共查询到20条相似文献，搜索用时 46 毫秒
1.
基于2016年冬季和2017年夏季在北京、2016年夏季在邢台的三次气溶胶外场观测实验,选取三次观测期间典型的新粒子生成事件,分析其对气溶胶吸湿和云凝结核（CCN）活化特性的影响。两地分别位于华北平原北部超大城市区域和中南部工业化区域,两地不同季节新粒子形成机制不同,对应的凝结汇、生长速率以及气溶胶化学组分也不同。北京站点新粒子生成事件的发生以有机物的生成主导,而邢台站点新粒子生成事件的发生则以硫酸盐和有机物的生成共同主导。邢台站点新粒子生成过程中气溶胶吸湿性及云凝结核活化能力明显强于北京站点,此特点在核模态尺度粒子中表现尤为明显。以上结果表明,在估算新粒子生成对CCN数浓度的影响时,应充分考虑气溶胶吸湿和活化特性的差异。 相似文献
2.
Under cloudy conditions at the Gosan Climate Observatory (GCO), Korea, we observed distinct new particle formation and growth (NPF) events from simultaneous co-located measurements of aerosol and cloud profiles, cloud cover, shortwave radiation, and the number concentration and size distribution of aerosols. The high frequency of NPF was observed at GCO under decreased downwelling solar radiation caused by clouds. Although we observed about 15 and 40 % decreases in downwelling surface shortwave radiations, in the presence of thick mid-level (low-level) clouds, on January 28 and 30, 2012, respectively, distinct NPFs with a growth rate of 3.3 (3.9) nm h?1 were observed. We examined a 4-year series (May 2008 to April 2012) of continuous measurements of the size distribution of aerosol numbers and visually observed cloud cover. We found that approximately 13 % (i.e., 35 days out of 280 days) of total NPF events were observed under cloud-free conditions (i.e., cloud cover of 0/10). About 20 % (i.e., 57 days out of 280 days) of total NPF events occurred under mostly overcast conditions (i.e., cloud cover of 9/10–10/10). Although NPF events occurring under cloudy conditions were also found elsewhere, the frequency of NPF occurring at GCO seems much higher. The average value of relative humidity for the strong-NPF event days is lower than that of the weak and non-NPF event days for all cloud categories. No significant difference in the condensation sink was found among strong-, weak-, and non-NPF days, but the condensation sink showed a slight decreasing tendency with increasing cloudiness. Further investigations on precursor gases and preexisting aerosols under cloudy conditions are needed. 相似文献
3.
气溶胶对环境、气象和人体健康都有较大影响,这些影响与气溶胶理化特性(粒子尺度谱、化学组分、混合状态等)密切相关。为了深入研究气溶胶的环境和气候效应,发展了一套气溶胶在线综合观测系统。本文介绍了利用该系统在北京、上海、广州三个超大城市开展的综合观测实验结果。通过对比分析发现,广州气溶胶数浓度最高,其粒子尺度谱分布特征与北京特征相似,均以核模态为主,上海气溶胶数浓度则整体较低。对比三个超大城市的新粒子生成(New Particle Formation,NPF)特征发现,北京NPF的发生频率低于广州,主要由于北京地区大气中大粒径气溶胶更多,较高的碰并汇抑制了NPF的发生和发展。研究发现,观测期间北京和上海站点气溶胶的吸湿性强于广州,人为一次性排放气溶胶吸湿性较弱。气溶胶吸湿性日变化特征与人为活动、气溶胶老化程度密切相关。此外,三个超大城市中气溶胶光吸收系数的日变化特征存在明显差别,北京站点的气溶胶吸收系数呈现白天高、夜间低的特点,而广州站点气溶胶的吸收系数呈现相反的日变化趋势,这可能是由观测站周边的环境差异及大气边界层的变化特征差异造成的。 相似文献
4.
