修正的拉格朗日K模式及其在区域尺度中的应用

本文建立了模拟区域尺度的大气污染物输送与扩散过程的拉格朗日K模式，该模式结构简单，计算量小。初始浓度场采用高斯烟流扩散模式确定大气污染物的垂直分布，克服了区域模式在近距离短时间预测浓度精度不高的缺点。应用修正的拉格朗日K模式预测了江苏省区域排放的SO2在大气中输送与散布过程，验证结果表明该模式的精度能够满足区域环境污染物分布预测等环境应用的需要。     

修正的拉朗日K模式及其在区域尺度中的应用

本文建立了模拟区域尺度的大气污染物输送与扩散过程的拉格朗日Ｋ模式，该模式结构简单，计算量小。初始浓度场采用高斯烟流扩散模式确定大气污染物的垂直分布，克服了区域模式在近距离短时间预测浓度精度不高的缺点。应用修正的拉格朗日Ｋ模式预测上江苏省区域排放的ＳＯ２在大气中输送与散布过程，验证结果表明该模式的精度能够满足区域环境污染物分布预测等环境应用的需要。     

辽宁中部城市群主要大气污染物时空分布特征的数值模拟

利用美国第三代空气质量模式系统Models-3对2002年1月17～18日辽宁中部城市群大气污染物SO2,NO2和PM10的浓度分布进行了数值模拟,并将模拟结果与监测结果进行了对比分析。结果表明:污染物的模拟值与观测值变化趋势具有一致性,模式反映了SO2,NO2和PM10浓度的时空分布特征和变化规律,再现了污染物浓度呈波峰波谷日变化的重要特征,可用于辽宁中部城市群区域大气污染物的研究。     

复杂地形城市冬季大气污染的数值模拟研究

采用中尺度大气动力模式与大气扩散模式相结合的方法，针对复杂地形条件下兰州市冬季无明显冷空气入侵天气过程时段（1994年12月2－3日）的大气污染状况，进行污染物（二氧化硫和烟尘）浓度分布的数值模拟研究，分析了模拟的风场的气温层结随时间的变化以及污染物浓度的分布及其变化，进一步分析了模拟的风场和气温层结与污染物浓度分布的关系。结果表明，该模式系统对兰州市大气边界层结构及污染物浓度的分布有较好的模拟能力，并证明了该模式系统可适用于兰州市大气质量预测预报研究。     

基于WRF模式的兰州秋冬季大气污染预报模型研究

随着城市化进程的加快,城市大气环境问题成为人们关注的热点问题之一。诸多研究表明,特殊气象条件是造成城市大气污染事件的主要因子之一。本文利用WRF模式模拟得到的高时空分辨率气象场,结合污染物浓度监测数据,分析了风速、稳定能量、Froude数、边界层高度、位温递减率、输送指数和梯度理查森数与兰州大气污染物浓度的关系,并根据WRF的模拟要素建立了污染物浓度与气象影响因子的回归方程。研究发现,兰州城区边界层高度和位温递减率与大气污染物浓度的相关系数高,NO2与气象影响因子的相关性较PM10好。建立的回归方程对NO2的模拟效果好于对PM10的模拟效果,其对城区污染物浓度的模拟效果好于郊区。通过与不同地区空气质量数值模式模拟效果对比,结果表明：回归方程对污染物的模拟效果与数值模式模拟效果相当,甚至好于部分地区空气质量数值模式的模拟效果。因此,该研究方法为我国城市空气质量预报和大气污染研究提供了科学依据。     

南昌市空气质量预报产品检验分析及统计订正试验

利用南昌市环境空气质量监测数据,对比分析了WRF-Chem模式和国家级空气质量预报指导产品对6种污染物浓度的预报效果,并采用时序法、时刻法和标准化法3种训练样本构建方案,利用BP神经网络法对WRF-Chem模式和国家级空气质量预报指导产品6种污染物浓度的预报结果进行订正试验。结果表明:1)WRF-Chem模式预报的6种污染物浓度的预报误差整体比国家级空气质量预报指导产品的预报误差要小,即WRF-Chem模式的预报效果优于国家级空气质量预报指导产品。2)WRF-Chem模式6种污染物浓度预报值与观测值的均方根误差的日变化均呈波动形式,除了O3在10时开始升高到18时达到峰值以外,其余的污染物均是从10时开始下降到16时或18时达到谷值。国家级指导产品6种污染物浓度预报值与观测值的均方根误差日变化则略有不同,除了NO2和O3分别在08时和20时达到谷值以外,其他4种污染物均是在14时达到谷值。3)采用标准化法对CO、SO2、PM10、PM2.5集合订正后的误差比WRF-Chem模式的要小;时刻法、时序法对NO2、SO2、PM2.5集合订正后的误差比WRF-Chem模式的要小,预报效果对单一模式预报结果有一定改进作用。     

