Non-Kyoto radiative forcing in long-run greenhouse gas emissions and climate change scenarios

Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in total forcing result in increases in global average temperature. Non-Kyoto forcing modeling is a relatively new component of climate management scenarios. This paper describes and assesses current non-Kyoto radiative forcing modeling within five integrated assessment models. The study finds negative forcing from aerosols masking (offsetting) approximately 25 % of positive forcing in the near-term in reference non-climate policy projections. However, masking is projected to decline rapidly to 5–10 % by 2100 with increasing Kyoto emissions and assumed reductions in air pollution—with the later declining to as much as 50 % and 80 % below today’s levels by 2050 and 2100 respectively. Together they imply declining importance of non-Kyoto forcing over time. There are however significant uncertainties and large differences across models in projected non-Kyoto emissions and forcing. A look into the modeling reveals differences in base conditions, relationships between Kyoto and non-Kyoto emissions, pollution control assumptions, and other fundamental modeling. In addition, under climate policy scenarios, we find air pollution and resulting non-Kyoto forcing reduced to levels below those produced by air pollution policies alone—e.g., China sulfur emissions fall an additional 45–85 % by 2050. None of the models actively manage non-Kyoto forcing for climate implications. Nonetheless, non-Kyoto forcing may be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited.     

Characterization of Organic Aerosol at a Rural Site in the North China Plain Region: Sources,Volatility and Organonitrates

The North China Plain(NCP) is a region that experiences serious aerosol pollution. A number of studies have focused on aerosol pollution in urban areas in the NCP region; however, research on characterizing aerosols in rural NCP areas is comparatively limited. In this study, we deployed a TD-HR-AMS(thermodenuder high-resolution aerosol mass spectrometer) system at a rural site in the NCP region in summer 2013 to characterize the chemical compositions and volatility of submicron aerosols(PM_1). The average PM_1 mass concentration was 51.2 ± 48.0 μg m~(-3) and organic aerosol(OA) contributed most(35.4%) to PM_1. Positive matrix factorization(PMF) analysis of OA measurements identified four OA factors, including hydrocarbon-like OA(HOA, accounting for 18.4%), biomass burning OA(BBOA, 29.4%), lessoxidized oxygenated OA(LO-OOA, 30.8%) and more-oxidized oxygenated OA(MO-OOA, 21.4%). The volatility sequence of the OA factors was HOA BBOA LO-OOA MO-OOA, consistent with their oxygen-to-carbon(O:C)ratios. Additionally, the mean concentration of organonitrates(ON) was 1.48-3.39 μg m~(-3), contributing 8.1%–19% of OA based on cross validation of two estimation methods with the high-resolution time-of-flight aerosol mass spectrometer(HRToF-AMS) measurement. Correlation analysis shows that ON were more correlated with BBOA and black carbon emitted from biomass burning but poorly correlated with LO-OOA. Also, volatility analysis for ON further confirmed that particulate ON formation might be closely associated with primary emissions in rural NCP areas.     

重庆市区大气能见度变化特征及其影响因素分析

为研究重庆市区大气能见度变化特征,对2000～2005年的重庆能见度观测资料进行了统计分析。结果表明:市区能见度以差和较差为主,能见度的季节变化、日变化特征明显,且近年来日平均能见度有所下降。能见度与同期的地面气象条件、主要空气污染物的相关分析结果表明,在气象条件中,相对湿度和风速对能见度的影响最为明显,各季能见度均与相对湿度呈显著负相关,与地面风速呈正相关;在污染物因子中,PM10是能见度下降的最主要原因,且不同季节PM10对能见度的影响程度不同,其中以冬、夏季影响较强。     

