Aerosol spectra and new particle formation observed in various seasons in Nanjing

The aerosol number spectrum and gas pollutants were measured and the new particle formation （NPF） events were discussed in Nanjing. The results showed that the size distributions of aerosol number concen- trations exhibited distinct seasonal variations, implying the relations of particle sizes and their sources and sinks. The number concentrations of particles in the nuclei mode （10-30 nm）, Aitken mode （30-100 nm）, accumulation mode （100 -1000 nm） and coarse mode （〉1μm） varied in the order of summer 〉 spring 〉 autumn, summer 〉 autumn 〉 spring, autumn 〉 summer 〉 spring, and spring 〉 autumn 〉summer, re- spectively. The diurnal variation of total aerosol number concentrations showed three peaks in all observed periods, which corresponded to two rush hours and the photochemistry period at noon. In general, the NPF in summer occurred under the conditions of east winds and dominant air masses originating from marine areas with high relative humidity （50%-70%） and strong solar radiations （400 -700 W m-2）. In spring, the NPF were generally accompanied by low relative humidity （14%-30%） and strong solar radiations （400-600 W m-2）. The new particle growth rates （GR） were higher in the summertime in the range of 10- 16 nm h-1. In spring, the GR were 6.8-8.3 nm h-1. Under polluted air conditions, NPF events were seldom captured in autumn in Nanjing. During NPF periods, positive correlations between 10- 30 nm particles and 03 were detected, particularly in spring, indicating that NPF can be attributed to photochemical reactions.     

利用MODIS光学厚度遥感产品研究北京及周边地区的大气污染

对2001年在北京地区利用太阳光度计观测的气溶胶光学厚度和NASA发布的MODIS气溶胶产品进行了比较,验证了这一卫星遥感产品的可靠性;比较了2001年MODIS气溶胶光学厚度(AOD)产品和由空气污染指数(API)计算的每日平均可吸入颗粒物(PM10)浓度,得到了比较高的相关系数,证实该气溶胶产品可用于污染分析.将北京地区AOD与气象能见度观测资料进行比较,得到了不同季节的气溶胶"标高".利用统计的不同季节的气溶胶标高,从光学厚度的季节分布得到了能见度(能见距离)的季节分布.气溶胶光学厚度图像的个例分析表明,除局地排放外,周边区域(主要为西南和南向)的输送对北京市区的空气污染贡献份额较大.卫星遥感气溶胶可以比较直观地再现污染物的区域分布和输送,不仅为研究全球气候变化也为研究区域环境的空气质量提供了一种有效手段.     

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.     

Seasonal Variation of Columnar Aerosol Optical Properties in Yangtze River Delta in China

In order to understand the seasonal variation of aerosol optical properties in the Yangtze River Delta,5 years of measurements were conducted during September 2005 to December 2009 at Taihu,China.The monthly averages of aerosol optical depth were commonly >0.6;the maximum seasonal average(0.93) occurred in summer.The magnitude of the Angstr¨om exponent was found to be high throughout the year;the highest values occurred in autumn(1.33) and were the lowest in spring(1.08).The fine modes of volume size distribution showed the maxima(peaks) at a radius of ～0.15 μm in spring,autumn,and winter;at a radius of ～0.22 μm in summer.The coarse modes showed the maxima(peaks) at a radius of 2.9 μm in spring,summer,and autumn and at a radius of 3.8 μm in winter.The averages of single-scattering albedo were 0.92(spring),0.92(summer),0.91(autumn),and 0.88(winter).The averages of asymmetry factor were found to be larger in summer than during other seasons;they were taken as 0.66 at 440-1020 nm over Taihu.The real part of the refractive index showed a weak seasonal variation,with averages of 1.48(spring),1.43(summer),1.45(autumn),and 1.48(winter).The imaginary parts of the refractive index were higher in winter(0.013) than in spring(0.0076),summer(0.0092),and autumn(0.0091),indicating that the atmosphere in the winter had higher absorbtivity.     

