北京地区单双频地基GPS大气水汽遥测试验与研究   总被引：5，自引：3，他引：5       下载免费PDF全文

谢璞  张朝林  王迎春  楚艳丽  张京江  王京丽  李矩  Ying Hwa Kuo  John Braun 《应用气象学报》2006,17(Z1):28-34

该文对北京地区单双频地基GPS大气水汽监测网布网依据、单频与双频地基GPS测量数据解算技术应用、GAMIT和Bernese地基GPS数据分析处理软件应用、远程遥控GPS数据采集与通讯系统、资料分析与数值同化应用等方面的工作进展进行简要介绍,重点讨论了单双频地基GPS大气水汽资料的解算技术及其应用效果。结果表明:在北京天气敏感区通过单双频地基GPS接收机合理组网布局,可构建并利用高分辨率电离层延迟订正技术将单频接收机的大气水汽监测精度提高到实用水平,为强降水天气预报提供有价值的产品。  相似文献   

数字化测绘的图形数据整理   总被引：1，自引：0，他引：1  

郑楚 《地理空间信息》2007,5(2):94-95

由于数据标准滞后和技术手段局限等原因,以往传统的CAD图形数据已经不能满足GIS入库的要求,因此数据整理已成为测绘工作者面临的一个重要课题。在分析图形数据的现状及其存在问题的基础上,对数据整理技术要求和方法提出了探讨,仅供同行们参考。  相似文献   

Estimation of peak relative velocity and peak absolute acceleration of linear SDOF systems     

Jianwei Song Yi-Lun Chu Zach Liang George C. Lee 《地震工程与工程振动(英文版)》2007,6(1):1-10

In the seismic analysis and design of structures, the true velocity and absolute acceleration are usually approximated by their corresponding pseudo-values. This approach is simple and works well for structures with small damping (say, less than 15%). When the damping of a structure is enhanced for the purpose of response reduction, it may result in large analysis and design errors. Based on theory of random vibration and the established mechanism of seismic response spectra analysis, a method is developed (1) to predict the relative velocity spectra with any damping ratio level directly from the 5% standard pseudo-acceleration spectrum; and (2) to estimate the peak absolute acceleration. The accuracy of both is validated by using two selected ensembles of ground motion records.  相似文献   

1975年海城7.3级地震在朝鲜半岛的震害及对日本九州地区的影响s          下载免费PDF全文

李裕澈  秋教昇  石川有三 《地震学报》2007,29(2):214-221

1975年中国海城7.3级地震波及整个朝鲜半岛，乃至日本九州地区. 本文系统收集了该震有关资料，并通过整理分析勾画出其烈度分布，以探讨该震的震害特点. 在半岛的北部， 除局部地区为Ⅵ度之外，大部分地区为Ⅴ度区，其震害情况与相同烈度的典型特征基本相符； 半岛南部大部分地区为Ⅳ度区. 然而，韩国首尔等大城市，除高层建筑强烈振动之外，还有人出现眩晕症状等特别的感觉，个别街区变压器跳闸造成一时停电. 这些可能是大震的长周期波在远场的效应所致.   相似文献   

Impact of 4DVAR Assimilation of Rainfall Data on the Simulation of Mesoscale Precipitation Systems in a Mei-yu Heavy Rainfall Event   总被引：1，自引：0，他引：1  

储可宽  谈哲敏 《大气科学进展》2007,24(2):281-300

The multi-scale weather systems associated with a mei-yu front and the corresponding heavy precipitation during a particular heavy rainfall event that occurred on 4 5 July 2003 in east China were successfully simulated through rainfall assimilation using the PSU/NCAR non-hydrostatic, mesoscale, numerical model （MM5） and its four-dimensional, variational, data assimilation （4DVAR） system. For this case, the improvement of the process via the 4DVAR rainfall assimilation into the simulation of mesoscale precipitation systems is investigated. With the rainfall assimilation, the convection is triggered at the right location and time, and the evolution and spatial distribution of the mesoscale convective systems （MCSs） are also more correctly simulated. Through the interactions between MCSs and the weather systems at different scales, including the low-level jet and mei-yu front, the simulation of the entire mei-yu weather system is significantly improved, both during the data assimilation window and the subsequent 12-h period. The results suggest that the rainfall assimilation first provides positive impact at the convective scale and the influences are then propagated upscale to the meso- and sub-synoptic scales.
Through a set of sensitive experiments designed to evaluate the impact of different initial variables on the simulation of mei-yu heavy rainfall, it was found that the moisture field and meridional wind had the strongest effect during the convection initialization stage, however, after the convection was fully triggered, all of the variables at the initial condition seemed to have comparable importance.  相似文献   

