Recombination rates of small ions and their attachment to aerosol particles

It could be shown by measurements of the air conductivity and using a mean profile for the ionization rate that experimental and theoretical values of the recombination rate of small ions based on a three body recombination process (Thomson) are in very good agreement up to 20 km altitude. The divergency of the experimental and theoretical curves above 20 km can be interpreted by assuming that there exists in this altitude region a crossover from the three body recombination to a two body recombination process. The value of the recombination coefficient is about 4·10^–7 cm³ s^–1 in 25 km altitude, compared with 1.4·10^–6 cm³ s^–1 at ground level. Furtheron it was possible for the first time to get some experimental data of attachment coefficients up to 13 km from simultaneous measurements of the air conductivity and Aitken nuclei concentration. These values are in good agreement with those obtained by theoretical considerations.     

The application of least squares analysis for the estimation of low atmospheric concentrations of short-lived radon daughters and studies on their disequilibrium

The application of the weighted and unweighted least-squares method to the analysis of the individual concentrations of short-lived radon daughters in the open atmosphere, where, unlike in the mines the levels are low, is discussed. The method can be optimized to give minimum counting errors by proper choice of collection times and counting periods. By analysing a large number of samples it is shown that the least squares method gives better accuracy than the simultaneous equations method generally in use. The calculation can be simplified by using the unweighted least-squares analysis without significant loss in accuracy. The levels of RaA, RaB and RaC in surface air at Bombay during the period January-June 1975, calculated using the least-square method, are presented. The activity ratios of RaC/RaB are shown to have an average value around 0.6–0.9 even at 18 m height. The RaB/RaA activity ratios however show a much larger scatter than the RaC/RaB values. The possible reasons for these differences are discussed. The application of the least-squares method to the analysis of Th-B and Th-C is also described.     

Humidity effects on gravitational settling and Brownian diffusion of atmospheric aerosol particles

The dependency on relative humidity of the settling velocity of aerosol particles in stagnant air and of the diffusion coefficient due to Brownian motion of aerosol particles was computed for six aerosol types and different particles sizes in dry state. The computations are based (1) on mean bulk densities of dry aerosol particles obtained from measurements or from the knowledge of the chemical composition of the particles, (2) on micro-balance measurements of the water uptake per unit mass of dry aerosol substance versus water activity at thermodynamic equilibrium, and (3) on measurements of the equilibrium water activity of aqueous sea salt solutions. The results show a significant dependence of the settling velocity and Brownian diffusion of aerosol particles on relative humidity and on the particle's chemical composition.Nomenclature A surface parameter of a particle - B surface parameter of a particle - c _L velocity of sound in moist air - C 1+Kn[A+Qexp(–B/Kn]=slip correction - D diffusion coefficient of a particle - D ₁ D(=1)=diffusion coefficient of a spherical particle - f P _w /P _we (T,P)=relative humidity (f=0 dry air,f=1 saturated air) - g acceleration due to gravity - g |g| - k 1.3804×10^–16 erg/°K=Boltzmann constant - Kn _L /r=Knudsen number of a particle - Kn _{0 0L} /r ₀=Knudsen number of a dry particle - m 4r ³/3=mass of a particle - m _L 4r ³ _L /3=mass of the moist air displaced by a particle - M mobility of a particle - M ₀ molar mass of dry air - M _w molar mass of water - Ma |u–u _L |/c _L =Mach number of the particles motion relative to the ambient air - n particle number per unit volume of air - P P ₀+P _w =pressure of the moist air - P ₀ partial pressure of the dry air - P _w partial pressure of the water vapour - P _we P _we (T,P)=equilibrium partial water vapour pressure over a plane surface of water saturated with air - Q surface parameter of a particle - r equivalent radius of a particle (radius of a sphere with the particles volume) - r ₀ equivalent radius of a particle in dry state - R 1+0.13Re ^0.85=inertia correction - R ₀ specific gas constant of dry air - R _w specific gas constant of water - Re 2r _L u–u _L / _L =Reynolds number of the particles motion relative to the ambient air - t time - T absolute temperature - u velocity of a particle - u (amount of the) settling velocity of a particle in stagnant air - u ₁ u(=1)=(amount of the) settling velocity of a spherical particle in stagnant air - u _L velocity of the ambient moist air (far enough from the particle where the flow pattern remains undistorted) - W drag coefficient of a particles equivalent sphere - empirical parameter in equation (3.1) - dynamic viscosity of a particles liquid cover - _L dynamic viscosity of moist air - _0L dynamic viscosity of dry air (at the same pressure and temperature like the moist air) - celsius temperature - dynamic shape factor of a particle (=1 for a sphere) - ₀ dynamic shape factor of a dry particle - _L mean free path of the molecules in moist air - _0L mean free path of the molecules in dry air (at the same pressure and temperature like the moist air) - _Po mean free path of the molecules in dry air at the pressureP ₀ of the dry air and the temperature given - factor of solid to liquid change-over (=1 for a solid particle) - mean bulk density of a particle - _L density of the moist air - _0L density of the dry air at the same pressure and temperature like the moist air - ₀ mean bulk density of a dry particle - ₀ mean diameter of the molecules of dry air - _w diameter of water molecules - relaxation time of a particle - gradient operation - 3.141593     

