首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 115 毫秒
1.
To investigate the seasonal variation of aerosol optical depth(AOD), extinction coefcient(EXT), single scattering albedo(SSA) and the decomposed impacts from sulfate(SO4 2) and black carbon(BC) over China, numerical experiments are conducted from November 2007 to December 2008 by using WRF-Chem. Comparison of model results with measurements shows that model can reproduce the spatial distribution and seasonal variation of AOD and SSA. Over south China, AOD is largest in spring(0.6–1.2) and lowest in summer(0.2–0.6). Over north, northeast and east China, AOD is highest in summer while lowest in winter. The high value of EXT under 850 hPa which is the reflection of low visibility ranges from 0.4–0.8 km 1and the high value area shifts to north during winter, spring and summer, then back to south in autumn. SSA is 0.92–0.94 in winter and 0.94–0.96 for the other three seasons because of highest BC concentration in winter over south China. Over east China, SSA is highest(0.92–0.96) in summer, and 0.88–0.92 during winter, spring and autumn as the concentration of scattering aerosol is highest while BC concentration is lowest in summer over this region. Over north China, SSA is highest(0.9–0.94) in summer and lowest(0.82–0.86) in winter due to the significant variation of aerosol concentration. The SO4 2 induced EXT increases about 5%– 55% and the impacts of BC on EXT is much smaller(2%–10%). The SO4 2-induced increase in SSA is 0.01–0.08 and the BC-induced SSA decreases 0.02–0.18.  相似文献   

2.
Light-absorbing carbonaceous aerosols including black carbon(BC) and brown carbon(BrC)play significant roles in atmospheric radiative properties. One-year measurements of aerosol light absorption at multi-wavelength were continuously conducted in Xiamen,southeast of China in 2014 to determine the light absorption properties including absorption coefficients(σabs) and absorption ?ngstr?m exponent(AAE) in the coastal city.Light absorptions of BC and BrC with their contributions to total light absorption were further quantified. Mean σabsat 370 nm and 880 nm were 56.6 ± 34.3 and 16.5 ± 11.2 Mm-1,respectively. σabspresented a double-peaks diurnal pattern with the maximum in the morning and the minimum in the afternoon. σabswas low in warm seasons and high in cold seasons. AAE ranged from 0.26 to 2.58 with the annual mean of 1.46, implying that both fossil fuel combustion and biomass burning influenced aerosol optical properties. σabsof BrC at 370 nm was 24.0 ± 5.7 Mm-1, contributing 42% to the total absorption. The highest AAE(1.52 ± 0.02) and largest BrC contributions(47% ± 4%) in winter suggested the significant influence of biomass burning on aerosol light absorption. Long-distance air masses passing through North China Plain and the Yangtze River Delta led to high AAE and BrC contributions. High AAE value of 1.46 in July indicated that long-range transport of the air pollutants from intense biomass burning in Southeast Asia would affect aerosol light absorption in Southeast China. The study will improve the understanding of light absorption properties of aerosols and the optical impacts of BrC in China.  相似文献   

3.
Aerosol plays a key role in determining radiative balance, regional climate and human health. Severe air pollution over Northeast China in recent years urges more comprehensive studies to figure out the adverse effects caused by excessive aerosols. In this study, column aerosol measurements over urban Harbin, a metropolis located at the highest latitude in Northeast China, during May 2016 to March 2017 were conducted using a CIMEL sun-photometer to analyze local aerosol properties and its variation from different aspects. According to the observations, aerosol optical depth at 440 nm (AOD440) ranges from 0.07 up to 1.54, and the large variability in both AOD440 and Angstrom Exponent (AE440–870) indicates the frequent change of aerosol types due of different emission sources. Coarse mode particles dominated Harbin during the studying period because of the long-range transported dust and probably the suspended snow crystals in winter. As the wavelength increases, relatively consistent decrease trends of single scattering albedo (SSA) and asymmetry factor (ASY) were observed in spring, autumn, and winter, indicating the presence of absorbing polluted aerosols. Mixed type (MIX) aerosol dominated the study region with a total percentage of 34%, and biomass burning and urban industry (BB/UI), clean continental (CC), and desert dust (DD) aerosols were found to be 31%, 27%, and 8%, respectively. The current work fills up the optical characteristics of aerosols in Harbin, and will contribute to the in-depth understanding of local aerosol variation and regional climate change over Northeast China.  相似文献   

