1979～2020年北极和青藏高原臭氧低值区的动力输送特征比较     

王启璐  徐雯雯  涂静怡  于淑洋  饶建  郭栋 《大气科学》2023,(3):866-880

基于ERA5月平均再分析资料,利用Lorenz环流分解方法从定常和瞬变以及基流和涡旋的角度对比了北极与青藏高原臭氧低值区的动力输送特征。结果表明：动力总输送在两地上平流层作用最强,均使其臭氧浓度降低,且定常输送均强于瞬变输送,纬向与经向输送的作用均大致相反。然而,动力输送在北极地区的作用强度远大于青藏高原地区。北极地区纬向输送使得平流层中上层臭氧浓度降低,平流层下层臭氧浓度升高,经向输送的作用与之相反且强度明显偏弱,二者均主要作用于上平流层。青藏高原地区纬向和经向输送除在上平流层均使得臭氧浓度降低外,二者作用大致相反且强度相当,输送大值区在垂直方向上存在双中心结构,分别位于上平流层与上对流层—下平流层（Upper Troposphere–Lower Stratosphere,简称UTLS）区。两地区纬向和经向输送的差异均主要由定常涡旋输送所造成。青藏高原地区定常与瞬变输送的强度差异没有北极地区大。此外,两地定常和瞬变输送中涡旋对臭氧纬向平均的输送均起到主要作用,体现出涡旋输送在两地臭氧浓度变化的动力输送过程中发挥着至关重要的作用。  相似文献   

一种基于天基的瞬变电磁高分辨探测小尺度太空碎片的方法          下载免费PDF全文

李文翰  李贺  鲁凯亮  崔洪亮 《地球物理学报》2018,61(12):5066-5076

目前,太空碎片的天基探测方法一般是激光雷达法.由于激光雷达的辐射频率一般为可见光或红外波段,在分辨厘米量级的太空碎片时具有一定的优势.但激光雷达在探测时也面临一些客观问题：即（1）难以捕捉快速移动的太空碎片;（2）对目标体穿透能力低;（3）外层空间的强干扰环境对激光雷达的不良影响等.这些问题在一定程度上限制了激光雷达在太空碎片探测方面的应用.本文针对太空碎片体积小、预警距离远和强干扰环境等特点,提出使用高性能瞬变电磁辐射源对远距离、小尺度的太空碎片进行探测.通过三维矢量有限元方法,分析了利用高性能瞬变电磁辐射源的优点,对比不同瞬变电磁辐射源的幅频特性,从发射机理上证明高性能瞬变电磁辐射源在辐射能力与频率带宽方面都优于传统瞬变电磁辐射源.并通过调整脉冲宽度,得到最适合探测本文太空碎片模型的辐射脉冲.最后通过电场分布图和多测道图对太空碎片的明显电场分异结果,证实了高性能瞬变电磁辐射源在探测远距离、小尺度太空碎片方面的有效性.  相似文献   

瞬变电磁采样函数优化法降噪技术          下载免费PDF全文

武欣  薛国强  肖攀  饶丽婷  郭睿  方广有 《地球物理学报》2017,60(9):3677-3684

常用的双极性同步采样方法对瞬变电磁系统的观测噪声具有一定的抑制作用,但在实际工作中其噪声抑制能力仍显不足.本文在双极性同步采样方法基础上提出一种优化方法,以提升瞬变电磁系统的噪声抑制能力,即:通过对取样道加高斯窗函数的方式,赋予取样道内各采样点合适的累加权重,提升系统对取样道内高频噪声的抑制能力;使用高斯窗函数与梳状滤波器构造复合窗函数,通过对包含所有叠加周期的完整观测序列加复合窗函数的形式优化各周期的叠加权重,提升系统对实际工频噪声的抑制能力.对优化前后不同采样函数的谱特性及野外实测数据的处理效果进行比较,结果表明本文提出的方法较传统双极性同步采样方法具有更强的噪声抑制能力.  相似文献   

几种典型近地表有限导体瞬变电磁特征响应研究          下载免费PDF全文

陈曙东  郭树旭  张爽  袁志文  朱俊  张海洋  方东 《地球物理学报》2017,60(1):403-412

近地表有限导体的瞬变电磁响应中包含其形状、结构特征,如何建立这些特征与其响应之间的关系是近地表有限导体探测与识别的核心问题.本文建立了几种典型有限导体响应的三维感应偶极子模型,通过有限导体早期幂函数衰减的幅度与速率、晚期指数衰减的幅度与时间常数共四个模型参数表征有限导体的形状和结构特征,利用最小二乘拟合算法提取这些模型参数,揭示有限导体的形状、结构特征与模型参数之间的内在联系.理论与实验研究结果表明:具有绕球心旋转对称性的球形目标体,其三维感应偶极子响应完全相同,早期响应呈幂函数衰减,晚期呈e指数衰减,信号幅度和时间常数均能很好反映球体半径与材料特性;具有绕轴旋转对称性目标体,其三维感应偶极子响应部分相同,早期幂函数衰减的幅度与速率主要体现目标体的长度特征,晚期e指数衰减的时间常数体现了目标体的外径与壁厚特征;非轴对称性目标体,其三维感应偶极子响应均不相同,各个感应偶极子参数差异较大.本文的研究对提高瞬变电磁系统区分轴对称目标体与金属碎片能力,降低系统探测虚警率具有重要意义.  相似文献   