Water uptake and equilibrium sizes of aerosol particles at high relative humidities: Their dependence on the composition of the water-soluble material

Equilibrium water uptake and the sizes of atmospheric aerosol particles have for the first time been determined for high relative humidities, i.e., for humidities above 95 percent, as a function of the particles chemical composition. For that purpose a new treatment of the osmotic coefficient has been developed and experimentally confirmed. It is shown that the equilibrium water uptake and the equilibrium sizes of atmospheric aerosol particles at large relative humidities are significantly dependent on their chemical composition.List of symbols A proportionality factor - a _w activity of water in a solution - c _{p v} specific heat of water vapour at constant pressure - c _w specific heat of liquid water - f relative humidity - l _w specific heat of evaporation of water - M _i molar mass of solute speciesi - M _s mean molar mass of all the solute species in a solution - M _w molar mass of water - m ₀ mass of an aerosol particle in dry state - m _i mass of solute speciesi - m _s mass of solute - m _w mass of water taken up by an aerosol particle in equilibrium state - m total molality=number of mols of solute species in 1000 g of water - m _i molality of solute speciesi - m _k total molality of a pure electrolytek - O(m ²) remaining terms being of the second and of higher powers ofm - p ⁺ standard pressure - p total pressure of the gas phase - p pressure within a droplet - p ₁,p ₂,p ₃ coefficients in the expansion of M - p _1i, p_2i, p_3i specific parameters of ioni - p _s saturation vapour pressure - p _w water vapour pressure - R _w individual gas constant of water - r radius of a droplet - r ₀ equivalent volume radius of an aerosol particle in dry state - T temperature - T ₀ standard temperature - T ₁ temperature of the pure water drop in the osmometer - v _w specific volume of pure water - z _i valence of ioni - _i relativenumber concentration of ioni in a solution - correction term due to the adsorption of ions at liquid-solid interfaces - activity coefficient of solute speciesi in a solution, related to molalities - I bridge current - T temperature difference between solution and pure water drop in the osmometer - exponential mass increase coefficient - _w specific chemical potential of water vapour - _w specific chemical potential of water - ⁰ _w specific chemical potential of pure water vapour - ⁰ _w specific chemical potential of pure water - ₀ density of an aerosol particle in dry state - _w density of pure water - surface tension of a droplet - ₀ surface tension of pure water, i.e., at infinite dilution of the solute - osmotic coefficient - _k osmotic coefficient of a solution of a pure electrolytek - _k osmotic coefficient of a solution of a mixed solute - _M fugacity coefficient of water vapour - ^s _{i=1 i} z ² _i This work is part of a Ph.D. thesis carried out at the Meteorological Institute of the Johannes Gutenberg-Universität, Mainz.     

The equation of motion for a small aerosol in a continuum

Summary The motion of an aerosol can be described by a general force balance equation, independent of the detailed structure of the flow, provided that the interaction between the external flow field and the local flow induced by the aerosol is weak. A necessary and sufficient condition for the interaction to be weak is that the length scale of the aerosol is much less than that of the external flow. High and low Reynolds number regimes can be distinguished for the motion of an aerosol relative to the external flow. In some extreme conditions the equation of motion reduces to an algebraic equation for the aerosol velocity.After submission of this article the author was made aware of a similar treatment published inTopics of Appl. Phys., 12 (Turbulence, Chapter 7), Springer Verlag, Berlin, which at the time of the article's submission had not yet appeared in Australia. (Ed.)     

On the efficiency with which aerosol particles of radius less than 1 μm are collected by columnar ice crystals

A theoretical model is presented which allows computing the efficiency with which aerosol particles of 0.001 r1 m are collected by columnar ice crystals in air of various relative humidities, temperatures, and pressures. Particle capture due to Brownian diffusion, thermo- and diffusiophoresis is considered. It is shown that phoretic effects importantly determine the particle capture process of 0.01r1 m. The various pressure-temperature levels studied are found to affect the collection efficiency only ifr>0.1 m. Comparison shows that water drops generally are better aerosol particle scavengers than columnar ice crystals.     

On the efficiency with which aerosol particles of radius larger than 0.1 μm are collected by simple ice crystal plates

A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1r10 m are collected by simple ice crystal plates of radius 50a _c 640 m in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1r1 m. For aerosol particles ofr>1 m the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops.     

