Analysis on the Meso-scale System Activity and the Structure Characteristics of A Short-time Rainstorm

By using the rainfall data in the regional automatic station,FY-2E satellite data,NCEP reanalysis data,the evolution features and the structure characteristics of a meso-scale convective system(MCS) which happened on May 6 in 2010 in Loudi City of Hunan Province were analyzed.The results showed that MCS was the important influence system for the generation and development of strong precipitation.The equivalent blackbody brightness temperature(TBB) field of satellite inversion could directly reflect the convective activity of cumulus,the precipitation distribution and the intensity characteristics in the rainstorm process.TBB low value belt had the good corresponding relationship with the rainstorm falling zone.The disturbance flow field and the height field which passed Barnes band-pass wave filtering represented that there existed the obvious high-layer anticyclonic circulation and the low-layer cyclonic circulation near the rainstorm zone.The divergence in the high layer and the convergence in the low layer enhanced the occurrence and development of MCS.In addition,the disturbance temperature field revealed the main source of energy which the occurrence and development of strong convective weather needed.

Design of Web System for Meso-scale Meteorological Observational Station Based on SVG

The web of meso-scale meteorological observational station based on WebGIS realized by SVG technology was briefly introduced.Through grasping and applying SVG technology,the high-density automatic observational station in Anhui Province was developed.The web of meso-scale meteorological observational stations constructed by SVG technique can display the network graphics of weather data and intuitionistic vector graphics interface.

The Impact of Meso-Scale Eddies on the Subtropical Mode Water in the Western North Pacific

Based on the temperature and salinity from the Argo profiling floats and altimeter-derived geostrophic velocity anomaly (GVA) data in the western North Pacific during 2002-2011, the North Pacific Subtropical Mode Water (NPSTMW) distribution is investigated and cyclonic and anti-cyclonic eddies (CEs and AEs) are constructed to study the influence of their vertical structures on maintaining NPSTMW. Combining eddies identified by the GVA data and Argo profiling float data, it is found that the average NPSTMW thickness of AEs is about 60 dbar, which is thicker than that of CEs. The NPSTMW thicker than 150 dbar in AEs accounts for 18%, whereas that in CEs accounts for only 1%. About 3377 (3517) profiles, which located within one diameter of the nearest CEs (AEs) are used to construct the CE (AE). The composite AE traps low-PV water in the center and with a convex shape in the vertical section. The 'trapped depth' of the composite CE (AE) is 300 m (550 m) where the rotational velocity exceeds the transitional velocity. The present study suggests that the anticyclonic eddies are not only likely to form larger amounts of NPSTMW, but also trap more NPSTMW than cyclonic eddies.

Flame Imaging in Meso-scale Porous Media Burner Using Electrical Capacitance Tomography

This study was conducted to investigate the characteristics of meso-scale combustion.The technique of electrical capacitance tomography(ECT) was used to locate flame position and monitor the effect corresponding to varied air/fuel ratio in a meso-scale combustor.Combustion phenomena including igniting,quenching and unsteady combustion have been visualized using ECT.The method of metallization protecting ECT sensor from high temperature damage and the novel calibration method adapted to ECT monitoring of unknown permittivity flame have been shown to be successful.At the same time,electrical nature of combustion and dielectric characteristics of hy-drocarbon flame were studied.The relationship between flame permittivity and state parameters of combustion gas was demonstrated preliminarily.

Meso-scale modeling of chloride diffusion in concrete with consideration of effects of time and temperature

A meso-scale truss network model was developed to predict chloride diffusion in concrete. The model regards concrete as a three-phase composite of mortar matrix, coarse aggregates, and the interfacial transition zone （ITZ） between the mortar matrix and the aggregates. The diffusion coefficient of chloride in the mortar and the ITZ can be analytically determined with only the water-to-cement ratio and volume fraction of fine aggregates. Fick＇s second law of diffusion was used as the governing equation for chloride diffusion in a homogenous medium （e.g., mortar）; it was discretized and applied to the truss network model. The solution procedure of the truss network model based on the diffusion law and the meso-scale composite structure of concrete is outlined. Additionally, the dependence of the diffusion coefficient of chloride in the mortar and the ITZ on exposure duration and temperature is taken into account to illustrate their effect on chloride diffusion coefficient. The numerical results show that the exposure duration and environmental temperature play important roles in the diffusion rate of chloride ions in concrete. It is also concluded that the meso-scale truss network model can be applied to chloride transport analysis of damaged （or cracked） concrete.