利用2011年和2013年夏秋季在青藏高原中东部开展的11架次气溶胶特征飞机观测数据,分析气溶胶数浓度、数谱及核化相关特征。结果表明:受天气系统、地形和地表影响,观测区内气溶胶数浓度（Na）和体积直径（Dv）的垂直和水平分布差异较大,Na呈西北高、东南低,Dv低层大、高层小,局地中高层有沙尘。格尔木盛行东风时,云降水对低层气溶胶有清除作用,Na和Dv明显降低,6.2 km高度和7.2~7.4 km高度的中高空受高原大风或对流影响形成沙尘;盛行西风时,低层Dv以0.5~0.8 μm为主,随高度升高和风速增大Na升高,Dv变幅较小,6.2 km高度也有沙尘;不同天气系统影响下6.5 km高度以上均输入亚微米颗粒,Na达5×103 cm-3,8.0 km高度盛行东风时比西风时Na更高,Dv更小,谱垂直分布也有以上特征,整层输入以偏北或偏西路径为主。不同过饱和度测量云凝结核数浓度（Nccn）表明,除格尔木6.0 km高度以下核化率（Nccn/Na）在21%~47%外,其他观测区平均核化率介于1%~16%,6.0~8.5 km高度的核化率总体偏低;当Na增加时核化率明显下降,且过饱和度1%~2%,-15~-5℃层或粒径1~3 μm时的核化率相对偏高。 相似文献
5.
《Atmospheric Research》2009,91(2-4):125-131
Particle detection by condensation particle counters (CPCs) is ultimately limited by the onset of homogeneous nucleation. At vapour supersaturations around the homogeneous nucleation limit the diameter of critical clusters is typically about 2 nm. It is widely assumed that only particles larger than critical clusters can be activated by vapour condensation and the general detection limit of CPCs is therefore currently accepted to be around 2 nm particle diameter. Using an expansion type CPC with n-propanol as working fluid we investigated the transition from heterogeneous to homogeneous nucleation, clearly showing that particles are activated much before the onset of homogeneous nucleation, even at particle diameters as small as 1.4 nm. For particle diameters below 2 nm we have usually found condensation particle counting to be influenced by the simultaneous presence of ions as generated in a bipolar diffusion charger. In this paper we illustrate how the presence of ions influences particle number concentration measurement and how ions can be removed in order to obtain accurate seed particle number concentrations for particle diameters down to 1 nm. 相似文献
6.
2017年9月14—27日在珠江三角洲地区开展了6个架次飞机观测试验。利用飞行获取的气溶胶、云凝结核、云滴及常规气象探头观测资料,结合天气形势、气象条件及气团后向轨迹分析,研究了珠江三角洲地区深圳气溶胶数浓度及其谱的垂直分布特征,配合不同过饱和度条件下云凝结核浓度观测,分析了气溶胶活化特性。结果表明:在不同天气条件下,深圳低层气溶胶数浓度变化范围为500~9000 cm-3;边界层内气溶胶分布相对均匀,谱型随高度变化与气象条件相关。将6个架次气溶胶观测资料根据数浓度及谱型分为3种类型:类型Ⅰ为海洋型气溶胶,数浓度小,粒子尺度大,谱型呈双峰分布;类型Ⅲ为大陆型气溶胶,数浓度高,粒子尺度小,谱宽较宽且呈三峰分布;类型Ⅱ为海洋大陆影响型气溶胶,即受海洋和大陆共同影响,数浓度低于类型Ⅲ高于类型Ⅰ,谱型为双峰分布。拟合了包含海洋型及大陆型气溶胶的3个架次近地面云凝结核活化谱,计算了气溶胶在不同过饱和度条件下的活化效率。 相似文献
7.