北京夏季空气质量的气象指数预报

该文提出一种参数化预报方法,制作北京及其周边地区夏季空气质量气象条件指数预报。采用2000-2007年7-9月北京市观象台大气成分 (PM₁₀) 逐日观测资料和华北区域气象站网加密地面观测及探空信息,分析北京地区夏季奥运会历史同期与高污染过程 (PM₁₀浓度>150μg/m3) 关系密切的敏感气象要素和变量。引入适应度函数分级方法,计算北京周边不同观测站可能形成污染向北京输送的权重,建立北京夏季空气质量气象条件参数PLAM (parameters linking air-quality and meteorology) 预报模型。PLAM指数给出北京局地污染气象条件的客观定量诊断和预测,并可指示周边地区有利 (或不利) 于污染向北京输送的强度和方位。夏季“静稳型”气象条件参数化PLAM方法为北京奥运气象保障任务实时提供预报产品,分别用PM₁₀及可吸入颗粒物指数 (API) 对2008年7-8月PLAM逐日预报进行检验,相关系数达到0.001显著性水平。     

京津冀周边秸秆燃烧对PM2.5无机组分影响

华北平原是我国主要农作物产区,田间秸秆焚烧现象普遍存在,选取秋收季节（2014年10月）分析了秸秆燃烧的排放特征,利用区域化学传输模型WRF-Chem模拟研究了燃烧排放对气态前体物及其氧化产物的影响,以及最终导致的PM_2.5中硫酸盐、硝酸盐和铵盐的变化。研究表明:2014年秋收季节,河南和山东等省份的秸秆燃烧排放会在东南风的输送作用下影响京津冀地区;秸秆燃烧排放大量挥发性有机物（VOCs）,导致火点源及周边地区大气中主要氧化剂浓度上升,提升了区域大气氧化能力;当携带大量VOCs的秸秆燃烧烟羽与以化石燃料排放为主的城市气团相混合时,大气氧化性增强会加速城市地区人为源排放的NO_x和SO₂等气态前体物的氧化过程,提高硫酸盐和硝酸盐的形成速率、促进二次无机气溶胶的生成。     

Economically consistent long-term scenarios for air pollutant emissions

Pollutant emissions such as aerosols and tropospheric ozone precursors substantially influence climate. While future century-scale scenarios for these emissions have become more realistic through the inclusion of emission controls, they still potentially lack consistency between surface pollutant concentrations and regional levels of affluence. We find that the default method of scenario construction, whereby emissions factors converge to similar values in different regions, does not yield pollution concentrations consistent with historical experience. We demonstrate a methodology combining use of an integrated assessment model and a three-dimensional atmospheric chemical transport model, whereby a reference scenario is constructed by requiring consistent surface pollutant concentrations as a function of regional income over the 21st century. By adjusting air pollutant emission control parameters, we improve consistency between projected PM_2.5 and economic income among world regions through time; consistency for ozone is also improved but is more difficult to achieve because of the strong influence of upwind world regions. Reference case pollutant emissions described here were used to construct the RCP4.5 Representative Concentration Pathway climate policy scenario.     

Chemical composition of PM2.5 at an urban site of Chengdu in southwestern China

PM2.5 aerosols were sampled in urban Chengdu from April 2009 to January 2010, and their chemical compositions were characterized in detail for elements, water soluble inorganic ions, and carbonaceous matter. The annual average of PM2.5 was 165g m－3, which is generally higher than measurements in other Chinese cities, suggesting serious particulate pollution issues in the city. Water soluble ions contributed 43.5% to the annual total PM2.5 mass, carbonaceous aerosols including elemental carbon and organic carbon contributed 32.0%, and trace elements contributed 13.8%. Distinct daily and seasonal variations were observed in the mass concentrations of PM2.5 and its components, reflecting the seasonal variations of different anthropogenic and natural sources. Weakly acidic to neutral particles were found for PM2.5. Major sources of PM2.5 identified from source apportionment analysis included coal combustion, traffic exhaust, biomass burning, soil dust, and construction dust emissions. The low nitrate: sulfate ratio suggested that stationary emissions were more important than vehicle emissions. The reconstructed masses of ammonium sulfate, ammonium nitrate, particulate carbonaceous matter, and fine soil accounted for 79% of the total measured PM2.5 mass; they also accounted for 92% of the total measured particle scattering.     

