Urban Atmospheric Chemistry During the PUMA Campaign 2: Radical Budgets for OH,HO<Subscript>2</Subscript> and RO<Subscript>2</Subscript>

A detailed photochemical box model was used to investigate the key reaction pathways between OH, HO₂ and RO₂ radicals during the summer and winter PUMA field campaigns in the urban city-centre of Birmingham in the UK. The model employed the most recent version of the Master Chemical Mechanism and was constrained to 15-minute average measurements of long-lived species determined in situ at the site. The results showed that in the summer, OH initiation was dominated by the reactions of ozone with alkenes, nitrous acid (HONO) photolysis and the reaction of excited oxygen atoms atoms with water. In the winter, ozone+alkene reactions were the primary initiation route, with a minor contribution from HONO photolysis. Photolysis of aldehydes was the main initiation route for HO₂, in both summer and winter. RO₂ initiation was dominated by the photolysis of aldehydes in the summer with a smaller contribution from ozone+alkenes, a situation that was reversed in the winter. At night, ozone+alkene reactions were the main radical source. Termination, under all conditions, primarily involved reactions with NO (OH) and NO₂ (OH and RCO₃). These results demonstrate the importance of ozone+alkene reactions in urban atmospheres, particularly when photolysis reactions were less important during winter and at nighttime. The implications for urban atmospheric chemistry are discussed.     

The Tambora eruption in 1815 provides a test on possible global climatic and chemical perturbations in the past

A coupled one-dimensional radiative-convective-photochemical diffusion model, which takes into account the influence of ocean inertia on global radiative perturbations is used to investigate the possible climatic and other atmospheric effects of a major volcanic eruption, thought to be similar in magnitude to that of the Tambora eruption, Indonesia, which took place in 1815. A volcanic cloud was introduced in the model stratosphere between 20–25 km and the global average peak aerosol optical thickness was assumed to be 0.25. Both the aerosol optical thickness and aerosol composition, which determine the optical properties, were allowed to vary in the model atmosphere during the life cycle of the volcanic cloud. The results indicate that the global average surface temperature decreases steadily from the date of eruption (7–12 April 1815) with maximum cooling of 1° K occurring in the spring of 1816. The calculations also show significant warming of the stratosphere, with temperature increasing up to 15° K at 25 km in less than six months after the date of eruption. The important effects of the Tambora eruption on stratospheric ozone and UV-B radiation at the surface are also mentioned.     

NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> change over China and its influences

A 3-D chemical transport model (OSLO CTM2) is used to investigate the impact of the increase of NOx emission over China. The model is capable to reproduce basically the seasonal variation of surface NOx and ozone over eastern China. NOx emission data and observations reveal that NOx over eastern China increases quite quickly with the economic development of China. Model results indicate that NOx concentration over eastern China increasingly rises with the increase of NOx emission over China, and accelerates to increase in winter. When the NOx emission increases from 1995 to its double, the ratio of NO2/NOx abruptly drops in winter over northern China. Ozone at the surface decreases in winter with the continual enhancement of the NOx level over eastern China, but increases over southern China in summertime. It is noticeable that peak ozone over northern China increases in summer although mean ozone changes little. In summer, ozone increases in the free troposphere dominantly below 500 hPa.Moreover, the increases of total ozone over eastern China are proportional to the increases of NOx emission.In a word, the model results suggest that the relationship between NOx and ozone at the surface would change with NOx increase.     

蒙特卡罗不确定性分析在O3模拟中的初步应用

利用蒙特卡罗不确定性分析方法,分析了嵌套网格空气质量模式系统(NAQPMS/IAP)中154个模式输入变量不确定性对臭氧模拟的影响,量化了模式在北京奥运会期间臭氧模拟的不确定性,并确定出了主要不确定性因子。结果表明:(1)在奥运会期间(2008年8月8日～2008年8月24日),北京城区臭氧模拟的平均不确定性为19ppb,不确定性存在明显的日变化特征,白天不确定性大,夜间不确定性小。(2)在白天,北京城区近地层臭氧模拟最重要的不确定性来源是局地前体物排放,其次是NO2光解系数、风向、北京周边前体物排放和垂直扩散系数。另外,地面约150m以上,对臭氧模拟影响最大的不确定性因子是风向和北京周边前体物排放;夜间,北京城区近地层臭氧模拟的最大不确定性来源是局地NOx排放和垂直扩散系数。     

北京奥运会期间CBM-Z化学机制的模拟应用

利用CBM-Z化学机制模拟了中国科学院大气物理研究所气象塔站在北京奥运会期间高臭氧时段O3浓度的日变化,评估了气象条件、北京奥运会加强控制措施以及O3前体物浓度对近地面O3生成的影响。结果表明:(1)CBM-Z化学机制较好地模拟了北京奥运会期间典型时段气象塔站O3、NO、NO2日变化特征。(2)有利于局地高臭氧事件发生的气象条件非常相似;北京奥运会加强控制措施的实施显著减少了NOx及VOCs的排放量,导致近地面O3浓度的明显下降。(3)奥运会期间VOCs和CO是影响气象塔站O3生成量的关键因素。     

