双基地激光测风雷达回波信号仿真研究          下载免费PDF全文

李绍辉  孙学金  邵连军  易欣  张传亮 《气象科学》2023,43(4):523-533

本文针对传统的体散射模型并未考虑大气不均匀性对信号传输的影响等问题,通过引入垂直非均匀的大气参数改进了模型,并利用其建立了体目标的双基地激光测风雷达方程,仿真了侧向散射回波信号,并与单基地雷达进行了对比分析。研究表明:水平方向上,双基地激光测风雷达的回波信号分布特征与单基地雷达差异较大,其回波信号等值线在近地面为卵形线,随着探测高度的增加,回波信号等值线逐渐变为以主、被动雷达为焦点的椭圆形,并最终趋近于圆形;垂直方向上,双基地激光测风雷达的回波信号随高度衰减剧烈,近地面的回波能量约为10^-10 J,4 km高度的回波能量约为10^-15J,在中低层大气(0~10 km),回波信号中气溶胶散射占比大,在高层大气(10 km以上),分子散射占比大。  相似文献   

Neotectonic transpressional intraplate deformation in eastern Eurasia: Insights from active fault systems in the southeastern Korean Peninsula     

《地学前缘(英文版)》2023,14(4):101559

Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries. The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and has been deformed under the ENE–WSW maximum horizontal compression since the late Pliocene. In this study, we analyzed short-term instrumental seismic (focal mechanism) and long-term paleoseismic (Quaternary fault outcrop) data to decipher the neotectonic crustal deformation pattern in the southeastern Korean Peninsula. Available (paleo-)seismic data acquired from an NNE–SSW trending deformation zone between the Yangsan and Ulleung fault zones indicate spatial partitioning of crustal deformation by NNW–SSE to NNE–SSW striking reverse faults and NNE–SSW striking strike-slip faults, supporting a strike-slip partitioned transpression model. The instantaneous and finite neotectonic strains, estimated from the focal mechanism and Quaternary outcrop data, respectively, show discrepancies in their axes, which can be attributed to the switching between extensional and intermediate axes of finite strain during the accumulation of wrench-dominated transpression. Notably, some major faults, including the Yangsan and Ulsan fault zones, are relatively misoriented to slip under the current stress condition but, paradoxically, have more (paleo-)seismic records indicating their role in accommodating the neotectonic transpressional strain. We propose that fluids, heat flow, and lithospheric structure are potential factors affecting the reactivation of the relatively misoriented major faults. Our findings provide insights into the accommodation pattern of strain associated with the neotectonic crustal extrusion in an intraplate region of the eastern Eurasian Plate in response to the collision of the Indian Plate and the subduction of the Pacific/Philippine Sea Plates.  相似文献   

川北山丘区地下水补给特征与定量研究          下载免费PDF全文

周志超  李杰彪  苏锐  郭永海  赵宏刚  王彦江  季瑞利  张明 《水文》2015,35(5):54-60

针对川北山丘区地下水资源和污染防护研究中地下水补给难以定量等问题,以川北典型山丘区平溪河北岸的山丘区子流域为研究对象,布设监测孔并对其地下水的水位和水温开展动态监测,并基于大气压监测数据校正地下水监测水位,分析了山丘区地下水水位及水温的年内动态变化特征;采用渗水试验和分段双栓塞水文地质试验获取含水层空间渗透系数;基于达西断面法定量计算了研究区内观测断面的地下水径流补给量,并建立了月降雨量与降水入渗系数的函数关系,结果显示:研究区多年平均大气降水入渗补给量为16.61mm,多年平均降水入渗系数为0.0182;月降雨量与降水入渗系数呈幂函数关系;此成果可为研究区地下水资源、地下水防污性能评价及地下水数值模拟等研究提供重要依据。  相似文献   