4.
The present study uses the data collected from Cimel Sunphotometer of Aerosol Robotic Network(AERONET) for the period from January to December, 2012 over an urban site,Pretoria(PTR; 25.75°S, 28.28°E, 1449 m above sea level), South Africa. We found that monthly mean aerosol optical depth(AOD, τa) exhibits two maxima that occurred in summer(February) and winter(August) having values of 0.36 ± 0.19 and 0.25 ± 0.14,respectively, high-to-moderate values in spring and thereafter, decreases from autumn with a minima in early winter(June) 0.12 ± 0.07. The Angstrom exponents(α440–870) likewise,have its peak in summer(January) 1.70 ± 0.21 and lowest in early winter(June) 1.38 ± 0.26,while the columnar water vapor(CWV) followed AOD pattern with high values(summer) at the beginning of the year(February, 2.10 ± 0.37 cm) and low values(winter) in the middle of the year(July, 0.66 ± 0.21 cm). The volume size distribution(VSD) in the fine-mode is higher in the summer and spring seasons, whereas in the coarse mode the VSD is higher in the winter and lower in the summer due to the hygroscopic growth of aerosol particles.The single scattering albedo(SSA) ranged from 0.85 to 0.96 at 440 nm over PTR for the entire study period. The averaged aerosol radiative forcing(ARF) computed using SBDART model at the top of the atmosphere(TOA) was- 8.78 ± 3.1 W/m2, while at the surface it was- 25.69 ± 8.1 W/m2 leading to an atmospheric forcing of + 16.91 ± 6.8 W/m2, indicating significant heating of the atmosphere with a mean of 0.47 K/day.  相似文献   

5.
Atmospheric aerosol samples(PM_(2.5–0.3), i.e., atmospheric particles ranging from 0.3 to2.5 μm) were collected during two periods: spring–summer 2008 and autumn–winter 2008–2009, using high volume samplers equipped with cascade impactors. Two sites located in the Northern France were compared in this study: a highly industrialised city(Dunkirk) and a rural site(Rubrouck). Physicochemical analysis of particulate matter(PM) was undertaken to propose parameters that could be used to distinguish the various sources and to exhibit seasonal variations but also to provide knowledge of chemical element composition for the interpretation of future toxicological studies. The study showed that PM2.5–0.3concentration in the atmosphere of the rural area remains stable along the year and was significantly lower than in the urban or industrial ones, for which concentrations increase during winter.High concentrations of polycyclic aromatic hydrocarbons(PAHs), dioxins, furans and dioxin like polychlorinated biphenyls(DL-PCBs), generated by industrial activities, traffic and municipal wastes incineration were detected in the samples. Specific criteria like Carbon Preference Index(CPI) and Combustion PAHs/Total PAHs ratio(CPAHs/TPAHs) were used to identify the possible sources of atmospheric pollution. They revealed that paraffins are mainly emitted by biogenic sources in spring–summer whereas as in the case of PAHs, they have numerous anthropogenic emission sources in autumn-winter(mainly from traffic and domestic heating).  相似文献   

6.
Biomass burning (BB) is a very important emission source that significantly adversely impacts regional air quality.BB produces a large number of primary organic aerosol (POA)and black carbon (BC).Besides,BB also provides many precursors for secondary organic aerosol (SOA) generation.In this work,the ratio of levoglucosan (LG) to organic carbon (OC)and the fire hotspots map was used to identify the open biomass burning (OBB) events,which occurred in two representative episodes,October 13 to Novem...  相似文献   

7.
As a main form of biomass burning in agricultural countries, crop residue burning is a significant source of atmospheric fine particles. In this study, the aging of particles emitted from the burning of four major crop residues in China was investigated in a smog chamber.The particle size distribution, chemical composition and cloud condensation nuclei(CCN)activity were simultaneously measured. The properties of crop residue burning particles varied substantially among different fuel types. During aging, the particle size and mass concentration increased substantially, suggesting condensational growth by formation of secondary aerosols. The particle composition was dominated by organics. Aging resulted in considerable enhancement of organics and inorganics, with enhancement ratios of 1.24–1.44 and 1.33–1.76 respectively, as well as a continuous increase in the oxidation level of organics. Elevated CCN activity was observed during aging, with the hygroscopicity parameter κ varying from 0.16 to 0.34 for fresh particles and 0.19 to 0.40 for aged particles.Based on the volume mixing rule, the hygroscopicity parameter of organic components(κorg) was derived. κorgexhibited an increasing tendency with aging, which was generally consistent with the tendency of the O:C ratio, indicating that the oxidation level was related to the hygroscopicity and CCN activity of organic aerosols from crop residue burning. Our results indicated that photochemical aging could significantly impact the CCN activation of crop burning aerosols, not only by the production of secondary aerosols, but also by enhancing the hygroscopicity of organic components, thereby contributing to the aerosol indirect climate forcing.  相似文献   

