Diffusion aerosol spectrometer

The diffusion aerosol spectrometer for the measurements of particle size spectra and concentration levels is described. It includes three principal parts: (i) a block of diffusion batteries for measuring the particles, whose size does not exceed 0.15 μm, (ii) the particle amplifier for growing the particles passing through the diffusion batteries up to optically distinguishable sizes and (iii) the laser aerosol spectrometer, which counts the amplified particles and may also serve for independent measurements of particle size spectra within submicron size range. The tandem including: diffusion batteries+laser aerosol spectrometer allows for detecting particles of radius >3 nm at maximal concentration up to 2×10⁴ particles/cm³. The tandem is managed either by PC or manually. The instrument is designed for studying aerosols in the atmosphere and for ecological measurements.     

云雾物理膨胀云室研制及参数测试

膨胀云室可形成水汽、水面和冰面过饱和环境,是研究气溶胶粒子、人工影响天气冷暖催化剂核化过程和机理的重要实验设备。但长期以来,我国缺乏装备先进云雾粒子谱和图像测量系统的膨胀云室。2019年完成的我国自主研制的膨胀云室系统由云室主体、控制系统、通讯系统及环境和云雾测量系统4个子系统组成。该系统首次采用了国产云粒子谱仪和成像仪测量系统。测试结果表明:该云室具有良好的温度和压力控制能力,平均降温速率达到0.26℃·min-1,温度分布均匀,-40℃时舱内温差小于0.29℃;膨胀造雾过程4 min,雾可维持4 min,雾滴较小;可以实现从室温到-50℃低温环境的控制,具备压力膨胀成云雾模拟和微物理参数监测能力,解决了我国缺乏气溶胶粒子和暖云催化剂室内实验装备的状况,对验证暖云催化剂核化性能和提高暖云人工增雨科技水平有重要价值。     

Particle size dependent response of aerosol counters

During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions.The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the specific instrument was found. An enhanced detection efficiency for ultrafine hygroscopic sodium chloride aerosols was observed with water operated systems, an analogous trend was found for n-butanol operated systems with nonhygroscopic silver and tungsten oxide particles.     

Balloon-Borne Optical Counter for in Situ Aerosol Measurements

A new balloon-borne optical particle counter has been developed to make in situ measurements of stratospheric aerosols. The intensity of light scattered at 60° from the forward direction by individual particles is measured. Aerosol number concentrations in seven size channels can be inferred. The counter has been calibrated using polystyrene and polyvinyl toluene latex spheres. There is good agreement between measured and calculated individual pulse intensities for aerosol with radii from 0.16 to 2.6 µm. The size resolution is limited by broadening of the pulse count/pulse height spectrum, arising mainly from the photoelectron statistics of photomultipliers. Stratospheric aerosol measurements have been made using this instrument at Kiruna (68°N, 21°E), Sweden, in February 1995, and at Aire sur l'Adour (44°N, 0°W), France, in 1992, 1993, and 1994. The uncertainties in the measurements are discussed. The retrieved aerosol concentrations and size distributions are presented, and shown to be broadly consistent with measurements made by the University of Wyoming optical particle counter.     

雨滴谱降水现象仪综合测试系统设计

针对目前国内对雨滴谱降水现象自动观测仪常用标定方法存在的问题:只能模拟一种标准的粒子直径和速度;可以测量粒子的直径但是不能准确测量粒子的速度;只能模拟直径较小的粒子;仅能模拟球状降水粒子无法模拟其他形状的降水粒子;无法涵盖各种类型降水的粒子直径和速度等等。根据气象业务需求,本文从模拟降水粒子设计依据、雨滴谱降水现象仪综合测试系统构成、降水粒子直径与下落速度模拟测量方法和测量精度等诸方面详细阐述一种新型的雨滴谱降水现象仪综合测试系统,并通过对涵盖多种类型降水的不同直径和速度的粒子进行模拟试验,检测其测量的精确性,为国内对雨滴谱降水现象自动观测仪的标定和检测提供一定的借鉴和参考。     

