GRACE和SLR观测的地球动力学扁率最大熵谱及小波相关分析          下载免费PDF全文

张子占  陆洋  许厚泽 《地球物理学报》2007,50(5):1383-1389

卫星重力测量技术的实现为测定地球动力学扁率提供了新的方式和途径，GRACE卫星是目前最新的重力测量卫星，据其恢复的低阶重力场较以往精度得到大大提高，然而其观测地球动力学扁率（二阶项）却与卫星激光测距（SLR）结果相差较大.本文采用最大熵谱和小波分析方法对GRACE和SLR观测的地球动力学扁率时间序列信号进行定量比较分析，结果表明：GRACE观测的地球动力学扁率年际周期变化振幅仅为SLR观测结果的25%，并且目前GRACE观测的地球动力学扁率数据中含有系统输入信息和相位差，但前者较后者包含有较强的短周期（2～6月）信息.造成这种差异的主要原因可能来自于GRACE与SLR全球观测数据时空分布不同.  相似文献   

渤海湾西北部潮间带沉积物激光法与筛析沉降法结果的比较     

车继英  王福  裴艳东  商志文  田立柱  刘志广  范昌福  王宏 《华北地质》2007,30(1):76-80

对渤海湾西北部潮间带16个样品分别进行了激光法与综合法（筛析沉降法）粒度测量。两种方法所获结果的相关分析表明，激光法测得的〉63μm的砂的百分含量平均仅比综合法低5％，相关系数高达0.9，相关性显著。两种方法测得的粉砂和粘土含量相关系数分别为0.39和0.48。进一步将〈63μm部分分为6个粒级对比两种方法的异同，结果显示〈1μm、1～2μm、2～4μm、4～8μm、8～16μm和16～63μm部分的相关系数分别为0.24、0．7、0.7、0.61、0.61和0.37。据此认为，16个样品粒径〈1μm和16～63μm部分两种方法的结果不能对比，其余粒级的激光法结果，通过各自的回归方程，可谨慎地代替传统的综合法。  相似文献   

Laser Scanning的基本原理及其应用前景     

WANG Ren    XU Qing 《测绘学院学报》2007,(Z1)

首先介绍了激光测距仪的发展历程,针对应用领域的不同,分别对3维激光成像仪和机载/星载激光测高仪的测量原理进行了阐述,并分别介绍了两种激光测距仪的工作流程以及数据处理流程,最后对两种激光测距仪的应用范围进行了阐述,并把两种激光测距技术和普通摄影测量进行了比较,指出了激光测距技术相对于普通摄影测量的优点,即高精度性、穿透性、实时性。  相似文献   

北半球高纬地区年际尺度循环过程中的气-海-冰相互作用关系     

刘喜迎刘海龙  李薇张学洪  宇如聪俞永强 《气象学报》2007,65(3):384-392

基于一个全球气-海-冰耦合模式数值模拟结果,对北半球高纬度地区年际尺度的气-海-冰相互作用进行了分析。在所使用的全球气-海-冰耦合模式中,大气环流模式和陆面过程模式来自国家气候中心,海洋环流模式和海冰模式来自中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室。采用一种逐日通量距平耦合方案实现次网格尺度海冰非均匀条件下大气环流模式和海洋环流模式在高纬地区的耦合。只对50 a模拟结果中的后30 a结果进行了分析。在分析中,首先对滤波后的北半球高纬度地区海平面气压、表面大气温度、海表面温度、海冰密集度及海表面感热通量的标准化距平做联合复经验正交函数分解,取第一模进行重建,然后讨论了在一个循环周期(约4 a)中北半球高纬度地区气-海-冰的作用关系。结果表明:(1)当北大西洋涛动处于正位相时,格陵兰海出现南风异常,使表面大气温度升高,海洋失去感热通量减少,海洋表面温度升高,海冰密集度减小;当北大西洋涛动处于负位相时,格陵兰海出现北风异常,使表面大气温度降低,海洋失去感热通量增多,海洋表面温度降低,海冰密集度增加。巴伦支海变化特点与格陵兰海相似,但在时间上并不完全一致。(2)多年平均而言,北冰洋内部靠近极点区域为冷中心。当北冰洋内部为低压异常时,因异常中心偏向太平洋一侧,使北冰洋内部靠近太平洋部分为暖平流异常,靠近大西洋一侧为冷平流异常。伴随着暖、冷平流异常,这两侧分别出现暖异常和冷异常,海表面给大气的感热通量分别偏少和偏多,上述海区海表面温度分别偏高和偏低,海冰密集度分别偏小和偏大。当北冰洋内部为高压异常时特点正好与上述相反。由上述分析结果可知,在海洋、大气年际循环中,大尺度大气环流变率起主导作用,海洋表面温度和海冰密集度变化主要是对大气环流变化的响应。  相似文献   

Detection of iodine monoxide radicals in the marine boundary layer using laser induced fluorescence spectroscopy     

Lisa K. Whalley  Kate L. Furneaux  Tom Gravestock  Helen M. Atkinson  Catherine S. E. Bale  Trevor Ingham  William J. Bloss  Dwayne E. Heard 《Journal of Atmospheric Chemistry》2007,58(1):19-39

