Impacts of Future NOx and CO Emissions on Regional Chemistry and Climate over Eastern China

A coupled chemical/dynamical model (SOCOL-SOlar Climate Ozone Links) is applied to study the impacts of future enhanced CO and NOx emissions over eastern China on regional chemistry and climate. The result shows that the increase of CO and NOx emissions has significant effects on regional chemistry, including NOx, CO, O₃, and OH concentrations. During winter, the CO concentration is uniformly increased in the northern hemisphere by about 10 ppbv. During summer, the increase of CO has a regional distribution. The change in O₃, concentrations near eastern China has both strong seasonal and spatial variations. During winter, the surface O₃, concentrations decrease by about 2 ppbv, while during summer they increase by about 2 ppbv in eastern China. The changes of CO, NOx, and O₃, induce important impacts on OH concentrations. The changes in chemistry, especially O₃, induce important effects on regional climate. The analysis suggests that during winter, the surface temperature decreases and air pressure increases in central-eastern China. The changes of temperature and pressure produce decreases in vertical velocity. We should mention that the model resolution is coarse, and the calculated concentrations are generally underestimated when they are compared to measured results. However, because this model is a coupled dynamical/chemical model, it can provide some useful insights regarding the climate impacts due to changes in air pollutant emissions.     

Satellite Measurements of Tropospheric Column O<Subscript>3</Subscript> and NO<Subscript>2</Subscript> in Eastern and Southeastern Asia: Comparison with a Global Model (MOZART-2)

Satellite measurements of tropospheric column O₃ and NO₂ in eastern and southeastern Asia are analyzed to study the spatial and seasonal characteristics of pollution in these regions. Tropospheric column O₃ is derived from differential measurements of total column ozone from Total Ozone Mapping Spectrometer (TOMS), and stratospheric column ozone from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS). The tropospheric column NO₂ is measured by Global Ozone Monitoring Experiment (GOME). A global chemical and transport model (Model of Ozone and Related Chemical Tracers, version 2; MOZART-2) is applied to analyze and interpret the satellite measurements. The study, which is based on spring, summer, and fall months of 1997 shows generally good agreement between the model and satellite data with respect to seasonal and spatial characteristics of O₃ and NO₂ fields. The analysis of the model results show that the industrial emission of NO_x (NO + NO₂) contributes about 50%–80% to tropospheric column NO₂ in eastern Asia and about 20%–50% in southeastern Asia. The contribution of industrial emission of NO_x to tropospheric column O₃ ranges from 10% to 30% in eastern Asia. Biomass burning and lightning NO_x emissions have a small effect on tropospheric O₃ in central and eastern Asia, but they have a significant impact in southeastern Asia. The varying effects of NO_x on tropospheric column ozone are attributed to differences in relative abundance of volatile organic compounds (VOCs) with respect to total nitrogen in the two regions.     

NUMERICAL SIMULATION OF THE SEASONAL VARIATION OF TROPOSPHERIC OZONE OVER CHINA

An updated version of the Regional Acid Deposition Model(RADM)driven by meteorologicalfields derived from Chinese Regional Climate Model(CRegCM)is used to simulate seasonal variationof tropospheric ozone over the eastern China.The results show that:(1)Peak O_3 concentration moves from south China to north China responding to the changing ofsolar perpendicular incidence point from south to north.When solar perpendicular incidence pointmoves from north to south,so does the peak O_3 concentration.(2)In the eastern China.the highest O_3 month-average concentration appears in July.thelowest in January and the medium in April and October.The pattern mainly depends on the solarradiation,the concentration of O_3 precursors NO_x and NMHC and the ratio of NMHC/NO_x.(3)Daily variations of O_3 over the eastern China are clear.Namely,O_3 concentrations rise withthe sun rising and the maximums appear at noon.then O_3 concentrations decrease.The highest dailyvariation range of O_3 appears in summer(40×10~(-9) in volume fraction)and the lowest in winter(20×10~(-9) in volume fraction).(4)Daily variations of O_3 over the western China are not clear.The daily variation range of O_3 isless than 10×10~(-9) in volume fraction.     

