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Case study on stratospheric and mesospheric concentric gravity waves generated by deep convection 深层对流产生平流层和中间层同心重力波的实例研究
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021002
GuoChun Shi, Xiong Hu, ZhiGang Yao, WenJie Guo, MingChen Sun, XiaoYan Gong

Concentric gravity waves (CGWs) in the middle and upper atmosphere show wave-coupling processes between the lower atmosphere and the middle and upper atmosphere. In this research, we analyzed a case of CGWs detected simultaneously by the AIRS (Atmospheric Infrared Sounder) and the VIIRS/DNB (Day/Night Band of the Visible Infrared Imager Radiometer Suite) in the stratosphere and mesosphere. Results showed that gravity waves (GWs) were generated by the collocated Hurricane Bejisa on the island of Mauritius. The AIRS data showed arc-like phase fronts of GWs with horizontal wavelengths of 190 and 150 km at 21:08 coordinated universal time (UTC) on 1 January 2014 and at 10:00 UTC on 2 January 2014, whereas the DNB observed arced GWs with horizontal wavelengths of 60 and 150 km in the same geographic regions at 22:24 UTC. The characteristics of CGW parameters in the stratosphere (~40 km) and the mesosphere (~87 km), such as the vertical wavelength, intrinsic frequency, and intrinsic horizontal phase speed, were first derived together with the background winds from ERA5 reanalysis data and Horizontal Wind Model data through the dispersion relationship of GWs and the wind-filtering theory.

中高层大气同心重力波(CGWs)表现了低层大气与中高层大气之间的波耦合过程。在本研究中,我们分析了大气红外探测器AIRS (Atmospheric Infrared Sounder)和可见光红外成像仪辐射计套件的昼/夜波段VIIRS/DNB (Visible Infrared Imager Radiometer Suite)在平流层和中间层同时探测到的CGWs。结果表明,飓风贝吉萨(Bejisa)在毛里求斯岛同时产生了重力波。在2014年1月1日协调世界时21:08和2014年1月2日10:00,AIRS数据显示水平波长为190和150 km的弧形GWs相位锋,而DNB在协调世界时22:24在同一地理区域观测到水平波长为60和150 km的弧形GWs。首先利用ERA5再分析资料和水平风模式资料,利用gw的频散关系和风滤波理论,结合背景风,导出了平流层(~40 km)和中间层(~87 km)的CGW参数的垂直波长、固有频率和固有水平相速度等特征。
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引用次数: 1
Statistical properties of kinetic-scale magnetic holes in terrestrial space 地球空间动力学尺度磁孔的统计性质
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021011
ShuTao Yao, ZongShun Yue, QuanQi Shi, Alexander William Degeling, HuiShan Fu, AnMin Tian, Hui Zhang, Andrew Vu, RuiLong Guo, ZhongHua Yao, Ji Liu, Qiu-Gang Zong, XuZhi Zhou, JingHuan Li, WenYa Li, HongQiao Hu, YangYang Liu, WeiJie Sun

Kinetic-scale magnetic holes (KSMHs) are structures characterized by a significant magnetic depression with a length scale on the order of the proton gyroradius. These structures have been investigated in recent studies in near-Earth space, and found to be closely related to energy conversion and particle acceleration, wave-particle interactions, magnetic reconnection, and turbulence at the kinetic-scale. However, there are still several major issues of the KSMHs that need further study — including (a) the source of these structures (locally generated in near-Earth space, or carried by the solar wind), (b) the environmental conditions leading to their generation, and (c) their spatio-temporal characteristics. In this study, KSMHs in near-Earth space are investigated statistically using data from the Magnetospheric Multiscale mission. Approximately 200,000 events were observed from September 2015 to March 2020. Occurrence rates of such structures in the solar wind, magnetosheath, and magnetotail were obtained. We find that KSMHs occur in the magnetosheath at rates far above their occurrence in the solar wind. This indicates that most of the structures are generated locally in the magnetosheath, rather than advected with the solar wind. Moreover, KSMHs occur in the downstream region of the quasi-parallel shock at rates significantly higher than in the downstream region of the quasi-perpendicular shock, indicating a relationship with the turbulent plasma environment. Close to the magnetopause, we find that the depths of KSMHs decrease as their temporal-scale increases. We also find that the spatial-scales of the KSMHs near the subsolar magnetosheath are smaller than those in the flanks. Furthermore, their global distribution shows a significant dawn-dusk asymmetry (duskside dominating) in the magnetotail.

