共查询到20条相似文献，搜索用时 187 毫秒
1.
应用TOGA-TAO实测海流资料(ADCP)和SODA同化海流和海温资料,分析探讨了赤道太平洋潜流的季节和年际变化特征,以及与赤道异常暖水东传的内在联系.揭示了El Nino事件中异常暖水东传的物理机制.结果表明,赤道太平洋潜流具有明显的季节变化和年际变化特征.潜流的垂直最大深度可由海表层至300~400 m,其多年平均最大流速可达100 cm/s.潜流最大中心的纬向变化位置基本维持在160°W-130°W之间.在年际变化中,赤道潜流变化特征非常明显,尤其是在El Nino事件发生过程中,赤道潜流出现明显的加强现象.其最大流速可达140 cm/s以上.在西太平洋暖池区域次表层暖水东传之前,位于中东太平洋次表层的赤道潜流就已出现加强,其最大流速中心沿温跃层不断加强和东移,“引导”来自西太平洋暖池区域次表层的异常暖水向东传播.因此,可以认为西太平洋暖池区域异常暖水的东传与赤道潜流的强度和东传存在密切关系,也就是说在El Nino事件中,赤道潜流的变化是导致西太平洋暖池区域次表层异常暖水东传的重要机制. 相似文献
2.
重力密度反演通过将地下剖分为多个网格,计算每个网格密度的方式来实现,现今方法计算结果分辨率较低。本文提出自适应权函数三维密度反演方法,通过上半空间不同高度异常凸显不同埋深地质体的特征,建立相应的空间异常权函数进行迭代反演,从而提升结果的收敛性和分辨率。模型试验表明,自适应异常权函数密度反演方法相对已有方法能有效提升分辨率和精度,且具有良好的抗噪声干扰能力。利用所提出的反演方法重建东海陆架盆地东部坳陷带空间密度结构,分析东部坳陷带中生界残留分布特征。结果表明,东部坳陷带内中生界分布南北差异明显,南部钓北凹陷中生界广泛分布,厚度较大,约4 km,颠覆了以往盆地北部西湖凹陷中生界较薄、两个凹陷中生界特征一致的认识。因此钓北凹陷中生界为陆缘坳陷型盆地,盆地范围局限于现今盆地中南部。 相似文献
3.
气候变化条件下青藏铁路沿线多年冻土概率预报(I):活动层厚度与地温 总被引：3，自引：3，他引：0
对1961-2100年IPCC气候模拟与预测结果进行降尺度处理,得到铁路沿线空间分辨率为1km、时间分辨率为1h的大气边界条件.对铁路和公路沿线钻孔资料在垂直和水平两个方向进行空间差值处理,得到水平1 km、垂直0.1m分辨率的沿线地下含水（冰）量的二维分布,作为初始条件.考虑气候模型预测误差和空间格网内地形的变化,以... 相似文献
4.
大深—福洋地区磁异常位于安溪县福田—漳平市大深一带,呈近东西向分布,长约19km,宽3~5km。该异常区规模大、强度高,磁场强度变化剧烈,磁场值-1 200~1 500nT;异常中心处位于漳平洛阳铁矿区,异常区出露石炭系下统林地组,二叠系下统文笔山组,三叠系上统文宾山组,侏罗系酸性火山岩及燕山期酸性岩体、喜山期中基性岩体。发育北西向断裂及近东西向复式褶皱。磁异常带反映了东西向构造带控制铁多金属矿及基性岩体的空间分布特征,区内成矿地质条件较好,具矽卡岩型铁矿和铁多金属矿的找矿前景。 相似文献
5.
高密度电阻率勘测方法分辨率研究与探讨 总被引：2，自引：0，他引：2
随着高密度电阻率法在工程中的应用日益广泛,对分辨率的影响因素分析研究也受到重视。论文以均匀半空间局部直立异常体为探测目标,建立多个基于温纳高密度电法装置的地电模型,采用有限元等方法进行正反演数值模拟分析,对高密度电阻率法探测分辨率的影响规律进行探讨。分析表明,地形起伏会引起异常体的位置与形态发生畸变和位移,分辨率降低; 电阻率差异增大,分辨率提高; 深径比增大,分辨率降低; 当异常体的水平范围一定时,探测分辨率随纵深的增大而提高。 相似文献
6.
