Analysis of the characteristics of snow drop size distribution in the Qilian Mountains   总被引：1，自引：0，他引：1  

Guo Zhao  RongZhong Chu  Tong Zhang  Wei Ji  Jin Shen  ZhongYuan Wu 《寒旱区科学》2010,2(5):0419-0426

Under the Watershed Allied Telemetry Experimental Research (WATER) project, a significant amount of snow size data was collected from March to April 2008. However, because of limited observation data for the Qinghai-Tibet Plateau, the modeling behavior was not satisfactory. This paper demonstrates characteristics of the snow drop size distribution (SSD) in this region. The experimental area is located in the northeastern part of the Qinghai-Tibet Plateau. The Heihe River Basin, which is the second largest interior river basin in China and is located on the northern slopes of the Qilian Mountains, was selected as the simulation region. This basin ranges from approximately 5,000 m to 1,000 m in elevation. A new generation Parsivel disdrometer, the OTT Parsivel, was used for measurements. Four data sets were compiled to determine the average distributions for four different snowfall rates. The characteristics of the snow particle size distribution in the mountainous area were analyzed. Similar to the raindrop distribution, there was a multi-peak structure. Most peaks appear in the D 2 mm region (D: diameter of the snow drop size). An M-P distribution and a Г distribution were developed based on the precipitation data observed in Qilian mountainous area. We found that the Г distribution has a better fit than the M-P distribution for the actual distribution. In addition, we observed that the intercept parameter (N0) and the slope parameter (Λ) correlate well with the shape parameter (μ). The disdrometer data can also be used to model the reflectivity factor (ZH) and differential reflectivity factor (ZDR). The radar reflectivity (ZHH, ZVV) and differential reflectivity (ZDR) were modeled in order to facilitate understanding of the connections between radar and ground measurements, and were used to support work for the improvement of rainfall estimates by polarimetric radar. Rain rate estimation using radar measurements was based on empirical models, such as the Z-R relationship and R(ZH, ZDR) in the Qilian mountainous areas. The relationship of R=0.017×100.079×ZH-0.022×ZDR is better than R=0.019×100.078×ZH for estimating R (melted snow). The normalized errors (NE) of R(ZH) and R(ZH, ZDR) are 13.22% and 5.20%, respectively.  相似文献   

爆炸波在地铁车站中的传播规律研究   总被引：1，自引：0，他引：1  

廖维张  杜修力 《地震学刊》2010,(5):538-543

应用LS-DYNA软件建立了北京比较典型的2层地铁车站有限元模型,通过数值模拟方法分析地铁车站发生内部爆炸时,爆炸波在地铁车站内部的传播规律。研究表明：①在0.3m/kg~（1/3）〈Z〈1.6m/kg~（1/3）范围内,车站内部超压峰值可用Henrych经验公式估算;②爆炸波在地铁车站的封闭空间不断出现反射、绕射现象,使得结构构件遭受多次冲击作用;③楼梯口起到了一定的泄爆作用。本文研究结果可供地铁车站的抗爆设计与安全分析参考。  相似文献   

Numerical simulation on the interaction of an internal solitary wave with a step-type topography     

Zhaoting Xu  Qun Li  Xu Chen  Jia Yu 《中国海洋大学学报(英文版)》2008,7(2):119-123

  相似文献   

Response of internal waves to 2005 Typhoon Damrey over the northwestern shelf of the South China Sea     

Gang Wang  Fangli Qiao  Yijun Hou  Dejun Dai  Min Lin  Qilong Zhang  Gang Wang  Baoshu Yin 《中国海洋大学学报(英文版)》2008,7(3):251-257