太原冬季PM2.5中有机碳和元素碳的变化特征

2005年12月—2006年2月在太原市区持续观测了气溶胶细粒子PM_2.5, 并应用Sunset碳分析仪进行了有机碳 (organic carbon, OC) 和元素碳 (elemental carbon, EC) 的测定。结果表明:太原冬季PM_2.5, OC和EC浓度均较高, 其中PM_2.5日平均浓度变化范围为25.4~419.0 μg/m3, 日平均浓度为193.4±102.3 μg/m3, OC平均浓度为28.9±14.8 μg/m3, EC平均浓度为4.8±2.2 μg/m3, OC/EC平均比值是7.0±3.9, 即太原市冬季PM_2.5和碳气溶胶污染严重。OC在PM _2.5中占18.6%, EC占2.9%, 这表明碳气溶胶是太原大气细粒子污染控制的关键组分。在太原市冬季, 采暖燃烧的煤是OC和EC的主要贡献源, 造成OC大大高于EC, 从而使OC/EC比值增大。各种气象条件对PM_2.5, OC, EC和OC/EC比值的变化都有不同程度的影响, 特别是大雾天气、相对湿度、风速和降雪是影响碳气溶胶浓度变化的重要因素。     

污染源、气象条件变化对我国SO2浓度及硫沉降量分布的影响

用三维欧拉型污染物长距离输送模式,模拟了中国大陆SOx的分布,并采用不同时期(1975、1980、1987年)的污染源与气象场资料,分析了污染源与气象条件变化对SOx分布产生的影响.研究表明,在该期间中国SOx污染比较严重的地区,气象条件变化导致SO2浓度和硫沉降量的相对变化通常在20%左右;污染源对SO2浓度与硫沉降量的作用通常大于气象条件,污染源变化产生的SO2浓度与硫沉降量的相对变化率为气象条件变化的几倍,甚至1～2个量级,尤其SOx污染比较严重的地区更为明显;但对西北及青藏高原地区,在源排放量变化不大,而气象条件变化较显著时,气象条件的作用通常大于排放源的影响.     

利用WRF-Chem模拟研究京津冀地区夏季大气污染物的分布和演变

应用WRF—Chem（Weather Research and Forecasting Model with Chemistry）模式模拟研究了2007年8月京津冀地区近地面O3、NO2、PM2.5浓度的时空变化特征,将模拟结果与观测数据进行详细对比,结果表明,模式可以较好地模拟O3、PM2.5,浓度的空间分布和时间变化特征,成功再现了8月33和PM2.5的几次积累增加过程,其中O,的模拟值与观测值的相关系数为0．69～0．86,PM2.5的相关系数为0．44～0．49,但模式对NO2的模拟相对较差,相关系数为0．27～0．43。北京、天津地区为O3月均低值区,月均体积浓度约30×10^-9,渤海及京津冀以西地区O3月平均体积浓度可达60×10^-9;PM2,呈现南高北低的分布特征,变化范围为120～240μg／m3。14时月平均03体积浓度在北京、天津地区低于周边地区,约为60×10^-9;而PM2.5质量浓度在环渤海地区和河北南部较高,为100～120μg/m^3。8月17日北京出现一次典型的高浓度O,污染事件,14时北京地区温度达到33℃,O3体积浓度为80×10^-9～110×10^-9。在局地排放、化学反应和外来输送的共同作用下,渤海西岸和北岸PM2.5的质量浓度超过120μg／m3,其中二次气溶胶质量浓度为50～100μg／m3,一次排放人为气溶胶质量浓度为10～20μg／m3,海盐质量浓度为1～7μg／m3,二次气溶胶是该地区PM2.5的主要贡献者。     

