Numerical Simulation of a Torrential Rain Event in the Northeast of Huaihe Basin. Part I: Model Verification and Analysis of MCSs

A torrential rain event accompanying Typhoon Prapiroon occurred in 2000, with 24-h rainfall amount reaching 800mm near the typhoon center. This event is simulated by the nonhydrostatic mesoscale model ARPS (V5.2), with thriple one-way nested-grids. Grid spacings of 45, 15, and 5 km are chosen for the three nested domains. The corresponding grid sizes are 75×75, 140×140, and 180×180, respectively. The NCEP/NCAR reanalysis data, radar echoes, and GMS-5 satellite images are assimilated with the ARPS model initially using a 3-D data assimilation system--ADAS. The simple ice phase scheme and the Kain-Fritsch cumulus parameterization scheme are used. There are 35 layers in the vertical, with a vertical grid spacing of about 625 m. The integration is performed up to 48 h from 0800 BT 29 to 0800 BT 31 August 2000. Compared with radar echoes, GMS-5 satellite images, and intensive surface observations, the results show that the heavy rain area down between the 500-hPa trough and the subtropical high in the left-front of Prapiroon is well simulated by the model ARPS, and the simulated rainfall centers are consistent with observations. A comparison of the radar echoes with these retrieved from the simulated hydrometeors reveals that there are meso-β scale convective systems that exhibit distinctive characteristics, and there are four convective belts converging in the vicinity of Xiangshui, where the maximum rainfall is observed. A further comparision of skew T-lgp diagrams from simulated and observed data demonstrates significant instability in this torrential rain process. The persistent vertical wind shear provides kinetic energy for the development of the MCSs, hence promoting the baroclinic development of convective cells, and the concentration of heavy rain at the specific location. The consistency between model results and observations encourages a further study of the torrential rain event using the simulation data.     

一种基于Voronoi多边形的海底底质表示方法

海底底质对舰船航行、锚泊、登陆、铺设海底管线等海上活动具有重要的影响。文中提出了一种基于同质Voronoi多边形的海底底质分布可视化方法。通过构建Delaunay三角网,求取Voronoi多边形顶点,并依次排序顶点,从而生成构成Voronoi图。在Voronoi图的基础上,提出了同底质Voronoi多边形合并的具体算法,并处理与岸线相交的区域。实验表明,文中所提方法对于海底底质分布的可视化表达,比传统方法更为形象、直观。     

基于加权Voronoi图评价安徽省城市空间吸引力影响范围

为了评价安徽省城市空间吸引力的影响范围,本文利用Voronoi图的空间剖分特性,结合主客观综合赋权法,提出了运用组合权计算中心性强度,将其作为权重引入模型,建立安徽省城市加权Voronoi图,与周长-面积分形理论和新一线城市研究所2019年发布的新一线城市排名作对比分析,分析了安徽省城市的空间吸引力影响范围。经分析验证,建立的组合权Voronoi图能够有效地对安徽省城市的吸引力影响范围进行评价。此外对城市等级的划分,也提供了借鉴和参考。     

Comparative analysis of predictive methods for drought durations: a case of monthly and annual streamflow droughts in Atlantic Canada

Methods based on the recursive probability, the extreme number theorem, and Markov chain (MC) concepts were applied to predict drought lengths (duration) on the standardized (termed as standardized hydrological index, SHI) sequences of monthly and annual river flows from Atlantic Canada. Results of the study indicated that the MC-based method is the most efficient, reliable and versatile method for predicting drought durations followed by the extreme-number-based method. The recursive-probability-based method was found to be computationally intensive and less efficient, although it provided a powerful means for calibrating the empirical plotting position formula needed in the MC-based method. The Weibull plotting position formula turned out to be a suitable measure of the exceedance probability in MC methodology for predicting drought lengths in Atlantic Canada. Based on results, it can be inferred that the MC-based method can be extended to MC2 and higher-order chains for predicting drought lengths on SHI sequences. The predictive capability of the extreme-number-theorem-based method is limited only to independent or weakly first-order persistent SHI sequences.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR Q. Zhang     

