Budget Calculations for Ozone and Its Precursors: Seasonal and Episodic Features Based on Model Simulations

Results from two air quality models (LOTOS, EURAD) have been used toanalyse the contribution of the different terms in the continuity equationto the budget of ozone, NO_x and PAN. Both models cover largeparts of Europe and describe the processes relevant for troposphericchemistry and dynamics. One of the models is designed to simulate episodesin the order of 1–2 weeks (EURAD), the other is focussing on theseasonal scale (LOTOS). Based on EURAD simulations it is found that theatmospheric boundary layer (ABL) in Central Europe during a summer-smogepisode in 1990 acts as a source of ozone, which is partly exported from theproduction region in Central Europe. About 40% of the ozone producedchemically in the ABL is lost from Central Europe due to net transport(large-scale and turbulent), 40% are deposited within the domain. Vertical mass exchange of ozone is dominated by the prevailing subsidenceand averaged vertical mass fluxes are directed downward. Averaged massfluxes of PAN, which has no stratospheric source, are upward in the upperpart of the ABL. The results from LOTOS are discussed for the same episodeand for a two month period (July/August 1990). The budget calculation showlarger chemical production for the LOTOS model compared to EURAD. Therelative importance of deposition and net transport, however, is in the sameorder. Differences between the two-month calculation and the one weekepisode are only important for Western Europe where the chemical production is enhanced by 30% during the summer-smog episode. The dependence ofthe results on initial and boundary values is discussed for ozone on thebasis of a simple sensitivity study with EURAD where ozone in the FT is setto 10 ppb initially. This leads to a reversal in the direction of averagedozone mass fluxes in the upper part of the ABL.     

Estimation of transboundary transport contribution to the air pollution in the far east region using the chemistry transport model

The CHIMERE mesoscale chemistry transport model is used for the quantitative assessment of the contribution of transboundary transport of anthropogenic admixtures from China to the surface concentrations of major suspended pollutants, aerosol PM₁₀, ozone O₃, and nitrogen oxides NO_x in the Far Eastern region. Analyzed in detail are the time series of concentration of mentioned substances computed with the model taking account and not taking account of anthropogenic emissions in China. It is revealed that the transboundary transport of anthropogenic pollutants can cause the recurring episodes of manyfold increase in the concentration of PM₁₀ in the south of Khabarovsk region, as well as more rare variations of O₃ and NO_x concentration. The trajectory and synoptic analysis demonstrated that the episodes of the increase in the concentration of PM₁₀ and O₃ in the south of the region mainly depend on the carryover of air masses from northeastern China in the front part of continental cyclones.     

A Eulerian air pollution model for Europe with nonlinear chemistry

A long-range transport model with nonlinear chemical reactions is described. The model contains 35 pollutants and 70 chemical reactions. This is a Eulerian model defined on a space domain containing the whole of Europe. The spherical space domain (corresponding to the Earth's surface covered by the model) is mapped into a square plane domain and discretized by using a 32×32 grid. The grid increments are equidistant (both along the Ox axis and along the Oy axis). The choice of values of the physical parameters involved in the model and the numerical treatment of the model are shortly discussed. The model is tested with meteorological data for 1985 and 1989. The numerical results are compared with measurements at stations located in different European countries. Extensive comparisons of ozone concentrations for July 1985 with measurements taken at 24 European stations are also carried out. Results concerning three episodes in July 1985 as well as results obtained in the study of the sensitivity of the ozone concentrations to variations of NO _x and/or anthropogenic VOC emissions are presented. The advantages and the limitations of such a model are discussed. The model is continuously improved by adding new modules to it. The plans for improvements in the near future are outlined.     

Modeling of Regional High Ozone Episode Observed at Two Mountain Sites (Mt. Tai and Huang) in East China

A high O₃ episode was observed during 23–25 May 2004 at two high-mountain sites reflecting the regional pattern of air pollutants over East China. This episode lasted about three days with the maximum hourly O₃ mixing ratios reaching 111 and 114 ppbv at Mt. Tai and Huang, respectively. Backward trajectories and meteorological analysis indicated that regional transport, associated with a weak high pressure system over the East China Sea, might play an important role in the formation of this high ozone episode. The nested air quality prediction modeling system (NAQPMS) was applied to investigate the formation and evolution of this high O₃ event. The comparison of model results with observations showed that NAQPMS successfully reproduced the main observed patterns of O₃ and meteorological parameters during the simulated period. The model results with emission over the Yangtze Delta and the East Central China switched on/off clearly showed that ozone and its precursors transported from the Yangtze Delta and the East Central China enhanced the high ozone episode at two sites, with a contribution of 20%–50% during the episode. In addition, based on process analysis with the model, chemical production and regional transport appeared to be the main causes of high ozone episode involving a large amount of high-ozone air masses and precursors transported from the surrounding areas. The horizontal transport is more active during the period of high ozone episode than that during the non-episode at Mt. Tai as well as Mt. Huang.     