K. S. Madhava Rao T. S. Verma S. Chimidza Shibu K. John 《Meteorology and Atmospheric Physics》2014,124(1-2):83-96
Africa is one of the sources of biomass burning emissions. It is estimated that about 6 million tons of fuel per day is consumed in the southern hemisphere. Biomass burning has an important contribution on aerosol particle concentrations in the atmosphere. Efforts have been made to conduct research in Gaborone to monitor the concentration of atmospheric aerosol particles. These studies were mainly confined to measurement of concentration of aerosol particles and establishing a relation with determinants such as carbon dioxide concentration, biomass burning, and precipitation among others. However, very little seems to have been done in relating the empirical data to levels of aerosol concentrations through a mathematical model. In this paper an objective criterion of classifying levels of aerosol concentrations in terms of their severity is provided. A mathematical model for severity levels is built. Furthermore, two indices, namely, an index of dispersion when applied to the observed annual data indicated that intensity of atmospheric aerosol are on increase in the city of Gaborone, Botswana, and an index of drift which establishes that aerosol severity states showed larger drift during the year 2006–2007 than in the year 2007–2008. 相似文献
8.
Gerson P. Almeida Stephan Borrmann João B. V. Leal Junior 《Meteorology and Atmospheric Physics》2014,125(3-4):159-176
Ground-based aerosol instrumentation covering particle size diameters from 25 nm to 32 µm was deployed to determine aerosol concentration and cloud condensation nuclei (CCN)-activation properties at water vapor supersaturations in the range of S = 0.20–1.50 % in the remote Brazilian northeast semi-arid region (NEB) in coastal (maritime) and continental (inland) regimes. The instruments measured aerosol number concentration and activation spectra for CCN and revealed that aerosol properties are sensitive with respect to the sources as a function of the local wind circulation system. The observations show that coastal aerosol total number concentrations are above 3,000 cm?3 on average, exhibiting concentration peaks depending on the time of the day in a consistent daily pattern. The variation on aerosol concentration has also influences on the fraction of particles active as CCN. At 1.0 % water vapor supersaturation, the fraction can reach as high as 80 %. Inland aerosol total concentrations were about 1,800–1,900 cm?3 and did not show much diurnal variation. The fraction of particles active as CCN observed inland depend on the history of the air masses, and was much higher when air masses were originated over the sea. It was found that (NH4)2SO4 and NaCl are the major soluble inorganic fraction of the aerosols at the coast. The major fraction of NaCl was present in the coarse mode, while ammonium sulfate dominates the inorganic fraction at the submicron range, with about 10 % of the total aerosol mass at 0.32 µm. Inorganic compounds are almost absent in particles with sizes around 0.1 μm. The study suggests that the air masses with high concentration of CCN originate at the sea. The feasible explanation lies in the fact that the NEB’s beaches have a particular morphology that produces a wide surf zone and creates a large load of aerosols when combined with strong and permanent winds of the region. 相似文献
9.
2016年11月13日在北京地区上空存在持续稳定的层状云天气背景下,利用飞机开展气溶胶粒径谱、化学组成、云滴谱等参量的垂直观测,研究该个例云底气溶胶的活化能力。结果表明:探测期间北京地区为轻度污染天气,地面气溶胶浓度(0.11~3 μm)达到4600 cm-3。云层高度为800~1200 m,云底气溶胶数浓度相对于近地面大幅度降低,有效粒径显著增大(0.3~0.6 μm)。同时,近地面气溶胶中疏水性的一次有机气溶胶贡献显著,而云底气溶胶中一次有机气溶胶的贡献大幅降低,无机组分和二次有机气溶胶的贡献明显增大,造成吸湿性参数κ由0.25(地面)增大至0.32(云底)。云中气溶胶和云滴的谱分布衔接较好,且两者的数浓度之和与云底气溶胶浓度一致,可分别代表未活化和已活化的粒子。基于云底气溶胶粒径谱和吸湿性参数计算得到不同过饱和比下云凝结核的活化率,通过与云中观测结果对比,反推得到云底过饱和度约为0.048%。 相似文献
10.