气溶胶对雷暴云电过程影响的数值模拟研究

本文在已有的三维雷暴云起、放电模式中加入了一种经典的气溶胶活化参数化方案,结合一次长春雷暴个例,进行了雷暴云起放电数值模拟试验.研究显示气溶胶浓度改变对雷暴云微物理、起电及放电过程都有重要影响.结果表明：（1）污染型雷暴云中气溶胶浓度增加时,云滴数目增多,上升风速加强;云中冰晶与霰粒子数浓度增加但尺度减小;（2）相对于清洁型雷暴云,污染型雷暴云非感应起电过程弱,感应起电过程强,起电持续时间长;（3）污染型雷暴云中首次放电时间延迟,闪电持续发生的时间长,总闪电频次增加,正地闪频次增加明显.

     

A theoretical model for change of shape of spring-water radon anomalies with epicentral distance

A model for radon anomalies before earthquakes, with a relatively fast increase in radon concentration at the beginning of the anomaly, is postulated. A calculation based on this model shows that a parameter can be deduced from the form of the radon anomalies, which depends on the epicentral distance of the measurement point. After adjustment of some parameters the model calculation is in good agreement with observed earthquake precursor anomalies.     

北京及周边气溶胶区域影响与大雾相关特征的研究进展

针对2011年12月初北京及华北持续近一周的严重大雾天气这一热点事件,从城市群大雾过程气溶胶区域影响的视角,基于"973"项目"北京及周边地区大气-水-土环境污染机理与调控原理"的研究工作,就北京及周边地区大雾天气与大气气溶胶区域影响的关系等方面进行了讨论.研究表明,北京城市大雾前低空SO2和NO2浓度存在"积聚"与"突增"现象.北京及周边地区冬季雾日数和气溶胶光学厚度则呈正相关,并具有"同位相"的年际变化趋势.研究同时发现北京及其南部周边的冬季气溶胶高值区呈南北向带状分布,其与北京周边居民户数高值区有所吻合,反映了冬季北京城市气溶胶颗粒物的远距离影响源区及大尺度输送效应.统计分析指出,冬季北京气溶胶颗粒物PM10、PM2.5主要影响成分是SO2和NOX,且有关研究也表明,电厂、采暖和工业面源是SO2的三大本地排放源,而机动车、电厂、工业为NOX的三大本地排放源,上述大气PM10、PM2.5主成分污染源亦与雾水样本化学分析结果相吻合,即冬季由于燃煤在生活能源中的比例较大,北京雾水中硫元素和碳元素的含量都较高.因此,北京冬季大雾不仅与北京城区气溶胶及其污染排放影响存在相关关系,而且与北京周边天津、河北、山东等地气溶胶及大气污染物的远距离输送和气溶胶区域影响效应有着重要的联系.因此,北京雾霾天气及相关大气污染的治理工作首先要着眼于局地污染物的减排,但同时如何做好区域大气污染的协同治理也是不容忽视的问题.     

Geophysical radar for the observation of ionized clouds in the atmosphere above the earthquake preparation region

The authors propose to use a modified geophysical radiolocator for the detection and investigation of local quasi-plasma anomalies in the atmosphere. This radiolocator should control the large region of the atmosphere, filled with scattering objects, connected with the precipitation of radioactive substances. Such phenomena could arise in connection with earthquakes and could also be caused by technogenic origins. Contrary to standard radar, the noise of scattering objects is the aim of the analysis of geophysical radar. The discussion of technical characteristics of such radar is presented.     

ENSO对平流层气溶胶分布的影响

本文采用ONI(Oceanic Nino Index)和HALOE(Halogen Occultation Experiment)气溶胶面积密度资料,从其滞后相关性入手分析了ENSO循环对平流层气溶胶的影响,通过对滞后于El Nino和La Nina时气溶胶含量的比较探讨了ENSO强迫的影响程度,并用剩余环流及其输送量解释了平流层气溶胶变化的动力机制.结果表明:ENSO对平流层气溶胶的分布有明显影响,在赤道和低纬度上空尤为显著,El Nino发生后半年内热带平流层低层的气溶胶面积密度较平均值偏大,平流层中层的面积密度则偏小,而La Nina反之.El Nino和La Nina影响的差异显著,在分别滞后于El Nino和La Nina事件2~8个月间的60 hPa气溶胶含量差异甚至高达45%,海表温度变化1 K则在滞后半年内气溶胶面积密度的变化可达到16%.ENSO的强烈影响能够维持大约半年,两年后基本消退.热带的变化幅度明显强于中高纬度,南北半球的变化特征也有所不同.ENSO通过影响剩余环流导致气溶胶输送量发生变化,进而引起气溶胶分布出现上述差异.     