7.
利用卫星数据考察平流层传播性行星波活动特征 总被引：2，自引：0，他引：2
中层大气是大气波动盛行的区域。这些波动不仅是这里大气扰动的主要形态,伴随其传播的耗散成为作用在背景流场上的动力强迫和作用于环境物质上的湍流混合,影响到了中层大气的各个方面,尤其对一些典型环流结构的形成起着控制作用。简要地回顾了这个研究领域发展的历史。与此同时,利用美国卫星温度探测数据（SABER/TIMED温度数据）考察了平流层（20~70 km高度范围）传播性行星波活动的整体性质,给出了他们的空间分布和年变化形式。利用温度标准差（T SDEV）代表行星波活动的强度,当前研究显示无论在热带外地区或以赤道为中心的热带地区,全年传播性行星波活动都是相当显著的。结合同期定常行星波活动强度分析结果,通过比较说明在热带外地区,传播性波动和定常波动表现出相近的季节活动性;从T SDEV数值看,在定常波活动达到最强的季节(冬末春初),这两类波动活动的强度达到了相当的程度（TSDEV=12~14 K）。当前结果还显示,在定常波活动受到显著抑制的夏季条件下,传播性波动成为平流层行星波活动的主导成分。在赤道地区的分析结果表明传播性波动是这里的控制性波动,并且其活动强度在全年都处在相当稳定的状态;T SDEV分析结果还给出了一个值得关注的现象,从平流层下部开始（20 km高度）逐渐随高度增大（大于2 K）,但是这种随高度增长的趋势在30 km高度左右突然终止;从30 km开始直到中间层底部,T SDEV几乎不随高度变化,这隐含地说明这里的波动处于一种饱和的状态。 相似文献
8.
9.
发现异常点是对逐时降水资料质量控制的有效方法,但简单的剔除未修正的异常点必然会影响其周围一定范围内降水量的空间变化。本文提出综合评分法定量的分析不同时段不同异常监测点被剔除后对降水量变化幅度的影响,探讨剔除区域异常点后降水量的时空变化分布特征。对宁德市降水资料进行实例验证,分析结果表明:在相邻站点数大于12个、相邻站点最近距离小于3km、相邻站点平均监测值大于6mm时,其降水量变化幅度相对较小,可剔除异常点。综合考虑三个相邻站点指标的综合分析可以显著表现不同时段不同监测站点降水量空间变化的地带性分布,在宁德市西北和东南区域出现高变化幅度站点的概率最高,呈现出高变化幅度站点多、分布范围广特点;在其东北区域监测站点分布不均匀,降水高变化幅度站点易受逐时降水量大小影响,呈现出小雨大范围、大雨小范围分布;在其西南和中部区域监测站点分布密集,出现高变化幅度站点的可能性最小。因此,综合分析可剔除区域异常点对降水量空间变化的影响特征,确定对降水量变化幅度影响最小的监测站点,有效提高了降水资料的质量控制水平。 相似文献
10.
在中国最大的铬铁矿罗布莎周边地区有着数目众多的含铬超镁铁岩体;分布广阔,具有很好的找矿前景,选择泽当岩体进行了重、磁、大地电磁法的剖面探测,结果表明:泽当岩体被近南北向断裂切割成多块,其西端岩体向北推移的距离远于东段的岩体,总体上呈北西西向展布;岩体磁异常由蛇纹石化产生的磁铁矿和岩体生成时剩余磁化引起,磁异常指出了岩体浅部的范围;航磁较大范围的异常表明存在较深部的磁性体;重力异常说明岩体局部存在高密度体,且与磁异常相吻合,地表出露的矿点多分布在此范围内;岩体表层为高阻薄层,在剖面中段高阻体厚度最大处达1.5 km,范围不大.在薄高阻体下为薄层低阻层.电阻率剖面两侧以高阻体为主,中段有多个低阻体,且与深部5～25km深度上的低阻体相连,中地壳范围的低阻体与幔源物质上涌在地壳范围留下的熔融体有关,与地壳上部的超镁铁岩体有关.综合各种地球物理场的特征认为在磁异常分布区内具有局部重力异常、低阻体异常较多的地段是泽当岩体最有利于进一步详细探测找矿的部位. 相似文献
11.