8.
Uneven distribution of volatile organic compounds (VOCs) and biomass, and excess biomass accumulation in some biofilters hinder the application of biofiltration technology. An innovative multilayer rotating drum biofilter (RDB) was developed to correct these problems. The RDB was operated at an empty bed contact time (EBCT) of 30 s and a rotational rate of 1.0 r/min. Diethyl ether was chosen as the model VOC. Performance of the RDB was evaluated at organic loading rates of 32,1, 64.2, 128, and 256 g ether/(m^3·h) (16.06 g ether/(m^3·h) ≈ 1.0 kg chemical oxygen demand (COD)/(m^3·d)). The EBCT and organic loading rates were recorded on the basis of the medium volume. Results show that the ether removal efficiency decreased with an increased VOC loading rate. Ether removal efficiencies exceeding 99% were achieved without biomass control even at a high VOC loading rate of 128 g ether/(m^3·h). However, when the VOC loading rate was increased to 256 g ether/(m^3·h), the average removal efficiency dropped to 43%. Nutrient limitation possibly contributed to the drop in ether removal efficiency. High biomass accumulation rate was also observed in the medium at the two higher ether loading rates, and removal of the excess biomass in the media was necessary to maintain stable performance. This work showed that the RDB is effective in the removal of diethyl ether from waste gas streams even at high organic loading rates. The results might help establish criteria for designing and operating RDBs.  相似文献   

9.
Understanding the aerosol vertical characterization is of great importance to both climate and atmospheric environment. This study investigated the variations of aerosol profiles over eight regions of interest in China after clean air policy (2013-2019) and discussed the drivers of the vertical aerosol structure, using observations from active satellite measurements (CALIPSO). From the annual variation, the amplitude of extinction coefficient profiles showed a decreasing trend with fluctuations, and the maximum was 0.21 km−1 in Beijing-Tianjin-Hebei (JJJ). For regions suffered from air pollution, the variation was greatest below 0.45 km, while it was between 1-1.5 km for Sichuan Basin. The correlation coefficient between the relative humidity (RH) and the extinction coefficient indicated that the increase of RH inhibited the decrease of the extinction coefficient in the Yangtze River Delta. In most regions, the main aerosol subtypes were polluted dust and polluted continental, but they were coarser in JJJ and North West. The frequency of concurrency of dust and polluted dust aerosols decreased in JJJ, but polluted continental aerosols occurred more frequently. Further, the aerosol extinction coefficient profiles under different pollution conditions showed that it changed most during heavy pollution periods in JJJ, especially in 2017, with a significant aerosol loading between ∼700 and 1200 m. The atmospheric reanalysis data revealed that the weak convergence at low level and the divergence at high level supported the upward transport of aerosols in 2017. Overall, the differences in divergence allocation, RH, and wind filed were the main meteorological drivers.  相似文献   

10.
The impact of air masses motion on marine aerosol properties was investigated using an on-board single particle mass spectrometer(SPAMS) deployed for the determination of single particle size resolved chemical composition over Southeast China Sea. Two aerosol blooms(E1 and E2) were observed during the cruise. High average particle number count occurred in E1(7320), followed by E2(5850), which was more than 100–150 times of the average particle number count during normal periods. Particles were classified as four major sources, including continental source, shipping source, marine source, and transport source based on the mass spectral similarity. Transport source was identified as those particles with high particle number count occurred only during aerosol bloom period. Three sub-types of EC-Ca, OC-Ca, and Al-rich were classified as transport source.EC-Ca was the dominant particles of the transport source, accounting for more than 70%of the total particles in aerosol bloom events. A uni-modal size distribution in the size range of 0.1–2.0 μm was observed during normal period, while a bimodal distribution with a tiny mode(0.3 μm) and a coarse mode between 0.4 and 0.6 μm was present during aerosol bloom. The variation of aerosol source is consistent with air masses back trajectories, for the reason that most of the long-range air trajectories are from the ocean,while short air trajectories originate in the continental regions, which means that air masses have a significant impact on the aerosol physical–chemical properties along their tracks.  相似文献   

