Numerical study on the spatially varying drag coefficient in simulation of storm surges employing the adjoint method

From the simulation of storm surges resulting from Typhoons 7203 and 8509 in the Bohai Sea, Yellow Sea and East China Sea, water level data at tide stations are assimilated into a two-dimensional storm surge model, to study the spatially varying drag coefficient (DC) by employing the adjoint method. In this study, the DC at some grid points is uniformly selected as the independent DC, while the DC at other grid points is obtained through linear interpolation of the independent DC. The DC at independent points is optimized by employing the adjoint assimilation method, and global optimization is achieved by optimizing the independent DC. To demonstrate the method's performance, three comparative experiments are carried out. In the first experiment, the DC is treated as a constant. In the second and third experiments, the DC is derived using an empirical formula. Comparing the experimental results, it is found that the simulation accuracy for both Typhoons 7203 and 8509 increases greatly when optimizing the independent DC. However, the number of independent points makes no great difference to the precision of simulation. Moreover, the DC inverted from Typhoons 7203 and 8509 differs in some sea areas because of the different typhoon tracks. However, the spatial distribution of the inverted DC, for both Typhoons 7203 and 8509, demonstrates a clear effect of the DC on the storm surge modeling near the coastal areas where the DC is highest or lowest.

The Reliability Evaluation Method Study of Power System Communication Networks in Case of Ice Storm

This paper is divided into two cases to study the communication transmission equipment reliability in the state of the ice storm, according to the huge losses of power system communication caused by the ice storm. For the nodes or links which are not affected by the ice storm, we use the calculation with “the mean time between failures (MTBF)” and “the mean time to repair” (MTTR) to put forward the calculation methods;for the OPGW cable which influenced greater in ice storm, we use the fiber excess length and the elongation of fiber optic cable. It obtains all the paths of the network through improved adjacency matrix method, and then it uses binary decision diagram to obtain the overall reliability of the network. By testing the network nodes and links using “N-1” inspection, the key nodes and key links can be obtained. Finally, considering the importance degree of network transmission business, the reliability evaluation method of power system communication network based on the risk theory in the case of the ice storm has been put forward, and the example to verify that the method can provide the basis for the reliability assessment of the power system communication in the case of the ice storm has been given.

关于推理公式流量是否为设计重现期最大流量的数学模型检验探讨

采用数学模型计算雨水设计流量方法发展一直受到缺乏雨水设计数学建模规范性方法的制约。有技术路线是根据推理公式建模,即建立和推理公式等效的模型。推理公式的作用是计算设计重现期最大降雨径流量,其可靠性依赖理论假设和参数取值。基于教材上推理公式案例的研究表明,固定产流系数-漫流模型不能和推理公式等效。扣损法产流-漫流模型中28/31实现了和推理公式等效,用等效模型求设计重现期最大流量并与推理公式结果作比较发现,支撑推理公式的实质性假设在25个情境下被证伪,在3个情境下成立,即理论上推理公式可求得设计重现期最大流量,然而它们中只有1个求得,原因在于仅靠经验难以周全考虑降雨-漫流-产流过程来对推理公式参数取值。推理公式不能保证求得设计重现期最大流量,因此根据推理公式建模的技术路线需商榷。

查图法与公式法在尾矿库洪水计算中的应用

文章系统阐述了暴雨径流查算图表法和小流域推理公式法计算洪水的计算过程。对云南山区某尾矿坝流域面积内按200年及500年防洪标准分别采用暴雨径流查算图表法和小流域推理公式法进行洪水计算,通过分析计算结果得出小流域推理公式法计算结果略小于暴雨径流查算图表法。暴雨径流查算方法计算洪水过程为单峰陡涨陡落,符合云南山区性河流的洪水特性,并且考虑推理公式采用的参数是基于全国综合而定的,不一定适合该地区,另外,从防洪安全角度考虑,采用暴雨径流查算法计算的成果更为合理。