北京市房山区大气污染物时空分布特征及气象影响因素分析

利用北京市房山区良乡镇和琉璃河镇内的区域自动气象站和环境监测站观测数据,对2013年至2015年PM_(2. 5)、PM_(10)、NO_2、SO_2、CO 5种大气污染物浓度变化特征进行了统计分析。结果显示,近3年来,两个镇综合污染物指数呈现逐年下降趋势,各污染物对房山区整体大气污染的贡献率从大至小依次为PM_(2. 5)、PM_(10)、SO_2、NO_2、CO,PM_(2. 5)已取代传统大气污染物SO_2成为房山区的主要大气污染贡献体。两个站点各污染物浓度均表现出明显的季节、月、日变化特征。在不同季节条件下,局地气象要素与污染天气发生概率之间有着很好的相关关系。因此,可根据气象要素分级方法找出各季节污染天气发生时最敏感的气象因素,为局地污染天气预报提供参考指标,也为防范空气污染、制定科学的综合管理措施提供科学参考。     

两类厄尔尼诺事件对中国东部冬季气溶胶的影响

利用MERRA-2再分析气溶胶光学厚度及气象观测资料,在剔除人为排放长期变化产生的气溶胶光学厚度扰动的基础上,从气候学角度探讨了两类厄尔尼诺事件对中国东部冬季气溶胶的影响。结果表明,东部型厄尔尼诺事件使绝大部分区域气溶胶光学厚度呈正异常分布,尤其对华北至东北的气溶胶污染加剧作用显著;而中部型厄尔尼诺事件使气溶胶光学厚度异常由南至北呈显著的“+-”双极型分布。进一步成因分析发现,虽然两类厄尔尼诺事件都具有削弱冬季风从而减弱北方气溶胶向南传输的作用,但中部型对水平流场的削弱作用不显著,尤其是东北地区没有通过90%的显著性检验。同时二者对北方大气垂直扰动和气溶胶的湿清除作用相反,其中东部型表现为大气垂直扰动和对流有效位能减弱,降水减少,湿清除减弱;而中部型则表现为垂直扰动和对流有效位能增强,降水增多,湿清除增强。对于南方,强东部型事件引发的强降水可能是产生该区域气溶胶污染影响不稳定的主因,而中部型则主要通过气流削弱作用加剧长江中下游地区气溶胶的局地污染。      

A study of marine aerosols over the Pacific Ocean

Aerosol samples were collected on a Pacific cruise from 47°N to 55°S. Particle morphology, concentrations, and size distributions were analyzed with an electron microscope; elemental compositions of individual particles were determined with an X-ray energy spectrometer; and chemical compositions of bulk samples were measured with an ion chromatograph. Temporal and spatial variations of aerosol physico-chemical characteristics were studied in relation to ocean currents and atmospheric parameters. The results show that number and mass concentrations of primary particles depend mainly on surface wind speeds. However the ratios between the major ions, e.g., Na⁺, Cl^-, and Mg⁺⁺, are similar to the ratios in seawater regardless of location or meteorological conditions. The concentrations of secondary aerosols, e.g., non-seasalt sulfate, nitrate, and ammonium particles, show maxima at upwelling regions, such as along the California coast, at the Equator, and near the Chatham Rise where ascending motion brings nutrient-riched deep water into the surface layer. The number concentrations of small sulfate particles and large nitrate-coated particles showed diurnal variations with maxima in the early afternoon and minima at night, indicating that the particles are the products of photo-chemical reactions. Their precursor gases, e.g., CH₃SCH₃, NO, and NH₃ are known to be released from seawater in upwelling regions where biological activities thrive.     

The Interannual Variation of Transboundary Contributions from Chinese Emissions of PM_(2.5) to South Korea

In recent years,several studies pointed out that anthropogenic emission sources in China which significantly contribute to the PM_2.5mass burden was an important cause of particulate pollution in South Korea.However,most studies generally focused upon a single pollution event.It is rare to see comprehensive research that captures those features prone to interannual variations concerning the transboundary pollutant contribution in South Korea using a unified method.In this paper,we establish the emission inventories covering East Asia in 2010,2015,and 2017,and then conduct the source apportionment by applying a coupled regional air quality model called the Integrated Source Apportionment Module(ISAM).Comparison of simulated and observed PM_2.5mass concentration at 165 CNEMC(China National Environmental Monitoring Center)sites suggests that the PM_2.5concentrations are well represented by the modeling system.The model is used to quantitatively investigate the contribution from emission sources in China to PM_2.5concentrations over South Korea and those features found to be prone to interannual variations are then discussed.The results show that the average annual contribution of PM_2.5has dropped significantly from 28.0%in 2010 to 15.7%in 2017,which strongly suggests that China has achieved remarkable results in the treatment of atmospheric particulates.     