A novel high-resolution small ion spectrometer to study ion nucleation of aerosols in ambient indoor and outdoor air

An electrically based ion spectrometer is described, capable of measuring particle sizes and mobilities from molecular ions (small ions) to aerosol particles across a size range of 0.4 to 30 nm in diameter. It consists of a single cylindrical capacitor divided into three electrically insulated sections. The current arriving at the central section is measured by an electrometer and represents the ion flux over a known range of mobilities determined by the applied voltage. The applied voltage is scanned in steps to measure the ion fluxes over a large number of overlapping mobility ranges. The recorded signal and the response function of the instrument are unfolded using a maximum entropy procedure to give a high-resolution measured mobility spectrum. The maximum entropy approach offers a considerable improvement over traditional aspiration collectors and can approach the resolution of a drift tube system. In this way, the spectrometer successfully overcomes the diffusion limit to small ion resolution. Illustrative spectra are shown, demonstrating for the first time the presence of some resolved structure within the small ion spectrum at the highest mobilities. It is demonstrated that the actual mobility spectrum of small ions falls in the range 0.8–2.0 × 10⁻⁴ m² V⁻¹ s⁻¹. This represents a narrower range than that previously measured which is attributed to improved spectral resolution in the present work.     

南京一次重霾天气纳米气溶胶观测研究

为加深对南京地区重霾天气过程纳米尺度气溶胶物理特征的了解,对2017年12月21—25日的一次重霾天气过程进行了综合探测,利用宽范围粒径谱仪观测了此次过程中10～1 000 nm颗粒物数浓度,并结合能见度等气象要素,对重霾期间纳米气溶胶谱分布进行了分析。结果表明:此次霾重污染过程出现在低温、高湿、气压上升期间;与非重污染时期相比,重污染期间N_(10-20)与N_(20-100)降低,N_(100-1000)升高;重污染期间气溶胶粒子平均数浓度为17 035个/cm~3,低于非重污染期间粒子数浓度,N_(100-1000)占总数浓度的55.05%;重霾发生期间纳米气溶胶数浓度谱为单峰结构,峰值在100 nm附近,随着污染加重,纳米气溶胶峰值粒径向大粒径偏移,粒子向大粒径段集中;不同温度对不同粒径粒子数浓度的影响不同,20～100 nm粒径段气溶胶与数浓度与温度呈反相关性,100～500 nm粒子数浓度与温度呈正相关性.     

The investigations of aerosol particle formation in urban background area of Helsinki

In this study the possible conditions for new aerosol particle formation in a background area of Helsinki have been analysed. The measurements of aerosol particle size distribution, main gaseous pollutant compounds, UV spectra and meteorological parameters were performed during April–May 1993. The main interest was concentrated on the investigations of photochemical OH radical formation, the oxidation of gas phase SO₂ to H₂SO₄ and the formation of H₂SO₄---H₂O aerosol particles. The measurements were analysed using a model for OH radical formation and aerosol dynamics. The analysis of aerosol size distributions was carried out using positive matrix factorization. The main conclusion is that based on our model analysis no evidence of new particle formation in the vicinity of the measurement station was found. However, the high concentrations of aerosol particles in the ultrafine size range indicate that some other particle formation pathways are to be considered.     

