自动站与人工观测数值的比较分析

对 2 0 0 2年 1 0月 1日～ 1 2月 31日逐日的自动站观测数值与人工观测值进行了比较 ,结果认为 ,大多数要素差别不大 ,对地温等差值较大的原因进行了分析。

我国西南地区春季典型雹暴观测与数值模拟研究

为了进一步厘清我国西南地区春季典型雹暴宏微观物理过程及成雹机制,本文选取X波段双偏振天气雷达资料、ADTD闪电定位系统监测资料以及地面降雹观测资料,运用模糊逻辑算法和耦合了NSSL双参方案的WRF-Elec模式,对2018年3月13日一次典型的雹暴单体降雹过程中热动力、微物理和闪电活动特征进行对比分析,并构建了单体雹暴过程各阶段的微物理模型。结果表明:(1)发展和成熟阶段是雹暴过程的关键阶段,霰粒子继续通过液滴与冰晶和雪与液滴的碰撞生成,而雹在“累积带”区域由液滴-低密度霰碰撞形成,并通过液态水的吸积而增大。(2)正地闪发生阶段与上升气流位置、雹含量和地闪的快速增加阶段相对应,反三极性电荷结构是正地闪在此次雹暴过程中占优的重要原因,它主要表现为对流起电机制作用,在云上部感应出一个较弱的负电荷区而生成,持续时间较短。(3)此次雹暴过程中强烈的上升气流对雹胚增长、冰雹形成、反极性结构的形成起主要作用,利用数值模式可以再现雹暴的反极性电荷结构演变特征和闪电活动特征。(4)基于观测结果与数值模拟构建的单体雹暴过程各阶段微物理模型,有利于理解雹暴中热动力过程、微物理过程、反极性电荷结构的形成及其与闪电活动特征的关系,对我国西南复杂地形区域的雹暴预报具有一定的指导意义。

贵州威宁一次雹暴过程的雷达观测与数值模拟研究

为系统了解中国西南复杂地形区域雹暴的动力及微物理特征,聚焦贵州威宁,主要利用多普勒双偏振雷达对该地区发生的典型雹暴进行观测,并通过三维对流云模式对雹暴进行数值模拟。观测中,在对雷达观测资料进行质量控制的基础上,通过模糊逻辑的算法识别雹暴系统中的水成物粒子;数值模拟中,利用模式对雹暴的动力与微物理过程进行模拟,并对雹暴的人工消雹潜力进行分析。研究结果如下:(1)高原小槽东移及高低空急流的配合导致研究区域内产生雹暴;(2)雹暴的发展期及成熟期是冰雹形成的关键时段,雹暴系统中冰雹主要是低密度霰粒子及高密度霰粒子在过冷的环境下,与过冷水及其他水成物粒子相互作用后形成的;(3)利用三维对流云模式可以较好地再现雹暴的发展过程,模拟与观测结果基本一致,模拟也证实霰粒子与过冷液滴相互作用对于冰雹的形成至关重要;研究对于中国西南复杂地形区域雹暴预警预报及人工消雹具有一定的指导意义。

降水性层状云系结构和降水过程的观测个例与模拟研究

2004年7月4-6日,在我国东北地区有一次大范围的降雨过程。作者分析了此次层状云降雨的观测资料,包括机载PMS资料、雷达资料以及地面雨强计资料等,并用包含详细微物理过程的一维层状云模式进行了数值模拟,用顾震潮的三层概念模型(把层状云垂直结构分为三层:第一层为冰晶层,第二层为过冷水层,第三层为暖水层)分析了云的结构及降水形成过程。结果表明,这个模型基本反映了降水性层状云的结构和降水产生的物理过程。在第一层中,冰晶的凝华增长很重要,也存在冰晶的碰并过程。在第二层中,冰晶和雪的增长主要是通过凝华过程,Bergeron过程作用很大,但不同时刻Bergeron过程的作用程度不同。第三层中主要有云滴、雨滴和从第二层降落下来以后融化的雪和霰。云的第一层对第二层有播种作用,冰晶层对降水的贡献为7%,过冷水层对降水的贡献为54%,暖水层对降水的贡献为39%,降水的产生中冷云过程作用稍大,但暖云过程也起重要作用。

经验正交函数与广义数值环境模式重构声速剖面的比较

本文利用Argo资料对经验正交函数(EOF)和GDEM模式拟合声速剖面的效果进行了比较。结果表明,两种方法都能较好地重构局地声速剖面。EOF方法的拟合精度与选取的EOF阶数有关,阶数越高,精度越高;GDEM模式的拟合精度介于EOF的前5阶到前10阶之间。EOF易受到样本数量和采样深度的限制,难以提供完整的声速剖面;而GDEM模式能够将剖面扩展到更深的深度,与仅有上层海洋采样数据的声速剖面相比,结合深海水团的信息可使拟合结果达到更高的精度。

