贵阳市SO2浓度分布的数值模拟

本文使用有限元的ｃｈａｐｅａｎ函数法，数值求解一阶闭合的三维欧大气平流扩散方程（Ｋ模式），并以个性后的Ｍａｓｓ一层中尺度气象数值模式计算复杂地形条件下的水平风场，据实测风廓线推广到三维，将其平流扩散方程的气象背景场输入，联接两模式使之成为研究城市多源污染物分布状况的实用数值模式。利用现有的常规资料作初始值，对贵阳市ＳＯ２浓度分布值进行模拟，结果表明与实测浓度分布基本一致。     

一个考虑地形影响的三维中尺度Monte-Carlo多源模式

本文设计了一个考虑地形、湍流统计量垂直非均匀和非平稳过程影响的三维中尺度Monte-Carlo多源模式。模式模拟了珠海地区大气SO_2浓度时空分布,很好地揭示了由海陆风和山谷风控制下浓度的日变化规律,计算与实测浓度之间平均比值为0.94±0.2388,其结果是令人满意的。本模式具有概念清楚,没有作人为的特别假设和数值解平流扩散方程时出现的伪扩散问题,更能反映湍流扩散本身具有随机性这一本质的优点。     

用K理论研究南京大厂地区污染物扩散

本文用三维K理论扩散方程对南京大厂地区污染物浓度分布特征进行了讨论。在K理论扩散方程中,输入的风速廓线、扩散系数廓线采用Businger通量廓线关系式。用塔层风资料求取了南京地区近地面特征量。用具有四阶精度的Chapeau函数方法对三维K理论扩散方程进行数值求解,计算了大厂地区SO_2年平均浓度分布,和实测值基本上吻合。本文还研究了忽略水平扩散系数、不考虑风速随高度变化,对污染物地面浓度分布的影响。结果表明:在点源的下风方1—5千米范围内,不管是较强的还是较弱的风,忽略水平扩散系数都会使计算的地面浓度估计过高;忽略风速随高度的变化,会给计算带来一定的误差。     

一种考虑风切变的区域多源实用烟团轨迹模式

本文建立并论述了一种区域多源实用烟团轨迹模式。模式在作者先前工作的基础上,加进了对两个重要方面问题的处理,即:(1)运用质量连续风场调整的客观分析方法,得出三维风场并供作轨迹计算和扩散计算联接输入;(2)考虑风存在垂直切变的处理方案,使得模型更接近实际。对52×56km~2模拟域,含50个高架点源,非定常气象条件下的空气污染物输送与扩散作了计算,模式输出逐时网格风场和地面SO_2浓度分布以及日平均SO_2地面浓度分布与实测结果合理地一致。模式效能表明能够适应区域空气污染管理的需要。     

一个模拟SO2浓度分布的数值模式研究

初步发展了一个空气污染准业务数值模式,该模式将修改过的二维Mass风场模式预报的风场据实测风廓线推广到三维,用有限元法求解欧拉平流扩散方程,在此基础上,预报上海地区SO2指数和浓度分布.通过半年的试验,其结果与实测值基本一致,初步可用于业务预报使用.通过模拟表明,上海市的浓度高值区一般位于市区和郊区宝山,一天中早晨的浓度最大,傍晚次之,中午最小.     

一个模拟SO2浓度分布的数值模式研究

初步发展了一个空气污染准业务数值模式，该模式将修改过的二维Mass风场模式预报的风场据实测风廓线推广到三维，用有限元法求解欧位平流扩散方程，在此基础上，预报上海地区SO2指数和浓度分布。通过半年的试验，其结果与实测值基本一致，初步可用于业务预报使用。通过模拟表明，上海市的浓度高值区一般位于市区和郊区宝山，一天中早晨的浓度最大，傍晚次之，中午最小。     

论几种点源模式及其在平坦地形上的应用

本文用高斯(正态)模式(G·S)、SCIM模式,GDM模式以及GCDM模式,分别计算了南京大厂区在各种稳定度条件下SO_2瞬时浓度,并与SO_2的实测浓度作了对比分析。结果表明:GCDM模式的计算误差最小,并与实测浓度有较好的一致性。     