北京PM1中的化学组成及其控制对策思考

通过分析北京城区2007年夏季和秋季、2008年冬季和春季4个季节PM₁中硫酸盐、硝酸盐、铵盐、有机物和黑碳等气溶胶化学组成,结合对我国及全球主要区域PM₁₀中上述气溶胶组分及矿物气溶胶组成的评估,发现因受干旱区产生的沙尘和城市逸散性粉尘的共同影响,整个亚洲大陆,尤其是我国的矿物气溶胶浓度与欧美国家城市区域气溶胶总和的平均值相当或更高。我国在重视控制PM_2.5等细粒子污染的同时,不应忽视对PM_2.5~PM₁₀之间粗粒子的控制力度;北京城区春、夏、秋、冬的PM₁平均质量浓度分别约为94,74,66 μg·m-3和91 μg·m-3,全年平均约为81 μg·m-3,其中有机物气溶胶约占41%,硫酸盐占16%,硝酸盐占13%,铵盐占8%,黑碳和氯化物分别占11%和3%,细矿物气溶胶约贡献7%。对于PM_2.5污染的控制,关键是消减PM₁中主要气溶胶粒子的排放与转化,其中对有机物的控制更为重要,尽管对于北京而言进一步污染控制的难度已经很大。从科学上来说,即使我国的控制措施能百分之百实现,也很难稳定地达到欧美国家的空气质量水平,因为我国本底矿物气溶胶的浓度较高。应进一步评估各项控制措施的适用性,并制定考虑我国人群健康状况的PM_2.5空气质量标准。     

乌鲁木齐市MODIS气溶胶光学厚度与空气质量指数相关性分析

利用MODIS气溶胶光学厚度(AOD,Aerosol Optical Depth)产品与同期乌鲁木齐市空气质量指数进行相关性分析,得到二者的相关系数为0.664。对MODIS AOD产品进行垂直和湿度订正后,二者的相关性显著提高,相关系数从0.664提高到0.805。订正后按季节分类统计,春、夏、秋3季的相关系数分别为0.775、0.608和0.822,其中秋季的订正更为有效,可用性更高。这可能受到不同季节气溶胶来源、特征以及数据样本差异的影响。最后分别建立全年、春季、夏季和秋季的线性、对数、一元二次、乘幂和指数5种类型的拟合模型。考虑模型易于利用的因素,依据各拟合模型相关系数的大小得到全年以及各季节最优拟合模型,该模型函数可用来反演和监测乌鲁木齐市空气质量指数。     

First Surface-based Estimation of the Aerosol Indirect Effect over a Site in Southeastern China

The deployment of the U.S. Atmospheric Radiation Measurement mobile facility in Shouxian from May to December2008 amassed the most comprehensive set of measurements of atmospheric, surface, aerosol, and cloud variables in China.This deployment provided a unique opportunity to investigate the aerosol–cloud interactions, which are most challenging and, to date, have not been examined to any great degree in China. The relationship between cloud droplet effective radius(CER) and aerosol index(AI) is very weak in summer because the cloud droplet growth is least affected by the competition for water vapor. Mean cloud liquid water path(LWP) and cloud optical depth(COD) significantly increase with increasing AI in fall. The sensitivities of CER and LWP to aerosol loading increases are not significantly different under different air mass conditions. There is a significant correlation between the changes in hourly mean AI and the changes in hourly mean CER,LWP, and COD. The aerosol first indirect effect(FIE) is estimated in terms of relative changes in both CER(FIECER) and COD(FIECOD) with changes in AI for different seasons and air masses. FIECODand FIECERare similar in magnitude and close to the typical FIE value of ~ 0.23, and do not change much between summer and fall or between the two different air mass conditions. Similar analyses were done using spaceborne Moderate Resolution Imaging Spectroradiometer data. The satellite-derived FIE is contrary to the FIE estimated from surface retrievals and may have large uncertainties due to some inherent limitations.     