动力学尺度磁孔(KSMHs)是一种具有显著磁凹陷的结构,其长度尺度在质子陀螺半径量级。这些结构在最近的近地空间研究中被发现与能量转换和粒子加速、波粒相互作用、磁重联和动力学尺度上的湍流密切相关。然而,ksmh仍有几个主要问题需要进一步研究,包括:(a)这些结构的来源(在近地空间局部产生,或由太阳风携带),(b)导致其产生的环境条件,以及(c)它们的时空特征。在本研究中,利用磁层多尺度任务的数据对近地空间的ksmh进行了统计研究。从2015年9月到2020年3月,观测到大约20万次事件。得到了这种结构在太阳风、磁鞘和磁尾中的发生率。我们发现ksmh在磁鞘中的发生速率远高于它们在太阳风中的发生速率。这表明大多数结构是在磁鞘中局部产生的,而不是与太阳风平流。此外,ksmh发生在准平行激波下游区域的速率显著高于准垂直激波下游区域,这表明ksmh与湍流等离子体环境有关。在接近磁层顶时,我们发现ksmh的深度随其时间尺度的增大而减小。我们还发现,亚太阳磁鞘附近的ksmh的空间尺度小于侧翼的ksmh。此外,它们的全球分布在磁尾中显示出明显的黎明-黄昏不对称(黄昏占优势)。
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引用次数: 11
Characteristic analysis of layered PMSEs measured with different elevation angles at VHF based on an experimental case 基于实验的VHF不同仰角层状pmse测量特性分析
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021001
ShuCan Ge, HaiLong Li, Bin Xu, Tong Xu, Lin Meng, MaoYan Wang, Abdel Hannachi, MengYan Zhu, Lina Broman, Safi Ullah, Abdur Rauf

Polar Mesosphere Summer Echoes (PMSEs) are very strong radar echoes observed at altitudes near the polar summer mesopause. One of the essential properties of these radar echoes is that they can give useful diagnostic information about the physics of the scattering process. In this paper, the related characteristics of PMSEs measured with the European Incoherent SCATter Very High Frequency (EISCAT VHF) 224 MHz radar on 13–15 July 2010 are studied at different elevation angles from 78° to 90°. It is found that the PMSEs peak power and strongest PMSEs average power occur at the same elevation angles. Also interesting is that the strongest PMSEs occur at off-vertical angles when a PMSEs has a layered (multilayer) structure. And reflection may have more significant effects on PMSEs when there are double or multilayer PMSEs. Possible explanations regarding these observations are discussed.

极地中间层夏季回波是在极地夏季中间层顶附近高度观测到的非常强的雷达回波。这些雷达回波的基本特性之一是它们可以提供有关散射过程的物理诊断信息。本文研究了2010年7月13-15日欧洲非相干散射甚高频(EISCAT VHF) 224 MHz雷达在78°~ 90°不同仰角下测得的pmse相关特性。结果表明,在相同的俯仰角下,pmse的峰值功率和最强平均功率出现在相同的俯仰角下。同样有趣的是,当pmse具有分层(多层)结构时,最强的pmse会出现在非垂直角度。当存在双层或多层pmse时,反射对pmse的影响更为显著。对这些观察结果的可能解释进行了讨论。
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引用次数: 2
Nighttime meridional neutral wind responses to SAPS simulated by the TIEGCM: A universal time effect TIEGCM模拟的夜间经向中性风对SAPS的响应:普遍时间效应
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021004
KeDeng Zhang, Hui Wang, WenBin Wang, Jing Liu, ShunRong Zhang, Cheng Sheng

The present work uses the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), under geomagnetically disturbed conditions that are closely related to the southward interplanetary magnetic field (IMF), to investigate how the nighttime poleward wind (30°–50° magnetic latitude and 19–22 magnetic local time) responds to subauroral polarization streams (SAPS) that commence at different universal times (UTs). The SAPS effects on the poleward winds show a remarkable UT variation, with weaker magnitudes at 00 and 12 UT than at 06 and 18 UT. The strongest poleward wind emerges when SAPS commence at 06 UT, and the weakest poleward wind develops when SAPS occur at 00 UT. A diagnostic analysis of model results shows that the pressure gradient is more prominent for the developing of the poleward wind at 00 and 12 UT. Meanwhile, the effect of ion drag is important in the modulation of the poleward wind velocity at 06 and 18 UT. This is caused by the misalignment of the geomagnetic and geographic coordinate systems, resulting in a large component of ion drag in the geographically northward (southward) direction due to channel orientation of the SAPS at 06 and 18 UT (00 and 12 UT). The Coriolis force effect induced by westward winds maximizes (minimizes) when SAPS commence at 12 UT (00 UT). The centrifugal force due to the accelerated westward winds shows similar UT variations as the Coriolis force, but with an opposite effect.