Continuous observation of sea water temperature and current was made at Wenchang Station (19°35′N, 112°E) in 2005. The data collected indicate vigorous internal waves of both short periods and tidal and near-inertial periods. The temperature and current time series during 18-30 September were examined to describe the upper ocean internal wave field response to Typhoon Damrey (0518). The strong wind associated with the typhoon, which passed over the sea area about 45 km south of Wenchang Sta- tion on 25 September, deepened the mixed layer depth remarkably. It decreased the mixed layer temperature while increasing the deep layer temperature, and intensified the near-inertial and high-frequency fluctuations of temperature and current. Power spectra of temperature and current time series indicate significant deviations from those obtained by using the deep ocean internal wave models characterized by a power law. The frequency spectra were dominated by three energetic bands: around the inertial frequency (7.75× 10-6 Hz), tidal frequencies (1.010-25 to 2.4×10-5 Hz), and between 1.4×10-4 and 8.3 × 10-4 Hz. Dividing the field data into three phases (before, during and after the typhoon), we found that the typhoon enhanced the kinetic energy in nearly all the frequency bands, es- pecially in the surface water. The passage of Damrey made a major contribution to the horizontal kinetic energy of the total surface current variances. The vertical energy density distribution, with its peak value at the surface, was an indication that the energy in- jected by the strong wind into the surface current could penetrate downward to the thermocline.  相似文献   

Peculiar velocities of 3000 spiral galaxies from the 2MFGC catalog     

I. D. Karachentsev  Yu. N. Kudrya  V. E. Karachentseva  S. N. Mitronova 《Astrophysics》2006,49(4):450-461

The 2MFGC catalog we have used contains 18020 galaxies selected from the extended objects in the 2MASS infrared sky survey as having apparent ratios of the axes b/a<0.3. Most of them are spiral galaxies of later morphological types whose disks are seen almost edge-on. The individual distances to the 2724 2MFGC galaxies with known rotation velocities and radial velocities are determined using a multiparameter infrared Tully-Fisher relation. A list of the distances and peculiar velocities of these galaxies is presented. The collective motion of the 2MFGC galaxies relative to the cosmic microwave background is characterized by a velocity V = 199 ± 37 km/s in the direction l = 304° ±11°, b = −8°±8°. Our list is currently the most representative and uniform sample for analyzing non-Hubble motions of galaxies on a scale of ∼100 Mpc. __________ Translated from Astrofizika, Vol. 49, No. 4, pp. 527–540 (November 2006).  相似文献   

On generation source sites of internal waves in the Luzon Strait   总被引：2，自引：0，他引：2  

ZHENG Quanan  SONG Y Tony  LIN Hui  HU Xiaomin  MENG Junmin  WANG Dan 《海洋学报(英文版)》2008,27(3):38-50

This effort aims to determine the generation source sites in the Luzon Strait for energetic, long-crest, transbasin internal waves （IW） observed in the northern South China Sea （NSCS）. The roles of islands distributed on eastern side of the strait, Kuroshio, submarine ridges, shoaling thennocline, and strait configuration played in the IW generation are examined using the cruise data analysis, satellite data interpretation, and dynamical analysis. The islands and channels on eastern side of the strait are excluded from a list of possible IW source sites owing to their unmatched horizontal dimensions to the scale of IW crest line length, and the relative low Reynolds number. The Kuroshio has a potential to be a radiator for the long-crest IW disturbances, meanwhile, the Kurosbio west （east） wing absorbs the eastward （westward） propagating IW disturbance. Namely, the Kuroshio blockades the outside west-east propagating IW disturbances. The 3-D configuration of the Luzon Strait is characterized by a sudden, more than one order widening of the cross-section areas at the outlets on both sides, providing a favorable condition for IW type initial disturbance formation. In the Luzon Strait, the thermocline is featured by a westward shoaling all the year around, providing the dynamical conditions for the amplitude growth （declination） to the westward （eastward） propagating IW type disturbance. Thus, the west slope of western submarine ridge at the western outlet of the Luzon Strait is a high possibility source sites for energetic, long-crest, transbasin IWs in the NSCS. The interpretation results of satellite SAR images during a 13 a period from 1995 to 2007 provide the convincing evidence for the conclusions.  相似文献   

顶部浮体激励下钢悬链线立管的动力响应分析     

郭海燕  孟丹  徐思朋 《中国海洋大学学报(自然科学版)》2009,39(5)