复杂地形上湍流扩散的数值模拟

本文采用准静力大气热力——动力学方程组和平流扩散方程的数值解方法,模拟了汾河河谷地区的流场、温度场和浓度场。所得结果和1984年春该地区进行的一次SF_6示踪试验资料做了对比。计算浓度场采用了三种方法:一般网格的数值模式、套网格数值模式和正态模式。和实测值的比较表明,套网格模式给出较好的计算结果,并且不需要增加过多的计算时间。     

三维指数型迎风格式以及在环境数值模拟中的初步应用

为了适应大气、海洋的环境数值模拟需要,在前人工作基础上提出了三维随流格式和指数型迎风格式.随流格式能使方程对流项中的对流速度误差明显减小.三维指数型迎风格式能有效抑制对流占优问题的数值振荡,并用简单的七点差分格式获得O(h2)精度的三维模式数值结果.因此,所建的模式具有格式简单,计算稳定性良好和计算精度较高的优点.初步计算表明,这个模式能有效应用于强迫-耗散型大气、海洋运动和环境问题的数值模拟.     

背风坡流场和浓度场的数值模拟

本文利用数值积分方法求解二维山地地形大气热力-动力学方程组以及扩散方程。模拟了山地背风坡的流场情况.作为应用,模拟了背风坡不同位置上的排放源在不同的大气稳定度条件下浓度场的分布情况,通过浓度场的垂直扩散方差σ_z~2和实测资料的比较表明:本模式能够反映不同地形和不同天气条件下的污染物质输送及扩散状况,因而有可能成为解决复杂地形上污染扩散的实用方法.     

A micrometeorological investigation of surface exchange of O3, SO2 and NO2: A case study

Data obtained in an intensive field study of the dry deposition of sulfur dioxide, ozone, and nitrogen dioxide, conducted in 1985 in central Pennsylvania, are used to illustrate the factors that must be considered to assure that high quality results are derived. In particular, the quality of the site must be such that flux measurements made above the surface are representative of surface values. For this purpose, tests involving momentum transfer and the surface energy budget are especially useful. In addition, conditions must not be changing rapidly, and the statistical uncertainty associated with flux measurement must be low. For the set of data presented here, conservative quality-assurance guidelines are used to reject potentially erroneous flux data. For ozone, most of the measured fluxes are of use in deriving surface resistances. For SO₂, far fewer data points are available. For NO₂, fluxes appear to lack the order of the O₃ and SO₂ fluxes, and do not enable surface resistances to be computed. The highest-quality SO₂ and O₃ data yield surface resistances in fair average agreement with model predictions for SO₂, but substantially higher than predictions for O₃.     

A linked three-dimensional PBL and dispersion model in coastal regions

In this paper a 3-D mesoscale PBL dynamic prognostic model for a coastal region with complex terrain was developed to simulate the 3-D flow field under a local sea-land breeze circulation. The output from the PBL model was used as an input to an Eulerian numerical model which can be used to simulate finely the temporal and spatial distributions of an air pollutant (SO₂) during a sea-land breeze developing in a coastal region. With respect to its use as a diagnostic model, only a few data would be required to simulate the background winds controlled by a larger scale synoptic system, and then provide initial winds for the PBL model.Having linked the three models and defined the coefficients of turbulent diffusion in a simple form, an integrated 3-D numerical air quality model suitable for the coastal environment was designed. The period of May 29, 1986 was selected for simulating and analysing the distribution of air pollutants over the coastal area of Bohai-sea in Northern China. The results indicated that the calculated concentrations corresponded with the observed ones on the whole. Thus this linked model has been shown to be feasible and useful in practice.     