本研究使用热层电离层电动力学环流模型(TIEGCM),在与南向行星际磁场(IMF)密切相关的地磁扰动条件下,研究夜间向极地风(30°-50°磁纬度和19-22磁地方时)如何响应于不同世界时(ut)开始的亚极光极化流(SAPS)。SAPS对极地风的影响表现出显著的UT变化,在00和12 UT的强度弱于06和18 UT。世界时06分SAPS开始时,极风最强,世界时00分SAPS开始时,极风最弱。对模式结果的诊断分析表明,压力梯度在0时和12时对极向风的发展更为突出。同时,离子阻力在06和18 UT的极向风速调制中起重要作用。这是由于地磁和地理坐标系的不对齐造成的,由于SAPS在06和18 UT(00和12 UT)的通道方向,导致离子阻力在地理上向北(南)方向的很大一部分。西风引起的科里奥利力效应在12 UT (00 UT)开始时达到最大(最小)。由加速的西风引起的离心力与科里奥利力表现出相似的UT变化,但效果相反。
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引用次数: 10
Formation of the mass density peak at the magnetospheric equator triggered by EMIC waves 磁层赤道质量密度峰的形成是由地源波触发的
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021008
ZuXiang Xue, ZhiGang Yuan, XiongDong Yu, Huang ShiYong, Zheng Qiao

We report a simultaneous observation of two band electromagnetic ion cyclotron (EMIC) waves and toroidal Alfvén waves by the Van Allen Probe mission. Through wave frequency analyses, the mass density ρ is found to be locally peaked at the magnetic equator. Perpendicular fluxes of ions (< 100 eV) increase simultaneously with the appearances of EMIC waves, indicating a heating of these ions by EMIC waves. In addition, the measured ion distributions also support the equatorial peak formation, which accords with the result of the frequency analyses. The formation of local mass density peaks at the equator should be due to enhancements of equatorial ion concentrations, which are triggered by EMIC waves’ perpendicular heating on low energy ions.

我们报告了范艾伦探测器任务同时观测到的两波段电磁离子回旋波和环形alfvsamn波。通过波频分析,发现质量密度ρ在磁赤道处局部达到峰值。离子的垂直通量(<100 eV)随着位向波的出现而同时增加,表明这些离子被位向波加热。此外,测量到的离子分布也支持赤道峰的形成,这与频率分析的结果一致。赤道处局部质量密度峰的形成应该是由于赤道离子浓度的增强,而赤道离子浓度的增强是由EMIC波对低能离子的垂直加热引起的。
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引用次数: 4
Treatment of discontinuities inside Earth models: Effects on computed coseismic deformations 地球模型内部不连续的处理:对计算同震变形的影响
IF 2.9 3区 地球科学 Pub Date : 2021-03-29 DOI: 10.26464/epp2021010
Jie Dong, Gabriele Cambiotti, HanJiang Wen, Roberto Sabadini, WenKe Sun

In this paper, we study how coseismic deformations calculated in 1066 Earth models are affected by how the models treat Earth discontinuities. From the results of applying models 1066A (continuous) and 1066B (discontinuous), we find that the difference in Love numbers of strike-slip and horizontal tensile sources are bigger than dip-slip and vertical tensile sources. Taken collectively, discontinuities have major effects on Green’s functions of four independent sources. For the near-field coseismic deformations of the 2013 Okhotsk earthquake (Mw 8.3), the overall differences between theoretical calculations in vertical displacement, geoid, and gravity changes caused by discontinuities are 10.52 percent, 9.07 percent and 6.19 percent, with RMS errors of 0.624 mm, 0.029 mm, and 0.063 μGal, respectively. The difference in far-field displacements is small, compared with GPS data, and we can neglect this effect. For the shallow earthquake, 2011 Tohoku-Oki earthquake (Mw 9.0), the differences in near-field displacements are 0.030 m (N-S), 0.093 m (E-W), and 0.025 m (up-down) in our study area with the ARIA slip model, which gives results closer to GPS data than those from the USGS model. The difference in vertical displacements and gravity changes on the Earth’s surface caused by discontinuities are larger than 10 percent. The difference in the theoretical gravity changes at spatially fixed points truncated to degrees 60, as required by GRACE data, is 0.0016 μGal and the discrepancy is 11 percent, with the theoretical spatial gravity changes from 1066B closer to observations than from 1066A. The results show that an Earth model with discontinuities in the medium has a large effect on the calculated coseismic deformations.