EFFECTS OF AEROSOLS ON AUTUMN PRECIPITATION OVER MID-EASTERN CHINA

Long-term observational data indicated a decreasing trend for the amount of autumn precipitation (i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s (~ 5.6% per decade). To examine the cause of the decreasing trend, the mechanisms associated with the change of autumn precipitation were investigated from the perspective of water vapor transportation, atmospheric stability and cloud microphysics. Results show that the decrease of convective available potential energy (i.e. 12.81 J kg-1/ decade) and change of cloud microphysics, which were closely related to the increase of aerosol loading during the past twenty years, were the two primary factors responsible for the decrease of autumn precipitation. Our results showed that increased aerosol could enhance the atmospheric stability thus weaken the convection. Meanwhile, more aerosols also led to a significant decline of raindrop concentration and to a delay of raindrop formation because of smaller size of cloud droplets. Thus, increased aerosols produced by air pollution could be one of the major reasons for the decrease of autumn precipitation. Furthermore, we found that the aerosol effects on precipitation in autumn was more significant than in other seasons, partly due to relatively more stable synoptic systems in autumn. The impact of large-scale circulation dominant in autumn and the dynamic influence on precipitation was more important than the thermodynamic activity.     

Sulfate and methanesulfonate in the maritime aerosol at Cape Grim,Tasmania

High-volume aerosol filters, exposed in maritime air masses at Cape Grim since late 1976, were analysed for excess sulfate (not of seasalt origin) and methanesulfonate. The mean concentrations (standard errors) of 2.80(0.59) and 0.176(0.027) nmole/m³ respectively are about half those reported in a recent study of aerosol samples from various locations in the Atlantic and Pacific oceans.Methanesulfonate concentration varied seasonally by at least an order of magnitude with a summer maximum and winter minimum. No comparable cycle was found for excess sulfate.     

Optical Properties and Source Analysis of Aerosols over a Desert Area in Dunhuang,Northwest China

Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China(Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth(AOD) at 500 nm was 0.32 ± 0.06, and the ?ngstr?m exponent(α) was 0.73 ± 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM(March–April–May) resulted in the seasonal maximum AOD, 0.41 ± 0.04, and a relatively smaller αvalue, 0.44 ± 0.04. The tourism seasons, JJA(June–July–August) and SON(September–October–November) coincide with serious emissions of small anthropogenic aerosols. While in DJF(December–January–February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and αwere 0.29 ± 0.02 and 0.66 ± 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD(0.11–1.18) and α(0.06–0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and α under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.     

塔克拉玛干沙漠地区气溶胶光学厚度卫星遥感产品验证

基于塔克拉玛干沙漠地区地基太阳光度计数据,系统验证2007～2008年星载多角度成像光谱仪(MISR)、中分辨率成像光谱仪(MODIS)和臭氧监测仪(OMI)气溶胶反演产品,旨在定量评估这些产品在我国沙漠地区的气溶胶光学厚度(AOD)反演精度。结果表明:MODIS/AOD的相关系数在4种产品中最高(0.91),OMI/AOD次之(0.87),其次为MISR/AOD(0.84),OMI/UVAI相关系数偏低(0.51)。MISR/AOD均方根误差(0.14)和平均偏差(-0.06)在4种反演产品中最低。与地基观测相比,MISR/AOD、MODIS/AOD系统偏低,OMI/AOD、OMI/UVAI系统偏高。在相同比较条件下(地基观测气溶胶光学厚度值限定在2.0以内),MISR的均方根误差和平均偏差在4种反演产品中最低,且相关系数也较高(0.84)。尽管存在诸多不同,但3种探测器气溶胶反演产品均能较好地展示该地区的气溶胶季节变化。塔克拉玛干沙漠春、夏季AOD较大,秋、冬季AOD相对较小。ngstrm波长指数的结果表明,春季(3～5月)最小(均值为0.11),夏季(6～8月)次之,秋季(9～11月)和冬季(12月至次年2月)较大(均值达到0.61),这表明在春、夏季气溶胶粒子偏大,秋、冬季气溶胶粒子偏小。此外,通过研究2000～2010年AOD年际变化表明,由于塔克拉玛干沙漠地区属于沙尘源区,气溶胶类型较为单一,所以总体来说,变化趋势不是较为明显。从反演结果来看,2003年的气溶胶含量为此10年中最高,年均值达到0.32;2005年的气溶胶含量在这10年中最低,年均值为0.28。     