TAREQ HUSSEIN JYRKI MARTIKAINEN HEIKKI JUNNINEN LARISA SOGACHEVA ROBERT WAGNER MIIKKA DAL MASO ILONA RIIPINEN PASI P. AALTO MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(4):509-521
Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997–December 2006), in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm−3 s−1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h−1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere. 相似文献
11.
Particle detection by condensation particle counters (CPCs) is ultimately limited by the onset of homogeneous nucleation. At vapour supersaturations around the homogeneous nucleation limit the diameter of critical clusters is typically about 2 nm. It is widely assumed that only particles larger than critical clusters can be activated by vapour condensation and the general detection limit of CPCs is therefore currently accepted to be around 2 nm particle diameter. Using an expansion type CPC with n-propanol as working fluid we investigated the transition from heterogeneous to homogeneous nucleation, clearly showing that particles are activated much before the onset of homogeneous nucleation, even at particle diameters as small as 1.4 nm. For particle diameters below 2 nm we have usually found condensation particle counting to be influenced by the simultaneous presence of ions as generated in a bipolar diffusion charger. In this paper we illustrate how the presence of ions influences particle number concentration measurement and how ions can be removed in order to obtain accurate seed particle number concentrations for particle diameters down to 1 nm. 相似文献
12.
Rita Van Dingenen Aki O. Virkkula Frank Raes Timothy S. Bates Alfred Wiedensohler 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):439-451
We propose an analytical expression for the relation between aerosol accumulation number and sub‐micron volume over the marine boundary layer (MBL), based on a simple balance equation. By providing appropriate source and sink terms which account for entrainment, coagulation, in‐cloud scavenging and condensational growth, the model is able to reproduce the observed ratio between MBL particles larger than 80 nm diameter (as a proxy for accumulation mode number) and submicron aerosol volume, from freshly polluted to background conditions. Entrainment and coagulation are essential in predicting the observed ratio. Budget and lifetime calculations show that, due to relatively low source rates of oceanic non‐sea‐salt‐sulfate and sea‐salt, the anthropogenic signature in aerosol volume remains significant even after 8 days of MBL transport. 相似文献
13.
通过对南海腹地岛屿测站和南海北岸测站气溶胶样品中水溶性成分的分析，以及与华南大陆清洁测点和城市测点的对比，结果表明:海岛测点气溶胶总质量与诸离子浓度均大大低于海岸与大陆测点。其分布以三峰型出现的比较多，海岛与海岸气溶胶中水溶性成分以SO2-4，Cl-与Ca2+，Na+为含量比重最大的离子成分；与华南大陆测点相比，Cl-，Na+比重显著增加而NH+4的含量比重有所下降。 相似文献
14.
2014年8月15日,山西省人工降雨防雹办公室在山西忻州开展了气溶胶和浅积云的飞机观测,本文利用机载云物理资料,详细分析了华北地区气溶胶、云凝结核（CCN）和浅积云微物理特性及其相互影响。主要结论有:（1）此次过程的边界层高度约为3600 m,不同层结情况下,0.1～3 μm尺度范围内的气溶胶粒子浓度Na、有效直径Da和CCN数浓度的垂直廓线明显不同,近地面Na可达2500 cm?3。（2）CCN的主要来源为积聚模态、爱根模态或者核模态的气溶胶颗粒,0.2%过饱和度下,气溶胶活化率（AR）在各高度层的结果变化不大;0.4%过饱和度下,AR随着高度增加而降低。（3）后向轨迹模式分析表明,2 km以下的气溶胶主要来自于当地城市排放,由细颗粒污染物组成;2 km以上的气溶胶主要来源于中国西北和蒙古地区的沙漠,由亚微米沙尘组成,溶解度相对较低,可作为潜在的冰核。（4）本文细致分析了两块相邻浅积云（Cu-1和Cu-2）的云物理特性。Cu-1云底高度约4500 m,云厚约600 m,云体松散,夹卷较多;云中液态含水量（LWC）基本保持在0.5 g m?3,云粒子浓度Nc平均值为278.3 cm?3,云滴有效直径Dc整体在15 μm以内;毛毛雨滴粒子浓度最大值为0.002 cm?3,云中几乎无降水粒子;粒子谱宽随着高度增加而增大,主要集中在30 μm以内。Cu-2云底高度约3900 m,云厚约1200 m,云体密实;云中过冷水丰沛,LWC有多个超过1 g m?3的区域,云顶附近出现冰晶,云中粒子从凝结增长状态直接进入到混合相态;积云内部粒子水平分布不均,同一高度Nc相差较大,最大可达1240 cm?3。Dc随着高度增加而增大;粒子谱宽随着高度增加而拓展,最大可达1100 μm,谱型由单峰向多峰转变;降水粒子和冰晶图像大多为霰粒子、针状和板状。 相似文献
15.