Pollutant scavenging in a mesoscale meteorological model with quasi-spectral microphysics

Pollutant scavenging parameterizations have been combined with meteorological predictions in a three-dimensional mesoscale numerical model (1). This meteorological model with detailed quasi-spectral microphysics is well-suited to include gas and aerosol removal by cloud droplets and raindrops. Two-dimensional sensitivity tests have been performed for both meteorological and chemical scenarios. Both maritime and continental clouds over an idealized topography have been considered to determine their relative efficiencies for wet sulfur deposition. A second example deals with night-time nitric acid production which has been simulated in a case of moist advection. A threshold behaviour for NO₃ disappearance at relative humidities above 60 % was observed in agreement with experiments. The results obtained through such idealized tests emphasize the need for simultaneous treatment of dynamical, microphysical and physicochemical processes.     

Comparison of the DRAIS and EURAD model simulations of air pollution in a mesoscale area

Summary In this paper the results of simulations of air pollution carried out with the mesoscale model system KAMM/DRAIS are presented. They are compared with results of the European scale model EURAD which have been provided by the EURAD-Group, Cologne. With this comparison it is intended to analyse to what extent better resolution of topography and emission data used by the mesoscale model effects the model results. The simulations have been carried out for July 15, 1986, a typical summer day. The model domain contains south-west Germany and part of Alsace with a resolution of 5 km. The emissions for this resolution have been derived by a combination of the coarse EURAD emission data with the data of the TULLA experiment which are available on a much finer grid. The initial and boundary conditions for the species concentrations are determined from the results of the EURAD model. This coupling introduces the long range transport of pollutants into the mesoscale simulation.The meteorological and concentration data of the EURAD model are compared with the corresponding DRAIS model results. The mesoscale flow field is characterized by the channeling along the Upper Rhine Valley, which is not resolved in the EURAD model. The concentration distributions of both models are similar during midday, because of the strong vertical mixing. In the night and especially, in the morning and evening hours the spatial distribution is much better represented by the DRAIS model results. The better resolution of the emissions and the topography in the DRAIS model compared with the EURAD model (80 km grid size) becomes really noticeable. The difference of the ozone concentrations between cities and the, surrounding areas and between the Rhine Valley and the limiting mountains are in the order of 30 ppb as compared to a few ppb in the EURAD simulation. In the morning NO concentrations of about 200 ppb are simulated in the area between Heilbronn and Stuttgart. The EURAD model provides only about 5 ppb. Comparisons with measurements show that the DRAIS simulations are more realistic than the EURAD model results. The features mentioned are also found in an evaluation of the concentration variations in areas corresponding to a grid cell of the EURAD model. Two completely different areas are selected to demonstrate the possible range of the concentration variation. In the area around the City of Stuttgart the ozone concentration in the morning and the evening varies between zero ppb and 50 ppb, approximately. The mean value is nearly the same in both simulations.List of Abbreviations DRAIS Dreidimensionales Regionales Ausbreitungsund Immissions-Simulationsmodell - EMEP European co-operative program for Monitoring and Evaluation of the long-range transmission of air Pollutants - EUMAC European Modelling of Atmospheric Constituents - EURAD European Acid Deposition Model - EUROTRAC EUROpean experiment on TRAnsport and transformation of environmentally relevant trace Constituents in the troposphere over Europe - JDR Joint Dry Case - KAMM Karlsruher Atmosphärisches Mesoskaliges Modell - MM4 Mesoscale Model 4 - NCAR National Center for Atmospheric Research - RADM Regional Acid Deposition Model - TADAP Transport and Deposition of Acidifying Pollutants - TULLA Transport und Umwandlung von Luftschadstoffen im Lande Baden-Württemberg und aus Anrainerstaaten; in English: Transport and Transformation of Air Pollutants in the State of Baden-Württemberg and from neighbouring countries With 17 Figures     

The parametrization of the sulfate-nitrate-ammonia aerosol system in the long-range transport model EURAD

