隧道结构断面测量方法及对比分析     

杨志坚 《测绘通报》2019,(11):160-162

隧道结构断面测量的目的是准确测出隧道开挖的实际轮廓线，并与设计轮廓线进行对比分析，从而计算超欠挖量。断面测量根据使用的仪器不同主要有断面仪法、全站仪法和三维激光扫描仪法，本文对这3种方法的工作效率及测量精度等情况进行了对比分析，并得出了一些有益的结论。  相似文献   

南海东北部陆坡冷泉系统的浅地层剖面特征与分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘伯然  宋海斌  关永贤  拜阳  陈江欣  耿明会 《地球物理学报》2015,58(1):247-256

本文通过对南海东北部陆坡区浅地层剖面资料的处理,结合横跨陆坡区的长地震测线,总结了该区浅层气聚集、海底流体运移、泥火山和冷泉活动在浅地层剖面中的特征,并对剖面中出现的声学空白带现象做了分类.研究认为浊反射、增强反射等现象,反映了该区域存在广泛的浅层气聚集.对声学空白带成因的分析,认为窄空白带很可能对应海底流体运移的通道,而宽空白带则可能由沿地层分布的浅层气引起,同时提出了自生碳酸盐岩体散落分布造成声学空白的可能性.我们在南海东北部陆坡区发现了泥火山,并讨论了其运移通道及对BSR的破坏.同时发现研究区水体中存在声学异常体,推断为冷泉羽状流,指示该区存在活动的冷泉.本文依托大量的浅地层剖面数据,对南海东北部陆坡区的冷泉系统有了较全面的认识,对冷泉系统剖面特征的成因进行了初步探讨,可为南海冷泉系统研究的进一步开展提供有益参考.  相似文献   

Detection and reconstruction of large‐scale coherent flow structures in gravel‐bed rivers          下载免费PDF全文

Mário J. Franca  Ulrich Lemmin 《地球表面变化过程与地形》2015,40(1):93-104

Large‐scale flow structures (LSFS) in the streamwise direction are important features of gravel‐bed river flows, because they may contribute to sediment transport and gas exchange. In the present study, these structures are detected using Huang's empirical mode decomposition and reconstructed with phase‐averaging techniques based on a Hilbert transform of the velocity signal. The analysis is based on the fluctuating component of 15 quasi‐instantaneous velocity profiles measured with a three‐dimensional (3D) acoustic Doppler velocity profiler (ADVP) in an armoured gravel‐bed river with a low relative submergence of 2.9 (ratio between flow depth and bed grain diameter). LSFS were identified in most of the measured profiles and consistently showed similar features. We were able to characterize the geometry of these large‐scale coherent structures: the front has a vertical linear shift in the time domain and a vertical profile corresponding to a first quarter moon with the apex situated at z/h ≈ 0.4. In the vertical, the front scales with flow depth h, and in the streamwise direction, LSFS scale with three to seven times the mean flow depth. On the bed, the effect of LSFS is a periodic non‐linear variation of the friction velocity on average between 0.90 and 1.10 times the mean value. A model for the friction velocity cycle resulting from LSFS oscillation is presented. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

云南大理风廓线结构随雨季进程的演变特征分析     

董保举  张成稳  杨南 《云南地理环境研究》2012,24(1):17-24

利用大理国家气候观象台2008年4月至6月的风廓线雷达观测数据,分析风廓线结构在雨季进程的演变特征,发现随着雨季的进程风速逐渐减小,风速振幅逐渐变小,高空自由大气动量下传效应逐渐减弱,高层大气有明显的转变,西风减小,北风增强;大气低层风速日变化雨季前明显,随着雨季的到来逐渐减弱,雨季风速日变化不明显。通过这样的分析对研究边界层风的季节变化具有重要的意义。  相似文献   

风廓线雷达资料在暴雪天气过程中的应用   总被引：1，自引：0，他引：1  

周之栩 《气象与环境科学》2012,35(4):69-72

通过对2010年12月15日湖州市暴雪过程的风廓线雷达资料分析发现：风廓线雷达风资料可以清楚地展示暴雪过程风场变化特点,通过分析高低层冷暖平流的分布变化情况,进一步了解暴雪过程的大气层结结构;风廓线雷达探测到的垂直速度、折射率结构常数及探测高度等指标的变化能反映降雪的开始、结束以及降雪的强度,为精细化预报提供参考。  相似文献   

基于极大似然算法的风廓线雷达谱矩估计     

惠建新  吴蕾  高玉春  周杰 《气象科技》2012,40(1):9-14

在风廓线雷达谱数据处理中,雷达低层取样体积探测的谱数据通常出现地物杂波、间歇性杂波、地磁杂波与大气回波谱混杂交叠的情况。为了有效抑制和去除杂波干扰,并且提高风廓线雷达探测范围和测量精度,必须对大气回波谱的谱矩进行有效的估计。通过对风廓线雷达多普勒回波功率谱分析,提出基于极大似然算法估计雷达回波谱谱数据的方法,并且进行了实际数据仿真分析,通过与常规方法进行对比分析,验证了算法的可行性和有效性,在低层取样体积谱矩估计得到了显著的改善。  相似文献   