11.
利用气象站点能见距的历史资料和NASA的MOD1S卫星遥感手段获取10km*10km分辨率的气溶胶光学厚度资料,建立二者之间的季节平均关系。得到了上海地区季节变化的气溶胶标高,并利用标高数据和气溶胶光学厚度的季节分布。反演出上海地区季节变化的区域能见距分布,研究近地层大气气溶胶与地面能见距的关系,分析上海市能见度时空分布特征,结果显示:上海城区在冬春季平均能见距较差,市区中心能见距在lOkm以下;低能见距中心分布明显。且主要分布在杨浦、桃浦、吴淞等工业区范围。  相似文献   

12.
MODIS遥感气溶胶光学厚度产品在地面能见距中的应用   总被引:1,自引:0,他引:1  
利用气象站点能见距的历史资料和NASA的MODIS卫星遥感手段获取10km*10km分辨率的气溶胶光学厚度资料,建立二者之间的季节平均关系,得到了上海地区季节变化的气溶胶标高,并利用标高数据和气溶胶光学厚度的季节分布,反演出上海地区季节变化的区域能见距分布,研究近地层大气气溶胶与地面能见距的关系,分析上海市能见度时空分布特征,结果显示:上海城区在冬春季平均能见距较差,市区中心能见距在10km以下;低能见距中心分布明显,且主要分布在杨浦、桃浦、吴淞等工业区范围.  相似文献   

13.
利用北黄海圆岛岛基太阳光度计气溶胶光学厚度(aerosol optical depth,AOD)实测数据,在优选时空匹配窗口的基础上,对最新版本MODIS C061 AOD产品开展了有效性验证。结果表明,相对于其他尺度的采样窗口,采用30 km×30 km空间采样窗口、±0.5 h时间采样窗口可以得到更加准确的验证结果。在此时空窗口下,MODISA AOD产品(550 nm)与岛基观测数据具有非常好的一致性,相关系数达到0.98,春季、秋季和冬季AOD产品精度满足NASA的设计要求,夏季数据存在较大误差,符合NASA期望误差([(0.04+0.1*AOD),(-0.02-0.1*AOD)])的比例仅为40%,气溶胶模型假定不合理是其可能的误差来源。  相似文献   

14.
本文以京津冀为研究区,对该地区的大气气溶胶光学厚度的分布及变化进行分析.利用AERONET地基观测的气溶胶光学厚度(AOD)数据,对最新发布的MODIS/Aqua C6.1 3 km AOD产品在京津冀地区的适用性进行验证,并将3 km产品与MODIS/Aqua C6.1 10 km产品进行对比.分析结果表明:MODIS 3 km AOD产品比AERONET地基AOD的相关性高,相关系数达到了0.95;与MODIS 10 km AOD产品相比,其下垫面为城市地区的反演精度低;在时空分布上,MODIS 3 km AOD产品更好的呈现了气溶胶梯度变化,季平均结果中,四季3 km AOD值都略高于10 km产品.以上结论可为MODIS 3 km AOD产品在京津冀地区的使用提供了借鉴与参考.  相似文献   

15.
周茹  朱君 《中国环境科学》2020,40(4):1429-1436
利用2013年地基CE-318太阳光度计观测数据,结合中分辨率成像光谱仪(MODIS)遥感产品和HYSPLIT后向轨迹分析,研究了一次东南亚生物质燃烧污染长距离输送至中国西南昆明站点过程(2013年4月5~8日)中,气溶胶光学特性和辐射特性的变化及其可能来源.结果表明,此次污染过程期间,我国西南地区生物质燃烧活动较少,而中南半岛地区生物质燃烧活动显著.4月5~7日,昆明站点气溶胶光学厚度(AOD)升高,消光波长指数(EAE)和吸收波长指数(AAE)均增大.此外,依据EAE和AAE分类方法,5~6日昆明站点以城市工业气溶胶为主,7~8日以生物质燃烧气溶胶为主,其细模态峰值半径(0.11μm)小于5~6日(0.15μm),7日细模态粒子体积浓度峰值(约为0.16μm3/μm2)是5日的2倍.气溶胶直接辐射强迫(ARF)日变化结果表明4月7日气溶胶对地表的降温效应达到最大,对大气的加热作用最强.气溶胶直接辐射强迫效率值(ARFE)的变化表明生物质燃烧气溶胶对大气顶的降温作用减弱.MODIS遥感以及HYSPLIT模式后向轨迹表明,此次昆明站点生物质燃烧气溶胶主要来源于东南亚地区(主要是印度北部、印缅北部和不丹地区).  相似文献   