Summary Because of the obvious importance of aerosols for atmospheric modelling, an aerosol module has been developed as part of the European Acid Deposition Model (EURAD). The chemical and physical processes have been restricted to the sulfate-nitrate-ammonia system to study the influence of aerosols on acid deposition. Special consideration is given to the reversible formation process ofNH ₄ NO ₃ aerosols and the influence of the dissociation constant on the aerosol and gas phase concentrations. This component appears to be important in particular for regions where large ammonia emissions are found as in Europe.Concentration and deposition fields as predicted by EURAD are analysed for a simulation with and without the new aerosol module. Due to their smaller dry deposition velocities in the aerosol phase, the amount of nitrogen species in air is larger and the spatial distribution is considerably different if aerosols are taken into account. On the other hand wet deposition of nitrogen is enhanced due to the presence of easily soluble ammonium nitrate aerosols.A comparison with observations from the EMEP network has been conducted to evaluate the performance of the aerosol module. Modelling with the aerosol phase leads to a much better agreement between modelled and measured concentration fields.With 12 Figures     

Emission characteristic of ozone related trace gases at a semi-urban site in the Indo-Gangetic plain using inter-correlations

Measurements of surface O₃, CO, NO_x and light NMHCs were made during December 2004 at Hissar, a semi-urban site in the state of Haryana in north-west region of the Indo-Gangetic Plain (IGP). The night-time O₃ values were higher when levels of CO, NO and NO₂ were lower but almost zero values were observed during the episodes of elevated mixing ratios of CO (above 2000 ppbv) and NO_x (above 50 ppbv). Slopes derived from linear fits of O₃ versus CO and O₃ versus NO_x scatter plots were also negative. However, elevated levels of O₃ were observed when CO and NO_x were in the range of 200–300 ppbv and 20–30 ppbv, respectively. Slope of CO-NO_x of about 33 ppbv/ppbv is much larger than that observed in the US and Europe indicating significant impact of incomplete combustion processes emitting higher CO and lesser NO_x. Correlations and ratios of these trace gases including NMHCs show dominance of recently emitted pollutants mostly from biomass burning at this site.     

湖北2015年冬季PM2.5重污染过程的气象输送条件及日变化特征分析

PM_2.5污染仍然是湖北省冬季大气污染的首要污染类型,且具有明显区域传输特征,重污染过程的空气污染气象条件有别于华北地区,值得关注。采用WRF/Chem不同排放情景下的模拟结果,并结合观测分析,研究了2015年12月—2016年1月湖北省PM_2.5重污染过程的气象输送条件及日变化特征,从大尺度输送条件和局地边界层动力作用分析了外来污染物水平传输、悬浮聚集和向下传输的过程,并解释了该地区观测到的午后PM_2.5浓度特殊峰值的气象成因。结果表明,湖北重污染爆发以区域传输为主,地面观测PM_2.5极值对应10 m风速可达8—10 m/s,边界层0—1 km为较强偏北风输送,污染传输通量极值位于400 m高度附近,为重要传输通道,低空无明显逆温,重污染过程具有“非静稳”边界层气象特征。重污染形成的大尺度输送条件为,长江中下游及北部地区偏北风异常偏强,南部地区风速减缓,使污染物在中游平原堆积,鄂北边界风速越大,越有利污染输送增长。传输性污染主要来自偏北和东北方向的污染源输送,潜在源区贡献主要为途经偏北通道上的豫中、南阳盆地和关中地区,以及途经东北通道上的鲁、皖、苏等部分地区。PM_2.5浓度日变化双峰结构的天气成因不同,21—24时（北京时）峰值为静稳性污染,11—14时峰值为传输性污染。污染输送受大气边界层高度影响,日出前大气边界层高度较低,层结稳定并伴有上升运行,使得低空外来输送悬浮聚集在400 m高度附近;日出后随大气边界层高度升高,静稳层结被破坏,在干沉降作用下高浓度PM_2.5开始向下传输,并在午后地面形成峰值。      