深海6000 m拖曳式瞬变电磁系统及其应用          下载免费PDF全文

周胜  宋刚  黄龙  席振铢  侯海涛  陈兴朋  亓庆新 《地球物理学报》2017,60(11):4294-4301

针对我国西南印度洋合同区热液硫化物矿快速、有效以及便捷地质勘探装备的要求,研发了由甲板控制系统、万米光电复合缆、仪器舱拖体和天线拖体组成的深海6000 m拖曳式瞬变电磁系统.为了便于拖体布放和快速发现异常,选择重叠回线收发装置类型;采用理论数值计算确定了在拖曳高度不大于50 m的前提下,观测1～100ms窗范围内的二次场响应,可以发现近海底深海热液硫化物矿堆;另外,通过不同拖延深度海上试验,研究了拖曳深度对瞬变电磁的影响规律及仪器性能.大洋第30航次第二航段在西南印度洋脊热液区,应用该系统发现了明显的瞬变电磁异常.印证了系统的有效性.  相似文献   

DQM2000d、UGM05和EGM2008地球重力场模型精度比较   总被引：1，自引：0，他引：1  

刘晓刚  吴晓平  田颜锋  卢成静 《测绘通报》2010,(2)

给出由地球重力场模型计算重力异常和垂线偏差的公式,利用36阶、360阶、1 800阶DQM 2000d、UGM 05以及EGM 2008地球重力场模型计算国内某地区格网点重力异常和地面垂线偏差,并将其与实测数据进行比较,从而对三种模型的精度进行评估。结果表明,在表示国内某地区格网点重力异常时,UGM 05模型精度最高,DQM 2000d模型精度次之,EGM 2008模型精度最低;在表示地面垂线偏差时,三种模型的精度相当。  相似文献   

基于瞬变电磁矩变换的快速三维反演方法   总被引：1，自引：0，他引：1       下载免费PDF全文

饶丽婷  武欣  吴超  张晓娟  方广有 《地球物理学报》2016,59(11):4338-4348

瞬变电磁法的严格三维反演计算复杂、占用资源多,在普通计算机上难以实现.本文引入瞬变电磁矩变换的概念,提出一种快速三维反演方法.该方法基于阻性限制(resistive limit)特性,建立包含异常体的三维大地的一阶矩响应正演算法,根据不同约束条件,选择优化的最速下降法实现瞬变电磁快速三维反演.文中通过含异常体的三维大地正演一阶矩与仿真数据一阶矩的对比,验证了快速三维正演算法的有效性,之后在不同约束条件下,利用优化的最速下降法实现了对含噪声的仿真瞬变电磁数据的快速三维反演.结果表明,该方法能够在普通计算机上短时间内较为准确地反演出地下异常体的体积和位置,在瞬变电磁数据的实时解释工作中具有良好的应用前景.  相似文献   

隧道强干扰环境瞬变电磁响应规律与校正方法:以TBM为例   总被引：3，自引：0，他引：3       下载免费PDF全文

孙怀凤  李貅  卢绪山  李术才  任宝宏 《地球物理学报》2016,59(12):4720-4732

以隧道掘进机(Tunnel Boring Machine,TBM)为例模拟了隧道强干扰环境下,瞬变电磁超前探测的响应曲线,系统分析了异常体(以直立充水断层为例)与掌子面距离、围岩电阻率差异、TBM长度、异常体规模等条件下的曲线特征和影响规律,发现TBM干扰源表现为低电阻率目标特征,其影响主要集中在早期,对于电性差异较大或目标规模较大的低电阻率异常(充水断层)模型能够明显地通过衰减曲线区分.根据电磁场叠加原理,将隧道腔体中包含TBM模型的响应减去纯隧道腔体响应可以获得TBM的响应信号,以此作为干扰背景,从实际包含TBM和充水断层的隧道模型总响应中减除,获得去除TBM干扰的响应信号.通过8组算例进行对比,发现经过校正的衰减曲线与模型计算曲线吻合较好,视电阻率曲线差异相对较小,能够表现探测区域的电性分布情况,确认该方法在不同情况下的适用性.即使在TBM响应计算时给定背景电阻率与实际电阻率差异达到100%的情况下,依然能够通过校正获得合理的响应信号和视电阻率曲线.该方法不仅仅适用于隧道环境,对于其他诸如地面、航空、半航空、海洋瞬变电磁勘探同样适用.  相似文献   