北京乡村地区分粒径气溶胶OC及EC分析

利用北京上甸子区域大气本底站2004年观测的分粒径大气气溶胶资料,分析了气溶胶中有机碳 (OC) 及元素碳 (EC) 的质量浓度水平、季节变化、尺度分布特征、OC与EC比值及其相关性。结果显示:上甸子站总悬浮颗粒物 (TSP) 中OC平均质量浓度为7.5~31.5 μg·m-3,EC质量浓度为1.4~6.6 μg·m-3;PM_2.1(粒径小于2.1 μm) 中OC质量浓度为4.0~19.1 μg·m-3,EC质量浓度大约为0.8~4.3 μg·m-3。冬季OC及EC质量浓度明显高于其他季节,其中冬、夏、秋季OC及EC峰值粒径出现为0.65~2.1 μm,但在春季峰值粒径移至2.1~4.7 μm。观测期间,OC与EC质量浓度比值平均为4~6,该比值略高于文献报道的我国一些城市地区的观测结果。     

An Evidence of Aerosol Indirect Effect on Stratus Clouds from the Integrated Ground-Based Measurements at the ARM Shouxian Site

The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky images from the Total Sky Imager (TSI), cloud base heights from the Ceilometer, and vertical temperature profiles from the Balloon-Borne Sounding System (BBSS). Six cases were chosen in summer, and seven in autumn. The averaged cloud effective radii (re), cloud optical depth (COD), aerosol total light scattering coefficient (σ), and liquid water path (LWP) are, respectivey, 6.47 μm, 35.4, 595.9 mm-1, 0.19 mm in summer, and 6.07 μm, 96.0, 471.7 mm-1, 0.37 mm in autumn. The correlation coefficient between re and σ was found to change from negative to positive value as LWP increases.     

Size Distributions of Aerosol Sulfates and Nitrates in Beijing during the 2008 Olympic Games: Impacts of Pollution Control Measures and Regional Transport

For the 2008 Olympic Games, drastic control measures were implemented on industrial and urban emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_x) and other pollutants to address the issues of poor air quality in Beijing. To investigate the effects of SO₂ and NO_x reductions on the particulate sulfate and nitrate concentrations as well as their size distributions, size-segregated aerosol samples were collected using micro-orifice uniform deposit impactors (MOUDIs) at urban and downwind rural sites in Beijing before and after full-scale controls. During the sampling period, the mass concentrations of fine particles (PM_1.8) at the urban and rural sites were 94.0 and 85.9 μg m^-3, respectively. More than 90% of the sulfates and ～60% of nitrates formed as fine particles. Benefiting from the advantageous meteorological conditions and the source controls, sulfates were observed in rather low concentrations and primarily in condensation mode during the Olympics. The effects of the control measures were separately analyzed for the northerly and the southerly air-mass-dominated days to account for any bias. After the control measures were implemented, PM, sulfates, and nitrates were significantly reduced when the northerly air masses prevailed, with a higher percentage of reduction in larger particles. The droplet mode particles, which dominated the sulfates and nitrates before the controls were implemented, were remarkably reduced in mass concentration after the control measures were implemented. Nevertheless, when the polluted southerly air masses prevailed, the local source control measures in Beijing did not effectively reduce the ambient sulfate concentration due to the enormous regional contribution from the North China Plain.     