Meso-scale available gravitational potential energy in the world oceans

The pitfalls of applying the commonly used definition of available gravitational potential energy （AGPE） to the world oceans are re-examined. It is proposed that such definition should apply to the meso-scale problems in the oceans, not the global scale. Based on WOA98 climatological data, the meso-scale AGPE in the world oceans is estimated. Unlike previous results by Oort et al. , the meso-scale AGPE is large wherever there is a strong horizontal density gradient. The distribution of meso-scale AGPE reveals the close connection between the baroclinic instability and the release of gravitational potential energy stored within the scale of Rossby deformation radius.

Statistical characteristics of meso-scale vortex effects on the track of a tropical cyclone

This paper examines initial meso-scale vortex effects on the motion of a tropical cyclone （TC） in a system where coexisting two components of TC and meso-scale vortices with a barotropic vorticity equation model. The initial mesoscale vortices are generated stochastically by employing Reinaud＇s method. The 62 simulations are performed and analysed in order to understand the statistical characteristics of the effects. Results show that the deflection of the TC track at t = 24 h induced by the initial meso-scale vortices ranges from 2 km to 37 km with the mean value of 13.4 km. A more significant deflection of the TC track can be reduced when several initial meso-scale vortices simultaneously appear in a smaller TC circulation area. It ranges from 22 km to 37 km with the mean value of 28 km, this fact implies that the initial meso-scale vortices-induced deflection may not be neglected sometimes.

Case study on the three-dimensional structure of meso-scale eddy in the South China Sea based on a high-resolution model

Meso-scale eddies are important features in the South China Sea（SCS）. The eddies with diameters of 50–200 km can greatly impact the transport of heat, momentum, and tracers. A high-resolution wave-tide-circulation coupled model was developed to simulate the meso-scale eddy in the SCS in this study. The aim of this study is to examine the model ability to simulate the meso-scale eddy in the SCS without data assimilations The simulated Sea Surface Height（SSH） anomalies agree with the observed the AVISO SSH anomalies well. The simulated subsurface temperature profiles agree with the CTD observation data from the ROSE（Responses of Marine Hazards to climate change in the Western Pacific） project. The simulated upper-ocean currents also agree with the main circulation based on observations. A warm eddy is identified in winter in the northern SCS. The position and domain of the simulated eddy are confirmed by the observed sea surface height data from the AVISO. The result shows that the model has the ability to simulate the meso-scale eddy in the SCS without data assimilation.The three-dimensional structure of the meso-scale eddy in the SCS is analyzed using the model result. It is found that the eddy center is tilted vertically, which agrees with the observation. It is also found that the velocity center of the eddy does not coincide with the temperature center of the eddy. The result shows that the model has the ability to simulate the meso-scale eddy in the SCS without data assimilations. Further study on the forming mechanism and the three-dimensional structure of the meso-scale eddies will be carried out using the model result and cruise observation data in the near future.

THE DYNAMICAL ANALYSIS OF THE STRUCTURE OF Β MESO-SCALE DOUBLE RAINBANDS IN MEIYU FRONT

In this paper, an idealized perturbation following the ＂surge-flow conceptual model＂ for typical Meiyu frontal structure is designed to explain the β meso-scale structure ofrainbands in the Meiyu front using a non-hydrostatic, full-compressible storm-scale model including multi-phase microphysical parameterization. In addition, sensitivity numerical experiment on the vertical distribution of the ambient meridional wind is conducted to investigate the generation mechanism of D meso-scale double rainbands. The results of numerical experiments show that the cool and dry downdraft invading strengthened by the environmental aloft northerly wind plays a very important role to the generation and maintenance of the β meso-scale double rainbands. Moreover, the intensity and scale of the dry and cool downdraft invading are related to the intensity of the second circumfluence induced by mass adjustment when the acceleration of the westerly jet aloft occurs.