Measurement of IO radical concentrations in the marine boundary layer using a cavity ring-down spectrometer

An open-path cavity ring-down spectroscopy (CRDS) instrument for measurement of atmospheric iodine monoxide (IO) radicals has been tested in the laboratory and subsequently deployed in Roscoff on the north-west coast of France as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project in September 2006. In situ measurements are reported of local IO mixing ratios in the marine boundary layer. To obtain these mixing ratios, accurate absorption cross sections of IO are required at the selected wavelengths used for spectroscopic measurements. Absorption cross sections at the bandheads of the IO A²Π_3/2–X²Π_3/2 (3,0) and (2,0) vibronic bands were thus verified by a combination of spectral simulation methods, inter-comparison of prior determinations of cross-sections at high and low spectral resolution, and by measurement of rates of loss of IO by its self-reaction. The performance of the open-path CRDS instrument was tested by measuring concentrations of NO₂ in ambient air, both within and outside the laboratory, with results that were in excellent agreement with a previously validated continuous wave CRDS apparatus for NO₂ detection. During the RHaMBLe campaign, the open-path CRDS instrument was located within a few metres of the shoreline and operated at wavelengths close to 435 nm to detect the absorption of light by trace levels of IO. The IO mixing ratios were obtained on two days, peaked close to low tide, and were approximately 5–10 times higher than values calculated from column densities previously reported by long-path, differential optical absorption spectroscopy (DOAS) in coastal regions. The typical detection limit of the instrument was estimated to be 10 pptv of IO, with some fluctuation around this value depending on the conditions of wind and atmospheric aerosol particles, and the total accumulation time was 30 s for each data point. The observations of relatively high concentration of IO, compared to the values previously reported by DOAS, are consistent with the concurrent observations using a LIF (Laser induced Fluorescence) instrument (Whalley et al. in press). The first such measurements of localized IO by CRDS and LIF should contribute to an improved understanding of the chemistry of halogen compounds and the formation of iodine oxide aerosol particles in the marine boundary layer.     

省级MODIS植被指数序列的建立与应用

本文采用安德森分级采样直接获得的大气气溶胶质量密度换算成数密度。在此基础上,根据气溶胶数密度谱分布,验证了大气气溶胶的Junge谱与分段三参数谱相结合的谱模式。并且在得出气溶胶粒子谱基础上计算了大气气溶胶的散射、消光、吸收系数。     

Vertical fluxes and micrometeorology during aerosol particle formation events

Fluxes of aerosol particles with sizes larger than 10 nm together with fluxes of momentum, sensible and latent heat and CO₂ were measured 10 m above a Scots pine forest with the eddy covariance method. During days when nucleation events were observed particle size distribution measurements showed particle growth from 3 nm sizes to the Aitken mode. Analysis of the experimental data showed systematic differences in fluxes during the days when new particle production was observed compared to other days. During the nucleation events the particle flux measurements showed downward aerosol particle transport, i.e., indicating an elevated source, with respect to the measurement level, of particles larger than 10 nm. Furthermore the turbulence intensity and the heat fluxes were observed to be significantly higher. Evidences of mesoscale circulation were observed in wind speed records as well as in turbulent fluxes on nucleation days. The measurement results show that micrometeorology, the synoptic scale conditions and the particle formation are closely related.     

基于航测的云底气溶胶活化率与过饱和度估算

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%。     

山东地区秋季飞机观测气溶胶特征的初步分析

综合分析了2006年秋季在山东省进行的0.5—8.0μm范围内的大气气溶胶飞机观测的0—4500m气溶胶数浓度垂直分布,初步讨论了气溶胶与温度的关系,并分析了对气溶胶粒子谱的垂直分布情况。结果显示,气溶胶数浓度随高度呈递减趋势,在逆温层附近气溶胶有累计现象;受城市环境的影响,同一区域城市上空或者城市的下风方气溶胶粒子平均浓度都大于上风方;气溶胶粒子谱受不同天气背景的影响,出现不同类型的谱型,随高度的变化,谱型也有很大的变化。     

The effects of the Arctic haze as determined from airborne radiometric measurements during AGASP II

