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.

Determining the environmental and atmospheric effects of coronavirus disease 2019(COVID-19)quarantining by studying the total aerosol optical depth,black carbon,organic matter,and sulfate in Blida City of Algeria

Background:To study,estimate and discuss the variations of the aerosol optical depth(AOD),black carbon,sulfate and organic matter,in the atmosphere in Blida City of Algeria,which was greatly affected by COVID-19 pandemic.Methods:We analyzed the effects of changes in the total AOD,black carbon,sulfate,and organic matter in the atmosphere(λ=550 nm)in the same period of 2019 and 2020,following the COVID-19 epidemic in Blida City,which was the most-affected city in Algeria.Results:The quarantine that was enacted to limit the spread of COVID-19 resulted in side effects that were identifiable in the total AOD and in some of its atmospheric components.Comparing these variables in 2019 and 2020(in the months during the quarantine)revealed that in April,the BCAOD values were much lower in 2020than in 2019.Conclusion:Based on the effects of the emerging COVID-19,the research listed the changes received from the AOD,and is considered as a comparative study and represents a significant side effect of the quarantine that was mainly designed to limit COVID-19.

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.

Black Carbon Particles in the Urban Atmosphere in Beijing

A study of the concentration of black carbon particles and its variation in the urban atmosphere has been carried out since 1996 in the Beijing area. The measurements were done in the late autumn and early winter each year, the period before and after domestic heating activities begin. The results show the presence of black carbon particles at the high level that vary over a large range in the urban atmosphere in Beijing. The mean value of daily average concentration for the whole observation period of 1996-2004 is 20.0 μgm^-3. An evident decrease of black carbon particle concentration in the Beijing area is observed after 2000, and the daily average concentration of black carbon particles is estimated to be 16.0 μgm^-3 with a variation range of 2.10-50.50 μgm^-3 for the period of 2000-2004. The observation method and main variation behavior characteristics of black carbon particles in the urban atmosphere in the Beijing area are given and discussed.

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.

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.

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.

Role of the Radiative Effect of Black Carbon in Simulated PM_(2.5) Concentrations during a Haze Event in China

The authors quantify the radiative effect of black carbon(BC) on simulated aerosol concentrations during the heavily polluted haze event of 11–14 January 2013 in northern China using the chemistry version of the Weather Research and Forecasting Model(WRF-Chem). As a result of the stable synoptic conditions, simulated concentrations of BC and PM2.5 averaged over the study period were about 8–16 μg m-3 and 80–100 μg m-3, respectively, in the control simulation(CTRL). When BC emissions were doubled(2BC), tripled(3BC), and quadrupled(4BC) relative to the CTRL run, the simulated concentrations of aerosols in different regions showed distinct changes. The radiative effect of BC was simulated to increase concentrations of aerosols over Tianjin(Dom1) and southern Henan(Dom3), but to decrease in southern Hebei(Dom2). Relative to the CTRL simulation, concentrations of PM2.5 over Dom1, Dom2, and Dom3 were simulated in 4BC to change by +18.6 μg m-3(+32.3%),-5.7 μg m-3(-7.3%), and +7.2 μg m-3(+12.6%), respectively. The BC-induced increases in aerosol concentrations corresponded mainly to the reductions in planetary boundary layer height over Dom1 and Dom3. The reductions of aerosol concentrations in Dom2 were mainly caused by the weakened wind convergence at 850 hPa and reduced concentrations of sulfate and nitrate associated with the reduced surface-layer ozone levels and relative humidity.

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.

Measurement of Atmospheric Black Carbon Concentration in Rural and Urban Environments: Cases of Lamto and Abidjan

Black carbon is one of the primary aerosols directly emitted from biomass known to have strong absorbing properties. The INDAAF and PASMU observational field campaigns which took place (2018) in Abidjan (urban area) and Lamto (rural area) allow the analysis of Black carbon concentration at different time scales through real-time measurements using an analyzer named Aethalometer AE-33. Results presented here show at Lamto: 1) for the diurnal scale an average of 1.71 ± 0.3 μg⋅m-3 (0.34 ± 0.09 μg⋅m-3) in the dry (wet) season;2) for the monthly scale an average of 1.14 ± 0.84 μg⋅m-3;3) on the seasonal scale, an average of 2.2 ± 0.02 μg⋅m-3 (0.6 ± 0.19 μg⋅m-3) in the dry (wet) season. The black carbon variation at Lamto is seasonal with an amplification factor of 85.6. Regarding the urban area of Abidjan, due to sampling issues, our analyses were limited to daily, diurnal and weekly time scales. We observed: a) at a daily scale an average of 5.31.± 2.5 μg⋅m-3, b) diurnal scale, an average ranging from 6.87 to 13.92 μg⋅m-3. The analysis indicated that emissions from urban areas are more related to social and economic activities, with weekday concentrations (7.24 μg⋅m-3) higher than concentrations over the weekend (e.g. Saturday 6.59 μg⋅m-3 and Sunday 6.00 μg⋅m-3). Moreover, BC concentration in Abidjan is quite noticeable compared to that of rural areas (Lamto). The ratio between the maximum values of the two areas is of the order of 5.86. In addition, concentrations in some urban areas are slightly above the daily threshold set by the WHO (10 μg⋅m-3). Therefore, the levels of urban BC concentrations are alarming whilst rural BC concentrations remain below daily WHO thresholds and are of the same magnitude as those of West African megacities. This study underlies that BC concentrations at Lamto are mainly related to biomass combustion sources while those from urban areas are related to traffic sources. The latter is permanently active, unlike those in rural Lamto, which is seasonal.