本文研究了1066个地球模型计算的同震形变如何受到模型处理地球不连续面的方式的影响。从1066A(连续)和1066B(不连续)模型的应用结果来看,走滑和水平张拉震源Love数的差异大于倾滑和垂直张拉震源Love数的差异。总的来说,不连续对四个独立来源的格林函数有主要影响。对于2013年鄂霍次克8.3级地震近场同震形变,不连续面引起的垂直位移、大地面和重力变化的理论计算总体差异为10.52%、9.07%和6.19%,均方根误差分别为0.624 mm、0.029 mm和0.063 μGal。与GPS数据相比,远场位移的差异很小,我们可以忽略这种影响。对于2011年Tohoku-Oki地震(Mw 9.0)的浅层地震,ARIA滑动模型在研究区内的近场位移差异为0.030 m (N-S), 0.093 m (E-W)和0.025 m(上下),与USGS模型相比,结果更接近GPS数据。不连续性引起的地球表面垂直位移和重力变化的差异大于10%。在GRACE数据要求的空间不动点截断到60度的理论重力变化差值为0.0016 μGal,差值为11%,1066B的理论空间重力变化比1066A的更接近观测值。结果表明,具有介质不连续的地球模型对计算的同震变形有较大影响。
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引用次数: 5
Preliminary experimental results by the prototype of Sanya Incoherent Scatter Radar 三亚非相干散射雷达样机的初步实验结果
IF 2.9 3区 地球科学 Pub Date : 2020-11-16 DOI: 10.26464/epp2020063
XinAn Yue, WeiXing Wan, Han Xiao, LingQi Zeng, ChangHai Ke, BaiQi Ning, Feng Ding, BiQiang Zhao, Lin Jin, Chen Li, MingYuan Li, JunYi Wang, HongLian Hao, Ning Zhang

In the past decades, the Incoherent Scatter Radar (ISR) has been demonstrated to be one of the most powerful instruments for ionosphere monitoring. The Institute of Geology and Geophysics at the Chinese Academy of Sciences was founded to build a state-of-the-art phased-array ISR at Sanya (18.3°N, 109.6°E), a low-latitude station on Hainan Island, named the Sanya ISR (SYISR). As a first step, a prototype radar system consisting of eight subarrays (SYISR-8) was built to reduce the technical risk of producing the entire large array. In this work, we have summarized the preliminary experimental results based on the SYISR-8. The amplitude and phase among 256 channels were first calibrated through an embedded internal monitoring network. The mean oscillation of the amplitude and phase after calibration were about 1 dB and 5°, respectively, which met the basic requirements. The beam directivity was confirmed by crossing screen of the International Space Station. The SYISR-8 was further used to detect the tropospheric wind profile and meteors. The derived winds were evaluated by comparison with independent radiosonde and balloon-based GPS measurements. The SYISR-8 was able to observe several typical meteor echoes, such as the meteor head echo, range-spread trail echo, and specular trail echo. These results confirmed the validity and reliability of the SYISR-8 system, thereby reducing the technical risk of producing the entire large array of the SYISR to some extent.

在过去的几十年中,非相干散射雷达(ISR)已被证明是电离层监测中最强大的仪器之一。中国科学院地质与地球物理研究所成立的目的是在海南岛的低纬度站点三亚(北纬18.3°,东经109.6°)建立一个最先进的相控阵ISR,命名为三亚ISR (SYISR)。作为第一步,一个原型雷达系统由8个子阵列(SYISR-8)组成,以减少生产整个大型阵列的技术风险。在这项工作中,我们总结了基于SYISR-8的初步实验结果。首先通过嵌入式内部监测网络对256个通道的幅度和相位进行校准。校正后振幅和相位的平均振荡分别约为1 dB和5°,基本满足要求。通过国际空间站的交叉屏确认了光束的方向性。SYISR-8进一步用于对流层风廓线和流星的探测。通过与独立的无线电探空仪和基于气球的GPS测量结果进行比较,评估了导出的风。SYISR-8能够观测到几种典型的流星回波,如流星头回波、距离扩展尾迹回波和镜面尾迹回波。这些结果证实了SYISR-8系统的有效性和可靠性,从而在一定程度上降低了生产整个SYISR大阵的技术风险。
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引用次数: 8
The semiannual variation of transpolar arc incidence and its relationship to the Russell–McPherron effect 过极弧入射的半年变化及其与罗素-麦克费龙效应的关系
IF 2.9 3区 地球科学 Pub Date : 2020-11-16 DOI: 10.26464/epp2020066
Tao Tang, Jun Yang, QuanQi Shi, AnMin Tian, Shi-Chen Bai, Alexander William Degeling, SuiYan Fu, JingXian Liu, Tong Shao, ZeYuan Sun