Analyzing long-term spatial variability of blue and green water footprints in a semi-arid mountainous basin with MIROC-ESM model (case study: Kashafrood River Basin,Iran)

Atmospheric modeling is considered an important tool with several applications such as prediction of air pollution levels, air quality management, and environmental impact assessment studies. Therefore, evaluation studies must be continuously made, in order to improve the accuracy and the approaches of the air quality models. In the present work, an attempt is made to examine the air pollution model (TAPM) efficiency in simulating the surface meteorology, as well as the SO₂ concentrations in a mountainous complex terrain industrial area. Three configurations under different circumstances, firstly with default datasets, secondly with data assimilation, and thirdly with updated land use, ran in order to investigate the surface meteorology for a 3-year period (2009–2011) and one configuration applied to predict SO₂ concentration levels for the year of 2011.The modeled hourly averaged meteorological and SO₂ concentration values were statistically compared with those from five monitoring stations across the domain to evaluate the model’s performance. Statistical measures showed that the surface temperature and relative humidity are predicted well in all three simulations, with index of agreement (IOA) higher than 0.94 and 0.70 correspondingly, in all monitoring sites, while an overprediction of extreme low temperature values is noted, with mountain altitudes to have an important role. However, the results also showed that the model’s performance is related to the configuration regarding the wind. TAPM default dataset predicted better the wind variables in the center of the simulation than in the boundaries, while improvement in the boundary horizontal winds implied the performance of TAPM with updated land use. TAPM assimilation predicted the wind variables fairly good in the whole domain with IOA higher than 0.83 for the wind speed and higher than 0.85 for the horizontal wind components. Finally, the SO₂ concentrations were assessed by the model with IOA varied from 0.37 to 0.57, mostly dependent on the grid/monitoring station of the simulated domain. The present study can be used, with relevant adaptations, as a user guideline for future conducting simulations in mountainous complex terrain.     

Seasonal variations of atmospheric sulfur dioxide and dimethylsulfide concentrations at Amsterdam Island in the southern Indian Ocean

Daily measurements of atmospheric sulfur dioxide (SO₂) concentrations were performed from March 1989 to January 1991 at Amsterdam Island (37°50 S–77°30 E), a remote site located in the southern Indian Ocean. Long-range transport of continental air masses was studied using Radon (²²²Rn) as continental tracer. Average monthly SO₂ concentrations range from less than 0.2 to 3.9 nmol m^-3 (annual average = 0.7 nmol m^-3) and present a seasonal cycle with a minimum in winter and a maximum in summer, similar to that described for atmospheric DMS concentrations measured during the same period. Clear diel correlation between atmospheric DMS and SO₂ concentrations is also observed during summer. A photochemical box model using measured atmospheric DMS concentrations as input data reproduces the seasonal variations in the measured atmospheric SO₂ concentrations within ±30%. Comparing between computed and measured SO₂ concentrations allowed us to estimate a yield of SO₂ from DMS oxidation of about 70%.     

Analysis of summertime atmospheric transport of fine particulate matter in Northeast Asia

In Northeast Asia, the effect of long-range transport of air pollutants is generally pronounced in spring and winter, but can be important even in summer. This study analyzed summer-time atmospheric transport of elemental carbon (EC) and sulfate (SO₄ ^2?) with the Community Multiscale Air Quality (CMAQ) model driven by the Weather Research and Forecasting (WRF) model. The WRF/CMAQ modeling system was applied to regions ranging from Northeast Asia to the Greater Tokyo Area in Japan in summer 2007. In terms of EC, while the model simulated well the effect of long-range transport, the simulation results indicated that domestic emissions in Japan dominantly contributed (85%) to EC concentrations in the Greater Tokyo. In terms of SO₄ ^2?, the simulation results indicated that both domestic emissions (62%) and long-range transport from the other countries (38%) substantially contributed to SO₄ ^2? concentrations in the Greater Tokyo. Distinctive transport processes of SO₄ ^2? were associated with typical summer-time meteorological conditions in the study region. When a Pacific high-pressure system covered the main island of Japan, domestic emissions, including volcanic emission, dominantly contributed to SO₄ ^2? concentrations in the Greater Tokyo. When a high-pressure system prevailed over the East China Sea and low-pressure systems passed north of Japan, synoptic westerly winds associated with this pressure pattern transported a large amount of SO₄ ^2? from the continent to Japan. In addition, although heavy precipitation and strong wind decreased SO₄ ^2? concentrations near the center of a typhoon, peripheral typhoon winds occasionally played an important role in long-range transport of SO₄ ^2?.     