《Atmósfera》2014,27(3):227-237
The O+ ion density measured by the SROSS-C2 satellite during solar minima (year 1995, F10.7 = 77) and maxima (year 2000, F10.7 = 181) has been analyzed for studying diurnal, seasonal, latitudinal and geomagnetic variations. The study region covers an area encompassed between 5-3 5° N latitude and 65-95° E longitude over India at a ~500 km altitude (F2 region). The year 2000 shows significant enhancement in the annual average of O+ ion density and attainment of post sunset secondary enhancement compared to 1995. Attributed to photoionization, daytime shows a maximum ionization compared to nighttime. However, attainment of post sunset secondary maxima is attributed to the strong pre-reversal enhancement in the vertical E x B drift. The effect of geomagnetic activity Kp through the E x B drift dynamic movement on O+ ion density distribution studies indicates periodicities of seven and nine days in 1995 and 2000, respectively, and polynomial dependency of the O+ ion density on geomagnetic activity Kp. Further on, stratification of the O+ ion density according to latitude (5-35° N) indicates high density in mid-latitudes (12-24° N) compared to high and low latitudes, except in the winter of 1995, which shows a distinct trend (i.e., density decreases with increasing latitude). 相似文献
12.
The present study is carried out to examine the performance of a regional atmospheric model in forecasting tropical cyclones
over the Bay of Bengal and its sensitivity to horizontal resolution. Two cyclones, which formed over the Bay of Bengal during
the years 1995 and 1997, are simulated using a regional weather prediction model with two horizontal resolutions of 165 km
and 55 km. The model is found to perform reasonably well towards simulation of the storms. The structure, intensity and track
of the cyclones are found to be better simulated by finer resolution of the model as compared to the coarse resolution. Rainfall
amount and its distribution are also found to be sensitive to the model horizontal resolution. Other important fields, viz.,
vertical velocity, horizontal divergence and horizontal moisture flux are also found to be sensitive to model horizontal resolution
and are better simulated by the model with finer horizontal grids. 相似文献
13.
Short-term vertical velocity field in the Apennines (Italy) revealed by geodetic levelling data 总被引：2，自引：0，他引：2
E. D'Anastasio P.M. De Martini G. Selvaggi D. Pantosti A. Marchioni R. Maseroli 《Tectonophysics》2006,418(3-4):219-234
We estimate current vertical movements along the Apennines (Italy) through repeatedly measured high precision levelling routes. In order to highlight regional crustal deformation the analysis of a geodetic database, with a minimum benchmark density of 0.7 bm/km (1943–2003 time period), is carried out. We evaluate systematic and random error and their propagation along the levelling routes. Tests on original raw height data have been carried out to define error propagation. The computed relative vertical rates stand significantly above error propagation. A series of traverses along and across the Apennines and a map of relative vertical velocities reveal a geodetic signal characterised by values up to 2.5–3.0 mm/a and by wavelengths up to 100 km. 相似文献
14.