考虑钢悬链线立管大变形的特性以及内流的影响,利用Kane方法和拉格朗日应变理论建立钢悬链线立管的二维动力学模型。将顶部浮体的激励简化为一个沿顺流向的周期作用力施加于立管顶部,采用平均加速度法求解立管的动力响应。探讨顶部浮体不同激励频率下立管的非线性动力响应以及内流流速的大小对管道共振响应幅值的影响。  相似文献   

GIS空间线目标间拓扑关系形式化描述模型     

张水舰  李永树 《测绘学院学报》2009,(4)

针对现有拓扑关系描述模型的不足,首先以点集拓扑学基本理论为基础,定义了空间线目标的端点、内部、边界等概念,在此基础上提出了一种描述空间线目标间拓扑关系完善的形式化模型——New 9交模型。根据线目标的物理意义,提出了5条取值规则以排除模型描述的拓扑关系中没有意义的类型,并在此基础上总结出了空间线目标间拓扑关系的最小集,定义了6种线目标间的基本拓扑关系,并且证明了此最小集的互斥性与完备性。  相似文献   

Evolution and breaking of a propagating internal wave in stratified ocean   总被引：2，自引：2，他引：0  

LI Bingrui  FAN Haimei  TIAN Jiwei  SUN Bo  ZHANG Zhanhai 《海洋学报(英文版)》2008,27(1):13-22

The evolution and breaking of a propagating internal wave are directly numerically simulated using a pseudo-spectral method. The mechanism of PSI （ parametric subharmonic instability） involved in the evolution is testified clearly. It dominates gradually in nonlinear resonant interactions. As a consequence, the energy cascades to a second plant wave packet which has lower frequencies and higher wavenumbers than that of the primary wave. With the growth of this wave packet, wave breaking occurs and causes strongly nonlinear regime, i.e. stratified turbulence. The strong mixing and intermittent of the turbulence can be learned from the evolution of the total energy and kurtosis of vorticity vs. time. Some statistic properties of the stratified turbulence are also analyzed, including the spectra of KE （kinetic energy） and PE （potential energy）. The results show that the PE spectra display a wavenumber range scaling as 0. 2 N^4ky^-3 （N is the Brunt - Vaisala frequency, k, is the vertical wavenumber）, which is called buoyancy sub-range. However, the KE spectra cannot satisfy the negative cubic law of vertical wavenumber, which have a much larger downtrend than that of the PE spectra, for the potential energy is transferred more efficiently toward small scales than the kinetic energy. The Cox number of diapycnal diffusivity is also calculated, and it shows a good consistency with the observations and deductions in the ocean interior, during the stage of the stratified turbulence maintaining a fairly active level.  相似文献   

The internal tide of the Gareloch,a Scottish Fjord     

Peter E. Robins  Alan J. Elliott 《Estuarine, Coastal and Shelf Science》2009

Previous observations in the Gareloch, a Scottish silled fjord, have identified yet failed to explain the baroclinic circulation pattern. Additional fieldwork was carried out in April 2005, showing the loch to be stratified with two distinct layers and currents in each layer 180° out of phase at the M₂ frequency. The currents did not display the expected sinusoidal signal that is characteristic of the tide and instead were pulsated and stronger than predicted by barotropic forcing. Fourier analysis showed that the flow was dominated by short period non-linear oscillations that were harmonics of the semi-diurnal tide. Two hydrostatic estuarine models were applied to the Gareloch: a 2D vertical model (SLICE) and a 3D model (ECOMSED). Both models were capable of reproducing the observed (2005) baroclinic circulation at the M₂ time scale but failed to simulate the higher frequency, non-linear oscillations. However, each model generated higher harmonics in idealised scenarios. Because lateral motion was negligible and SLICE was an order of magnitude more efficient than ECOMSED, the 2D model was used to simulate the higher harmonics and showed that their generation was attributed to the non-linear distortion of the internal tide. When the internal Froude number (determined by barotropic velocity, stratification and water depth) was increased from a sub-critical value, non-linear advection became more important and higher harmonics were generated. The internal tide was further modified by wave reflection and interaction off steep boundaries, and by flow over the sill.  相似文献