泰山PM10及其中化学成分变化特征

为研究华北平原区域背景气溶胶成分及其变化特征,2010年6月至2011年7月在泰山顶采集了64个PM10滤膜样品,分析了样品的PM10及其中无机盐离子和有机碳（OC）、元素碳（EC）的质量浓度,并对各成分相关性等进行了分析。泰山PM10年均质量浓度约为68.4 mg/m³,其中无机盐离子约占总质量的64.8%,碳气溶胶约占17.4%。无机盐离子的质量浓度从春季逐渐增大,夏季达到峰值,秋季下降,冬季最小;OC质量浓度从春季至秋季逐渐增高,冬季最低,EC变化类似,但夏秋两季差别不大。二次有机碳（SOC）与OC的比值四季均在50%以上,年均值约为58.5%。通过后向轨迹聚类分析发现,在经过城市的较短轨迹以及南方较短混合轨迹的影响下,泰山PM10质量浓度较高,而西北长距离传输气团PM10浓度均较低。     

基于CALIPSO卫星资料的华东地区气溶胶垂直分布特征

基于2010年12月1日—2011年11月30日美国国家航空航天局云—气溶胶激光雷达与红外探测者卫星搭载的激光雷达CALIPSO的监测数据,通过分析消光后向散射系数、体积退偏比和色比,得到了华东地区垂直方向上气溶胶粒子的散射能力、尺度、规则程度随高度的变化及其季节变化特征。结果表明:随着高度的增加华东地区大气的散射能力减弱。整层大气不同季节粒子的形状大小不同,春季不规则、大粒径粒子所占比例与其他季节相比较大。夏季较规则、小粒径的粒子较多。各高度层的后向散射系数值分布范围为5×10-4~20×10-4 km-1·sr-1。对不同高度消光后向散射系数、体积退偏比和色比随时间变化的研究表明,春季受沙尘输送的影响,0~4 km大气层中不规则大粒径粒子较多;4~8 km大气层由于所含气溶胶粒子较少,大气散射能力随季节变化不明显;而8~10 km大气层中粒子含量最少,导致大粒径粒子所占比例较高,此外该高度层在秋季不规则、大粒径粒子相对较多,冬季规则、小粒径粒子相对较多。     

Measurement of Ambient,Interstitial, and Residual Aerosol Particles on a Mountaintop Site in Central Sweden using an Aerosol Mass Spectrometer and a CVI

The Aerodyne aerosol mass spectrometer (Q-AMS) was coupled with a counterflow virtual impactor (CVI) for the first time to measure cloud droplet residuals of warm tropospheric clouds on Mt. Åreskutan in central Sweden in July 2003. Operating the CVI in different operational modes generated mass concentration and species-resolved mass distribution data for non-refractory species of the ambient, interstitial, and residual aerosol. The ambient aerosol measurements revealed that the aerosol at the site was mainly influenced by long-range transport and regional photochemical generation of nitrate and organic aerosol components. Four different major air masses were identified for the time interval of the experiment. While two air masses that approached the site from northeastern Europe via Finland showed very similar aerosol composition, the other two air masses from polar regions and the British Islands had a significantly different composition. During cloud events the larger aerosol particles were found to be activated into cloud droplets. On a mass basis the activation cut-off diameter was approximately 150 nm for nitrate and organics dominated particles and 200 nm for sulfate dominated particles. Generally nitrate and organics were found to be activated into cloud droplets with higher efficiency than sulfate. While a significant fraction of the nitrate in ambient particles was organic nitrates or nitrogen-containing organic species, the nitrate found in the cloud droplet residuals was mainly ammonium nitrate. After passage of clouds the ambient aerosol size distribution had shifted to smaller particle sizes due to the predominantly activation of larger aerosol particles without a significant change in the relative composition of the ambient aerosol.     