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.

老化黑碳颗粒诱导人神经母细胞瘤细胞SH-SY5Y炎症反应及机制

以人神经母细胞瘤细胞SH-SY5Y为研究对象,分析被臭氧氧化的黑碳(oxidized black carbon,OBC)颗粒引起的炎症反应以及核因子-κB(nuclear factor-κB,NF-κB)和磷脂酰肌醇3激酶(phosphatidylin-ositol-3-kinase,PI3K)/蛋白激酶B(protein kinase B,PKB,又称Akt)信号通路的作用.结果显示:随着OBC颗粒染毒质量浓度的增加(5、10、20、40µg/mL),细胞内线粒体跨膜电位(mitochondrial membrane potential,MMP)水平逐渐下降,DNA损伤程度逐渐升高,呈现质量浓度和时间依赖性;细胞外泌白细胞介素-4(interleukin-4,IL-4)水平升高和细胞内肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)基因高表达,说明OBC颗粒会促进SH-SY5Y细胞发生炎症反应;细胞内活性氧(reactive oxygen species,ROS)水平升高,超氧化物歧化酶(superoxide dismutase,SOD)、血红素加氧酶-1(heme oxygenase-1,HO-1)基因表达量升高,且HO-1蛋白水平升高,说明细胞发生氧化应激;胞内NF-κB和PI3K/Akt通路相关蛋白显著变化,表明OBC颗粒激活了NF-κB和PI3K/Akt信号通路.综上,OBC颗粒可诱导SH-SY5Y细胞发生氧化应激造成DNA损伤,促进炎症反应,且对NF-κB和PI3K/Akt信号通路有重要调控作用.

济南市区黑碳污染变化特征及来源解析

黑碳(BC)作为细颗粒物(PM2.5)的重要来源之一,探究其变化特征及来源对PM2.5管控具有指导意义。为了研究济南市区大气黑碳颗粒物污染变化特征及来源,于2020年1月-2021年12月在济南市区选择市中心站(1#)利用Magee公司AE33型黑碳仪对黑碳浓度展开了在线连续观测,还开展了PM2.5、氮氧化物(NOx)、一氧化碳(CO)质量浓度的同步在线观测,获得了市区黑碳浓度变化特征,探究了BC与主要大气污染物的关系,并结合省中心站(2#)BC监测,定量解析了济南市区BC排放来源的日变化特征,同时选取典型污染过程研究不同排放源黑碳的传输影响。结果表明,整个观测时段1#BC平均质量浓度为(1.86±1.21)μg·m^(-3),BC与PM2.5和CO呈正相关关系。BC质量浓度呈现明显的年、季节、周和日变化特征,2021年BC较2020年下降约0.28μg·m^(-3),下降比例为14%,BC质量浓度春(1.47±0.51)μg·m^(-3)<夏(1.60±0.43)μg·m^(-3)<秋(1.99±0.77)μg·m^(-3)<冬(2.48±1.17)μg·m^(-3);BC受交通早晚高峰的影响呈现双峰型日变化特征,春夏季周末浓度高于工作日,具有比较明显的“周末效应”。源解析结果表明,交通排放为BC主要来源,2020年和2021年BC交通源贡献均值占比(BCtraffic/BC)夏(0.81)>秋(0.79)>春(0.76)>冬(0.67),不同季节BCtraffic日变化特征也证实了交通源对BC贡献占主导作用,2#省中心站与1#市中心站变化相似,但受交通流量与工业源影响BC浓度通常高于1#市中心站,典型PM2.5污染期间BC除受近距离局地排放源影响外,还有济南北部、德州市和河北衡水市传输影响。风场对BCtraffic和BCnontraffic浓度的影响显示该站点以周边源排放为主,BCtraffic受西南方向的旅游路隧道及东北方向舜华路等交通繁忙路段排放影响明显。

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。

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.