Modeling development on the meso-scale reacting transport phenomena in proton exchange membrane fuel cells

The catalyst layer （CL） of proton exchange mem-brane fuel cell （PEMFC） involves various particles and pores in meso-scale, which has an important effect on the mass, charge （proton and electron） and heat transport coupled with the electrochemical reactions. The coarse-grained molecular dynamics （CG-MD） method is employed as a meso-scale structure reconstruction technique to mimic the self-organization phenomena in the fabrication steps of a CL. The meso-scale structure obtained at the equilibrium state is further analyzed by molecular dynamic （MD） software to provide the necessary microscopic parameters for understanding of multi-scale and-physics processes in CLs. The primary pore size distribution （PSD） and active platinum （Pt） surface areas are also calculated and then compared with the experiments. In addition, we also highlight the implementation method to combine microscopic elementary kinetic reaction schemes with the CG-MD approaches to provide insight into the reactions in CLs. The concepts from CG modeling with particle hydrodynamics （SPH） and the problems on coupling of SPH with finite element modeling （FEM） methods are further outlined and discussed to understand the effects of the meso-scale transport phenomena in fuel cells.

Propagation of shock waves in dry and wet sandstone:Experimental observations,theoretical analysis and meso-scale modeling

Methods of experimental observations, theoretical analysis and meso-scale modeling were used to study the propagation processes of shock waves in dry and wet sandstone under dynamic impact in this paper.According to the results from the dynamic impact experiments with velocity of 0.2-0.5 km/s, it was found that the velocity of shock wave increases linearly with water content. Additionally, the velocity of the shock wave in the sandstone showed a linearly increased regularity with the increasement of the impact velocity, which was proved by theory in this paper. Furthermore, meso-scale simulation models were performed and the simulation results showed that sandstone's porosity reduced the shock waves velocity compared to nonporous materials. Pore space filled with water counteracts the effects of porosity, resulted in larger shock wave velocity.

On the Development of Meso-Scale Heavy Rain Parcels in China

Heavy rains occur in China frequently, which often bring us floods and serious disasters in the summer half-year. The meso-scale heavy rain parcels (MHRP) in the mid-latitude are usually developed in following cases:I.By the approaching, meeting and / or overlapping of different weather systems, when two or more different rainfall systems are getting to conjugate, some MHRPs could be developed, such as: 1) a new cold/warm front or squall line approaches an old front or squall, even when the old one is somewhat decrepit; 2) at the places where two or more synoptic systems with different characteristics are meeting together, such as the meeting of tropical cyclone with the cold airs coming from the mid- and / or high-latitudes, or the low latitude vortex meeting with the westerly trough; 3) at the intersections of some different weather systems, such as the intersection of drylines, squall lines or fronts moving from different directions; and 4) by the overlapping of rainfall parcels produced continuously from a meso-generation centre.II.Resonance Effect and Tibetan Plateau Influence are two reasons why high frequency of heavy and torrential rains arround the meiyu front is discussed also.

Electrical Characteristics,Electrode Sheath and Contamination Layer Behavior of a Meso-Scale Premixed Methane-Air Flame Under AC/DC Electric Fields

Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC （0-4300 V, 0-500 Hz） and DC （0-3300 V） electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 10^0-10^2μA, the electron density 10^15-10^16 m^-3 and further the power dissipation 〈 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10^-4-10^-3 Ω^-1. m^-1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length （31-98 μm） and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process.

Analysis on the Meso-scale Characteristics of a Hail Process in Linyi Area

[Objective] The research aimed to study the meso-scale characteristics of a hail process in Linyi area. [Method] By comprehensively using MICAPS conventional observation data, automatic encryption ground station, MM5 model product and Doppler weather radar data, a strong convective hail weather process which happened in Shandong Peninsula and southeast of Shandong on May 30, 2010 was analyzed. The circulation background and physical mechanism of strong convection weather occurrence, the features of meso- and micro-scale systems were discussed. Some occurrence and development rules of such weather were found. [Result] The strong convective weather was mainly affected by the cold vortex and translot. The high-altitude northwest airflow, low-level southwest airflow, dry and cold air at the high layer, warm and wet air at the low layer, forward-tilting trough caused the strong convective weather. The radar echo analysis showed that the radar echo in the process belonged to the typical multi-monomer windstorm echo, and the strong echo zone was in the forefront of echo. When the convection development was the strongest, the echo intensity reached 65 dBz, and the echo top height surpassed 11 km. As the development of windstorm monomer, the big-value zone of vertical liquid water content product had the jumping formation and disappearance. Moreover, there was obvious weak echo zone. The windstorm monomer moved to the southeast direction as the precipitation system. In the right front of monomer moving direction, there was hook echo feature. The evolution characteristics of radial speed field at the different elevation angles before and after the hail weather occurrence were analyzed. It was found that the radial speed field had some premonitory variations before the hail weather occurrence. Doppler radar product was used to improve the initial field of MM5 model, which could improve the forecast effect in the certain degree and the accuracy of short-time forecast and nowcasting. [Conclusion] The research accumulated the experience for the short-term forecast and nowcasting work of strong convective weather in future.