钨在矿物/熔体和溶液/熔体中的分配行为及其对成矿作用的影响   总被引：1，自引：0，他引：1  

喻晓  赵博  张德会  黄诚  王新彦  和成忠 《矿物岩石地球化学通报》2015,(3)

总结了钨(W)在地球不同圈层、不同相以及不同集合体之间的分配行为,并据此来探讨与花岗岩有关的热液型钨矿床的某些成因机制,并将W矿化所需的较高的浓集系数归因于这一系列不均匀分配行为的累积。同时强调了W在溶液/熔体体系,尤其是富F体系中的分配行为是理解其成矿机理的关键。热液中W主要以钨酸(根)和碱性钨酸盐离子存在,后因流经理化条件(温度、盐度、p H值)骤变而沉淀成矿。  相似文献   

The use of remotely sensed land cover to derive floodplain friction coefficients for flood inundation modelling     

M. D. Wilson  P. M. Atkinson 《水文研究》2007,21(26):3576-3586

Remotely sensed land cover was used to generate spatially‐distributed friction coefficients for use in a two‐dimensional model of flood inundation. Such models are at the forefront of research into the prediction of river flooding. Standard practice, however, is to use single (static) friction coefficients on both the channel and floodplain, which are varied in a calibration procedure to provide a “best fit” to a known inundation extent. Spatially‐distributed friction provides a physically grounded estimate of friction that does not require fitting to a known inundation extent, but which can be fitted if desired. Remote sensing offers the opportunity to map these friction coefficients relatively straightforwardly and for low cost. Inundation was predicted using the LISFLOOD‐FP model for a reach on the River Nene, UK. Friction coefficients were produced from land cover predicted from Landsat TM imagery using both ML and fuzzy c‐means classifiction. The elevetion data used were from combined contour and differential global positioning system (GPS) elevation data. Predicted inundation using spatially‐distributed and static friction were compared. Spatially‐distributed friction had the greatest effect on the timing of flood inundation, but a small effect on predicted inundation extent. The results indicate that spatially‐distributed friction should be considered where the timing of initial flooding (e.g. for early warning) is important. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Synthetic seismograms in laterally heterogeneous, anelastic media by modal summation of P-SV-waves     

F. Vaccari  S. Gregersen  M. Furlan  G. F. Panza 《Geophysical Journal International》1989,99(2):285-295

  相似文献   

Evaluation of the accuracy of the EIGEN-1S and -2 CHAMP-derived gravity field models by satellite crossover altimetry     

J. Klokoník  J. Kostelecký  C.A. Wagner  P. Schwintzer  Ch. Förste  R. Scharroo 《Journal of Geodesy》2005,78(7-8):405-417

Since the advent of CHAMP, the first in a series of low-altitude satellites being almost continuously and precisely tracked by GPS, a new generation of long-wavelength gravitational geopotential models can be derived. The accuracy evaluation of these models depends to a large extent on the comparison with external data of comparable quality. Here, two CHAMP-derived models, EIGEN-1S and EIGEN-2, are tested with independent long-term-averaged single satellite crossover (SSC) sea heights from three altimetric satellites (ERS-1, ERS-2 and Geosat). The analyses show that long-term averages of crossover residuals still are powerful data to test CHAMP gravity field models. The new models are tested in the spatial domain with the aid of ERS-1/-2 and Geosat SSCs, and in the spectral domain with latitude-lumped coefficient (LLC) corrections derived from the SSCs. The LLC corrections allow a representation of the satellite-orbit-specific error spectra per order of the models spherical harmonic coefficients. These observed LLC corrections are compared to the LLC projections from the models variance–covariance matrix. The excessively large LLC errors at order 2 found in the case of EIGEN-2 with the ERS data are discussed. The degree-dependent scaling factors for the variance-covariance matrices of EIGEN-1S and –2, applied to obtain more realistic error estimates of the solved-for coefficients, are compatible with the results found here.  相似文献   

‘Surface Drag in the Arctic Marginal Sea-ice Zone: A Comparison of Different Parameterisation Concepts’   总被引：1，自引：0，他引：1  