灾害性大风发生机理与飑线结构特征的个例分析模拟研究

2009年6月3日在我国河南发生了历史罕见的强飑线天气过程,造成了严重的人员伤亡和灾害。为了解此次飑线天气的特征和产生的机理,本文采用卫星、雷达及地面加密观测资料,结合中尺度WRF(Weather Research and Forecasting)数值模式,研究了此次飑线产生的天气背景、宏微观结构特征及造成灾害性大风的机理。结果表明,此次飑线过程的主要影响系统是东北冷涡,其后部横槽引导的南下冷空气与西南暖湿气流在河南新乡南部一带交汇促发强对流过程,最后演变为飑线。但由于低层西南风偏弱,水汽条件不足,飑线发生的环境较为干冷。飑线产生区大气处于条件性不稳定状态,对流有效位能(CAPE,Convective Available Potential Energy)在1300J/kg左右,并具有适平的垂直风切变。地面气象场显示飑线具有相对冷湿的雷暴高压和强冷池,飑线过程产生的灾害性天气以大风而非强降水为主。数值模式结果显示飑线下沉气流的最大值仅为-13m/s,而地面风速最大值达到35m/s,是最大下沉气流的2.7倍。进一步的数值敏感试验表明,降水粒子的蒸发和融化冷却过程对降低地面温度和产生地面强风速具有重要影响,其中雨水蒸发过程产生的最大等效冷却率为-3K/min,远大于霰融化冷却率-0.7K/min,因此雨水蒸发过程是影响冷池强度的关键因素,而地面强冷池在此次飑线灾害性大风的产生中具有重要作用。

岩腔内泥岩压裂风化特性研究

危岩崩塌是山区主要地质灾害类型及动力地质作用现象,其演绎规律受控于陡崖或陡坡下部岩腔的发育特征。通过对三峡库区2 000余个危岩体的查勘和观测,发现陡崖或陡坡下部岩腔内壁面60%以上的裂隙具有压张性或压剪性,表征泥岩风化具有显著的压裂特点,泥岩压裂风化速度是自然状态下风化速度的2~7倍;运用地貌分析法提出了岩腔后壁平行后退的演化模型,通过有限元数值模拟初步揭示了岩腔后壁顶部竖向位移及脚部压应力随岩腔深度增加而近似线性增大的规律。

地表开采沉陷监测技术研究

随着地下矿产资源开采进入迅猛发展时期,地表沉陷、滑坡、裂缝等问题引起研究者的关注。研究者力图通过多期观测及成果分析,探寻地表运动的规律,从而预防地质灾害的发生。基于此,该文对近年来矿山地面沉陷监测技术的知识背景和理论方法进行综述,并结合工程案例分析传统监测、UAV-Li DAR、D-InSAR技术在地表沉陷监测中的应用。对不同技术的适用范围及优缺点进行简单地总结,为相关领域的研究者提供最新研究进展和技术参考。

小倾角LEO多星天基平台光学跟踪GEO精密定轨

针对地基卫星测控系统(TrackingTelemetryandCommand,TT&C)系统对地球静止轨道(Geostationary EarthOrbit,GEO)卫星在空间和时间覆盖上的局限性,提出小倾角低地球轨道(LowEarthOrbit,LEO)多星组网天基平台对GEO卫星进行跟踪定轨的方法.根据空间环境和光学可视条件对仿真数据进行筛选以模拟真实的观测场景,利用光学测角数据,使用数值方法对GEO卫星的轨道进行确定.结果与参考轨道进行重叠对比,在平台轨道精度5 m、测量精度5′′、定轨弧长12 h的情况下,两颗LEO卫星对GEO卫星进行跟踪定轨的精度可达到千米量级,4颗LEO卫星对GEO目标进行跟踪定轨的精度可达到百米量级.随着LEO组网卫星数量的增加,定轨精度得到了较大的提高.