Some steps were taken recently for Hungary aiming at the determination of geoid heights with a cm-accuracy. The present HGTUB98 gravimetric solution was based on terrestrial gravity data, height data and the EGM96 geopotential model, and was computed with the 1D Spherical FFT method. The gravity data were used in the area 45.5 ° ≤ϑ ≤ 49 °, 16 ° ≤ λ ≤ 23 °, the resolution of the grid was 30″ × 50″. The DTM used had a resolution of 1 km × 1 km.Our solution was evaluated using GPS/levelling data at 340 and 308 points respectively and at 138 vertical deflection points. We have compared our solution to the European EGG97 geoid solution, the gravimetric solution HGR97B developed by A. Kenyeres and the litospheric geoid solution by G. Papp. We have correlated our recent HGTUB98 solution to the Moho model of Central Europe. The comparison with GPS/levelling yielded respectively an accuracy of ±8.7 cm and ±4.4 cm (in terms of standard deviation) when a linear trend was removed. The comparison of the 1D planar FFT solution for the deflections of the vertical with 138 astrogeodetic deflections yielded an accuracy (in terms of standard deviation) of ±0.62″ and ±0.52″ for ξ and η, respectively. 相似文献
15.
在详细论述GPS高程转换基本原理的基础上,利用二次多项式模型,对区域高程异常进行了拟合分析,并进行了精度评定。结果显示,利用二次多项式模型进行GPS高程转换能够取得较好的结果,参与建模的点位拟合精度较高,而远离建模点分布区域的点位拟合精度相对较低,建模点的选取能够对GPS高程拟合结果产生重要影响。 相似文献
16.
A modified ionospheric correction method and the corresponding approximate algorithm for spaceborne single-frequency Global Positioning System (GPS) users are proposed in this study. Single Layer Model (SLM) mapping function for spaceborne GPS was analyzed. SLM mapping functions at different altitudes were calculated. Ionospheric Pierce Point (IPP) trajectories of the dlft station (An IGS station located at the longitude of 4°23′15.22′′E and the latitude of 51°59′9.63′′N, in the TU Delft University, The Netherlands.) and the GRACE satellite were computed with the corresponding single layer height of 350 and 500 km, respectively. The Klobuchar model was used to compute ionospheric delays for the dlft station, and modified Klobuchar model, together with scale factors, was used to compute the fractional ionospheric corrections above the GRACE altitudes. Calculation results were validated using dual-frequency observations. The study shows that the single layer height needs to be changed from 350 to 500 km according to the altitude of GRACE. Approximate forms of Earth angle and slant factor developed for modified Klobuchar model are applicable to GRACE, with accuracy adequate to preserve the essential elements required to compute ionospheric delays. Results show that the Klobuchar model is effective for ground GPS, and the modified Klobuchar model corrects more than 80% on average of the ionospheric delays for spaceborne single-frequency GPS. 相似文献
17.
The spatial relations between ore deposits in Sikhote-Alin and deep density inhomogeneities of the Earth??s crust down to a depth of 30 km have been examined. The ore areas and regions show a discrete correlation with the anomalies of the normalized density of the equivalent spherical sources of gravity anomalies at depths of 1 to 2, 4 to 5, 10?C12, and 24 km presumably provoked by magmatic bodies of different compositions. The depth of the magmatic bodies with the intermediate-to-basic composition of the initial magmas and the southeastward-decreasing vertical range of their correlation with the ore regions depend on their structural position. In the case of magmatic bodies of felsic and mixed compositions, the metallogenic specialization of the corresponding ore-magmatic systems is correlated with their inferred vertical range. Tin ore systems are characterized by a smaller vertical range (5?C10 km) of the correlation with density inhomogeneities, whereas tin-tungsten-gold ore systems are marked by a wider range (20?C25 km). Tin-lead-zinc systems occupy an intermediate position (12?C20 km). The ore-controlling role of the boundaries between the lithostructural complexes of the Earth??s crust and the central-type structures in the distribution of deep sources of ore mineralization is shown. 相似文献
18.