Variation of dispersion of radon content in the groundwater and short-term and imminent precursors of earthquakes

A lot of observational data both at home and abroad suggested that before some strong earthquakes anomalous variations of radon concentration appear in the chemical composition of groundwater. In order to further study these anomalies and get reliable precursory anomalies, a special packet of precursory data processing has been developed recently. By using a computer program of first-order difference method, it is discovered that the scatter of radon content increased systematically before earthquakes at some observation posts where observational conditions are fairly good. This change may be a new criterion for evaluating short-term and imminent earthquake precursors.     

Impulsive radon emanation on a creeping segment of the San Andreas fault,California

Radon emanation was continuously monitored for several months at two locations along a creeping segment of the San Andreas fault in central California. The recorded emanations showed several impulsive increases that lasted as much as five hours with amplitudes considerably larger than meteorologically induced diurnal variations. Some of the radon increases were accompanied or followed by earthquakes or fault-creep events. They were possibly the result of some sudden outbursts of relatively radon-rich ground gas, sometimes triggered by crustal deformation or vibration.     

Effect of synoptic meteorological conditions on aerosol properties over urban environment: A study over tropical urban region of Hyderabad,India

Aerosol particle size distribution and chemical properties are important in studies related to human health and climate. The present study describes an analysis of aerosol mass loading, Aerosol Optical Depth (AOD), black carbon aerosol mass concentration and carbon monoxide over tropical urban region of Hyderabad, India, during March 2006, coinciding with active forest fires season over India. Aerosol optical depth, particulate matter mass loading and carbon monoxide were observed to be high on days with air mass coming from north of the study area. Spatial occurrence of forest fires was analysed using MODIS daytime data and DMSP-OLS nighttime data sets. Aerosol optical depth measured using Microtops-II sunphotometer correlated well with MODIS derived AOD values. Results of the study suggested that synoptic meteorological conditions play an important role in the observed aerosol properties over the study area during the forest fire season.     

煤田陷落柱氡气场的数值计算及空间形态分布特征

根据流体场的扩散理论和对流理论,建立了扩散系数与对 流速度为常量或变量情况下的氡气场三维状态方程;对于陷落柱柱体侧面有源氡气场和柱体 体内有源氡气场两种理论模型,给出了不同系数和边界条件下的数值解的形式. 针对模型的 特点及其边界条件用差分法分别进行了数值计算,结果表明陷落柱氡气场的空间形态 分布特征. 野外实测和模型试验的结果相互吻合.     

An application of Mie's series to soft particles

Summary The scattering of electromagnetic radiation from soft particles has been studied by a new method which allows to transform the Mie series into a simplified form through the use of some auxiliary expansions derived in the Appendix of this article. This simplified form (eq. 1) converts into the Hulst and Rayleigh-Debye-Gans' formulae if the parameters of eq. I are properly restricted. A further simplified form (eq. II), improves the well-known Hulst approximation.     

Results of the studies of monsoon circulation with radon as a tracer

Radon-222 activity levels have been measured at deck level in regions of the Arabian Sea, Indian Ocean, and Bay of Bengal during the summer monsoon periods of 1973, 1977, and 1979, as part of the Monex programme. The aim of the measurements was to find the source regions of the monsoon air and the variations in its composition under different synoptic conditions. The radon data confirm that the monsoon air is predominantly of southern-hemisphere origin, with a small continental component. The continental component, as indicated by radon values, increases at higher latitudes and seems to vary with different circulation patterns in the synoptic scale. The use of radon as a tracer in monsoon studies is thus demonstrated.     

考虑电子吸附效应的低电离层加热研究

基于低电离层自洽加热模型,综合考虑了低电离层中电子的复合效应及典型吸附效应,本文数值仿真了大功率高频无线电波持续加热低电离层所产生的电子温度、电子密度的扰动,并且首次模拟分析了由于电子温度扰动造成的加热电波自吸收效应.结果表明：电子吸收大功率加热电波能量导致了电子温度的增加,同时改变了电离层的吸收指数,引起了加热电波的自吸收效应.加热电波的自吸收效应对低电离层较高区域的电子温度扰动有重要的抑制作用.因此,随着加热频率的减小或有效辐射功率的增大,低电离层较低区域的电子温度增量明显增大而在高度100 km以上区域的电子温度增量始终较小.另一方面,随着电子温度的增加,电子的复合系数减小而电子的吸附系数增加,导致了电子密度在低电离层中较高区域出现正扰动而在较低区域出现负扰动.当饱和电子温度较大时,继续减小加热频率或增大有效辐射功率对电子密度扰动所造成的改变较小,尤其当电子温度超出复合系数和吸附系数的温度敏感区间.此外,电子温度与电子密度的饱和时间相差较大,电子温度的饱和时间为微秒量级而电子密度的饱和时间为秒量级.