Joint inversion of long‐offset and central‐loop transient electromagnetic data: Application to a mud volcano exploration in Perekishkul,Azerbaijan          下载免费PDF全文

J. Adrian  R. Bergers  M. Gurk  B. Tezkan  A. L. Mammadov  A. G. Novruzov 《Geophysical Prospecting》2015,63(2):478-494

Mud volcanism is commonly observed in Azerbaijan and the surrounding South Caspian Basin. This natural phenomenon is very similar to magmatic volcanoes but differs in one considerable aspect: Magmatic volcanoes are generally the result of ascending molten rock within the Earth's crust, whereas mud volcanoes are characterised by expelling mixtures of water, mud, and gas. The majority of mud volcanoes have been observed on ocean floors or in deep sedimentary basins, such as those found in Azerbaijan. Furthermore, their occurrences in Azerbaijan are generally closely associated with hydrocarbon reservoirs and are therefore of immense economic and geological interest. The broadside long‐offset transient electromagnetic method and the central‐loop transient electromagnetic method were applied to study the inner structure of such mud volcanoes and to determine the depth of a resistive geological formation that is predicted to contain the majority of the hydrocarbon reservoirs in the survey area. One‐dimensional joint inversion of central‐loop and long‐offset transient electromagnetic data was performed using the inversion schemes of Occam and Marquardt. By using the joint inversion models, a subsurface resistivity structure ranging from the surface to a depth of approximately 7 km was determined. Along a profile running perpendicular to the assumed strike direction, lateral resistivity variations could only be determined in the shallow depth range using the transient electromagnetic data. An attempt to resolve further two‐dimensional/three‐dimensional resistivity structures, representing possible mud migration paths at large depths using the long‐offset transient electromagnetic data, failed. Moreover, the joint inversion models led to ambiguous results regarding the depth and resistivity of the hydrocarbon target formation due to poor resolution at great depths (>5 km). Thus, 1D/2D modelling studies were subsequently performed to investigate the influence of the resistive terminating half‐space on the measured long‐offset transient electromagnetic data. The 1D joint inversion models were utilised as starting models for both the 1D and 2D modelling studies. The results tend to show that a resistive terminating half‐space, implying the presence of the target formation, is the favourable geological setting. Furthermore, the 2D modelling study aimed to fit all measured long‐offset transient electromagnetic Ex transients along the profile simultaneously. Consequently, 3125 2D forward calculations were necessary to determine the best‐fit resistivity model. The results are consistent with the 1D inversion, indicating that the data are best described by a resistive terminating half‐space, although the resistivity and depth cannot be determined clearly.  相似文献   

Multi‐method virtual electromagnetic experiments for developing suitable monitoring designs: A fictitious CO2 sequestration scenario in Northern Germany          下载免费PDF全文

Jana H. Börner  Feiyan Wang  Julia Weißflog  Matthias Bär  Ines Görz  Klaus Spitzer 《Geophysical Prospecting》2015,63(6):1430-1449

We present a numerical study for 3D time‐lapse electromagnetic monitoring of a fictitious CO₂ sequestration using the geometry of a real geological site and a suite of suitable electromagnetic methods with different source/receiver configurations and different sensitivity patterns. All available geological information is processed and directly implemented into the computational domain, which is discretized by unstructured tetrahedral grids. We thus demonstrate the performance capability of our numerical simulation techniques. The scenario considers a CO₂ injection in approximately 1100 m depth. The expected changes in conductivity were inferred from preceding laboratory measurements. A resistive anomaly is caused within the conductive brines of the undisturbed reservoir horizon. The resistive nature of the anomaly is enhanced by the CO₂ dissolution regime, which prevails in the high‐salinity environment. Due to the physicochemical properties of CO₂, the affected portion of the subsurface is laterally widespread but very thin. We combine controlled‐source electromagnetics, borehole transient electromagnetics, and the direct‐current resistivity method to perform a virtual experiment with the aim of scrutinizing a set of source/receiver configurations with respect to coverage, resolution, and detectability of the anomalous CO₂ plume prior to the field survey. Our simulation studies are carried out using the 3D codes developed in our working group. They are all based on linear and higher order Lagrange and Nédélec finite‐element formulations on unstructured grids, providing the necessary flexibility with respect to the complex real‐world geometry. We provide different strategies for addressing the accuracy of numerical simulations in the case of arbitrary structures. The presented computations demonstrate the expected great advantage of positioning transmitters or receivers close to the target. For direct‐current geoelectrics, 50% change in electric potential may be detected even at the Earth's surface. Monitoring with inductive methods is also promising. For a well‐positioned surface transmitter, more than 10% difference in the vertical electric field is predicted for a receiver located 200 m above the target. Our borehole transient electromagnetics results demonstrate that traditional transient electromagnetics with a vertical magnetic dipole source is not well suited for monitoring a thin horizontal resistive target. This is due to the mainly horizontal current system, which is induced by a vertical magnetic dipole.  相似文献