The Apuseni Mountains are located between the Pannonian Basin and the Transylvanian Basin along a direction of SE convergence with the Carpathian belt. A flexural model based on the cylindrical bending of a semi-infinite, isostatically supported, thin elastic plate is here examined with the Apuseni playing the role of flexural bulge, and under the assumption that the plate is deforming under the action of a vertical shear force and a bending moment applied at the end of the plate, beneath the Carpathians. The model yields estimates of the plate thickness ranging between 13 and 14.5 km, depending on the assumed density contrast between crust/sediments and mantle providing buoyancy. The vertical shear force which is necessary to bend the plate is in the range between 60 and 300 × 1011 N m− 1, depending on the assumed density contrast. This force is shown to be modelled by a gravitational ‘slab pull’ force, using model parameters derived from seismic tomography. If the height of the flexural bulge, after correction for erosion, is allowed to increase, the model yields an estimate of the horizontal strain rate at the top of the bulge. For example, 5 mm/yr vertical change of the flexural bulge of a 14 km thick plate results in a horizontal deformation rate of approximately 7 nanostrain/yr at the top of the bulge, a value which is at the threshold of sensitivity of continuous GPS measurements. Different vertical rates will change the horizontal strain rate almost proportionally. 相似文献
19.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(5):449-454
A new composite map of magnetic surface (MAGSURF) anomaly for Italy and its adjacent region has been derived from sea and ground surveys on the basis of an improved definition of the Italian Magnetic Reference Field and its temporal change. Spectral analysis of the MAGSURF anomaly field shows a regional scale energy in the wavelength range 145–500 km, due to the presence of various crustal sources. The regional MAGSURF anomaly map shows poor correlation with the corresponding MAGSAT scalar anomaly map, whose power spectrum reveals wavelength components in the range 300–700 km. The MAGSURF data are upward-continued to an elevation of 100 km for comparison with MAGSAT satellite data, downward-continued to the same altitude of 100 km and low-pass filtered for wavelengths larger than 500 km. Upward-continued surface data and downward continued satellite data show good morphological similarity for wavelengths in the range 300–500 km at an altitude of 100 km. Satellite data permit the characterization of magnetic signatures due to sources located in the middle-lower crust of Sardinia, Lombardia, Molise and Dalmatia, while further surface regional anomalies are connected with upper crust bodies of Mid Tyrrhene and East Sicily. 相似文献
20.
S. Suresh Babu S. K. Satheesh K. Krishna Moorthy C. B. S. Dutt Vijayakumar S. Nair Denny P. Alappattu P. K. Kunhikrishnan 《Journal of Earth System Science》2008,117(1):263-271
During the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) over India, high-resolution airborne measurements of the altitude profiles of the mass concentrations (MB) of aerosol black carbon (BC) were made off Bhubaneswar (BBR, 85.82°E, 20.25°N), over northwest Bay of Bengal, in the altitude region upto 3 km. Such high-resolution measurements of altitude profiles of aerosols are done for the first time over India. The profiles showed a near-steady vertical distribution of MB modulated with two small peaks, one at 800m and the other at ～2000m. High resolution GPS (Global Positioning System) sonde (Vaisala) measurements around the same region onboard the research vessel Sagar Kanya (around the same time of the aircraft sortie) revealed two convectively well mixed layers, one from ground to ～700m with an inversion at the top and the other extends from 1200m to ～2000m with a second inversion at ～2200m and a convectively stable region in the altitude range 700–1200m. The observed peaks in the MB profile are found to be associated with these temperature inversions. In addition, long-range transport from the Indo-Gangetic Plain (IGP) and deserts lying further to the west also influence the vertical profile of BC. Latitudinal variation of MB showed a remarkable land ocean contrast at the 500m altitude (within the well mixed region) with remarkably lower values over oceans, suggesting the impact of strong sources over the mainland. However, above the ABL (at 1500m), the latitudinal variations were quite weak, and this appears to be resulting from the impact of long-range transport. Comparison of the altitude profiles of MB over BoB off BBR with those obtained during the earlier occasion over the inland stations of Hyderabad and Kanpur showed similarities above ～500m, with MB remaining around a steady value of ～1 μg m?3. However, large differences are seen within the ABL. Even though the observed MB values are not unusually high, their near constancy in the vertical column will have important implications to radiative forcing. 相似文献