时序数据年变信息提取及地震预测指标评估方法研究

针对时序数据中的破年变异常,基于S变换时频方法构建信息提取流程,在提取常规短周期破年变信号(ONA)的同时分析背景年变信号(ANA)的演化过程。在此基础上,基于双向非对称阈值策略,结合R值评分及Molchan图表法构建预测指标确定和效能定量评估方法。新疆库尔勒水平摆倾斜北南测项的实际应用结果显示,该测项的ANA信息对台站周边250 km内6级以上地震具有较好的预测效能,ONA信息对200 km范围内5级以上地震的预测效果相对更优。     

基于道路网络分析的Voronoi面域图构建算法

提出一种基于网络分析的Voronoi面域图和加权Voronoi面域图构建算法。鉴于道路网络在城市中心地、公共设施引力传导与功能覆盖上的重要作用,采用网络最短路径距离分析和最短路径时间分析构建的Voronoi面域图可以模拟出中心功能的辐射影响范围空间划分的实际情形,进而为空间分析和空间优化提供有力支持。算法过程主要包括:设施邻近道路结点检索和分界结点计算;基于网络最短路径分析Dijkstra算法和分界结点计算的网络Voronoi划分;基于空间离散化、邻近道路分析的空间Voronoi划分及其矢量化处理算法。计算实验结果表明本文提出算法可靠和高效,能够模拟出具有预期精度和形态复杂的网络Voronoi面域图形。     

TIN中边侧向关系在三角形定位、Voronoi图和等值线生成等算法中的应用

使用一种含有边拓扑关系的TIN数据结构,从三角网的拓扑关系角度利用这种结构中的边拓扑关系设计了三角形定位、Voronoi图生成和等值线生成的算法.这些算法避免了在三角形中拓扑关系查询时的不必要的搜索.更重要的是,在算法的编写过程中,如果避免一些不必要的搜索,则意味着算法更加清晰,并减少了出错的机率.经过上机验证,三种算法都获得了正确、满意的结果.     

第二次农村土地调查技术与实践

第二次土地调查工作,包括农村土地调查和城镇土地调查两部分,是一项统一由政府组织实施的重大任务。结合生产实践阐述了基于遥感影像建立影像解译标志,并在GIS软件上解译影像信息,采用内外业相结合方法,全面掌握城镇、村庄以及独立工矿区内部工业用地、基础设施用地、住宅用地以及农村宅基地等行业用地、农用地、未利用地的数量和分布,并建立土地利用现状数据库的过程。     

New measurement of melting and thermal conductivity of iron close to outer core conditions

The amount of literature on both melting and thermal conductivity of iron at Earth’s core conditions is overwhelming and the discrepancies are very large.There is a broad range of experimental techniques each of which is flawed to a certain degree,which may explain the discrepancy.In this report,we present new data using a different method for determining the phase behavior and resistivity of iron in the laser-heated diamond cell by measuring the electrical resistance of both solid and liquid iron wires.The experiment avoids some of the major flaws of previous experiments,the most important of which is the detection of the onset of melting.These measurements confirm a shallow melting curve found earlier and the resistivity data imply a trend towards low thermal conductivity in the liquid outer core.     

Preliminary study on strontium-rich characteristics of shallow groundwater in Dingtao Area,China

Based on the analysis of element correlation, the Gibbs diagram, hydro-geochemical ion ratios, isoline maps of groundwater and soil, and change patterns of strontium content after normalization, the study examines water-rock interaction of shallow groundwater in Dingtao area. The results suggest that strontium in the study area mainly comes from water-rock interactions, and the strata interacting with groundwater are the top of Quaternary and Neogene. The element correlation analysis shows that the formation of strontium-rich groundwater is sufficiently affected by sulfate and carbonate. The Gibbs diagram suggests that the chemical composition of groundwater is mainly influenced by water-rock interactions, accompanied by evaporation crystallization. c(Ca²⁺+Mg²⁺)/c(HCO₃^-+SO₄^2-) reflects that the main reactions in the groundwater system is weathering dissolution of carbonate and sulfate, and ion exchange takes place. c(Na⁺)/c(Cl^-) indicates that Na⁺ in groundwater may have water-rock interactions with rocks it flows through. c(Cl^-)/c(Ca²⁺) indicates that the hydrodynamic condition in the pumping well is poor and the water circulation is slow. The study examines the macro isoline map change patterns, correlation curves of change of strontium content in groundwater and shallow soil, and correlation curves of change of strontium content in groundwater, shallow soil, and deep soil. The results suggest that the strontium content in the study area has the same change pattern in groundwater and in soil, which further indicates that strontium in the study area comes from water-rock interactions.