A study of ozone in the Colorado mountains

The seasonal and diurnal variations of ozone mixing ratios have been observed at Niwot Ridge. Colorado. The ozone mixing ratios have been correlated with the NO _x (NO+NO₂) mixing ratios measured concurrently at the site. The seasonal and diurnal variations in O₃ can be reasonably well understood by considering photochemistry and transport. In the winter there is no apparent systematic diurnal variation in the O₃ mixing ratio because there is little diurnal change of transport and a slow photochemistry. In the summer, the O₃ levels at the site are suppressed at night due to the presence of a nocturnal inversion layer that isolated ozone near the surface, where it is destroyed. Ozone is observed to increase in the summer during the day. The increases in ozone correlate with increasing NO _x levels, as well as with the levels of other compounds of anthropogenic origin. We interpret this correlation as in-situ or in-transit photochemical production of ozone from these precursors that are transported to our site. The levels of ozone recorded approach 100 ppbv at NO _x mixing ratios of approximately 3 ppbv. Calculations made using a simple clean tropospheric chemical model are consistent with the NO _x -related trend observed for the daytime ozone mixing ratio. However, the chemistry, which does not include nonmethane hydrocarbon photochemistry, underestimates the observed O₃ production.     

Impacts of Global Emissions of CO, NOx, and CH4 on China Tropospheric Hydroxyl Free Radicals

Using the global chemistry and transport model MOZART,the simulated distributions of tropospheric hydroxyl free radicals(OH) over China and its sensitivities to global emissions of carbon monoxide(CO),nitrogen oxide(NO x),and methane(CH 4) were investigated in this study.Due to various distributions of OH sources and sinks,the concentrations of tropospheric OH in east China are much greater than in west China.The contribution of NO + perhydroxyl radical(HO 2) reaction to OH production in east China is more pronounced than that in west China,and because of the higher reaction activity of non-methane volatile organic compounds(NMVOCs),the contributions to OH loss by NMVOCs exceed those of CO and take the dominant position in summer.The results of the sensitivity runs show a significant increase of tropospheric OH in east China from 1990 to 2000,and the trend continues.The positive effect of double emissions of NO x on OH is partly offset by the contrary effect of increased CO and CH 4 emissions:the double emissions of NO x will cause an increase of OH of 18.1%-30.1%,while the increases of CO and CH 4 will cause a decrease of OH of 12.2%-20.8% and 0.3%-3.0%,respectively.In turn,the lifetimes of CH 4,CO,and NO x will increase by 0.3%-3.1% with regard to double emissions of CH 4,13.9%-26.3% to double emissions of CO and decrease by 15.3%-23.2% to double emissions of NO x.     

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.     

东亚区域对流层臭氧及其前体物的季节性关联

利用2010—2012年对流层臭氧（O₃）及其多种前体物的卫星遥感资料和全球水汽再分析资料,研究东亚区域O₃及其前体物的时空分布,以及在中国东部（分为南、北两部分）相关性的季节变化。结果表明:东亚区域NO₂与CO的对流层柱含量均表现为冬季高、夏季低的时空变化形式。O₃对流层柱含量夏季达到峰值,冬季为谷值。中国东部的北部与南部地区O₃与NO₂均在夏秋季呈正相关,冬春季呈负相关。夏季大部分地区NO_x的光化学循环反应对O₃生成有积极的促进作用,冬季大部分地区O₃的光化学循环生成受到抑制。O₃与CO在北部地区夏秋季和南部地区夏季正相关性最大,无论是在北部还是南部地区,O₃与CO的相关性在轻污染情况下最大,而在重污染和背景情况下较小,表明重污染气团向下风方的输送更有利于O₃的光化学生成。O₃与水汽在北部和南部地区的多数时间均呈较显著的正相关性,而在南部地区夏季和北部地区冬季具有较大的负相关性,反映出不同的环流形式、气团来源及伴随的天气条件变化对O₃分布的影响。     

Seasonal changes in the daily emission rates of terpenes by Quercus ilex and the atmospheric concentrations of terpenes in the natural park of Montseny, NE Spain

We studied the daily patterns in the rates of terpene emissions by the montane holm oak, Quercus ilex, in three typical days of winter and three typical days of summer in Montseny, a natural park near Barcelona, and related them to the air concentrations of terpenes, ozone and NO₂. Terpene emission rates were about 10 times higher in summer than in winter. Emissions virtually stopped in the dark. In both seasons, rates of terpene emissions were well correlated with light, air temperature and relative humidity. Rates of emissions were also correlated with stomatal conductance and the rates of transpiration and photosynthesis. Almost all the individual terpenes identified followed the same pattern as total terpenes. The most abundant terpene was ??-pinene, followed by sabinene + ??-pinene, limonene, myrcene, camphene and ??-phellandrene. Atmospheric terpene concentrations were also about 10 times higher in summer than in winter. A significant diurnal pattern with maxima at midday was observed, especially in summer. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources. Atmospheric concentrations of O₃ and NO₂ were also significantly higher in summer and at midday hours. In both seasons, concentrations of O₃ were significantly correlated with concentrations of terpenes and NO₂ in the air and with rates of terpene emission.     