洛阳市城市环境气象监测预报服务研究

利用洛阳市环境监测资料和气象资料,分析了洛阳市污染物浓度的日变化、季节变化、年际变化规律,并分析了污染物浓度与气象因子的关系。在此基础上,通过回归分析预报方法、污染潜势预报方法、CAPPS模式预报方法对洛阳市3种主要污染物的浓度和级别进行了24 h和48 h预测,并建立了气象局与环保部门共享的气象和污染数据库平台,为双方今后的合作奠定了基础。     

洛阳市城市环境气象监测预报服务研究

利用洛阳市环境监测资料和气象资料,分析了洛阳市污染物浓度的日变化、季节变化、年际变化规律,并分析了污染物浓度与气象因子的关系.在此基础上,通过回归分析预报方法、污染潜势预报方法、CAPPS模式预报方法对洛阳市3种主要污染物的浓度和级别进行了24 h和48 h预测,并建立了气象局与环保部门共享的气象和污染数据库平台,为双方今后的合作奠定了基础.     

珠江三角洲城市群污染综合指数预报的模式方法

应用全二阶矩表示的商斯烟团模式,重点引入烟团的合并与分解及各种清除过程,并利用广州热带模式（GZTM）所提供的华南地区细网格的三维数字化流场,来计算污染物浓度的长期变化。具体先模拟计算SO2、NOx、TSP的地面浓度日变化,通过求平均得到每种污染物的日均浓度,并和对应的污染物的日均浓度二级标准比较,得到每种污染物的污染指数Pi,最后求和得出污染综合指数P,从而对珠江三角洲地区的污染综合指数作出预报。     

北京交通环境污染诊断模拟初步研究

建立了能够用于评估大型城市交通环境污染与气象条件关系的数值模拟技术,即三维边界层光化学数值模式.其中,高分辨率的精细城市边界层气象场、细致的城市地理与环境参数、空气污染物输送扩散与大气化学模拟以及交通废气污染源的分布等诸多因子是实施模拟研究的几个重要环节.从模拟结果看出,各污染物在地面附近浓度相对高值区位于排放源附近和下风方.在边界层顶附近,污染物浓度分布较均匀,分布趋势和气流一致.虽然仅仅考虑了城区污染物本底浓度和主要交通干道机动车的排放,但交通排放对城区污染物浓度的贡献是较大的.     

A microscale model for air pollutant dispersion simulation in urban areas: Presentation of the model and performance over a single building

A microscale air pollutant dispersion model system is developed for emergency response purposes. The model includes a diagnostic wind field model to simulate the wind field and a random-walk air pollutant dispersion model to simulate the pollutant concentration through consideration of the influence of urban buildings. Numerical experiments are designed to evaluate the model's performance, using CEDVAL(Compilation of Experimental Data for Validation of Microscale Dispersion Models) wind tunnel experiment data, including wind fields and air pollutant dispersion around a single building. The results show that the wind model can reproduce the vortexes triggered by urban buildings and the dispersion model simulates the pollutant concentration around buildings well. Typically, the simulation errors come from the determination of the key zones around a building or building cluster. This model has the potential for multiple applications; for example, the prediction of air pollutant dispersion and the evaluation of environmental impacts in emergency situations; urban planning scenarios;and the assessment of microscale air quality in urban areas.     

局地废气排放污染影响的实验模拟

本文给出了一项在南京大学NJU环境风洞中实施的实验模拟研究。试验模拟一座位于城市街区的排放塔的废气排放，通过流场测量，放烟显示和示踪气体扩散试验，分析气流分布与污染物浓度分布，得出对局地环境影响的一些结论。文中还以模拟扩散试验资料为实验基础，建立修正的扩散模式，探讨污染物浓度预测的可靠途径。研究结果表明，风洞流体模拟手段是有成效且实用的。     

Evaluation of a micro-scale wind model’s performance over realistic building clusters using wind tunnel experiments

The simulation performance over complex building clusters of a wind simulation model(Wind Information Field Fast Analysis model, WIFFA) in a micro-scale air pollutant dispersion model system(Urban Microscale Air Pollution dispersion Simulation model, UMAPS) is evaluated using various wind tunnel experimental data including the CEDVAL(Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models) wind tunnel experiment data and the NJU-FZ experiment data(Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data). The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier–Stokes equations, and can produce very high-resolution(1–5 m) wind fields of a complex neighborhood scale urban building canopy(～ 1 km ×1km) in less than 3 min when run on a personal computer.     