1979～2020年北极和青藏高原臭氧低值区的动力输送特征比较

基于ERA5月平均再分析资料,利用Lorenz环流分解方法从定常和瞬变以及基流和涡旋的角度对比了北极与青藏高原臭氧低值区的动力输送特征。结果表明：动力总输送在两地上平流层作用最强,均使其臭氧浓度降低,且定常输送均强于瞬变输送,纬向与经向输送的作用均大致相反。然而,动力输送在北极地区的作用强度远大于青藏高原地区。北极地区纬向输送使得平流层中上层臭氧浓度降低,平流层下层臭氧浓度升高,经向输送的作用与之相反且强度明显偏弱,二者均主要作用于上平流层。青藏高原地区纬向和经向输送除在上平流层均使得臭氧浓度降低外,二者作用大致相反且强度相当,输送大值区在垂直方向上存在双中心结构,分别位于上平流层与上对流层—下平流层（Upper Troposphere–Lower Stratosphere,简称UTLS）区。两地区纬向和经向输送的差异均主要由定常涡旋输送所造成。青藏高原地区定常与瞬变输送的强度差异没有北极地区大。此外,两地定常和瞬变输送中涡旋对臭氧纬向平均的输送均起到主要作用,体现出涡旋输送在两地臭氧浓度变化的动力输送过程中发挥着至关重要的作用。     

From highly polluted inland city of China to “Lanzhou Blue”: The air-pollution characteristics

Air quality was improved considerably and the so-called "Lanzhou Blue" appeared frequently in Lanzhou due to implementation of some strict emission-control measures in recent years. To better understand whether the concentration of each air pollutant had decreased significantly and then give some suggestions as to urban air-quality improvement in the near future, the variations of the Air Quality Index (AQI) and six criterion air pollutants (PM_2.5, PM₁₀, CO, SO₂, NO₂, and O₃) at five state-controlled monitoring sites of Lanzhou were studied from 2013 to 2016. The AQI, PM_2.5, PM₁₀, and SO₂ gradually decreased from 2013 to 2016, while CO and NO₂ concentrations had slightly increasing trends, especially in urban areas, due to the large number of motor vehicles, which had an annual growth rate of 30.87%. The variations of the air pollutants in the no-domestic-heating season were more significant than those in the domestic-heating season. The increase of ozone concentration for the domestic-heating season at a background station was the most significant among the five monitoring sites. The vehicle-exhaust and ozone pollution was increasingly severe with the rapid increase in the number of motor vehicles. The particulate-matter pollution became slight in the formerly highly polluted Lanzhou City. Some synergetic measures in urban and rural areas of Lanzhou should be taken by the local government in the near future to control fine particulate-matter (PM_2.5) and ozone pollution.     

基于定量化植物防御效应的臭氧通量模型的优化

继SUM06、AOT40之后,基于气孔臭氧累计吸收通量（AFstY）的研究方法被广泛应用于臭氧风险评估中.然而通量模型中的阈值Y并不能很好地代表植物对臭氧的抗氧化能力以及自我修复能力,如何动态模拟植物自身的防御机制对于提高臭氧风险评估的准确性尤为重要.本文基于前人的研究成果探讨如何定量化植物对臭氧的防御效应,运用光合定量方法动态模拟伤害阈值并计算臭氧有效吸收通量,运用SODA模型从气孔吸收和质外体解毒两个方面探讨细胞内抗坏血酸对臭氧原生质膜通量的影响,旨在为臭氧通量模型研究开辟一个新的视角,并为后续的臭氧胁迫效应研究打下基础.     

Impact of Taihu Lake on City Ozone in the Yangtze River Delta

The lake-breeze at Taihu Lake generates a different specific heat capacity between the water body and the surrounding land. Taihu Lake has a significant impact on the atmospheric conditions and the air quality in the Yangtze River Delta. This phenomenon is referred to as the Taihu Lake effect. In this study, two simulations were conducted to determine the impact of the Taihu Lake effect in the reference experiment(R-E) and sensitivity experiments(NO TH). The control simulations demonstrated that the meteorological field and the spatial distribution of ozone(O3) concentrations over Taihu lake obviously changed once the land-use type of water body was substituted by cropland. The surface temperature of Taihu Lake was reduced under the impact of Taihu Lake, and a huge temperature difference caused a strong lake-breeze effect. The results also showed that the difference in the average concentrations of O3 between the R-E and NO TH experiments reached 12 ppbv in most areas of Taihu Lake, all day, on 20 May 2014. During daytime(0800–1600 LST, LST=UTC+8), the influence of the Taihu Lake effect on O3 in the Suzhou region was not significant. However, the influence of the Taihu Lake effect on O3 in the Suzhou region was obvious during nighttime(1800–2400 LST). The larger changes in the physical and chemical processes were horizontal and vertical advections under the influence of the Taihu Lake effect in Taihu Lake.     

北半球中纬度地区上层臭氧变化的合成分析研究

应用逆转方法（C）,对北半球中纬度地区8个观测质量较好的O3地面站的近30年地面遥感逆转资料进行标准处理。采用合成分析方法,对中纬度带上层O3进行了分析研究,发现上层O3总的长期演变趋势较为平坦,仅80年代初及90年代初在36km以上层O3含量有突降现象。这可能与EL Chichon大火山焊发和Pinatubo大火山爆发有较大关系。此外。在上层O3含量的长期演变过程中,还可看到准11年周期,并证实28～36km层及36km以上层O3含量季节变化位相相反。本研究结果可能对南极O3洞的形成机制及近年来O3层变浅薄的机制的认识提供依据并产生影响。