Evaluation of wind vectors observed by HY-2A scatterometer using ocean buoy observations,ASCAT measurements,and numerical model data

The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer （HYSCAT） data based on comparison with ocean buoy data, the Advanced Scatterometer （ASCAT） data, and numerical model data from the National Centers for Environmental Prediction （NCEP）. The in-situ observations include those from buoy arrays operated by the National Data Buoy Center （NDBC） and Tropical Atmosphere Ocean （TAO） project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km, respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors （RMSEs） of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°, respectively. For the HYSCAT-ASCAT comparison, the temporal and spatial differences were limited to 1 h and 25 km, respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°, respectively. The global distribution of wind speed residuals （HYSCAT-NCEP） is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data, it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements, which were 2 rn/s and 20° for wind speeds in the range 2-24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.

On the Generation Algorithm of VRS Virtual Observations

In the past few years, network RTK positioning technology, especially the VRS technology, has been widely used in some parts of China and in many countries around the world. The principle of the VRS technology is discussed with corresponding formula deduction, and detailed descriptions and applications of VRS corrections and virtual observations generation algorithm are given.

Numerical Simulation of Motion Response of an Offshore Observation Platform in Waves

Offshore observation platforms are required to have great ability to resist waves when they are operating at sea. Investigation on the motion characteristics of the platforms in the sea can provide significant reference values during the platform design procedure. In this paper, a series of numerical simulation on the interaction of a triple-hulled offshore observation platform with different incident waves is carried out. All of the simulations are implemented utilizing our own solver naoe-FOAM-SJTU, which is based and developed on the open source tools of OpenFOAM. Duration curves of motion characteristics and loads acting on the platform are obtained, and a comparison between the results of the amplitude in different incident waves is presented. The results show that the solver is competent in the simulation of motion response of platforms in waves.

Cloud Seedability Study with a Dual-Model System

In this research, one-dimensional stratiform a novel dual-model system, cold cloud model （1DSC） coupled to Weather Research and Forecast （WRF） model （WRF-1DSC for short）, was employed to investigate the effects of cloud seeding by silver iodide （AgI） on rain enhancement. Driven by changing environmental conditions extracted from the WRF model, WRF-1DSC could be used to assess the cloud seeding effects quantitatively. The employment of WRF- 1DSC, in place of a one-dimen- sional two-moment cloud seeding model applied to a three-dimensional mesoscale cloud-resolving model, was found to result in massive reduction of computational resources. Numerical experiments with WRF-1DSC were conducted for a real stratiform precipitation event ob- served on 4-5 July 2004, in Northeast China. A good agreement between the observed and modeled cloud system ensured the ability of WRF-1DSC to simulate the observed precipitation process efficiently. Sensitivity tests were performed with different seeding times, locations, and amounts. Experimental results showed that the optimum seeding effect （defined as the percentage of rain enhancement or rain enhancement rate） could be achieved through proper seeding at locations of maximum cloud water content when the updraft was strong. The optimum seeding effect was found to increase by 5.61% when the cloud was seeded at 5.5 km above ground level around 2300 UTC 4 July 2004, with the maximum AgI mixing ratio （As） equaling 15 ng kg-1. On the other hand, for an overseeded cloud, a significant reduction occurred in the accumulated precipitation （-12.42%） as Xs reached 100 ng kg^-1. This study demonstrates the potential of WRF- 1DSC in determining the optimal AgI seeding strategy in practical operations of precipitation enhancement.

Numerical simulation of ground motion amplification in Modong area, Lushan

The April 20,2013,Ms 7.0 Lushan Earthquake was a major earthquake that followed the Ms 8.0 Wenchuan Earthquake on May 12,2008.Frequent earthquakes have caused heavy casualties and property loss in Western Sichuan.Earthquake disasters are often closely related to the amplification effect of ground motion.Studying the ground motion characteristics of near-surface geological structures helps to understand the distribution of potential earthquake disasters.In this study,we investigated ground motion amplification in the downtown area of Lushan using numerical simulation and aftershock data from the Lushan Earthquake.Using the Lushan earthquake aftershock data from nine seismic stations distributed in the area,the amplification effect of the sites was determined using the"reference site spectral ratio"method.The results show that the frequency of the ground motion amplification in the area was in the range 5–10 Hz,and the corresponding amplification peak was from 3 to 14.Among the study sites,the amplification(14 times)at L07 was the most prominent.To study further the amplification characteristics,shear-wave velocity models for the structures under these sites were established using passive-source Rayleigh surfacewave exploration.One-dimensional(1 D)and two-dimensional(2 D)seismic amplification effects were simulated using horizontally propagating shear-wave modeling.Except Site L07,the 1 D simulation results of each site well reflected the variation feature of the seismic amplification on the frequency band below the observed peak frequency,although the overall simulated amplification peaks were smaller than the observed results.The 2 D simulation of the remarkable amplification phenomenon at L07 was in better agreement with the observation result than was the 1 D simulation,indicating that the seismic amplification in the Modong area is influenced by lateral variation of the Quaternary sediments.