The factors which affect the formation of new sulphuric acid particles in different atmospheric conditions are investigated. An atmospheric chemistry gas phase box model coupled to a three mode integral aerosol dynamics model is used. The simulations show the dependence of the concentration of nucleation mode particles on initial pre-existing particles, the intensity of UV radiation, the emissions of dimethylsulphide (DMS) and the ratio of emissions of hydrocarbons (HC) and NOx present in the atmosphere. Eight different basic cases are simulated in urban, rural and marine conditions. The effects of pre-existing particles as a sink of sulphuric acid are clearly seen. The increased UV radiation is also seen to enhance particle formation via sulphuric acid route significantly. 相似文献
16.
T. Anttila A. Kiendler-Scharr Th. F. Mentel R. Tillmann 《Journal of Atmospheric Chemistry》2007,57(3):215-237
Organic aerosol formation resulting from the ozonolysis of α-pinene, myrcene and sabinene was investigated in a large aerosol
chamber in the presence of aqueous seed aerosols. The chemical composition of the particles was monitored by an aerosol mass
spectrometer (Aerodyne Research Inc.) as a function of time and the particle size. Smaller particles were found to contain
more organics relative to sulfate than the larger ones. In contrast, the water to sulfate mass ratio was not dependent on
the particle size. These experimental findings indicate the formation of organic layers on the particles. With the aid of
an aerosol dynamic model we demonstrate that the observations are consistent with the formation of multilayered organic films
having thicknesses of approximately 10 nm. The results also suggest that the films were formed through condensation of low-volatile
oxidation products that did not take up water considerably. Even though dissolution of oxidation products into the particle
aqueous phase cannot be conclusively ruled out, the most plausible interpretation of the results is that the monoterpene ozonolysis
lead to the formation of organic coatings on aqueous aerosols. Such films are likely to form in regions with monoterpene emissions. 相似文献
17.
Stefaan Hoornaert Ricardo Henrique Moreton Godoi René Van Grieken 《Journal of Atmospheric Chemistry》2004,48(3):301-315
Aerosol sampling in Kazakhstan was performed at a remote astronomical observatory in the Tien Shan mountain region. The background character of the site was considered by comparing the elemental concentrations, obtained by Energy Dispersive X-Ray Fluorescence (EDXRF), with those reported for other remote stations. On the basis of the variability of the elemental concentrations and the source of origin, the elements could be classified into two main groups. These findings, complemented with enrichment factor calculations revealed the first group of elements to be originating mainly from local sources, and the second group to be related to long-range transport of anthropogenic aerosol. Automated individual particle analysis by electron probe X-ray microanalysis (EPXMA) and subsequent cluster analysis resulted in the identification of 12 distinct aerosol particle types. Relative particle type abundances were converted to absolute abundances by estimating the particle number concentrations for the detected particles, exploring the seasonal particle variation. Based on the absolute abundances, a strong seasonal pattern was found for Si-Al-Fe-, Si-, Ca-S-Si-, Ca-Si-, Fe-Si- and Ti-Si-rich particles. These particle types can mainly be attributed to the local soil source. For most of the remaining particle types, a completely different seasonal trend was found, which can be related to anthropogenic emissions. Their abundance in winter can be related to long-range transport of anthropogenic aerosols. As a result, these data can be representative for the Tien Shan site and may be useful to climate modellers and environmentalists. 相似文献
18.