Numerical study of flow and gas diffusion in the near-wake behind an isolated building

To assist validation of the experimental data of urban pollution dispersion, the effect of an isolated building on the flow and gaseous diffusion in the wake region have been investigated numerically in the neutrally stratified rough-walled turbulent boundary layer. Numerical studies were carried out using Computational Fluid Dynamics (CFD) models. The CFD models used for the simulation were based on the steady-state Reynolds-Average Navier-Stoke equations (RANS) with κ-ε turbulence models; standard κ-ε and RNG κ-ε models. Inlet conditions and boundary conditions were specified numerically to the best information available for each fluid modeling simulation. A gas pollutant was emitted from a point source within the recirculation cavity behind the building model. The accuracy of these simulations was examined by comparing the predicted results with wind tunnel experimental data. It was confirmed that simulation using the model accurately reproduces the velocity and concentration diffusion fields with a fine-mish resolution in the near wake region. Results indicated that there is a good agreement between the numerical simulation and the wind tunnel experiment for both wind flow and concentration diffusion. The results of this work can help to improve the understanding of mechanisms of and simulation of pollutant transport in an urban environment.     

A Wind Tunnel and Numerical Investigation of Turbulent Dispersion in Coastal Atmospheric Boundary Layers

Thermal internal boundary layers in onshore air flows have a significant influence on pollutant diffusion in coastal areas. Although several models for this diffusion problem exist, measurements for model verification are scarce. In this paper, we present a set of wind tunnel observations and examine the performance of a Lagrangian stochastic model. The good agreement between the model simulation and the tunnel measurements confirms the usefulness of the Lagrangian stochastic model for practical purposes. Sensitivity tests of the model to turbulence statistics show that uncertainty in velocity skewness to the extent of observational scatter does not seem to have a significant influence on pollutant dispersion, while uncertainties in turbulence intensity (variance) significantly influence the dispersion pattern.     

Wind tunnel modeling of small-scale meteorological processes

After introductory remarks on similarity laws to be satisfied in wind tunnel experiments simulating small-scale meteorological processes, mean and turbulence characteristics of wind tunnel boundary layers are presented and compared with the characteristics of the atmospheric boundary layer. The results are used to evaluate the possibilities and limitations of physical modeling of pollutant dispersion in general. In the second part of the paper, the potential of wind tunnels to solve micro-meteorological problems of real practical interest will be demonstrated. The example involves the investigation of the effects of building downwash on ground-level concentrations for flue gases discharged from natural draft wet cooling towers.     

Fluid mechanical aspects of the pollutant transport to coniferous trees

Forest decline in some parts of Europe gave rise to various environmental studies concerning the intake and uptake of pollutants in the ecosphere. As far as fluid mechanics is concerned, the current interest is centered on flow-induced phenomena, e.g., the flow-enhanced deposition of pollutants to trees. In order to understand better the mechanisms of pollutant dispersion and deposition to trees, wind tunnel experiments carried out with small real coniferous trees and model trees are summarized in this paper. The flow around single trees and tree stands, both in flat terrain and on hillsides, has been analysed. The measurements were performed with a two-component laser Doppler anemometer system installed in an atmospheric boundary-layer wind tunnel. A chemical tracer method based on an ammonia-manganese chloride reaction was applied to visualize the deposition patterns around trees and modeled forest stands.     

区域复杂地形大气污染扩散的模拟研究

围绕复杂地形区域尺度大气污染物的扩散问题,以贵州西部山区"西电东送"大型火电厂六枝电厂所在区域为例,采用局部嵌套的高分辨率复杂地形大气扩散模式系统,模拟了该区域大气边界层气象场和污染物散布的浓度场,给出二级空气质量标准下各级保证率的小时平均和日均浓度分布,进而得出其年均浓度分布,分析其时空分布及变化特征,研究了山区复杂地形上大气污染物的扩散特性和散布规律。     

A numerical study on the meso-scale pollutant dispersion over a sloped surface in the stable boundary layer

A numerical model is used to study the properties of pollutant dispersion over a large uniformly-sloped surface in the stable atmospheric boundary layer. By simulating the structure of boundary layer flow to improve the advective wind field and vertical eddy diffusivities included in the advection-diffusion equa-tion, this numerical model permits an estimation of the distribution of pollutant concentration for more real-istic atmospheric diffusion conditions.