A budget analysis of NO x column losses over the Korean peninsula

In this study, the chemical and physical losses of nitrogen oxides (NO_x) over the Korean peninsula were discussed in order to better understand the effects of the NO_x losses on the tropospheric NO₂ columns. Initially, it was found that the physical loss processes due to dry and wet depositions had almost negligible impacts on the NO_x loss processes over the Korean peninsula. In contrast, the hourly NO_x chemical column losses were large at ??10¹⁴ molecules cm^?2 h^?1. The amounts of NO_x removed for 1 hour account for approximately 33?C35% of the episode-averaged tropospheric NO₂ columns during summer over the Korean peninsula. The NO_x chemical column loss rates were 24.1?C70.9 times larger than the NO_x physical column loss rates. In a budget analysis of the NO_x chemical column losses, HNO₃ formation via the reaction of OH + NO₂ had the largest contribution toward the NO_x chemical losses (42?C55% during fall and winter seasons; 76?C77% during spring; 92?C93% during summer). Large amounts of NO_x were also removed by heterogeneous nitrate formation via N₂O₅ condensation during the cold seasons (42?C56%) over the Korean peninsula. The columnar NO_x chemical losses took place mainly due to the two chemico-physical reaction processes, and also showed seasonal variations. PAN (Peroxyacetyl Nitrate) is another NO₂ reservoir of potential importance. If the influence of the PAN-related chemistry on the NO_x budget is considered, it can result in an approximate 69% increase in the NO_x chemical column loss during summer. Such increases in the amounts of NO_x removed for 1 hour due to the formation of PAN were equivalent to 56?C58% of the episode-averaged tropospheric NO₂ columns during summer over the Korean peninsula. Such active NO_x chemical losses during summer are another main factor for the tropospheric NO₂ columns exhibiting their smallest values during summer.     

Background ozone and anthropogenic ozone enhancement at niwot ridge,Colorado

The mixing ratios for ozone and NO_x (NO+NO₂) have been measured at a rural site in the United States. From the seasonal and diurnal trends in the ozone mixing ratio over a wide range of NO_x levels, we have drawn certain conclusions concerning the ozone level expected at this site in the absence of local photochemical production of ozone associated with NO_x from anthropogenic sources. In the summer (June 1 to September 1), the daily photochemical production of ozone is found to increase in a linear fashion with increasing NO_x mixing ratio. For NO_x mixing ratios less than 1 part per billion by volume (ppbv), the daily increase is found to be (17±3) [NO_x]. In contrast, the winter data (December 1 to March 1) indicate no significant increase in the afternoon ozone level, suggesting that the photochemical production of ozone during the day in winter approximately balances the chemical titration of ozone by NO and other pollutants in the air. The extrapolated intercept corresponding to [NO_x]=0 taken from the summer afternoon data is 13% less than that observed from the summer morning data, suggesting a daytime removal mechanism for O₃ in summer that is attributed to the effects of both chemistry and surface deposition. No significant difference is observed in the intercepts inferred from the morning and afternoon data taken during the winter.The results contained herein are used to deduce the background ozone level at the measurement site as a function of season. This background is equated with the natural ozone background during winter. However, the summer data suggest that the background ozone level at our site is elevated relative to expected natural ozone levels during the summer even at low NO_x levels. Finally, the monthly daytime ozone mixing ratios are reported for 0[NO_x]0.2 ppbv, 0.3 ppbv[NO_x]0.7 ppbv and 1 ppbv[NO_x]. These monthly ozone averages reflect the seasonal ozone dependence on the NO_x level.     