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 O_(3) 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 O_(3) 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 O_(3) 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.

Brown carbon in the cryosphere： Current knowledge and perspective

Recently, the light-absorbing organic carbon, i.e., brown carbon(Br C), has received an increasing attention, because they could significantly absorb the solar radiation in the range of short wavelengths rather than the purely scattering effect. Br C is ubiquitous in the troposphere. It could undergo long range transport within the atmospheric circulation. After the deposition on the surface of snow or ice in the cryospheric region, as the major light absorbing impurities with black carbon and dust, Br C could reduce the snow albedo and accelerate the glacier melting. In this context, this paper summarized the current knowledge of Br C(in aerosols and snow) in the cryospheric regions including the Arctic, Antarctic,and Alpines. Although some works have been conducted in those region, the current dataset on the optical properties of Br C like Absorption?ngstr€om Exponent(AAE) and Mass Absorption Efficiency(MAE) is still limited, which hampers stimulating an accurate evaluation of its climate effects. Especially in the Himalayas and Tibetan Plateau, where very limited information concerning Br C is available. Considering biomass burning as a dominant source of Br C, a large amount of emissions from biomass burning in South Asia could reach the Himalayas and Tibetan Plateau, where the climate effect of Br C merits more investigation in the future.

Spatial Variability and Radiative Impact of Aerosol along the Brahmaputra River Valley in India: Results from a Campaign

The first ever land campaign to study the spatial variability of the aerosol characteristics along the Brahmaputra river valley (BRV) in Assam, North-Eastern India, was conducted during 2011. Measurements were made over 13 locations for Aerosol Optical Depth (AOD), scattering coefficient, particulate matter, black carbon (BC) concentration and meteorological parameters. The BRV is divided into three sectors longitudinally viz western sector (WS), central sector (CS), and eastern sector (ES). Significant Spatial heterogeneity in AOD and BC concentration was observed (p < 0.05) with the highest values over WS and a continual decrease from WS to ES with aerosol dominance in PM2.5 category along the entire valley. The Angstrom coefficient measured using different wavelength pairs showed spatial variability indicating dominance of fine particles over WS and coarse particles in ES with a probable bimodal distribution. The scattering and absorption coefficient shows dominance of both types of aerosol over WS than other areas. The shortwave radiative forcing was higher over the WS than CS and ES of the valley. The campaign revealed that under favorable wind conditions, the BRV is loaded with significant amount of natural and anthropogenic aerosol during local winter and is influenced by the long-range transport of aerosols from the Indo-Gangetic plain.

THE RADIATIVE EFFECTS OF ANTHROPOGENIC AEROSOLS OVER CHINA AND THEIR SENSITIVITY TO SOURCE EMISSION

In this paper,the RIEMS 2.0 model,source emission in 2006 and 2010 are used to simulate the distributions and radiative effects of different anthropogenic aerosols over China.The comparison between the results forced by source emissions in 2006 and 2010 also reveals the sensitivity of the radiative effects to source emission.The results are shown as follows:(1) Compared with those in 2006,the annual average surface concentration of sulfate in 2010 decreased over central and eastern China with a range of-5 to 0 μg/m^3;the decrease of annual average aerosol optical depth of sulfate over East China varied from 0.04 to 0.08;the annual average surface concentrations of BC,OC and nitrate increased over central and eastern China with maximums of 10.90,11.52 and 12.50μg/m^3,respectively;the annual aerosol optical depths of BC,OC and nitrate increased over some areas of East China with extremes of 0.006,0.007 and 0.008,respectively.(2)For the regional average results in 2010,the radiative forcings of sulfate,BC,OC,nitrate and their total net radiative forcing at the top of the atmosphere over central and eastern China were-0.64,0.29,-0.41,-0.33 and-1.1 W/m^2,respectively.Compared with those in 2006,the radiative forcings of BC and OC in 2010 were both enhanced,while that of sulfate and the net radiative forcing were both weakened over East China mostly.(3)The reduction of the cooling effect of sulfate in 2010 produced a warmer surface air temperature over central and eastern China;the maximum value was 0.25 K.The cooling effect of nitrate was also slightly weakened.The warming effect of BC was enhanced over most of the areas in China,while the cooling effect of OC was enhanced over the similar area,particularly the area between Yangtze and Huanghe Rivers.The net radiative effect of the four anthropogenic aerosols generated the annual average reduction and the maximum reduction were-0.096 and-0.285 K,respectively,for the surface temperature in 2006,while in 2010 they were-0.063 and-0.256 K,respectively.In summary,the change in source emission lowered the cooling effect of anthropogenic aerosols,mainly because of the enhanced warming effect of BC and weakened cooling effect of scattering aerosols.