Detecting sand-dust storms using a wind-profiling radar

Sand-dust storm is a type of disastrous weather, typically occurring in arid and semi-arid climates. This study selected a region in the hinterlands of the Taklimakan Desert, called the Tazhong region, as the experimental area to quantitatively estimate the particle concentrations of sand-dust storms using the boundary layer wind-profiling radar. We thoroughly studied the radar echo signals and reflectivity factor features during the sand-dust storms. The results indicate that（1） under sand-dust storm conditions, boundary layer wind-profiling radar cannot capture the complete information regarding horizontal wind velocity and direction, but it can obtain the backscattering intensity of sand-dust storms; and（2） during sand-dust storms particle size distributions in the surface layer closely resemble log-normal distributions, with sand-dust particles sizes of 90–100 μm accounting for the maximum particle probability. Retrieved particle size distributions at heights of 600, 800, and 1000 m follow log-normal distributions, and the expected value of particle diameter decreases gradually with increasing height. From the perspective of orders of magnitude, the retrieved results for particle number concentrations and mass concentrations are consistent with previous aircraft-detected results, indicating that it is basically feasible to use boundary layer wind-profiling radar to quantitatively detect the particle concentrations of dust storms.

Storm surge simulation along the Meghna estuarine area:an alternative approach

In this study, numerical prediction of surges associated with a storm was made through the method of lines（MOL） in coordination with the newly proposed RKARMS（4, 4） method for the meghna estuarine region, along the coast of Bangladesh. For this purpose, the vertically integrated shallow water equations（SWEs） in Cartesian coordinates were firstly transformed into ordinary differential equations（ODEs） of initial valued, which were then soloved using the new RKARMS（4, 4） method. Nested grid technique was employed for resolving the complexities of the region of interest with minimum cost. Fresh water discharge through the lower Meghna River was taken into account along the north east corner of the innermost child scheme. Numerical experiments were performed with the severe cyclone on April 1991 that crossed the coast over the study area. Simulated results by the study were found to be in good agreement with some reported data and were found to compare well with the results obtained by the MOL in addition with the classical 4th order Runge-Kutta（RK（4, 4）） method and the standard finite difference method（FDM）.

Numerical Model of Storm Surge and Inundation in Bohai Bay

A two-dimensional numerical model of extratropical storm surge and inundation in Bohai Bay was built based on the unsteady flow Navier-Stokes equations. The model included two sections, one was for the simulation of storm surge tidal level and the other for the simulation of storm surge inundation in the coastal area. While simulating the storm surge tidal level, the alternating direction implicit (ADI) method was applied to dispersing and solving 2D storm surge equations. In the simulation of storm surge inundation, the 2D unsteady flow equations were dispersed and solved using the structureless grids of finite volume method (FVM). A coupling calculation mode of the process of inundation and storm surge tidal level variation was proposed, therefore the storm surge inundation process and area could be calculated while simulating and forecasting the process of storm surge tidal setup. Furthermore, an extratropical storm surge and inundation in Bohai Bay were simulated using this numerical model. Simulation results are in good agreement with the measured data, which shows that this numerical model provides a new method of simulating and forecasting storm surge and inundation in Bohai Bay.

组合风暴法促发“产品设计创意思维”课程创新

利用组合风暴法将产品设计中的功能因素与情感因素相结合,为解析设计创新策略与逻辑推导方法提供有益参考。结合组合风暴法的产品设计创意思维课程将成为一种探索性和实验性的教学模式,不但可以让不同学业程度的学生可以在良性互动和参与式课堂中收获更好的课程体验与创新思维,而且组合设计法与头脑风暴法联动的创新模式可以启发多门产品设计概念与实践课程实现改良并突破瓶颈。

蒙古高原春季沙尘暴分布数据集(2000-2021年)