16.
目的探测大气气溶胶的垂直分布,表征气溶胶的垂直结构和各层气溶胶的性质。方法使用金华站点激光雷达观测数据进行个例分析,用梯度法对边界层进行反演,利用退偏振比、颜色比和光学厚度对大气中不同高度的气溶胶层进行分析。结果大气垂直结构会出现多层不同性质的气溶胶层,激光雷达可以准确地探测气溶胶随时间变化的垂直结构特征。选取0点至8点进行分析表明,在1.5km高度上下出现两层气溶胶层,上下两层气溶胶层呈现出不同的性质,且其性质会随时间变化而改变。结论大气边界层以外气溶胶分布较为复杂,利用激光雷达探测的气溶胶消光系数、退偏振比、颜色比和光学厚度等参数能够较好地表征气溶胶的垂直结构和各层气溶胶的性质。  相似文献   

17.
This study finds out seasonal and monthly variations in Aerosol Optical Depth (AOD) over eastern and western routes of China Pakistan Economic Corridor (CPEC) and the relationship between AOD and meteorological parameters (i.e., temperature, rainfall and wind speed). The Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) data was used from the terra satellite for the period of 2000-2016. This study aims to overtake the conventional view of the purpose of using the satellite datasets. This study takes on to the concept that validated satellite data sets rather should be used for the analysis instead of just validation specifically for our study region. Hence, after comparing MODIS AOD with MISR AOD, only MISR AOD dataset is used for further analysis. The results show a decreasing trend of AOD in summer season, a positive relationship between temperature and AOD during winter and spring seasons whereas a positive relationship between wind speed and AOD in winter and spring seasons over eastern and western routes. Periodic analysis of MODIS AOD and MISR AOD depicts May-Aug as the peak period of aerosol concentration over central Pakistan. The inter-annual analysis shows the aerosol trend remained higher during summer season however rainfall shows the washout effect. Eastern route has higher standard deviation and larger values for aerosol prevalence as compared to western route. The trajectory analysis using the HYSPLIT model suggests the bias of air mass trajectory caused deviation in the aerosol trend in the year 2014.  相似文献   

18.
为研究2014年华北平原在夏收期间气溶胶污染的时空分布特征及形成原因,对2014年6月MODIS卫星的华北平原的气溶胶光学厚度(AOD)、细粒子比(FMF)、火点分布及后向轨迹进行了分析.结果表明,2014年6月华北平原的气溶胶光学厚度值在1.2~2.0之间,远高于年平均值1.0~1.2,而6月的火点分布主要集中在6—14日,此阶段的气溶胶光学厚度值高于6月6日前及14日以后的气溶胶光学厚度值.在两个特定研究区——华北南部及长三角地区,通过对6月的3个阶段的细粒子比进行分析,发现火点集中阶段细粒子排放增多,确定此次污染极有可能是由秸秆燃烧造成.在火点集中时期,两个研究区的后向轨迹说明,污染主要来自火点分布密集区域,进一步确定了秸秆燃烧是华北平原在夏收期间的主要污染源之一.  相似文献   

19.
利用MODIS和CALIPSO level2气溶胶产品,通过统计分析多个气溶胶光学参数(光学厚度、消光系数、色比和退偏振比)的时空分布及其变化,得出2007~2016年华东地区(27°N~37°N,113°E~123°E)气溶胶三维分布特征.结果表明,华东地区气溶胶光学厚度(AOD)年平均呈现出北高南低,平原高、山地低的分布特征.AOD季节分布表现为春夏高,秋冬低,夏季最高,冬季最低,且研究区域北部(31°N以北)AOD季节变化比南部地区剧烈.气溶胶消光系数(σ)随高度呈指数衰减,秋冬(春夏)低层σ较大(小)但随高度衰减较快(慢),2km以下北高南低.年平均色比(CR)随高度递增,变化范围为0.6~0.7,随时间有减小趋势.CR季节特征为4km以下春季最大,夏季最小且均一;4km以上冬季最大,夏季最小.年平均退偏振比(PDR)随高度递增,变化范围为0.1~0.25,北部较大.PDR季节特征为5km以下春季最大,夏季最小;5km以上冬季最大,夏季最小.从气溶胶组成来看,华东地区2km以下以污染沙尘为主;2~5km春季以沙尘为主,其它季节以烟尘为主;5km以上冬春以沙尘为主,夏秋以烟尘为主.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号