Study on circulation and meso-scale eddies in the South China Sea in summer of 1998

By using wide scope ADCP data which were got during SCSMEX (South China Sea Monsoon Experiment) period in the summer of 1998, and comparing these data with numerical modelling result, the distribution and variation characteristics of the circulation and meso-scale eddies in the South China Sea (SCS) were studied. The results show that: (1) in the SCS, 18 different scale eddies or motion systems with characteristics similar to meso-scale eddy were found during the investigation; (2) a strong westward current was found in the south of the Taiwan Shoal; (3) the energy of those eddies west of 114°E was much stronger than that of the east;(4) and there exist many powerful meso-scale eddies in the Nansha region south of 12°N. The distributions of numerous eddies reflect the complexity of the circulation in the SCS. It seems that the formation of those eddies should be caused by joint work of wind, coast feature, bottom topography, water density, inertial force and continental shelf waves.

弱天气系统强迫下一次突发性大暴雨成因分析

2021年7月18日西安东北部、渭南南部等地出现突发性暴雨、大暴雨及局地特大暴雨天气,全球模式和多个中尺度模式漏报,为了深入认识此类暴雨天气发生发展机制,提高其预报准确率,本文利用高空、地面观测、ERA5再分析、FY-2G云顶亮温TBB、临潼激光雷达风矢量、泾河雷达及微波辐射计等数据对此次大暴雨发生的环流形势、环境场条件、中尺度对流系统发展演变及触发机制进行分析。结果表明:(1)此次大暴雨天气是在弱天气系统强迫下发生的,大暴雨区位于500 hPa大陆高压边缘,850 hPa和700 hPa无切变线和暖平流、无较大风速输送水汽,地面无冷锋或暖锋。(2)大暴雨发生前环境场有着有利的抬升、充沛的水汽和不稳定能量等条件。地面弱降水造成低的大气抬升凝结高度和云底高度,有利于中尺度对流系统的生成及提高降水效率;低层偏东风风速增大并维持较大风速为大暴雨区输送充沛水汽及能量,大气有一定的对流有效位能,中低层弱上升运动使得暴雨区有着较厚的湿层和较大的整层可降水量。(3)突发性大暴雨由准静止孤立的中-β尺度对流系统造成,中-β尺度对流系统由多个中-γ或中-β尺度对流单体组成。对流单体最先在骊山附近生成,结构松散,组织性差,单体反射率因子有较低的质心及高效率暖云降水特征。(4)地面弱冷空气造成的地面辐合线与骊山地形抬升、灞河谷地狭管效应共同作用触发对流单体,产生强降水,形成地面冷池。冷池出流形成地面辐合线主要在泾河东侧高温、高湿、高能区触发多个新的对流单体。大暴雨区中-β尺度对流系统后向传播,其中多个中-γ或中-β尺度尺度对流单体自东北向西南方向缓慢移动,形成“列车效应”,经过泾河造成大暴雨天气。(5)对于弱天气系统强迫下的暴雨预报,需要增强对其形成机制的认识及新型观测资料的使用,密切关注前期弱降水对近地面增湿和抬升凝结高度的影响,增大的低层风对暴雨区水汽和不稳定能量的输送,地面弱冷空气及地形的触发作用,结合多家中尺度数值模式预报的极值,综合考虑突发性大暴雨的可能性。

Numerical study on dynamic properties of rubberised concrete with different rubber contents