蒙古高原是亚洲沙尘暴多发源地之一,其中蒙古国的戈壁地区及内蒙古西部的沙漠地区与蒙古国和中国近年多发的沙尘暴事件有密切的关系。本研究首先基于沙尘暴相关气象观测资料和新闻事件文本资料,统计整理获得蒙古高原2000-2021年来春季发生的76次沙尘暴事件。下载对应时空区域的MODIS数据,结合云量等对数据进行筛选处理,在ENVI软件中利用MRTK插件对MODIS数据进行几何校正等预处理。构建沙尘暴探测指数DSDI,提取沙尘空间分布信息,得到蒙古高原沙尘暴分布数据集。结合ArcGIS软件随机选取验证点,结合台站记录、文本数据、图像增强、目视解译等获取验证点真值,从而完成精度评价,总体分类精度达85.24%,Kappa系数为0.7636。本数据集直观反映蒙古高原沙尘暴空间分布状况,可为蒙古高原沙尘暴灾害治理提供详实可靠的数据支持,与此同时,还可为管控蒙古高原沙尘暴灾害风险提供决策支持。

相似路径台风风暴潮过程对比

基于MIKE 21模型和Holland台风风场模型,构建了1909号利奇马和0509号麦莎2次相似路径台风期间的风场和气压场,并模拟了相应的风暴潮过程。结果表明:台风中心附近增水变化显著,浙江东北部海域在台风登陆期间的增水更大;受台风强度影响,台风利奇马期间增水高值区更大,部分海域2次台风期间最大增水差值接近1.0 m;潮致欧拉余流速度较大值主要分布在100 m水深以浅的海域,量值超过20 cm/s,江苏沿海、台湾东北部海域存在欧拉余环流;台风利奇马期间近海斯托克斯余流值普遍小于麦莎期间;斯托克斯余流项对台风期间长江口、浙闽等近海浅水区短期物质输运过程起一定主导作用。用EMD方法和Hillbert变换分析了典型站点风暴潮位的特征,发现站点IMF1模态和天文潮位较吻合;水深和IMF3模态的最大功率谱密度呈现出较高的相关性,并且随着水深的增加,IMF3模态的最大功率谱密度逐步变大。

基于证据推理的应急医疗物资配送优化研究

为减轻突发公共卫生事件对灾民的二次伤害,针对初期应急医疗物资供不应求的情况,采用证据理论结合优劣解距离法(TOPSIS)计算需求紧急度,确定医疗点的实际物资分配量和风险等级,以高风险区优先配送且总配送成本最小化为目标,建立考虑时间窗的应急医疗物资配送模型,并应用头脑风暴算法(BSO)进行求解,通过算例验证模型的可行性和算法的有效性。结果表明,相较于传统配送模型,考虑需求紧急度的应急医疗物资配送模型可以保证所有高风险区优先配送,同时降低成本5.79%。证明该模型可以有效改善应急配送的盲目性,兼顾应急医疗物资配置的公平、效率和成本。

湖北省云溪水库设计洪水分析

为分析计算云溪水库的设计洪水,采用实测降雨资料和查图法计算设计暴雨,基于最不利原则选择暴雨结果,通过推理公式法和瞬时单位线法进行不同重现期设计洪水推算,并与原除险加固设计洪水成果作对比。结果表明:利用瞬时单位线法计算的0.1%~1%频率下的洪水设计成果与原除险加固成果差别在5%以内,相差不大,且千年一遇设计洪峰较原除险加固成果略小。因此,出于工程安全考虑,云溪水库除险加固工程最终采用原除险加固设计洪水成果。

不同设计雨型对雨水管网数值模拟影响研究

为探讨不同设计雨型对雨水管网数值模拟结果的影响,利用Infoworks ICM软件,分别使用暴雨强度公式推求出的特定雨型和芝加哥雨型,模拟相同下垫面条件下雨水管网系统的排水能力。结果表明,芝加哥雨型对雨水管网系统的排水能力要求更高。因此在进行城市雨水管网系统设计时不应忽视降雨时程分配对雨水管网排水能力的影响,应根据当地的降雨情况对设计雨水管网系统进行校核,以达到顺利排出雨水、降低内涝几率的目的。