Simulated Spatial Distribution and Seasonal Variation of Atmospheric Methane over China: Contributions from Key Sources简

We used the global atmospheric chemical transport model,GEOS-Chem,to simulate the spatial distribution and seasonal variation of surface-layer methane （CH4） in 2004,and quantify the impacts of individual domestic sources and foreign transport on CH4 concentrations over China.Simulated surface-layer CH4 concentrations over China exhibit maximum concentrations in summer and minimum concentrations in spring.The annual mean CH4 concentrations range from 1800 ppb over western China to 2300 ppb over the more populated eastern China.Foreign emissions were found to have large impacts on CH4 concentrations over China,contributing to about 85％ of the CH4 concentrations over western China and about 80％ of those over eastern China.The tagged simulation results showed that coal mining,livestock,and waste are the dominant domestic contributors to CH4 concentrations over China,accounting for 36％,18％,and 16％,respectively,of the annual and national mean increase in CH4 concentration from all domestic emissions.Emissions from rice cultivation were found to make the largest contributions to CH4 concentrations over China in the summer,which is the key factor that leads to the maximum seasonal mean CH4 concentrations in summer.     

Estimates of indirect global warming potentials for CH4, CO and NOX

Emissions may affect climate indirectly through chemical interactions in the atmosphere, but quantifications of such effects are difficult and uncertain due to incomplete knowledge and inadequate methods. A preliminary assessment of the climatic impact of changes in tropospheric O₃ and CH₄ in response to various emissions is given. For a 10% increase in the CH₄ emissions the relative increase in concentration has been estimated to be 37% larger. The radiative forcing from enhanced levels of tropospheric O₃ is estimated to 37% of the forcing from changes in CH₄. Inclusion of indirect effects approximately doubles the climatic impact of CH₄ emissions. Emissions of NO_x increase tropospheric O₃, while the levels of CH₄ are reduced. For emissions of NO_x from aircraft, the positive effects via O₃ changes are significantly larger than the negative through changes in CH₄. For NO_x emitted from surface sources, the effects through changes in O₃ and CH₄ are estimated to be of similar magnitude and large uncertainty is connected to the sign of the net effect. Emissions of CO have positive indirect effects on climate through enhanced levels of tropospheric o₃ and increased lifetime of CH₄. These results form the basis for estimates of global warming potentials for sustained step increases in emissions.     

PRELIMINARY ANALYSIS OF THE VARIATIONS OF SURFACE OZONE AND NITRIC OXIDES IN LIN’AN

The observational results in Lin;an show the elevated average concentrations of surface ozone and Nitric Oxides(NO_x)in the rural area in the eastern mid-latitudes of China.The mechanism of its variations was explained by the theoretical analysis.In the case of breeze,the photochemical reactions controlled by solar radiation is the determined factors affecting the variations of the surface O₃ and NO_x.A study of the correlation between NO_x and SO₂ demonstrates that the biomass burning is an important local emission source of NO_x.     

Measurements of Trace Gases in the Inflow of South China Sea Background Air and Outflow of Regional Pollution at Tai O, Southern China

We present a 16-month record of ozone (O₃), carbon monoxide (CO), total reactive nitrogen (NO_y), sulphur dioxide (SO₂), methane (CH₄), C₂ – C₈ non-methane hydrocarbons (NMHCs), C₁ – C₂ halocarbons, and dimethyl sulfide (DMS) measured at a southern China coastal site. The study aimed to establish/update seasonal profiles of chemically active trace gases and pollution tracers in subtropical Asia and to characterize the composition of the `background' atmosphere over the South China Sea (SCS) and of pollution outflow from the industrialized Pearl River Delta (PRD) region and southern China. Most of the measured trace gases of anthropogenic origin exhibited a winter maximum and a summer minimum, while O₃ showed a maximum in autumn which is in contrast to the seasonal behavior of O₃ in rural eastern China and in many mid-latitude remote locations in the western Pacific. The data were segregated into two groups representing the SCS background air and the outflow of regional continental pollution (PRD plus southern China), based on CO mixing ratios and meteorological conditions. NMHCs and halocarbon data were further analyzed to examine the relationships between their variability and atmospheric lifetime and to elucidate the extent of atmospheric processing in the sampled air parcels. The trace gas variability (S) versus lifetime (τ) relationship, defined by the power law, S_lnx = Aτ^{− b}, (where X is the trace gas mixing ratio) gives a fit parameter A of 1.39 and exponent b of 0.42 for SCS air, and A of 2.86 and b of 0.31 for the regional continental air masses. An examination of ln[n-butane]/ln[ethane] versus ln[propane]/ln[ethane] indicates that their relative abundance was dominated by mixing as opposed to photochemistry in both SCS and regional outflow air masses. The very low ratios of ethyne/CO, propane/ethane and toluene/benzene suggest that the SCS air mass has undergone intense atmospheric processing since these gases were released into the atmosphere. Compared to the results from other polluted rural sites and from urban areas, the large values of these species in the outflow of PRD/southern China suggest source(s) emitting higher levels of ethyne, benzene, and toluene, relative to light alkanes. These chemical characteristics could be unique indicators of anthropogenic emissions from southern China.     