Aerosol Properties and Their Impacts on Surface CCN at the ARM Southern Great Plains Site during the 2011 Midlatitude Continental Convective Clouds Experiment

Aerosol particles are of particular importance because of their impacts on cloud development and precipitation processes over land and ocean. Aerosol properties as well as meteorological observations from the Department of Energy Atmospheric Radiation Measurement(ARM) platform situated in the Southern Great Plains(SGP) are utilized in this study to illustrate the dependence of continental cloud condensation nuclei(CCN) number concentration(NCCN) on aerosol type and transport pathways. ARM-SGP observations from the 2011 Midlatitude Continental Convective Clouds Experiment field campaign are presented in this study and compared with our previous work during the 2009–10 Clouds, Aerosol, and Precipitation in the Marine Boundary Layer field campaign over the current ARM Eastern North Atlantic site. Northerly winds over the SGP reflect clean, continental conditions with aerosol scattering coefficient(σ_(sp)) values less than 20 Mm~(-1) and NCCNvalues less than 100 cm~(-3). However, southerly winds over the SGP are responsible for the observed moderate to high correlation(R)among aerosol loading(σ_(sp) 60 Mm~(-1)) and NCCN, carbonaceous chemical species(biomass burning smoke), and precipitable water vapor. This suggests a common transport mechanism for smoke aerosols and moisture via the Gulf of Mexico,indicating a strong dependence on air mass type. NASA MERRA~(-2) reanalysis aerosol and chemical data are moderately to highly correlated with surface ARM-SGP data, suggesting that this facility can represent surface aerosol conditions in the SGP, especially during strong aerosol loading events that transport via the Gulf of Mexico. Future long-term investigations will help to understand the seasonal influences of air masses on aerosol, CCN, and cloud properties over land in comparison to over ocean.     

1960-2005年京津冀地区地表太阳辐射变化及成因分析

利用1960—2005年京津冀地区的地面太阳辐射资料,综合分析了该地区45年太阳辐射的分布状况和变化趋势,并结合云量、降水量、气溶胶光学厚度和大气含水量,分析了该地区太阳辐射的变化原因。结果表明:(1)京津冀地区的太阳辐射并没有出现20世纪80年代末到90年代中期的"变亮"现象;同期冬、春季总辐射下降,夏、秋季上升;(2)在1985—1997年间,依据总辐射变化情况,京津冀地区被分为截然相反的两个区域:东部地区总辐射增加,倾向率为1.016 MJ.m-2.mon-1.(10a)-1;西部地区总辐射减少,倾向率为10.092MJ.m-2.mon-1.(10a)-1;(3)总辐射增加的区域,主要是由于云量减少、降水量减少所伴随的日照时数增加以及气溶胶光学厚度降低所造成的;(4)总辐射减少的区域,云量、气溶胶光学厚度和降水量变化并不显著,总辐射持续减少。     

上甸子本底站气溶胶散射系数变化特征的初步分析

根据上甸子大气成分本底站从2004～2006年的连续观测数据,分析了区域大气粒子光散射系数的变化特点,以了解本底地区大气气溶胶粒子的基本特征.卜甸子地区3年数据比较表明,散射系数平均水平较低,但在2006年有所升高,主要表现在受春季沙尘天气的影响,污染次数增多.其次,散射系数日变化规律表现为白大低夜间高,午后出现最低值,此变化与大气层结的日变化趋势一致.从季节变化看,冬季和春季的散射系数相对较低,而夏季和秋季的值较高,这与气象条件及内外源的影响都有关系.天气对粒子变化的影响表现为,晴天无云时的大气状况有利于污染物的重直输送,散射系数远远低于阴天时的数值.另一方面,风向对本底站粒子浓度影响也较明显.来自东北东方向的空气较干净,散射系数值通常较低,而西南西风向通常会引起散射系数值的增大,说明位于西南方向上的北京等城镇的污染输送对上甸子本底站的大气状况有一定影响.最后,通过拟和散射系数小时平均值出现频率曲线,对上甸子地区本底浓度值作了初步估算,其范围在10~20 Mm~(-1).