基于极端随机树方法的WRF-CMAQ-MOS模型研究

随着城市化、工业化的快速发展,空气污染已经成为了公众最关注的问题之一。为了提高空气质量预报的准确度,以多尺度空气质量模型（Community Multi-Scale Air Quality,CMAQ）为工具,结合中尺度WRF（Weather Research and Forecast Model）气象预报数据、气象观测数据、污染物浓度观测数据,基于极端随机树方法建立了WRF-CMAQ-MOS（Weather Research and Forecast Model-Community Multi-Scale Air Quality-Model Output Statistics）统计修正模型。结果表明,结合WRF气象预报的CMAQ-MOS方法明显修正了由于模型非客观性产生的模式预报偏差,提高了预报效果。使用线性回归方法不能获得较好的优化效果,选取极端随机树方法和梯度提升回归树方法对模型进行改进和比较,发现极端随机树方法对结合WRF气象要素的CMAQ-MOS模型有较大的提升。针对徐州地区空气质量预报,进一步使用基于极端随机树方法的WRF-CMAQ-MOS模型对2016年1、2、3月的空气质量指数（AQI）及PM_2.5、PM₁₀、NO₂、SO₂、O₃、CO六种污染物优化试验进行验证,发现优化效果最为明显的两种污染物分别是NO₂及O₃,2016年1、2、3月整体相关系数NO₂由0.35升至0.63,O₃由0.39升至0.79,均方根误差NO₂由0.0346减至0.0243 mg/m3,O₃由0.0447减至0.0367 mg/m3。文中发展的WRF-CMAQ-MOS统计修正模型可以有效提升预报精度,在空气质量预报中具有很好的应用前景。      

Temporal variations in surface ozone and its precursors and meteorological effects at an urban site in China

Continuous measurements of ozone and its precursors including NO, NO₂, and CO at an urban site (32°03′N, 118°44′E) in Nanjing, China during the period from January 2000 to February 2003 are presented. The effects of local meteorological conditions and distant transports associated with seasonal changed Asian monsoons on the temporal variations of O₃ and its precursors are studied by statistical, backward trajectory, and episode analyses. The diurnal variation in O₃ shows high concentrations during daytime and low concentrations during late night and early morning, while the precursors show high concentrations during night and early morning and low concentrations during daytime. The diurnal variations in air pollutants are closely related to those in local meteorological conditions. Both temperature and wind speed have significant positive correlations with O₃ and significant negative correlations with the precursors. Relative humidity has a significant negative correlation with O₃ and significant positive correlations with the precursors. The seasonal variation in O₃ shows low concentrations in late autumn and winter and high concentrations in late spring and early summer, while the precursors show high concentrations in late autumn and winter and low concentrations in summer. Local mobile and stationary sources make a great contribution to the precursors, but distant transports also play a very important role in the seasonal variations of the air pollutants. The distant transport associated with the southeastern maritime monsoon contributes substantially to the O₃ because the originally clean maritime air mass is polluted when passing over the highly industrialized and urbanized areas in the Yangtze River Delta. The high frequency of this type of air mass in summer causes the fact that a common seasonal characteristic of surface O₃ in East Asia, summer minimum, is not observed at this site. The distant transports associated with the northern continental monsoons that dominate in autumn and winter are related to the high concentrations of the precursors in these two seasons. This study can contribute to a better understanding of the O₃ pollution in vast inland of China affected by meteorological conditions and the rapid urbanization and industrialization.     

Modeling the concentration of pollutants using the WRF-ARW atmospheric model and CHIMERE chemistry transport model

Described is a system for analyzing and forecasting the air quality in the central regions of Russia, During the operation of the system, the detailed meteorological information provided by the WRF-ARW model is used by the CHIMERE chemistry transport model for simulating the processes of transport, chemical transformation, and deposition of atmospheric minor constituents. Considered is the quality of retrieved and forecasted (with the lead time up to three days) concentrations of O₃, NO₂, NO, CO, and PM₁₀. The presented verification scores of pollutant concentrations demonstrate a relative success of the system. Demonstrated is a need in improving the data on the emissions of the air pollutants used for simulations. A procedure for the statistical correction of computed concentrations is described and verification scores of its results are given.     

Convective Redistribution of Ozone and Oxides of Nitrogen in the Troposphere over Europe in Summer and Fall