As a green environmentally-friendly material,rubberised concrete(Ru C),which has the characteristics of low elastic modulus,large deformation capacity,high damping,good energy dissipation and good crack resistance,has attracted extensive attention and research in the civil engineering discipline.However,most of existing studies are based on experimental tests on Ru C material properties,and there has been no numerical study based on meso-scale modelling of Ru C yet.To more comprehensively investigate the Ru C dynamic material properties without conducting intensive experimental tests,this study developed a high-fidelity meso-scale model considering coarse and fine aggregates and rubber crumbs to numerically investigate the mechanical properties of rubberised concrete under different strain rates.The meso-scale model was verified against both quasi-static compressive testing data and Split Hopkinson Pressure Bar(SHPB)dynamic testing data.Using the verified numerical model,the dynamic properties of rubberised concrete with various rubber content(0%-30%)under different strain rates were studied.The numerical results show that the developed meso-scale model can use to predict the static and dynamic properties of rubberised concrete with high accuracy.The dynamic compressive strength of the rubberised concrete increases with the increment of the strain rate,and the strain rate sensitivity increases with the rubber content ranging from 0 to 30%.Based on intensive numerical simulation data,empirical DIFs is used as a function of strain rate and rubber content to predict the dynamic strength of rubberised concrete.

X波段天气雷达组网协同观测试验结果分析

2016-2021年成都和北京开展了X波段天气雷达组网观测实验,旨在检验组网观测策略对中小尺度天气过程演变的观测能力和对业务S波段雷达的补充作用。介绍了雷达性能指标、观测模式与风场反演算法,并通过在成都与北京选择天气个例,对X波段雷达组网资料与S波段业务雷达资料进行对比分析。在短时强降水个例中,该组网策略观测到强对流单体初生6分钟内过程面积与强度逐渐增大的过程,能有效提升快速演变的中小尺度对流天气的探测能力,弥补S波段雷达的时间上的探测盲区。在冰雹过程中,通过组网雷达的反演风场可以反映此次天气过程中的强对流中心不同高度的风场特征是中低层高度气流辐合压迫气流向上运动,到高层向四周散开形成辐散的结构。同时,S波段雷达在同一时刻观测的径向速度场和反演风场相互印证,但通过单部S波段雷达探测会丢失部分风场随高度变化的信息。通过雷达组网和风场反演算法得到的流场结构符合天气学原理,与S波段雷达探测到的径向速度结构一致,能够更精细地展现对流天气的动力结构。在冰雹过程中的智能RHI扫描结果显示强回波中心位置的中低层辐合和高层辐散的结构,体现了智能RHI探测算法的有效性。

Loop Quantum Gravity Harmonic Oscillator

Attempts to unify Gravity Theory and Quantum Field Theory (QFT) under Loop Quantum Gravity Theory (LQG), are diverse;a dividing line between classical and quantum is sought with Schrödinger cat-state experiments. A Primordial Field Theory-based alternative is presented, and a gravity-based harmonic oscillator developed. With quantum theory applied at micro-scales and gravity theory at meso- and macro-scales, this scale-gap contributes to the conceptual problems associated with Loop Quantum Gravity. Primordial field theory, spanning all scales, is used to conceptually stretch key ideas across this gap. An LQG interpretation of the wave function associated with the oscillator is explained.

指数分布型根系根-土复合体强度特性研究

指数分布型是排土场护坡植物根系中十分常见的根型,为进一步揭示根-土复合体固土护坡的内在机理,针对现有数值模拟方法不易还原自然条件下根系真实形态的问题,结合土工试验,优化数值模拟方法,研究了细观尺度下指数分布型根系根-土复合体的力学强度特性,结果表明:根-土复合体试样表现出与素土不同的颗粒位移特征,根系的存在能够显著提高土体的整体性,根的张拉作用限制了土体的侧向变形;构建的根-土复合体离散元模型可以较好地反映含根系土壤的力学效应,根系内部应力主要集中于剪切平面附近的根系部,各垂直荷载下未发现根系整体贯通断裂,断裂整体上呈现出在剪切平面集中、土体内零星分布的特点;素土试样的剪应力-剪切位移曲线呈现出带有波峰的应变软化趋势,而根-土复合体试样呈现出无波峰的应变硬化趋势;草本植物根系主要增大了根-土复合体的黏聚力,对内摩擦角的影响不明显。研究成果对于深入了解根土相互作用加固土壤的机理和推进根-土复合体的数值模拟研究具有重要的参考意义。