Earth's aurora is a luminescent phenomenon generated by the interaction between magnetospheric precipitating particles and the upper atmosphere; it plays an important role in magnetosphere–ionosphere (M-I) coupling. The transpolar arc (TPA) is a discrete auroral arc distributed in the noon-midnight direction poleward of the auroral oval and connects the dayside to the nightside sectors of the auroral oval. Studying the seasonal variation of TPA events can help us better understand the long-term variation of the interaction between the solar wind, the magnetosphere, and M-I coupling. However, a statistical study of the seasonal variation of TPA incidence has not previously been carried out. In this paper, we have identified 532 TPA events from the IMAGE database (2000–2005) and the Polar database (1996–2002), and calculated the incidence of TPA events for different months. We find a semiannual variation in TPA incidence. Clear peaks in the incidence of TPAs occur in March and September; a less pronounced peak appears in November. We also examine seasonal variation in the northward interplanetary magnetic field (IMF) over the same time period. The intensity and occurrence rate of the northward IMF exhibit patterns similar to that of the TPA incidence. Having studied IMFB z before TPA onset, we find that strong and steady northward IMF conditions are favorable for TPA formation. We suggest that the semiannual variation observed in TPA incidence may be related to the Russell–McPherron (R-M) effect due to the projection effect of the IMFB y under northward IMF conditions.

地球极光是磁层沉淀粒子与上层大气相互作用产生的一种发光现象;它在磁层-电离层(M-I)耦合中起重要作用。超极弧(TPA)是一个离散的极光弧,分布在极光椭圆的正午至午夜方向,连接着极光椭圆的昼侧和夜侧扇区。研究TPA事件的季节变化有助于我们更好地理解太阳风、磁层和M-I耦合相互作用的长期变化。然而,TPA发病率的季节性变化的统计研究以前没有进行过。本文利用IMAGE数据库(2000-2005年)和Polar数据库(1996-2002年)中的532个TPA事件,计算了不同月份的TPA事件发生率。我们发现TPA发病率每半年变化一次。tpa发病高峰出现在3月和9月;一个不太明显的峰值出现在11月。我们还研究了同一时期内北行星际磁场(IMF)的季节变化。北向IMF的强度和发生率与TPA的发生率相似。在TPA开始之前,我们研究了国际货币基金组织(IMF) z,发现强劲而稳定的北向IMF条件有利于TPA的形成。我们认为,在IMF向北的条件下,由于IMF的预测效应,TPA发生率的半年变化可能与罗素-麦克费龙(R-M)效应有关。
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引用次数: 3
Numerical simulation of the propagation of electromagnetic waves in ionospheric irregularities 电磁波在不规则电离层中传播的数值模拟
IF 2.9 3区 地球科学 Pub Date : 2020-11-16 DOI: 10.26464/epp2020059
ChunHua Jiang, LeHui Wei, GuoBin Yang, Chen Zhou, ZhengYu Zhao

The characteristics of high-frequency (HF) electromagnetic (EM) wave propagation can be affected when EM waves propagate in the ionosphere. When ionospheric irregularities appear in the ionosphere, they can have a serious impact on the propagation of HF EM waves. In this study, the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation. First, a two-dimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere. A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities. Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities. In addition, corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities. The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde. Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere. This result was consistent with the ionosonde observations.