The fluxes of ozone and NO_x out of the atmospheric boundary layer (ABL) over Europe are calculated in a mesoscale chemical transport model (MCT) and compared with the net chemical production or destruction of ozone and the emissions of precursors within the ABL for two 10 days' periods which had quite different synoptic situations and levels of photochemical activity (1–10 July 1991 (JUL91) and 26 October–4 November 1994 (ON94)). Over the European continent, about 8% of the NO_x emissions were brought from the ABL to the free troposphere as NO_x, while about 15% of the NO_x emissions were brought to the free troposphere as NO_y–NO_x, i.e. as PAN or HNO₃. The convection dominates over the synoptic scale vertical advection as a transport mechanism both for NO_x and NO_y out of the boundary layer in the summertime high pressure situation (JUL91), while in the fall situation (ON94) the convective part was calculated to be the smallest. NO_x was almost completely transformed to NO_y–NO_x or removed within the ABL. Also for NO_y the major part of the atmospheric cycle is confined to the ABL both for JUL91 and ON94. The vertical transport time out of the ABL is of the order of 100h both for the total model domain and over the European continent. The net convective exchange of ozone from the ABL is not a dominant process for the amount of ozone in the ABL averaged over 10 days and the whole domain, but convection reduces the maximum ozone concentration in episodes significantly. The ozone producing efficiency of NO_x is calculated to increase with height to typically 15–20 in the upper half of the troposphere from around 5 in the ABL, but in the middle free troposphere the concentration of NO_x is often too low to cause net chemical formation of ozone there.     

Global air quality change during the COVID-19 pandemic: Regionally different ozone pollution responses COVID-19: 疫情期间全球空气质量变化:臭氧响应的区域间差异

The explosive spread of the 2019 novel coronavirus (COVID-19) provides a unique chance to rethink the relationship between human activity and air pollution. Though related studies have revealed substantial reductions in primary emissions, obvious differences do exist in the responses of secondary pollutants, like ozone (O₃) pollution. However, the regional disparities of O₃ responses and their causes have still not been fully investigated. To better elucidate the interrelationship between anthropogenic emissions, chemical production, and meteorological conditions, O₃ responses caused by lockdowns over different regions were comprehensively explored at a global scale. Observational signals of air-quality change were derived from multi-year surface measurements and satellite retrievals. With similar substantial drops in nitrogen dioxide (NO₂), ozone shows rising signals in most areas of both East Asia and Europe, even up to ∼14 ppb, while a non-negligible declining signal exists in North America, by about 2–4 ppb. Furthermore, the drivers behind the different O₃ responses are discussed based on meteorological analysis and O₃ sensitivity diagnosis. On the one hand, O₃ responses to NO₂ declines can be affected by the primary dependence on its precursors. On the other hand, it is also highly dependent on meteorological factors, especially temperature. Our study further highlights the great importance of taking into consideration both the regional disparities and synergistic effects of precursor reductions and meteorological influence for scientific mitigation of O₃ pollution.摘要疫情期间全球各地一次排放大幅削减, 而臭氧等二次污染的响应则存在着区域间差异.结合地面和卫星观测发现, 同在氮氧化物大幅下降的情况下,臭氧在东亚和欧洲呈现出可达14ppb的上升信号, 而北美则下降为主 (约2–4ppb) .我们结合气象分析和臭氧敏感性进一步讨论了臭氧响应差异性的原因, 一方面受臭氧与前体物间关系的影响;另一方面来自于气象, 尤其是温度.研究明晰了人为排放,化学和气象三者的内在关联, 强调了在臭氧控制过程中考虑前体物削减和气象条件协同的重要性.     

Quality Assurance in TFS for Inorganic Compounds

A quality assurance program for the three main field experiments in TFScovering O₃, NO, NO_x, NO_y, CO,O₃ LIDARs and meteorological parameters was designed andexecuted. The results are presented and problems encountered during the execution phase are discussed. The need for and the benefit of independent quality assurance activities is demonstrated and documented in detailed meta data files that are part of the final data set.     

Impact of precursor levels and global warming on peak ozone concentration in the Pearl River Delta Region of China

The relationship between the emission of ozone precursors and the chemical production of tropospheric ozone(O3) in the Pearl River Delta Region(PRD) was studied using numerical simulation.The aim of this study was to examine the volatile organic compound(VOC)-or nitrogen oxide(NOx =NO+NO2)limited conditions at present and when surface temperature is increasing due to global warming,thus to make recommendations for future ozone abatement policies for the PRD region.The model used for this application is the U.S.Environmental Protection Agency’s(EPA’s) third-generation air-quality modeling system;it consists of the mesoscale meteorological model MM5 and the chemical transport model named Community Multi-scale Air Quality(CMAQ).A series of sensitivity tests were conducted to assess the influence of VOC and NOx variations on ozone production.Tropical cyclone was shown to be one of the important synoptic weather patterns leading to ozone pollution.The simulations were based on a tropicalcyclone-related episode that occurred during 14-16 September 2004.The results show that,in the future,the control strategy for emissions should be tightened.To reduce the current level of ozone to meet the Hong Kong Environmental Protection Department(EPD) air-quality objective(hourly average of 120 ppb),emphasis should be put on restricting the increase of NOx emissions.Furthermore,for a wide range of possible changes in precursor emissions,temperature increase will increase the ozone peak in the PRD region;the areas affected by photochemical smog are growing wider,but the locations of the ozone plume are rather invariant.     