Christof?LüpkesEmail author  Gerit?Birnbaum 《Boundary-Layer Meteorology》2005,117(2):179-211

Two parameterisation schemes for the turbulent surface fluxes and drag coefficients over the Arctic marginal sea-ice zone (MIZ) are (further) developed, and their results are compared with each other. Although the schemes are based on different principles (flux averaging and parameter averaging), the resulting drag coefficients differ only slightly in the case of neutral and stable stratification. For unstable stratification and sea-ice conditions being typical for the north-eastern Fram Strait, the drag coefficients resulting from the parameter-averaging concept are 5–10% larger than those of the flux-averaging concept. At a sea-ice concentration of 45%, the parameter-averaging method overestimates the heat fluxes by a factor of 1.2. An inclusion in the schemes of form drag caused by floe edges and ridges has a much larger effect on the drag coefficient, and on the momentum fluxes, than the choice between the parameter-averaging or flux-averaging methods. Based on sensitivity studies with the flux-averaging scheme, a simple formula for the effective drag coefficient above the Arctic MIZ is derived. It reduces the computational costs of the more complex parameterisations and could also be used in larger scale models. With this simple formula, the effective drag coefficient can be calculated as a function of the sea-ice concentration and skin drag coefficients for water and ice floes. The results obtained with this parameterisation differ only slightly from those using the more complex schemes. Finally, it is shown that in the MIZ, drag coefficients for sea-ice models may differ significantly from the effective drag coefficients used in atmospheric models.  相似文献   

Studies on turbulent diffusion processes and evaluation of diffusivity values from hydrodynamic observations in Corpus Christi Bay   总被引：1，自引：0，他引：1  

Temitope O. Ojo  James S. Bonner  Cheryl Page 《Continental Shelf Research》2006,26(20):2629-2644

The physical process of dispersion which can be attributed to turbulence (turbulent diffusion) or shear (shear-augmented diffusion) within the flow field is very important as it ultimately governs the distribution of constituents of interest within the environment. A series of diffusion experiments were conducted in Corpus Christi Bay, TX with the purpose of characterizing turbulent diffusion through dispersion coefficients or turbulent diffusivity, K_i (i=x, y, z) dependent on the degree of randomness or turbulence intensity, I.Measured with a boat-mounted acoustic doppler current profiler (ADCP), the Eulerian velocity time-series of fluid particles in random motion, u_i was used in the evaluation of the Eulerian time-scale of turbulence, T^E based on the velocity correlation function, R^E with T^E being related to the Lagrangian time-scale T^L through a scaling parameter, β(=T^L/T^E). Surface currents were obtained with high frequency (HF) Radar equipment deployed over the study area from which the horizontal velocity gradients were determined.Within the spatial scale of the experiment (1000 m), the observed low horizontal gradients (10⁻⁴ s⁻¹) allowed for the generation of velocity time-series from an ADCP mounted on a moving platform. A numerical scheme for evaluating turbulent diffusivity values was developed on the basis of Eulerian current measurements and calibrated through the statistics of an evolving dye patch for the scaling parameter β which in this scheme was found to be in the range 1–3.  相似文献   

电离层总电子含量时空特征分析及分区建模   总被引：1，自引：0，他引：1  

刘志平  赵自强  郭广礼 《武汉大学学报(信息科学版)》2012,37(11)

利用地统计方法研究了全球VTEC时空分区特征,提出了IONEX单天产品发布的改进策略和VTEC时空分区建模方法,包括组合函数与IRI2007模型背景场建模方法。纬度10°～70°、经度60°～180°范围内单天VTEC分区建模与结果分析表明,分区建模极大地降低了模型的复杂性。上述两种方法均可得中低纬分区B13约为高纬分区A23中误差（2～3TECU）的2倍,验证了顾及VTEC时空特征分区建模的有效性。  相似文献