风廓线仪与气球测风资料的对比分析   总被引：3，自引：0，他引：3  

孙旭映  韩晖  段海霞  张良  李忆平  闫敬泽  渠永兴 《干旱气象》2008,26(3):48-52

利用风廓线仪和气球同步探测风场资料对比,分析了风廓线仪探测风场资料的可靠性。结果表明：在稳定天气过程中,由于风廓线仪的探测盲区和地物杂波的影响,自地面至高空200m范围内,廓线仪探测的风向、风速与气球探测的风向风速值有一定偏差,200m高度以上风廓线仪和气球探空所测得的风场廓线具有很好的相关性;在复杂天气过程中风场廓线形状出现较大偏差,主要原因是由于气球探空资料在各高度层之间的整体连续性方面存在明显不足,而风廓线仪的观测资料无论在各高度层之间还是整体连续性方面都明显好于气球探空。这与在较高海拔地区,气球观测期间的大气局部不稳定有关。由于气球在经过某高度层时的取值明显受到当时大气层局部小湍流活动或者较强的下沉或上升气流影响,使气球经过该点时的位移与其相邻两点之间出现明显的飘逸,从而造成气球在某个高度范围内的风资料观测值出现较大偏离。但由于探空气球的资料不连续,无法准确判断气流扰动情况,而风廓线仪获取的不同高度上的风资料是10min内的平均观测值,一般不受小范围的空气扰动而出现较大偏离,另外,风廓线仪的观测是连续的,每组观测值之间只存在10min的时间差,通过对前后几组数据的对比分析,可以明显看出当时气流的扰动情况。因此,风廓线仪探测在资料的连续性和分析气流扰动情况,尤其是大尺度湍流活动方面更有探空气球不可替代的作用,风廓线仪观测资料的可靠性具有良好的应用价值。  相似文献   

Observations Of The Morning Transition Of The Convective Boundary Layer     

Wayne M. Angevine  Henk Klein Baltink  Fred C. Bosveld 《Boundary-Layer Meteorology》2001,101(2):209-227

The morning transition between the stable nocturnal situation and the daytime convective boundary layer (CBL) is of interest both for basic understanding and for initializing prognostic models. While the morning growth phase of the CBL has been studied in detail, relatively little has been published on the transition itself. In this paper, conventional observations of surface temperature, humidity, and turbulent fluxes,and data from a meteorological tower, are combined with measurements of the onset of convection by boundary-layer wind profilers to explore the timing and behaviour of the transition period. The transition is defined here as the period between sunrise and the time at which the depth ofconvection reaches about 200 m AGL. Diagnostic relationships based on surface heat flux, the temperature difference between 2 m and 200 m, and bulk Richardson number are explored. The transition is foundto be enabled by surface heating relaxing the surface stability, while the warming of the layerbetween 2 m and 200 m is in large part due to shear-driven entrainment.  相似文献   

Turbulent Dissipation Rate In The Boundary Layer Via Uhf Wind Profiler Doppler Spectral Width Measurements   总被引：2，自引：0，他引：2  

B. Campistron  S. Bernard  B. Bénech  F. Ardhuin-Girard  J. Dessens  E. Dupont  B. Carissimo 《Boundary-Layer Meteorology》2002,103(3):361-389

The study is focused on the retrieval and validation of the turbulent kinetic energy dissipation rate from spectral width measurements made by a UHF wind profiler in the convective atmospheric boundary layer. The possibility to deduce , which is one of the most important parameters for boundary-layer study and monitoring, from Doppler radar spectral width measurements has a firm theoretical basis established by numerous earlier works. However, the major drawback of this approach lies in various meteorological and instrumental sources of non-turbulent spectral width broadening which have to be recognised and accounted for. In the first part of the study, the theoretical background of the retrieval is detailed and all possible causes of spectral broadening are listed and evaluated. In the second part, the method is applied to four days of UHF diurnal boundary-layer observations, collected during the TRAC-98 experiment, for which in situ aircraft measurements were available. Comparison between radar-retrieved and in situ aircraft measurements yields a fairly good agreement with a linear correlation coefficient of about 0.9 and a residual bias less than 2 × 10^-4 m² s^-3. The analysis of derived from vertical and off-zenith observation leads to the recommendation, that in the boundary layer, where the wind is usually moderate, data collected by off-zenith beams should be used. Indeed, the measurement of the vertical spectral width, less affected by the large-scale broadening factor, can still be altered by the ground clutter removal.  相似文献   

一次长江三角洲飑线的综合分析   总被引：32，自引：5，他引：32       下载免费PDF全文

漆梁波  陈永林 《应用气象学报》2004,15(2):162-173

该文利用多种气象资料（包括常规观测、卫星云图、自动气象站、多普勒气象雷达以及风廓线仪资料），综合分析了2002年8月24日发生在长江三角洲的一次飑线过程。发现该飑线产生于一个中尺度对流系统（MCS）当中，地面冷锋、副高边缘的高能水汽输送带与高空小槽配合，使该MCS得以发展和加强，副高南撤和下游有利的动力和层结条件使得MCS中的雷暴群发展为飑线，并迅速东移南压，产生了大范围雷雨大风天气。多普勒雷达、自动站及风廓线仪的资料还很好地揭示了该飑线的发生、发展、爆发过程及其回波和风场的空间结构特点。  相似文献