Preliminary modelling results of an urban air quality model verifying the prediction of nitrogen dioxide, sulfur dioxide and ozone over the Sydney basin

Summary The air quality modelling system (HIRES-AIRCHEM) of The University of New South Wales is tested with regard to forecast distributions of sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and ozone (O₃) over the Sydney basin and surrounding area. This is achieved by assimilating the emissions inventory of the New South Wales State Environment Protection Authority. This inventory contains both road and non-road sources. The HIRES-AIRCHEM system was run over the greater Sydney metropolitan area for a four day period in February 1998. During this period O₃ readings, in particular, exceeded the EPAs threshold maximum of 80ppb. The model forecasts of the NO₂-, SO₂- and O₃-distributions verify well with the EPAs monitored readings. Diurnal concentrations are greatest in the late afternoon, as expected, when photochemical processes are most active. Furthermore, the forecast spatial distribution of NO₂ and SO₂ shows maximum values radiating out along major roads from the Sydney CBD and other population centres. This is consistent with NO₂ and SO₂ being major pollutants associated with vehicular traffic. These promising results have significant implications for possible future use of the system as a tool for routinely assessing air quality.     

基于空气质量模拟的江苏省大气污染物排放清单比较研究

大气污染物排放清单是空气质量模拟和空气污染治理的重要依据.本研究比较分析了两套覆盖江苏省的2017年大气污染物排放清单，即分别由上海市环境科学研究院、江苏省环境科学研究院编制的"长三角清单"和"江苏省清单"，并结合区域空气质量模型CMAQ评估不同清单对长三角地区2017年1、4、7、10月的空气质量模拟的影响.清单比较结果表明，除二氧化硫（SO₂）以外，江苏省清单估算的各污染物排放量较长三角清单低.通过与观测数据比较，发现两套清单对SO₂、氮氧化物（NO_x）、臭氧（O₃）和细颗粒物（PM_2.5）的模型模拟性能均较好.江苏省清单与长三角清单两者的模拟结果空间分布接近，其中江苏省清单模拟的PM_2.5和O₃在长三角多数地区略低于长三角清单的模拟结果（1月O₃除外）.江苏省清单与长三角清单均能够用于空气质量模式模拟，可为江苏地区的细颗粒物和光化学烟雾污染的控制策略制定提供参考.     

Episodes of extreme rainwater pollution and its relationship with synoptic situation (Wielkopolski National Park,Poland)

Synoptic conditions of extreme rainwater pollution episodes, evidenced by maximum values of parameters measured in the protected area of Wielkopolski National Park (western-central Poland), were analysed in this study. Precipitation samples were tested for the following parameters: pH, electrical conductivity and the concentration of the following elements: F^-, Cl^-, NO₂^-, NO₃^-, PO₄^3-, SO₄^2- and Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺. It was assumed, that in winter, western advection of Atlantic air masses was the most frequent aerosol and pollution transport scenario for the investigated area. In summer the most heavily pollution occur at the intensified meridional flow over the central Europe, indicating advection of cooler air from northern Europe and the North Sea. In most of cases, the weather conditions causing extreme concentration of examined pollutants, were determined by the movement of weather fronts over considerable parts of Poland and by precipitation caused by those fronts.     

Atmospheric dynamics in the center of the European part of Russia during intensive snowfall in April 2012

The dynamics of atmospheric characteristics in the zone of the cyclone which provoked the dangerous atmospheric phenomenon, the heavy snowfall over the center of the European part of Russia in April 2012, is studied using the data of surface and satellite measurements. Besides the observational data from the meteorological stations, the results are used of the measurement of meteorological variables at the high-altitude meteorological mast in Obninsk and of surface concentration of minor gas components. Revealed is a number of interesting features associated with the passage of the cyclone cloud system over the observational point: the dramatic air temperature drop throughout the 300-m layer of the atmosphere, the formation of intensive vertical motions, and the significant temporal variability of O₃ and NO₂ concentration. The intensity and the total amount of precipitation falling during the cyclone passage are determined using the data of optical measurements of SEVIRI, AVHRR, and MODIS instruments of geostationary and polar orbiting satellites. Demonstrated is the satisfactory agreement of the computed precipitation characteristics with the results of observations at the network of meteorological stations.