高频电磁波在电离层中传播会影响其传播特性。当电离层出现不规则现象时,会对高频电磁波的传播产生严重影响。本文采用数值模拟方法研究了高频电磁波在不规则电离层中的传播。首先,使用等离子体气泡的二维模型来产生电离层中的电离层不规则性。然后利用射线追踪方法来模拟高频无线电波在这些电离层不规则结构中的传播。结果表明,在电离层无规则条件下,高频无线电波在电离层中的传播比无规则条件下更为复杂。此外,利用这些不规则性在电离层中传播的射电射线合成了相应的电离图。然后将合成的离子图与离子探空仪记录的实验离子图进行比较。结果表明,当电离层发生不规则时,在电离层图上可以模拟出扩散F。这一结果与电离层探空仪的观测结果一致。
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引用次数: 3
Refinement of Bouguer anomalies derived from the EGM2008 model, impact on gravimetric signatures in mountainous region: Case of Cameroon Volcanic Line, Central Africa 基于EGM2008模型的布格异常的改进,对山区重力特征的影响——以中非喀麦隆火山线为例
IF 2.9 3区 地球科学 Pub Date : 2020-11-16 DOI: 10.26464/epp2020065
Paul Gautier Kamto, Cyrille Mezoue Adiang, Severin Nguiya, Joseph Kamguia, Loudi Yap

Global geopotential models have not included the very high frequencies of the Earth's external gravity field. This is called omission error. This omission error becomes more important in mountainous areas (areas with highly variable topography). The work reported here consists in reducing the omission error in measurements of Bouguer gravity anomalies, by refining the global geopotential model EGM2008 using the spectral enhancement method. This method consists in computing the residual terrain effects and then coupling them to the gravimetric signal of the global geopotential model. To compute the residual terrain effects, we used the Residual Terrain Model (RTM) technique. To refine it required a reference surface (ETOPO1) developed up to degree 2190 (the maximum degree of the EGM2008 model) and a detailed elevation model (AW3D30). Computation was performed with the TC program of the GRAVSOFT package. The topography of the study area was assumed to have a constant density of 2670 kg/m3. For the inner and outer zones, the respective integration radii of 10 km and 200 km have been chosen. We obtained very important RTM values ranging from −53.59 to 34.79 mGal. These values were added to the gravity anomalies grid of the EGM2008 model to improve accuracy at high frequencies. On a part of the Cameroon Volcanic Line and its surroundings (mountainous area), we made a comparison between the residual Bouguer anomalies before and after refinement. We report differences ranging from −37.40 to 26.40 mGal. We conclude that the impact of omission error on gravimetric signatures is observed especially in areas with high variable topography, such as on the Cameroon Volcanic Line and around the localities of Takamanda, Essu, Dumbo, and Ngambe. This finding illustrates the great influence that topography has on accurate measurement of these gravity anomalies, and thus why topography must be taken into account. We can conclude that in preparing a global geopotential model, a high resolution DTM must be used to decrease the omission error: the degree of expansion has to increase in order to take the higher frequencies into account. The refined Bouguer anomalies grid presented here can be used in addition to terrestrial gravity anomalies in the study area, especially in mountainous areas where gravimetric data are very sparse or non-existent.

全球地势模型没有包括地球外部重力场的非常高的频率。这被称为遗漏错误。这种遗漏错误在山区(地形高度多变的地区)变得更加重要。本文的工作包括利用谱增强方法改进全球地势模型EGM2008,以减少布格重力异常测量中的遗漏误差。该方法是计算剩余地形效应,然后将其与全球地势模型的重力信号耦合。为了计算剩余地形效应,我们使用了残余地形模型(RTM)技术。为了完善它,需要一个参考表面(ETOPO1)开发到2190度(EGM2008模型的最大度)和一个详细的高程模型(AW3D30)。使用GRAVSOFT软件包中的TC程序进行计算。假设研究区域的地形密度为2670 kg/m3。内外区分别选择10 km和200 km的积分半径。我们得到了非常重要的RTM值,范围从- 53.59到34.79 mGal。这些值被添加到EGM2008模型的重力异常网格中,以提高高频精度。在喀麦隆火山线及其周边部分地区(山区),对比了改进前后的残余布格异常。我们报告的差异范围从−37.40到26.40 mGal。我们得出的结论是,遗漏误差对重力特征的影响尤其在地形变化较大的地区,如喀麦隆火山线和Takamanda、Essu、Dumbo和Ngambe等地周围。这一发现说明了地形对这些重力异常的精确测量的巨大影响,因此必须考虑地形。我们可以得出结论,在准备全球地势模型时,必须使用高分辨率DTM来减少遗漏误差:为了考虑更高的频率,必须增加扩展程度。本文提出的精细化布格异常网格可用于研究区地面重力异常之外,特别是在重力数据非常稀疏或不存在的山区。
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Earth and Planetary Physics
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