Characteristics of gaseous pollutants near a main traffic line in Beijing and its influencing factors

Automobile exhaust emissions are becoming increasingly serious with the drastic increase of the number of vehicles in Beijing. In order to investigate the air pollution level and characteristics in the areas near the main traffic lines in Beijing and to identify the contributions from traffic and other sources, gaseous pollutants including NOx, CO, O₃, SO₂, and meteorological parameters have been monitored at a monitoring site and a contrasting site in winter and summer in 2006. The volumes of vehicles on Beiyuan Road were recorded. The average concentrations of NO, NO₂, NOx, CO, O₃, and SO₂ at the monitoring site were 0.148 mg/m³, 0.107 mg/m³, 0.333 mg/m³, 5.110 mg/m³, 0.006 mg/m³, and 0.157 mg/m³, respectively during the sampling period in winter and 0.021 mg/m³, 0.068 mg/m³, 0.101 mg/m³, 4.170 mg/m³, 0.083 mg/m³, and 0.056 mg/m³, respectively in summer. The high concentrations of CO and O₃ reflect the influence of vehicles emission near the traffic lines evidently. The higher concentrations of CO, NO and O₃ in summer may indicate that the characteristics of traffic pollution were more pronounced in summer. Results of regression analysis showed that in winter the concentrations of SO₂ and CO were significantly positively correlated with the emission of heating boilers at night and negatively correlated with wind speed in daytime. The concentrations of NO and NOx were negatively correlated with wind speed, positively correlated with emission of heating boilers in daytime and positively correlated with traffic density at nighttime. The concentrations of NO₂ were positively correlated with the emission of heating boilers in daytime and traffic density at nighttime. In summer, the air quality at the monitoring site and the contrasting site was mainly influenced by the traffic emissions.     

Tropospheric chemical composition measurements in Brazil during the dry season

Field measurement programs in Brazil during the dry seasons in August and September 1979 and 1980 have demonstrated the large importance of the continental tropics in global air chemistry. Many important trace gases are produced in large amounts over the continents. During the dry season, much biomass burning takes place, especially in the cerrado regions, leading to a substantial emission of air pollutants, such as CO, NO _x , N₂O, CH₄ and other hydrocarbons. Ozone concentrations are enhanced due to photochemical reactions. The large biogenic organic emissions from tropical forests play an important role in the photochemistry of the atmosphere and explain why CO is present in such high concentrations in the boundary layer of the tropical forest. Carbon monoxide production may represent more than 3% of the net primary productivity of the tropical forests. Ozone concentrations in the boundary layer of the tropical forests indicate strong removal processes. Due to atmospheric supply of NO _x by lightning, there is probably a large production of O₃ in the free troposphere over the Amazon tropical forests. This is transported to the marine-free troposphere and to the forest boundary layer.     

汾渭平原东部运城市空气污染变化特征及其气象因素影响分析

本文综合利用2015—2020年地面气象观测资料、欧洲中心ERA5再分析资料及大气环境监测数据,分析了汾渭平原东部运城市污染物浓度的变化特征以及与天气形势和气象要素的关系。结果表明：①2015—2020年期间运城市PM2.5、PM10、SO2、NO2、CO 5种污染物年平均浓度呈下降趋势,而O3浓度呈上升趋势;②冬季和夏季空气质量相对较差,首要污染物分别是PM2.5和O3,边界层高度的变化与近地层风向风速、污染物浓度的关系密切,冬季（夏季）PM2.5（O3）污染较重时边界层高度较低（较高）,以东北风（东南风）为主,风速偏小（偏大）;③最后利用自组织映射神经网络（SOM）算法分别对冬夏925 hPa位势高度场进行天气分型并开展不同天气形势下污染物浓度与气象要素的变化对比研究,发现冬季污染时以静稳天气为主,低层弱东北风将污染物输送至运城市,而夏季O3污染较重时受热低压形势控制,利于O3前体物汇合,太阳辐射较强时O3浓度较高。     