RMAPS_Chem V1.0系统SO2排放清单优化效果评估

RMAPS_Chem V1.0系统是基于WRF_Chem模式建立的服务于华北区域雾霾等污染预报业务的模式系统,该研究着重针对系统中污染排放清单不确定性带来的SO₂浓度预报偏差较大问题,采用EnKF源反演和误差统计订正相结合的方法对排放清单进行了改进,形成了一套优化后的华北区域SO₂排放清单。通过输入初始清单和优化清单对2017年10月进行模拟,并与华北地区616个地面环境监测站观测值进行对比,结果表明:EnKF源反演结合误差统计订正的排放清单优化方法适用于SO₂排放清单的改进,有效降低了清单系统性偏差,针对主要区域及重点城市的检验显示模拟结果接近观测值;排放清单优化后模拟误差显著降低,如河北南部、山东西部至北京一带模式预报均方根误差与归一化平均绝对误差明显下降,区域内站点模拟误差呈正态分布特征,误差分布范围、最大概率出现范围均明显变窄,且最大误差概率明显上升。     

Meteorology and haze structure during AGASP-II,Part 1: Alaskan Arctic flights, 2–10 April 1986

The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (b_sp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm^–3 and b_sp of 80×10^–6 m^–1 suggesting active SO₂ to H₂SO₄ gas-to-particle conversion. Calculations based upon observed SO₂ concentrations and ambient relative humidities suggest that 10⁴–10⁵ small H₂SO₄ droplets could have been produced in the haze layers. High concentrations of sub-micron H₂SO₄ droplets were collected in haze. Ozone concentrations were 5–10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm^–3 and b_sp values were about (20–40)×10^–6 m^–1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.     

On the scavenging of SO2 by cloud and rain drops: IV. A wind tunnel and theoretical study of the absorption of SO2 in the ppb(v) range by water drops in the presence of H2O2

An experimental study involving the Mainz vertical wind tunnel is described where the rate of SO₂ removed from the air by freely suspended water drops was measured for SO₂ concentrations in the gas phase ranging between 50 and 500 ppb, and for various H₂O₂ concentrations in the liquid phase. In a first set of experiments, the pH inside the SO₂ absorbing drops was monitored by means of colour pH indicators added to the drops. In a second set of experiments, the amount of SO₂ scavenged by the drops was determined as sulfate by an ionchromatograph after the drops had been removed from the vertical air stream of the wind tunnel after various times of exposure to SO₂. The results of our experimental study were compared with the theoretical gas diffusion model of Walcek and Pruppacher which was reformulated for the case of SO₂ concentrations in the ppbv(v) range for which the main resistance to diffusion lies in the gas phase surrounding the drop. Excellent agreement between experiment and theory was obtained. Encouraged by this agreement, the theory was used to investigate the rate of sulfate production inside a drop as a function of pH. The sulfate production rate, which includes transport and oxidation, was compared with the production rate based on bulk equilibrium, as cited in the literature.     

Size-resolved characteristics of inorganic ionic species in atmospheric aerosols at a regional background site on the South African Highveld

Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1 year at Welgegund in South Africa was conducted. SO₄^2? and ammonium (NH₄⁺) dominated the PM₁ size fraction, while SO₄^2? and nitrate (NO₃) dominated the PM_1–2.5 and PM_2.5–10 size fractions. SO₄^2? had the highest contribution in the two smaller size fractions, while NO₃^? had the highest contribution in the PM_2.5–10 size fraction. SO₄^2? and NO₃^? levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO₄^2? was significantly lower due to SO₄^2? being formed distant from SO₂ emissions and submicron SO₄^2? having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO₄^2?. PM₁ and PM_1–2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions.