Simulation of the Radiative Effect of Black Carbon Aerosols and the Regional Climate Responses over China

As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the transport model of BC aerosols has also been established and combined with the RIEMS model. Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.

SIMULATION OF SPATIO-TEMPORAL DISTRIBUTION CHARACTERISTICS AND RADIATIVE FORCING OF ORGANIC CARBON AEROSOLS IN CHINA

The International Centre for Theoretical Physics(ICTP,Italy) Regional Climate Model version 3.0(RegCM3) is used to simulate spatio-temporal distribution characteristics and radiative forcing(RF) of organic carbon(OC) aerosols in and around China.The preliminary simulation results show that OC aerosols are mostly concentrated in the area to the south of Yellow River and east of Tibetan Plateau.There is a decreasing trend of column burden of OC aerosols from south to north in China.The maximum value of column burden of OC aerosols is above 3 mg/m2 and located in the central and southern China,southeastern Tibet,and southwestern China's Yunnan,Guizhou,Sichuan provinces.The simulation on the seasonal variation shows that the maximum value of column burden of OC aerosols appears in winter and the secondary value is in spring and the minimum in summer.The RF of OC aerosols which varies seasonally is negative at the top of the atmosphere(TOA) and surface.The spatio-temporal characteristics of the RF of OC aerosols are basically consistent with that of IPCC,implying the high accuracy of the parameterization scheme for OC aerosols in RegCM3.

Seasonal variation of atmospheric elemental carbon aerosols at Zhongshan Station,East Antarctica

Elemental carbon(or black carbon)(EC or BC)aerosols emitted by biomass burning and fossil fuel combustion could cause notable climate forcing.Southern Hemisphere biomass burning emissions have contributed substantially to EC deposition in Antarctica.Here,we present the seasonal variation of EC determined from aerosol samples acquired at Zhongshan Station(ZSS),East Antarctica.The concentration of EC in the atmosphere varied between 0.02 and 257.81 ng·m^(-3)with a mean value of 44.87±48.92 ng·m^(-3).The concentration of EC aerosols reached its peak in winter(59.04 ng·m^(-3))and was lowest(27.26 ng·m^(-3))in summer.Back trajectory analysis showed that biomass burning in southern South America was the major source of the EC found at ZSS,although some of it was derived from southern Australia,especially during winter.The 2019–2020 Australian bush fires had some influence on EC deposition at ZSS,especially during 2019,but the contribution diminished in 2020,leaving southern South America as the dominant source of EC.

On board measurement of black carbon aerosols over the Arctic Ocean in summer

This paper presents aerosol black carbon （BC） concentrations measured at deck level on board the R/V XUE LONG icebreaker. The vessel cruised the Arctic Ocean carrying an in situ aethalometer during the summers of 2008 and 2010. The courses of the third Chinese National Arctic Research Expedition （3rd CHINARE- Arctic, August 2008） and fourth Chinese National Arctic Research Expedition （4th CHINARE-Aretic, from late July to August 2010） were bounded by 173°W-143°W and 178°E-150°W, with northernmost points 85°25′N and 88°26′N, respectively. Results show low surface BC concentrations over the ocean throughout the courses, with means （standard error） of 6.0 （：t_4.7） ng.m-a for 3rd CHINARE-Arctic, and 8.4（±7.1） ng.m^-3 for 4th CHINARE- Arctic. It is clear that these onboard BC concentrations are similar to reported data from coastal stations in the Arctic region. The latitude-average BC concentration varied from 3.0-26.2 ng.m-3 for 3rd CHINARE-Arctic, to 4.2-20.5 ng-m-a for 4th CHINARE-Arctic. At latitudes higher than 72°N for 3rd CHINARE-Arctic and 75°N for 4th CHINARE-Arctic, BC concentrations were lower and had negligible latitudinal gradients. Analysis indicates that the presence of the Arctic front isolates the lower atmosphere of the high-latitude Arctic Ocean from low-latitude terrestrial transport. This maintains the very low BC concentrations and negligible concentration gradients at high latitudes of the Arctic Ocean during summer. Calculated airmass backward trajectories for the two expeditions show that the Arctic front in 2010 was further north than in 2008, which caused different latitudinal variation of BC concentration in the two years.

MORPHOLOGY OF BLACK CARBON AEROSOLS AND UBIQUITY OF 50-NANOMETER BLACK CARBON AEROSOLS IN THE ATMOSPHERE

Different-sized aerosols were collected by an Andersen air sampler to observe the detailed morphology of the black carbon （BC） aerosols which were separated chemically from the other accompanying aerosols, using a Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer （SEM-EDX）. The results indicate that most BC aerosols are spherical particles of about 50 nm in diameter and with a homogeneous surface. Results also show that these particles aggregate with other aerosols or with themselves to form larger agglomerates in the micrometer range. The shape of these 50-nm BC spherical particles was found to be very similar to that of BC particles released from petroleum-powered vehicular internal combustion engines. These spherical BC particles were shown to be different from the previously reported fullerenes found using Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry （MALDI-TOF-MS）.

MODELING OF ORGANIC CARBON AEROSOL DISTRIBUTIONS OVER EAST ASIA IN THE SPRINGTIME

The Models-3 Community Multi-scale Air Quality (CMAQ) modeling system coupled with the Regional Atmospheric Modeling System (RAMS) is applied to East Asia to investigate the transport and evolution processes of organic carbon (OC) aerosols in the springtime of 2001. The simulated OC mixing ratios are compared with ground level observations at three remote sites in Japan during the Aerosol Characterization Experiment Asia (ACE-Asia) field campaign. It is found that the modeled OC concentrations are generally in good agreement with the observed ones, and the model reproduces the time variations in OC mixing ratios reasonably well. Model results show that high levels (larger than 16 mg.m-2) of column burden of OC aerosols concentrated in the middle reaches of Yangtse River and southern China, and that in most regions of China to the south of Yellow River the column burden was over 7 mg.m-2, while the isopleth of 4 mg.m-2 extended to the inner area of northwestern Pacific Ocean.

Observation of black carbon aerosol in Beijing, 2003

The objective of this study was to determine the black carbon concentration in Beijing in 2003.The aerosol properties were measured using an Aethalometer and a tapered element oscillating microbalance(TEOM)on the roof of the Physics Building of Peking University(39.99°N,116.31°E)from July to August 2003 and from November 2003 to January 2004.The average black carbon(BC)concentrations in the summer and winter were 8.80 and 11.4μg/m3,respectively.During winter,two different cyclone cut offs were installed at the inlet of an aethalometer.The BC mass concentration in TSP,PM_(10),and PM_(2.5)were obtained.The results indicated that in winter aerosol,90%of BC exited in PM_(10)and 82.6%of BC exited in PM_(2.5).The BC in PM_(10)accounted for 5.11%of the PM_(10)mass.

Characteristics and source of black carbon aerosol over Taklimakan Desert

Black carbon(BC) and PM10 in the center of the Taklimakan Desert were online monitored in the whole year of 2007.In addi-tion,TSP samples were also synchronously daily collected by medium-volume samplers with Whatman41 filters in the spring of 2007.BC in the dust aerosol was up to 1.14%of the total mass of PM10.A remarkable seasonal variation of BC in the aerosol was observed in the order of winter>spring>autumn>summer.The peak value of BC appeared at midnight while the lowest one in the evening each day,which was just the reverse of that in the urban area.The contribution of BC to the total mass of PM10 on non-dust storm days was～11 times of that in dust storm.Through back trajectory and principal component analysis,it was found that BC in the dust aerosol over Taklimakan Desert might be attributed to the emission from the anthropogenic activities,including domestic heating,cooking,combustion of oil and natural gas,and the medium-range transport from those oases located in the margins of the desert.The total BC aerosol from the Taklimakan Desert to be transported to the eastward downstream was estimated to be 6.3×104 ton yr-1.

A Modeling Study of the Climate Effects of Sulfate and Carbonaceous Aerosols over China

In this paper, the RIEMS 2.0 model is used to simulate the distribution of sulfate, black carbon, and organic carbon aerosols over China （16.2°-44.1°N, 93.4°-132.4°E） in 1998. The climate effects of these three anthropogenic aerosols are also simulated. The results are summarized as follows： （1） The regional average column burdens of sulfate, BC, OC, and SOC were 5.9, 0.24, 2.4, and 0.49 mg m-2, with maxima of 33.9, 1.48, 7.3, and 1.1 mg m-2, respectively. The column burden and surface concentration of secondary organic carbon accounted for about 20% and 7%, respectively, of the total organic carbon in eastern China. （2） The radiative forcings of sulfate, organic carbon, and black carbon at the top of the atmosphere were -1.24, -0.6, and 0.16 W m 2 respectively, with extremes of -5.25, -2.6, and 0.91 W m-2. （3） The surface air temperature changes caused by sulfate, organic carbon, and black carbon were -0.07, -0.04, and 0.01 K, respectively. The air temperature increase caused by black carbon at 850 hPa was higher than that at the surface. The net effect of the three kinds of anthropogenic aerosols together decreased the annual average temperature by -0.075 K; the maximum value was -0.3 K. （4） Black carbon can reduce the precipitation in arid and semi-arid areas of northern China and increase the precipitation in wet and semi-wet areas of southern China. The average precipitation increase caused by black carbon in China was 0.003 mm d^-1. The net effect of the three kinds of anthropogenic aerosols was to decrease the precipitation over China by 0.008 mmd ^-1.

Temporal Variability in Fine Carbonaceous Aerosol over Two Years in Two Megacities:Beijing and Toronto

Time-series of weekly total carbon （TC） concentrations of fine aerosol particles （PM2.5） in Beijing and Toronto were compared to investigate their respective levels and temporal patterns over two years from August 2001 through July 2003. In addition to this comparison, differences in the factors contributing to the observed concentrations and their temporal variations are discussed. Based upon past knowledge about the two megacities with highly contrasting air pollutant levels, it is not surprising that the average TC concentration in Belling （31.5 μg C m^-3） was greater than that in Toronto by a factor of 8.3. Despite their large concentration differences, in both cities TC comprised a similarly large component of PM2.5. TC concentrations exhibited very different seasonal patterns between the two cities. In Beijing, TC experienced higher levels and greater weekly fluctuations in winter whereas in Toronto this behavior was seen in summer. As a result, the greatest gap in TC concentrations between Beijing and Toronto （by a factor of 12.7） occurred in winter, while the smallest gap （a factor of 4.6） was in summer. In Beijing, seasonal variations in the emissions probably played a greater role than meteorology in influencing the TC seasonality, while in Toronto during the warm months more than 80% of the hourly winds were recorded from the south, along with many potential anthropogenic sources for the days with high TC concentrations. This comparison of the differences provides insight into the major factors affecting carbonaceous aerosol in each city.

Characteristics of Anthropogenic Sulfate and Carbonaceous Aerosols over East Asia: Regional Modeling and Observation

The authors present spatial and temporal characteristics of anthropogenic sulfate and carbonaceous aerosols over East Asia using a 3-D coupled regional climate-chemistry-aerosol model, and compare the simulation with the limited aerosol observations over the region. The aerosol module consists of SO2, SO4^2-, hydrophobic and hydrophilic black carbon （BC） and organic carbon compounds （OC）, including emission, advections, dry and wet deposition, and chemical production and conversion. The simulated patterns of SO2 are closely tied to its emission rate, with sharp gradients between the highly polluted regions and more rural areas. Chemical conversion （especially in the aqueous phase） and dry deposition remove 60% and 30% of the total SO2 emission, respectively. The SO4^2- shows less horizontal gradient and seasonality than SO2, with wet deposition （60%） and export （27%） being two major sinks. Carbonaceous aerosols are spatially smoother than sulfur species. The aging process transforms more than 80% of hydrophobic BC and OC to hydrophilic components, which are removed by wet deposition （60%） and export （30%）. The simulated spatial and seasonal SO4^2-, BC and OC aerosol concentrations and total aerosol optical depth are generally consistent with the observations in rural areas over East Asia, with lower bias in simulated OC aerosols, likely due to the underestimation of anthropogenic OC emissions and missing treatment of secondary organic carbon. The results suggest that our model is a useful tool for characterizing the anthropogenic aerosol cycle and for assessing its potential climatic and environmental effects in future studies.

Novel aerosol method for aligned carbon nanotubes synthesis

A novel aerosol method for the production of alighed carbon nanotubes was presented. Multi-walled carbon nanotubes(MWNTs) with fairly uniform diameters and aligned MWNT bundles were obtained by using solutions of organometallics such as ferrocene in hydrocarbon solvents. A hollow and multi-walled structure was observed with diameter ranging from 15 to 50 nm,leading aspect ratio to be over 200. The quality of the product is dependent on the pyrolysis temperature,carrier gas flow rate and the catalyst precursor concentration. For the sample synthesized at 900 ℃,G/D is 1.81. G/D of samples obtained at 850 ℃ and 800 ℃ are 1.18 and 0.77,respectively. The inclusion of acetylene to an atomized spray of ferrocene in hexane yield aligned MWNT bundles with a narrow diameter distribution.

内蒙古典型草原2010~2021年黑碳气溶胶浓度变化及影响因素分析

分析了2010~2021年内蒙古锡林浩特国家气候观象台大气成分观测站黑碳气溶胶浓度观测数据,阐明了黑碳气溶胶浓度时间变化规律,并初步讨论了其与气象要素的关系,以期为大气黑碳气溶胶污染防治工作提供科学依据.结果表明:不同季节、不同风速下,几乎均在南偏西风向时黑碳气溶胶浓度增大且最高,而在东北风向时其浓度几乎不变甚至略减少且最低;黑碳气溶胶浓度日变化整体呈现出明显的四季均为“单峰型”变化特征,冬季峰值出现时间较其他三个季节晚,四季谷值出现时间一致;季节变化总体上呈现出浓度及其标准差均为秋冬季高于春夏季的特征,说明观测点黑碳气溶胶浓度在高值期间的秋冬季,其变化幅度也较大;由于能源结构的改变及节能减排措施的成效,近10年观测点黑碳气溶胶浓度呈明显下降趋势,其变化与气温、降水呈极显著负相关,与相对湿度呈极显著正相关.

Characterization of Black Carbon in the Ambient Air of Agra,India:Seasonal Variation and Meteorological Influence

This study characterizes the black carbon in Agra, India home to the Taj Mahal--and situated in the lndo-Gangetic basin. The mean black carbon concentration is 9.5 μg m-3 and, owing to excessive biomass/fossil fuel combustion and automobile emissions, the concentration varies considerably. Seasonally, the black carbon mass concentration is highest in winter, probably due to the increased fossil fuel consumption for heating and cooking, apart from a low boundary layer. The nocturnal peak rises prominently in winter, when the use of domestic heating is excessive. Meanwhile, the concentration is lowest during the monsoon season because of the turbulent atmospheric conditions and the process of washout by precipitation. The ratio of black carbon to brown carbon is less than unity during the entire study period, except in winter （December）. This may be because that biomass combustion and diesel exhaust are major black carbon contributors in this region, while a higher ratio in winter may be due to the increased consumption of fossil fuel and wood for heating purposes. ANOVA reveals significant monthly variation in the concentration of black carbon; plus, it is negatively correlated with wind speed and temperature. A high black carbon mass concentration is observed at moderate （1-2 m s-1） wind speed, as compared to calm or turbulent atmospheric conditions.

THE DIRECT EFFECTS OF AEROSOLS AND DECADAL VARIATION OF GLOBAL SEA SURFACE TEMPERATURE ON THE EAST ASIAN SUMMER PRECIPITATION IN CAM3.0

Using the CAM3.0 model, we investigated the respective effects of aerosol concentration increasing and decadal variation of global sea surface temperature(SST) around year 1976/77 on the East Asian precipitation in boreal summer. By doubling the concentration of the sulfate aerosol and black carbon aerosol separately and synchronously in East Asia(100-150 °E, 20-50 °N), the climate effects of these aerosols are specifically investigated. The results show that both the decadal SST changing and aerosol concentration increasing could lead to rainfall decreasing in the center of East Asia, but increasing in the regions along southeast coast areas of China. However, the different patterns of rainfall over ocean and lower wind field over Asian continent between aerosol experiments and SST experiments in CAM3.0 indicate the presence of different mechanisms. In the increased aerosol concentration experiments, scattering effect is the main climate effect for both sulfate and black carbon aerosols in the Eastern Asian summer. Especially in the increased sulfate aerosol concentration experiment, the climate scattering effect of aerosol leads to the most significant temperature decreasing, sinking convection anomalies and decreased rainfall in the troposphere over the central part of East Asia. However, in an increased black carbon aerosol concentration experiment, weakened sinking convection anomalies exist at the southerly position. This weakened sinking and its compensating rising convection anomalies in the south lead to the heavy rainfall over southeast coast areas of China. When concentrations of both sulfate and black carbon aerosols increase synchronously, the anomalous rainfall distribution is somewhat like that in the increased black carbon concentration aerosol experiment but with less intensity.

拉萨市夏季含碳气溶胶的浓度水平与组成特征研究

利用颗粒物采样器采集拉萨市夏季(2021年8月30日~2021年9月23日)大气细颗粒物(PM_(2.5))样品,并对不同含碳气溶胶组分进行测定和探讨。根据碳组分挥发性的强弱,将有机碳(OC)分为易挥发组分(HOC)、中等挥发组分(MOC)和难挥发组分(LOC),元素碳(EC)分为焦碳(char)和烟炱(soot)。结果显示,拉萨市夏季大气环境白天OC和EC的平均浓度分别为4.39±0.98μg/m^(3)和1.09±0.69μg/m^(3),夜晚OC和EC的平均浓度分别为4.39±1.43μg/m^(3)和1.17±0.57μg/m^(3)。系统比较OC/EC和char/soot源示踪指标在源辨识上的差异,发现char/soot值比OC/EC值可以更准确地识别关键排放源对含碳气溶胶的影响,说明char/soot值是一个可靠的源解析工具。本研究测定的char/soot平均值为0.20,符合机动车尾气污染特征,远小于生物质燃烧和煤炭燃烧特征值,说明拉萨夏季大气环境主要受机动车尾气排放影响。LOC是拉萨夏季含碳气溶胶最丰富的OC组分,在所有碳组分中的占比为47.7%,其次为MOC(18.2%)和HOC(10.8%)。不同碳组分之间的相关性分析表明,HOC主要通过大气化学反应生成,未来可成为评估二次有机气溶胶的一个潜在指标。

2021年苏州黑碳气溶胶浓度特征及来源解析

于2020年12月1日—2021年11月30日利用7波段黑碳仪(AE-31)观测苏州地区黑碳(BC)浓度变化特征,并使用黑碳仪模型和后向轨迹模型分析BC排放来源和潜在源区。结果发现,苏州地区BC年平均质量浓度为(1.29±0.64)μg/m^(3),冬季BC质量浓度最高,为(1.61±0.89)μg/m^(3),秋季为(1.34±0.61)μg/m^(3),春季为(1.23±0.48)μg/m^(3),夏季最低,为(1.03±0.43)μg/m^(3)。各季节工作日、非工作日BC质量浓度日变化均呈早晚双峰分布规律。BC质量浓度与风速、气温、降水量呈负相关,与相对湿度相关性并不显著。黑碳来源解析结果表明,相比于固体燃料(如煤和生物质燃烧),液体燃料(如交通排放)对苏州BC质量浓度的贡献在各季节均占主要地位(74.2%~76.3%),且夏季最高,冬季最低。同时,后向轨迹模拟和浓度轨迹权重分析的潜在源区结果显示,与本地污染相比,影响苏州地区BC的更多为输送型气团;各季节BC的潜在源区也稍有差异,主要以西南方向的影响为主。

AE-31型黑炭监测仪及其使用维护与故障处理

本文介绍了黑炭气溶胶的基础知识和大气成分观测常用的黑炭气溶胶监测仪Aethalometer AE-31型的工作原理、构成部件、使用要点、巡查维护和故障排查处理等内容。对日常工作中常用的维护使用经验进行分析总结,给出简单故障的排查处理方法,以提高黑炭气溶胶监测仪运行的稳定性以及数据的完整性和准确性。

2023年8月6日德州地震地-气耦合响应分析

为探究2023年8月6日德州5.5级地震与大气参数之间的相关性,利用NCEP/NCAR再分析资料、多普勒测风激光雷达以及Sentinel-5P卫星遥感资料对地震前后地表潜热通量、气溶胶光学厚度和CO柱浓度进行研究.结果发现:①地震前3d地表潜热通量(SLHF)出现一个高峰,峰值接近2018—2022年SLHF的平均值与标准差之和.②德州地震前3h内大气气溶胶的状态极不稳定,气溶胶光学厚度(AOD)变化异常显著,地震的影响逐渐消除后,恢复至震前水平.③与地震前相比,CO柱浓度在地震后明显增加,升高趋势出现在地震的前两天.这些大气参数的异常特征表明,德州地震发生前后岩石圈和大气层之间有相互耦合的联系.

Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall

Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.