Macro-micro investigation of granular materials in torsional shear test

A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D.Stack wall technique boundary conditions are employed and optimized to reasonably capture the microstructure evolution.Parametric studies are conducted in terms of the ratio κ,normal and shear stiffness of particles,wall stiffness and friction coefficients.Afterwards,in comparison with physical test,numerical results for a fixed principal stress angle(α=45°) are presented.The results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle assembly.The evolution of the coordination number demonstrates that particles in shear banding undergo remarkable decrease.The effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized response.The shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.

Maneuvering target tracking algorithm based on cubature Kalman filter with observation iterated update

Reasonable selection and optimization of a filter used in model estimation for a multiple model structure is the key to improve tracking accuracy of maneuvering target.Combining with the cubature Kalman filter with iterated observation update and the interacting multiple model method,a novel interacting multiple model algorithm based on the cubature Kalman filter with observation iterated update is proposed.Firstly,aiming to the structural features of cubature Kalman filter,the cubature Kalman filter with observation iterated update is constructed by the mechanism of iterated observation update.Secondly,the improved cubature Kalman filter is used as the model filter of interacting multiple model,and the stability and reliability of model identification and state estimation are effectively promoted by the optimization of model filtering step.In the simulations,compared with classic improved interacting multiple model algorithms,the theoretical analysis and experimental results show the feasibility and validity of the proposed algorithm.

Feasibility of central loop TEM method for prospecting multilayer water-fi lled goaf

With deep mining of coal mines, prospecting multilayer water-filled goaf has become a new content that results from geophysical exploration in coalfields. The central loop transient electromagnetic （TEM） method is favorable for prospecting conductive layers because of the coupling relationship between its field structure and formation. However, the shielding effect of conductive overburden would not only require a longer observation time when prospecting the same depth but also weaken the anomalous response of underlying layers. Through direct time domain numerical simulation and horizontal layered earth forward modeling, this paper estimates the length of observation time required to prospect the target, and the distinguishable criterion of multilayer water-filled goal is presented with observation error according to the effect of noise on observation data. The observed emf curves from Dazigou Coal Mine, Shanxi Province can distinguish multilayer water-filled goaf. In quantitative inversion interpretation of observed curves, using electric logging data as initial parameters restrains the equivalence caused by coal formation thin layers. The deduced three-layer and two-layer water-filled goals are confirmed by the drilling hole. The result suggests that when observation time is long enough and with the anomalous situation of underlying layers being greater than the observation error, the use of the central loop TEM method to orosoect a multilaver water-filled goaf is feasible.

TAMDAR Observation Assimilation in WRF 3D-Var and Its Impact on Hurricane Ike (2008) Forecast

This study evaluates the impact of atmospheric observations from the Tropospheric Airborne Meteorological Data Reporting (TAMDAR) observing system on numerical weather prediction of hurricane Ike (2008) using three-dimensional data assimilation system for the Weather Research and Forecast (WRF) model (WRF 3D-Var). The TAMDAR data assimilation capability is added to WRF 3D-Var by incorporating the TAMDAR observation operator and corresponding observation processing procedure. Two 6-h cycling data assimilation and forecast experiments are conducted. Track and intensity forecasts are verified against the best track data from the National Hurricane Center. The results show that, on average, assimilating TAMDAR observations has a positive impact on the forecasts of hurricane Ike. The TAMDAR data assimilation reduces the track errors by about 30 km for 72-h forecasts. Improvements in intensity forecasts are also seen after four 6-h data assimilation cycles. Diagnostics show that assimilation of TAMDAR data improves subtropical ridge and steering flow in regions along Ike's track, resulting in better forecasts.

Bits, Mass and Acceleration Issues in BSC

The goal of the present paper is to expand already published works in the frame of＂Banded speed cosmology＂ （BSC）. In particular this paper gives validated values for physical quantities not so far investigated in previous publications, i.e., the number of individual physical entity in the universe, as well as the maximum value for acceleration. Validates values mean identical quantities from a numerical point of view obtained with different theoretical procedures, additionally compared with data based on NASA observations with Planck probe.

Impulse Control Problem of Partially Observed Diffusion Processes

The authors investigate the problem of impulse control of a partially observed diffusion process. The authors study the impulse control of Zakai type equations. The associated value function is characterized as the only viscosity solution of the corresponding quasi-variational inequality. The authors show the optimal cost function for the problem with incomplete information can be approximated by a sequence of value functions of the previous type.