平方向的磁场分量更接近南北方向的线极化而不是地球－电离层空腔中的椭圆极化;波阻抗随频率表现出不太规则的准正弦振荡,它会随着频率增加和飞行高度上升呈现减小的趋势.虽然舒曼共振信号和电离层密度梯度间的非线性作用可以解释舒曼共振空间观测的部分特征,但需加入其他机制,如电离层不稳定性,传播模式的耦合,进一步了解电离层高度上舒曼共振各种特征产生的原因. 相似文献