Current plate motions across the Red Sea   总被引：3，自引：0，他引：3  

Dezhi Chu  & Richard G. Gordon 《Geophysical Journal International》1998,135(2):313-328

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The Abundance of QSOs in Various Cold Dark Matter Models     

Wen-Bin Lin  Yao-Quan Chu 《Astrophysics and Space Science》1998,262(1):15-27

Based on the statistics of the peaks in the random Gaussian field, we put forward a method to model the evolution of quasars, which are assumed to be a phenomenon of the early stages for some massive galaxies. Our calculations show that the cold-hot mixed dark matter model with _h = 0.3 cannot match the observed quasar abundance at redshift z = 4.5, and other prevailing CDM models, such as the mixed dark matter model with _h = 0.2, the tilted CDM models with n = 0.7 or 0.8, and the flat CDM models with = 0.6 or 0.7, are compatible with the observation of the abundance of QSOs on the range of z = 2-5.  相似文献   

HIGH INPUT IMPEDANCE TRANSISTOR AMPLIFIER FOR ACCELERATION MEASUREMENT     

Li Chu 《岩土力学》1980,2(2):65-74

This paper describes a high input impedance preamplifier ,a main amplifier ,including its specification and the circuits theories .An acceleration measurement system consist of the piezoelectric acceleration 、preamplifier、cable 、main amplifier and oscilloscope for measureing the acceleration of vibration due to explosion .The features of the system are :1.good stability ,2.small zero shift ,3.The preamplifier is a new circuit which consists of four transistors 3DG6C,3DG4E. Its input impedance is as high as 1500MΩ and is able to undertake a high instantaneous impulse voltage ,4.There is no power supply set near the preamplifier .The signal transmiting cable is also the power supply cable so that the transmiting characteristic is very well .when the cable length is varied from 1 meter to 1000 meters ,the frequency response of system will not change .The decrement of output amplitude is less than 6% etc.  相似文献   

A Theoretical and Experimental Investigation of Energy-Containing Scales in the Dynamic Sublayer of Boundary-Layer Flows   总被引：2，自引：2，他引：0  

Gabriel Katul  Chia-Ren Chu 《Boundary-Layer Meteorology》1998,86(2):279-312

The existence of universal power laws at low wavenumbers (K) in the energy spectrum (E_u) of the turbulent longitudinal velocity (u) is examined theoretically and experimentally for the near-neutral atmospheric surface layer. Newly derived power-law solutions to Tchen's approximate integral spectral budget equation are tested for strong- and weak-interaction cases between the mean flow and turbulent vorticity fields. To verify whether these solutions reproduce the measured E_u at low wavenumbers, velocity measurements were collected in the dynamic sublayer of the atmosphere at three sites and in the inner region of a laboratory open channel. The atmospheric surface layer measurements were carried out using triaxial sonic anemometers over tall corn, short grass, and smooth desert-like sandy soil. The open channel measurements were performed using a two-dimensional boundary-layer probe above a smooth stainless steel bed. Comparisons between the proposed analytical solution for E_u, the dimensional analysis by Kader and Yaglom, and the measured Haar wavelet E_u spectra are presented. It is shown that when strong interaction between the mean flow and turbulent vorticity field occurs, wavelet spectra measurements, predictions by the analytical solution, and predictions by the dimensional analysis of Kader-Yaglom (KY) are all in good agreement and confirm the existence of a -1 power law in E_u(= C_uuu² _* K^-1, where C_uu is a constant and u_* is the friction velocity). The normalized upper wavenumber limit of the -1 power law (Kz = 1, where z is the height above the zero-plane displacement) is estimated using two separate approaches and compared to the open channel and atmospheric surface-layer measurements. It is demonstrated that the measured upper wavenumber limit is consistent with Tchen's budget but not with the KY assumptions. The constraints as to whether the mean flow and turbulent vorticity strongly interact are considered using a proposed analysis by Panchev. It is demonstrated that the arguments by Panchev cannot be consistent with surface-layer turbulence. Using dimensional analysis and Heisenberg's turbulent viscosity model, new constraints are proposed. The new constraints agree with the open channel and atmospheric surface-layer measurements, Townsend's inactive eddy motion hypothesis, and the Perry et al. analysis.  相似文献   

北京暴雨与旱涝关系的分析   总被引：11，自引：1，他引：10       下载免费PDF全文

吴正华  储锁龙 《应用气象学报》1998,9(4):492-495

根据北京近百年的逐日降水资料,分析了汛期暴雨与汛期旱涝的关系。指出:汛期暴雨多少和强度对汛期降水丰歉具有决定性作用;在给出的3种暴雨指数中,相当暴雨日数与旱涝级别的相关性最好。文中还讨论了旱涝短期气候预测与暴雨过程的短期气候预测相结合的必要性。  相似文献