Influence of South Asian Biomass Burning on Ozone and Aerosol Concentrations Over the Tibetan Plateau

In this work, the influence of South Asian biomass burning emissions on O₃ and PM_2.5 concentrations over the Tibetan Plateau (TP) is investigated by using the regional climate chemistry transport model WRF-Chem. The simulation is validated by comparing meteorological fields and pollutant concentrations against in situ observations and gridded datasets, providing a clear perspective on the spatiotemporal variations of O₃ and PM_2.5 concentrations across the Indian subcontinent, including the Tibetan Plateau. Further sensitivity simulations and analyses show that emissions from South Asian biomass burning mainly affect local O₃ concentrations. For example, contribution ratios were up to 20% in the Indo-Gangetic Plain during the pre-monsoon season but below 1% over the TP throughout the year 2016. In contrast, South Asian biomass burning emissions contributed more than 60% of PM_2.5 concentration over the TP during the pre-monsoon season via significant contribution of primary PM_2.5 components (black carbon and organic carbon) in western India that were lofted to the TP by westerly winds. Therefore, it is suggested that cutting emissions from South Asian biomass burning is necessary to alleviate aerosol pollution over the TP, especially during the pre-monsoon season.     

气溶胶对中国天气、气候和环境影响综述

空气污染、天气和气候与大众生活息息相关,全球变化与可持续发展更是全人类面临的共同挑战。空气污染与气候变化对发展中国家带来的挑战更为显著。中国作为人口最多、发展飞速的国家,面临这两方面的挑战尤为严峻。因此,深入了解空气污染与气候变化的成因和发展机制,摸清两者相互关系对提高人们的生活质量和科学发展方针政策的制定具有指导意义。随着全球变化研究的深入,气溶胶与温室气体作为影响地球气候的两个最重要的人类排放物,在气候变化科学中起着至关重要的作用,气溶胶研究也成为地球科学发展最快的一个分支学科。中国天气、气候的变化特征,如高温增多、寒潮变少、风速减小、大气变稳、小雨减少、大雨增多、雷暴增强、季风减弱等,与空气污染都存在不同程度的联系。本文主要综述气溶胶对我国天气、气候的影响以及与气象因素相关的空气污染问题,侧重于气溶胶与极端天气事件之间包括影响程度和影响机理在内的错综复杂的关系。研究方法涉及星、地、空综合观测资料分析和模式模拟等。观测资料包括长时间历史观测资料、短时段强化观测实验资料、全球卫星资料等。     

A Review of Atmospheric Chemistry Research in China: Photochemical Smog, Haze Pollution, and Gas-Aerosol Interactions

In this paper we present a review of atmospheric chemistry research in China over the period 2006-2010, focusing on tropospheric ozone, aerosol chemistry, and the interactions between trace gases and aerosols in the polluted areas of China. Over the past decade, China has suffered severe photochemical smog and haze pollution, especially in North China, the Yangtze River Delta, and the Pearl River Delta. Much scientific work on atmospheric chemistry and physics has been done to address this large-scale, complex environmental problem. Intensive field experiments, satellite data analyses, and model simulations have shown that air pollution is significantly changing the chemical and physical characters of the natural atmosphere over these parts of China. In addition to strong emissions of primary pollutants, photochemical and heterogeneous reactions play key roles in the formation of complex pollution. More in-depth research is recommended to reveal the formation mechanism of photochemical smog and haze pollution and their climatic effects at the urban, regional, and global scales.     

COVID-19疫情期间全球空气质量变化:臭氧响应的区域间差异

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.