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81.
该文从完整性、准确性、可靠性3个方面设计了自动气象站数据质量评估的流程,并对北京地区187个自动气象站1998—2009年逐时气温资料进行了质量评估。结果显示:北京地区自动气象站建设初期重点兼顾城区和山区的布设策略,为北京区域气候研究提供了较好的基础;北京地区正常运行的自动气象站发生中度和重度缺测的站点相对较少,离散和轻度连续的缺测较集中,具有较好的区域一致性;错误发生率最高为3.8%,大多数年份错误发生率均在1%以下,可见自动气象站错误数据相对较少;尽管可疑数据涉及的站点相对较多,但经空间一致性检查后,有超过50%可归并为正确数据。评估分析结果表明:北京地区自动气象站数据具有一定的准确性和可靠性,具有较强的应用潜力和前景。 相似文献
82.
利用CloudSat卫星资料、NCEP再分析资料和FY-2C卫星可见光云图分析了2006年7月20—24日我国东北一次冷涡过程不同时期对流云的垂直结构以及云内中小尺度的结构,发现在冷涡发展阶段的初期,暖锋对流结构表现为孤立的回波系统多,强对流深厚,对流系统体现为孤立、深厚的特征。在冷涡发展成熟阶段,回波强度比冷涡发展初期的对流系统有所减弱,且为浅薄的对流系统。冷涡系统影响下发展的锢囚锋回波系统顶部呈现独特的结构特征:东南部为干冷空气侵入造成的回波区, 中部为锢囚锋主体对流区, 西北部为暖锋遇冷锋抬升作用形成的回波区。在锢囚锋尾部存在冰水含量与液态水含量分层现象,干冷空气侵入层在5 km高度左右,在干冷空气侵入层上部为冰水含量分布的弱回波区,下部为液态水分布的弱回波区。在冷涡成熟阶段,对流系统分布在冷涡外沿,表现为孤立的对流系统,冰水含量多的对流系统主要在冷涡的北面,而液态水主要分布在冷涡中心零度层以下。 相似文献
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Coupling effect diagnoses of quasi-stationary mesoscale vortex in Guangxi rainstorm process of China
The mesoscale weather system which affected the Guangxi flash-flood-producing rainstorm of China in June 2008 is a quasi-stationary mesoscale vortex. Its genesis and development is closely related to the coupling effects of weather systems in different scales and different latitudes. On the one hand, the coupling of synoptic scale high- and low-level jets provides the environmental conditions for development of vortices and vertical circulations in the mesoscale vortex; On the other hand, the coupling of waves in mid-latitude westerlies and perturbations in low-latitude warm-moist flow under the influence of complex terrain makes the mesoscale vortex circulations strengthened. With the piecewise potential vorticity (PV) inversion method, PV anomalies in different regions are analyzed; also the vortex-vortex interactions and vortex-background flow interactions are diagnosed. Thus, the reasons why the mesoscale is quasi-stationary at first, while developing and deepening later are indicated. Under the condition of coupling effects, the vertical motions accompanied with the mesoscale vortex can be diagnosed with the PV-ω inversion system based on the analysis of quasi-balanced flow. 相似文献
86.
Study on the failure process of high concrete dams subjected to strong earthquakes is crucial to reasonable evaluation of their seismic safety. Numerical simulation in this aspect involves dynamic failure analysis of big bulk concrete dam subjected to cyclic loading. The Rock Failure Process Analysis (RFPA) proposed by C.A. Tang, with successful applications to failure modeling of rock and concrete specimens mainly subjected to static loading, is extended for this purpose. For using the proposed model, no knowledge on the cracking route needs to be known beforehand, and no remeshing is required. Simulation of the whole process of elastic deformation, initiation and propagation of microcracks, severe damage and ultimate failure of concrete dams in earthquakes with a unified model is enabled. The model is verified through a shaking table test of an arch dam. Finally a practical gravity dam is employed as a numerical example. Considering the uncertainty in ground motion input and concrete material, typical failure process and failure modes of gravity dam are presented. Several small cracks may occur due to tension particularly at dam neck, dam faces and dam heel, and a few of them evolve into dominant ones. Relatively smaller earthquake may cause damage to the dam neck while a bigger one may bring on cracks at lower parts of the dams. Cracking at the dam bottom may incline to a direction almost perpendicular to the downstream face after propagating horizontally for a certain distance when the shaking is strong enough. 相似文献
87.
Based on Fourier-Bessel series expansion of wave functions,an analytical solution to 2-D scattering ofincident plane SV waves by circular cylindrical canyons with variable depthto-width ratios is deduced in this paper. Unlike other analytical solutions,this paper uses the asymptotic behavior of the cylindrical function to directly define the undetermined coefficients of scattered waves,thus,avoiding solving linear equation systems and the related numerical computation problems under high-frequency incident waves,thereby broadening the applicable frequency range of analytical solutions. Through comparison with existing analytical solutions,the correctness of this solution is demonstrated. Finally, the incident plane SV wave scattering effect under circular cylindrical canyons in wider frequency bands is explored. 相似文献
88.
山东数字地震台网定位子台网 选取对定位结果的影响 总被引:2,自引:1,他引:1
选取山东及邻区4个不同区域的地震,分析“定位子台网”分布对地震定位精度的影响,研究“定位子台网”的选取规则.探讨两种台站分布情况下定位偏差、水平误差、拟合残差随空隙角、近台距离、远台距离的变化;定位偏差及水平误差与拟合残差的关系.结果显示,速报时选择4-9个分布相对合理的“定位子台网”参加定位,结果较好,使用水平误差估... 相似文献
89.
通过跟踪分析湖州地震台数字化水管倾斜仪和垂直摆倾斜仪连续2年的资料质量,发现水管倾斜仪观测精度高于垂直摆倾斜仪,并且资料稳定性逐年提高。从映震效能看,水管倾斜仪同震响应幅度远大于垂直摆,水管倾斜仪的自振周期远大于垂直摆倾斜仪而接近远震面波的周期,形成谐振,但两者的同震响应时间相当。 相似文献
90.
The size effect of copper wire radius (0.04–0.82 mm) on the diffusion-limited current density of an oxygen reduction reaction in stagnant simulated seawater (naturally aerated 0.5 mol/L NaCl) is investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) and compared with the results obtained in 0.5 mol/L H2SO4. In the oxygen diffusion-limited range, size effect is found to occur independent of electrolytes, which is attributed to non-linear diffusion. Additionally, to satisfy application in a marine setting, an empirical equation correlating oxygen diffusion-limited current density to copper wire radius is proposed by fitting experimental data. 相似文献