Tropospheric Ozone at High Latitudes in Clean and Polluted Air Masses, a Climatological Study

Several years of continuous measurements of surfaceozone at Norwegian monitoring sites are studied in aclimatological way. The monitoring sites are at rurallocations extending from 58°N, a few hundredkilometers from the European continent and into theArctic at 79°N. The ozone observations are sorted intoclasses of integrated NO_x emissions along 96 h backtrajectories. The average seasonal cycles of ozone areestimated for each class separately. The differencesindicate the change from the background air due toanthropogenic emissions. The average seasonal cycle ofozone in the cleanest air masses showed a maximum inspring and a minimum during summer and autumn at allsites, but the spring maximum was more pronounced atthe southernmost locations. Polluted air masses showedan ozone deficit during winter and a surplus duringsummer. The deviation from the background was clearlylinked to the integrated NO_x emission along thetrajectories. In summer the calculations indicate thatthe number of ozone molecules formed per NO_x moleculedrops with increasing emissions. The average seasonalcycle of ozone at Birkenes for different transportsectors indicate that the most pronounced ozoneformation takes place in air masses from E-Europe/Russia.     

Carboxylic Acids: Seasonal Variation and Relation to Chemical and Meteorological Parameters

Formic and acetic acid measured as daily averages in 1993–1994show equal and highly correlated concentrations up to 3 ppb in the summer(May–August). In the winter (October–March) the formicacid/acetic acid ratio was 0.6 and the formic acid concentrations wereusually below 1 ppb. In winter the carboxylic acids correlate withO_x, NO_y, SO₂ and particulatesulphur. The main sources are suggested to be ozonolysis of anthropogenicalkenes and reactions between peroxyacetyl radicals and RO₂radicals. In spring–summer the carboxylic acids correlate withO₃, O_x, HNO₃, PAN,NO_y, SO₂, particulate sulphur and temperature.In addition to the sources of the winter a contribution from ozonolysis ofbiogenic alkenes is likely. Quite similar formic acid/acetic acid ratios forall wind directions suggest that the source(s) are atmospheric oxidationprocesses distributed over large areas. The highest concentrations occurringfor winds from east to south and the correlation with e.g., particulatesulphur indicate chemical production in polluted air masses during longrange transport.     

The steady‐state structure of the natural stratosphere and ozone distribution in a 2‐D model incorporating radiation and O‐H‐N photochemistry and the effects of stratospheric pollutants

A mean meridional circulation model of the stratosphere, incorporating radiative heating and photochemistry of the oxygen‐hydrogen‐nitrogen atmosphere, is used to simulate the meridional distributions of O₃, HO_X, N₂O,NO_X, temperature and the three components of mean motion for the summer and winter seasons under steady‐state conditions. The results are generally in good agreement with the available observations in the normal stratosphere. The model has been applied to assess the effects of water vapour and nitrogen oxide perturbations resulting from aircraft emissions in the stratosphere. It is found that a fleet of 500 Boeing‐type sst's, flying at 20 km and 45°N in the summer hemisphere and inserting NO_x at a rate of 1.8 megatons per year, has the effect of reducing the global total ozone by 14.7%. Similar calculations for 342 Concorde/TU‐114's, cruising at 17 km and injecting NO_x at a rate of 0.35 megatons per year, show a global‐average total‐ozone reduction of 1.85%. Although water vapour is considered important, because of its ability to convert NO₂ into HNO₃, the direct effect on global‐average total‐ozone reduction resulting from the 100% increase in the stratospheric water content is less than 1%. The changes in the chemical structure (HO^NO^), temperature, and mean motions associated with the ozone reduction are also investigated in the case of the 1.8‐megaton‐per‐year NO_X perturbation. It is shown that the reduced meridional temperature gradient in the middle and upper stratosphere resulting from the NO_x perturbation leads to the weakening of the tropical easterly jet in the summer hemisphere and mid‐latitude westerlies in the winter season.

The sensitivity of the model solutions to an alternate choice of input parameters (diffusion coefficients and solar photodissociation data) is tested and the main deficiency of the model is pointed out.