The interaction of the Aretic winter aerosol (Arctic haze) with solar radiation produces changes in the radiation field that result in the enhancement of scattering and absorption processes which alter the energy balance and solar energy distribution in the Arctic atmosphere-surface system. During the second Arctic Gas and Aerosols Sampling Project (AGASP II) field experiment, we measured radiation parameters using the NOAA WP-3D research aircraft as a platform. State-of-the-art instrumentation was used to measure in situ the absorption of solar radiation by the Arctic atmosphere during severe haze events. Simultaneously with the absorption measurements, we determined optical depths, and total, direct, and scattered radiation fields. All optical measurements were made at spectral bands centered at 412, 500, 675, and 778 nm and with a bandpass of 10 nm. With this selection of spectral regions we concentrated on the measurement of the radiative effects of the aerosol excluding most of the contributions by the gaseous components of the atmosphere. An additional measurement performed during these experiments was the determination of total solar spectrum fluxes. The experimentally determined parameters were used to define an aerosol model that was employed to deduce the absorption by the aerosols over the full solar spectrum and to calculate atmospheric heating rate profiles. The analyses summarized above allowed us to deduce the magnitude of the change in some important parameters. For example, we found changes in instantaneous heating rate of up to about 0.6 K/day. Besides the increased absorption (30 to 40%) and scattering of radiation by the atmosphere, the haze reduces the surface absorption of solar energy by 6 to 10% and the effective planetary albedo over ice surfaces by 3 to 6%. The vertical distribution of the absorbing aerosol is inferred from the flux measurements. Values for the specific absorption of carbon are found to be around 6 m²/g for externally mixed aerosol and about 11.7 m²/g for internally mixed aerosol. A complete study of the radiative effects of the Arctic haze should include infrared measurements and calculations as well as physics of the ice, snow, and water surfaces.     

华北中部夏季气溶胶和云分布特征

气溶胶与云的垂直分布特征是气溶胶间接气候效应关注的重点。基于2018年7—8月华北中部6架次飞机观测数据,研究气溶胶和云滴的垂直和水平分布特征。结果表明:华北中部780~5687 m高度内气溶胶数浓度( N_a )平均值为821.36 cm-3,最大量级可达到104 cm-3,云中气溶胶数浓度(N_acc)占总颗粒浓度的80%以上,表明细颗粒占大多数,气溶胶粒子算术平均直径( D_m )平均值为0.12~0.52 μm;大气层结对气溶胶垂直分布影响较大,逆温阻挡气溶胶垂直输送,高空(高度2000 m以上) D_m 的垂直分布受到相对湿度影响较大; N_a 和 D_m 在垂直方向波动较大,水平方向波动较小;低层云中云滴数浓度(N_c)较大、液态水含量(L)较小,而中层和高层云中N_c较小、L较大,N_c和云滴有效半径(R_e)的概率密度函数均为双峰型分布,L的概率密度函数为单峰型分布;气溶胶数浓度谱基本呈现多峰型分布,而云滴数浓度谱多呈现单峰型分布。     

雷达-雨量计-粒子激光探测仪联合估算降水量

为了提高区域降水量观测的空间分辨率, 提出了雷达-雨量计-粒子激光探测仪联合校准法。首先, 利用粒子激光探测仪观测到的滴谱资料建立实时的Z-I关系, 然后, 利用变分法对同时有雷达回波和雨量计资料的点的实测校准因子进行校准, 获得最优校准因子分析场, 最后, 对有雨量计的点取雨量计实际观测值, 没有雨量计的点利用最优校准因子分析场估算降水。利用此方法对辽宁省2007年5月15日一次天气过程进行降水量估算, 结果表明: 雷达-雨量计-粒子激光探测仪联合校准法结合了雨量站观测资料单点精度高和雷达资料时空分辨率高的优点, 提高了降水量的估算精度, 更好地反映了降水的空间分布。     