地铁车辆段灰绿耦合雨水系统综合评价体系及应用

针对灰色措施生态价值低和绿色措施经济成本高的弊端,综合考虑环境、经济、工程以及社会等因素,以径流量削减率、洪峰削减率、施工难度、雨水资源利用、施工成本等作为评价指标,采用层次分析法和熵权法确定组合指标权重,基于云模型构建针对地铁车辆段特点的灰绿耦合雨水系统评价体系,并在西安地铁鱼化寨车辆段进行应用实践。研究结果表明,车辆段内灰绿耦合雨水系统方案性能总体优于单独灰色措施和单独绿色措施方案。本文构建的指标以及评价方法可以为后续地铁车辆基地灰绿雨水系统设计运行阶段评价提供参考。

基于MIKE+管网模型的城市雨水管渠水力计算方法分析比较

传统雨水管渠设计常采用推理公式法进行水力计算,推理公式法包括面积叠加法和流量叠加法2种计算方法。面积叠加法相比于流量叠加法计算更为简单方便,其在雨水管渠规划和雨水管网方案设计阶段经常使用。随着我国城市化率的提高,内涝防治越来越受到业界重视。通过对比分析基于MIKE+的管网模型模拟结果与传统推理公式法计算结果,给出传统推理公式法用于雨水管渠水力计算的优化建议。采用面积叠加法进行工程设计时,建议适当留有富余,进行内涝防治设计时,宜采用模型进行模拟。

暴雨的判定方法和评价指标

在分析暴雨特征的基础上,提出了以降雨量和降雨强度为参数的暴雨判别指标计算公式K=Pi,根据P=it得出K=P^2/t=i^2t,该表达式简单明了地反映了不同降雨历时的雨量大小,便于暴雨的分析和计算。同时,以日降雨量标准和时段降雨量或降雨强度标准为基础,定量化的确定了暴雨的判别指标和暴雨等级划分标准。对于暴雨2≤K<7,大暴雨7≤K<28,特大暴雨K≥28。在保持与日降雨量标准和时段降雨量或降雨强度标准基本一致的前提下,将二者有机地结合在一起,形成新的统一的暴雨判别和划分标准。

河西走廊东部沙尘暴预报方法研究

利用我国沙尘暴多发区,甘肃省河西走廊东部民勤、凉州区等五站近50a的气象资料,详细分析了河西东部沙尘暴频繁发生的气象因素,应用近20a的天气资料,结合近50a的典型个例做出沙尘暴的长期、中期、短期和短时预报预警系统。研究结果表明:长期预报取决于冬春季气温、降水量和大风日数;中期依靠使用国内外数值预报产品;短期与大气环流条件、分型指标有关;短时临近预报与高空大风形势、地面上游有无大风沙尘暴天气有关。

一次超级单体风暴多普勒天气雷达资料的低层风场反演研究

本文使用二维变分风场反演方法对浙江台州2003年4月12日一次超级单体风暴的多普勒天气雷达探测资料进行低层风场反演研究。二维变分方法以均匀风场反演结果作为初猜场,在目标泛函中加入散度和涡度约束作为正则项来降低不适定性的影响。反演得到的低层水平风场比较好的符合超级单体风暴的组织化的气流结构和强的风切变,通过对散度场垂直积分获得垂直速度,上升气流主要集中在强回波区域,下沉气流一个位于风暴前进的左侧的弱回波区,一个位于钩状回波的内侧。

平均时距对良态风气候地区极值风速的影响研究

在风气候分析中,风速观测历史数据一般来源于各气象站的归档测量,但不同气象站采用的平均时距并不统一,这导致基于风速观测历史数据的极值风速预测过程存在平均时距的转换问题。该文对美国11座处于良态风气候地区城市气象站记录的风速连续观测数据,进行处理得到不同时距下平均风速序列,并将改进独立风暴法与极值I型分布模型相结合分析得到各重现期的风速极值,分析了平均时距对极值风速预测结果的影响。研究结果表明:在良态风气候地区,一定重现期的极值风速随平均时距的增大而减小,近似呈指数律衰减;平均时距对极值风速的影响规律基本不受极值风速重现期的影响;1 min平均时距下的极值风速比10 min平均时距极值风速大19%左右。基于这些结果,拟合给出了良态风气候地区不同平均时距极值风速的转换关系式。