A Laser Induced Fluorescence (LIF) instrument has been developed to detect iodine monoxide (IO) radicals in the atmosphere. An all solid-state Nd:YAG pumped Ti:Sapphire laser operating at approximately 445 nm was used to excite the (2,0) band of the IO A²Π_3/2 ← X²Π_3/2 electronic transition, with off-resonance fluorescence in the (2,5) band detected at 521 nm. The sensitivity of the instrument was determined by calibration. IO (between 10 and 150 pptV) was generated following the 184.9 nm photolysis of N₂O/CF₃I/N₂ mixtures with O₃ actinometry used to determine the photolysis flux. The detection limit was determined to be 0.3 pptV for a 300 s integration period, with an uncertainty of 23% (1σ). The instrument was deployed in August/September 2006 during the RHaMBLe (Reactive Halogens in the Marine Boundary Layer) campaign in Roscoff, France. Located on a small jetty, a few metres from the water’s edge at high tide, the instrument measured significant levels of IO on 11 days, with a maximum of 27.6 ± 3.2 pptV observed on one day (averaged over 10 s) representing the highest IO mixing ratio recorded in the marine boundary layer to date. IO displayed a clear diurnal profile with a maximum at low tide during the daytime. These results represent the first point measurements of IO in the atmosphere by LIF.  相似文献   

GPS卫星的激光测距和应用研究   总被引：2，自引：0，他引：2  

许华冠 《天文学进展》1998,16(4):251-259

简述了SLR和GPS跟踪技术的发展概况。详细介绍了近几年来对GPS－35、36卫星的激光测距进展和应用研究的情况。给出了残差分析的初步结果,并指出了目前GPS卫星的稀少的激光测距资料对卫星精密定轨和站坐标的解算是有价值的。同时,也简单地评述了GPS卫星的微波和激光跟踪技术各自的优势和弱点．建议联合利用GPS-35、36卫星的SLR和GPS观测资料来开展有关的应用研究。最后,对今后的应用研究工作提出了建议．  相似文献   

A land surface model (IAP94) for climate studies Part II: Implementation and preliminary results of coupled model with IAP GCM     

Dai Yongjiu  Xue Feng  Zeng Qingcun 《大气科学进展》1998,15(1):47-62

The Institute of Atmospheric Physics Land Surface Model (IAP94) has been incorporated into the IAP two-level atmospheric general circulation model (IAP GCM). Global and regional climatology averaged over the last 25 years of 100 year integrations from the IAP GCM with and without IAP94 (“bucket” scheme) is compared. The simulated results are also compared with the reanalysis data. Major findings are:(1) The IAP GCM simulation without IAP94 has extensive regions of warmer than observed surface air tempera?tures, while the simulation with IAP94 very much improves the surface air temperature.(2) The IAP GCM simulation with IAP94 gives improvement of the simulated precipitation pattern and intensity, especially the precipitation of East Asian summer monsoon and its intraseasonal migration of the rainbelts.(3) In five selected typical regions, for most of the surface variables such as surface air temperature, precipitation, precipitation minus evaporation, net radiation, latent heat flux and sensible heat flux, the IAP GCM with IAP94 pro?vides better simulations.  相似文献   

Towing dynamics of a liferaft and fast rescue craft in a surface wave     

W. Raman-Nair  J. Power  A. Simoes Re 《Ocean Engineering》2008,35(11-12):1252-1258

The equations of motion for the coupled dynamics of a small liferaft and fast rescue craft in a surface wave are formulated in two dimensions using the methods of Kane and Levinson [1985. Dynamics: Theory and Applications. McGraw-Hill Inc., New York]. It is assumed that the motion normal to the wave surface is small and can be neglected, i.e. the bodies move along the propagating wave profile. The bodies are small so that wave diffraction and reflection are negligible. A Stokes second order wave is used and the wave forces are applied using Morison's equation for a body in accelerated flow. Wind loads are similarly modelled using drag coefficients. The equations are solved numerically using the Runge–Kutta routine “ode45” of MATLAB^®. The numerical model provides guidelines for predicting the tow loads and motions of small craft in severe sea states.  相似文献   

Distinct activity phases during the recent geologic history of a Gulf of Mexico mud volcano     

I.R. MacDonald  M.B. Peccini 《Marine and Petroleum Geology》2009

Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m²) surrounded by a continuous bed of methanotrophic mussels (Bathymodiolus childressi) covering 434 m² and a patchy bed covering an additional 214 m² of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m³, while the middle and upper stages deposited 7700 and 20,400 m³, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ¹⁴C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages.  相似文献   

多种激光扫描系统在数字城市中综合应用研究探索          下载免费PDF全文

丁莹莹  赵云昌 《山东国土资源》2015,31(4)

该文以多种类型的激光扫描系统为研究对象,综合利用激光扫描系统在不同尺度下获取的数据,展示城市各个方面的部件特征,探索出基于四层结构（地形数据层、街区数据层、室内数据层和实体数据层）的数字城市三维建模解决方案,为多种激光扫描系统在数字城市综合应用提供研究方向。  相似文献