利用2014年7月黄山光明顶观测获得的气溶胶数浓度、气溶胶数谱数据,对黄山夏季气溶胶数浓度及谱分布特征进行分析,并在此基础上对气溶胶数谱进行了对数正态分布拟合。研究结果表明:黄山夏季气溶胶平均数浓度约为3 518.27 cm~(-3),主要集中在爱根核模态;气溶胶平均数浓度日变化呈双峰分布,峰值浓度的出现伴随着小粒子的增多。气溶胶数浓度与相对湿度和风速成负相关,高浓度的气溶胶多出现在较弱的东南风时;积聚模态气溶胶数浓度受风向影响显著。不同气团背景下气溶胶数谱差异集中在小于100 nm和500~1 000 nm粒径范围。爱根核模态气溶胶在高湿的西南气团影响下数浓度最低、谱较窄,而高温、低湿的东南气团对应的气溶胶数浓度最高、谱最宽,北方气团对应的气溶胶数浓度和谱宽居中;500~1 000 nm粒径范围气溶胶数谱分布特征与之相反。不同背景的气溶胶数谱和体积谱均可采用爱根模态、积聚模态1和积聚模态2三个模态进行对数正态分布拟合,但不同气团背景下的各模态谱型参数差异较大。 相似文献
19.
MIHALIS LAZARIDIS SASTRY S. ISUKAPALLI PANOS G. GEORGOPOULOS 《Tellus. Series B, Chemical and physical meteorology》2001,53(1):83-93
A modelling platform for studying photochemical gaseous and aerosol phase processes from localized (e.g., point) sources has been presented. The current approach employs a reactive plume model which extends the regulatory model RPM‐IV by incorporating aerosol processes and heterogeneous chemistry. The physics and chemistry of elemental carbon, organic carbon, sulfate, nitrate, ammonium material of aerosols are treated and attributed to the PM size distribution. A modified version of the carbon bond IV chemical mechanism is included to model the formation of organic aerosol. Aerosol dynamics modeled include mechanisms of nucleation, condensation, dry deposition and gas/particle partitioning of organic matter. The model is first applied to a number of case studies involving emissions from point sources and sulfate particle formation in plumes. Model calculations show that homogeneous nucleation is an efficient process for new particle formation in plumes, in agreement with previous field studies and theoretical predictions. In addition, the model is compared with field data from power plant plumes with satisfactory predictions against gaseous species and total sulphate mass measurements. Finally, the plume model is applied to study secondary organic matter formation due to various emission categories such as vehicles and the oil production sector. 相似文献
20.
《Atmospheric Research》2008,87(3-4):194-206
This work aims at determining the aerosol particle radii in the atmosphere of Athens. Such a work is carried out in Athens for the first time. For this purpose, solar spectral direct-beam irradiance measurements were used in the spectral range 310–575 nm. To estimate the particle radius from aerosol optical depth retrieval, a minimization technique was employed based on the golden-section search of the difference between experimental and theoretical values of the aerosol optical depth. The necessary Mie computations were performed based on the algorithm LVEC.In this study, the mean particle radius of a given distribution was calculated every 30 min during cloudless days in the period November 1996 to September 1997. The largest particles were observed in the summer and the smallest during winter. The result was verified by the increased values of the aerosol optical depth and the turbidity factors calculated in the summer. The differences in the diurnal variation from season to season are attributed to the prevailing wind regime, pollutant emission and sink rates in the atmosphere of Athens. 相似文献