一次秋季冷锋降水过程气溶胶与云粒子分布的飞机观测

利用机载PMS（Particle Measuring Systems）测量系统,对2008年10月4—5日石家庄地区一次冷锋降水云系的3次气溶胶和云粒子探测资料进行了分析。结果表明,冷锋过境降水前后,气溶胶粒子分布差异较大。降水发生前,气溶胶粒子平均数浓度约为103cm-3,平均直径为0.95μm;气溶胶主要集中于3000m高度以下的对流层低层,云内气溶胶数浓度明显减少。降水发生后,气溶胶粒子平均数浓度约为102cm-3,比降水前约小1个量级,平均直径为1.28μm;气溶胶主要集中于1200m以下的近地面层,其数浓度随高度增加而降低。气溶胶粒子浓度在低层云区内水平变化较小,而在无云区和云下近地层水平起伏较大。云粒子平均浓度比气溶胶小1～2个量级。气溶胶粒子平均谱主要呈双峰型,而云粒子谱主要为单峰型。     

On the use of a modified clean-room optical particle counter for atmosperic aerosols at high relative humidity

This study is devoted to the performance of the CLIMET CI-8060, a white-light optical particle counter (OPC). Designed for clean-room monitoring, the off-the-shelf performance of this instrument is rather poor for outdoor studies. Modifications of this instrument are described turning this low-cost instrument into an OPC with excellent performance. The modifications include a reduction of the flow rate to 1.4 l/min, an altered design of the inlet nozzle, a buffer chamber to assure continuous flow, and a 16-channel pulse height analyzer.The modified version has been checked thouroughly. The counting efficiency is very close to 100% for particle sizes between 0.295 and 0.801 μm. The loss of giant particles is also marginal, as comparative tests with a cascade impactor show. The sizing calibration has been redetermined experimentally, using latex spheres, and theoretically, applying a software package by Jüngert [1988] using the Mie theory. With the help of the established relationship between experimental and theoretical response for latex, calibration tables for any other particle material are obtained (in particular for ambient aerosols and H₂O for fog and cloud condensation studies).The modified counter has been used for monitoring the growth of hygroscopic aerosols in humid conditions, using two different inlet lines, one of them drying the aerosol before entering the OPC, the other one preserving ambient conditions. This system allows to observe haze and fog formation and cloud condensation processes in situ at a one-minute time resolution.     

气溶胶粒径区间对其消光、后向散射及消光后向散射比影响的数值分析

我们利用Junge谱对多道光电粒子计数器的测量谱进行了模拟,根据光散射的米氏理论,考察了气溶胶小粒子对其消光、后向散射及消光后向散射比的影响情况,对估计由实测谱及折射指数计算以上三个参量所带来的误差具有一定参考价值.     

三参数云微物理方案中气溶胶谱函数对云滴谱影响的数值模拟研究

观测和分档方案的数值模拟都证明气溶胶的谱分布特征对云滴谱的演变有直接影响继而作用于降水的发展。目前广泛使用的总体双参数云滴谱方案因为表征云滴谱的预报量不足,在凝结过程中云滴谱呈不正常的拓宽现象。因此在参数化方案中,气溶胶谱对云滴谱的影响未有明确结论。中科学院大气物理研究所(IAP)云降水物理与强风暴重点实验室(LACS)新研发的三参数方案(IAP-LACS)通过增加的预报量克服了云滴谱的拓宽问题,提高了云滴谱模拟的准确性。为了研究在参数化方案中气溶胶谱分布特征对云滴谱的影响,本文采用新方案进行WRF(Weather Research and Forecasting mode)大涡理想性试验,验证了新方案中气溶胶对数正态谱函数中数浓度、几何半径和标准差3个参量对云滴谱演变的影响。针对3个参量的敏感性试验表明新的气溶胶活化方案和三参数云滴凝结增长方案能够描述气溶胶谱对云滴谱演变的影响规律:气溶胶数浓度对云滴谱影响最显著,数浓度越高活化生成的云滴数量越多,云滴半径越小,云滴谱趋向窄谱,气溶胶数浓度低时,云滴数量少、半径大。较大的几何半径使气溶胶谱向大粒径移动,导致大云滴生成,标准差对云滴谱的影响最不显著。