An ionometric counter for condensation nuclei

Summary Condensation nuclei detectable in the range of supersaturation used in the expansion method do not play the role expected earlier, for the production of water droplets in natural clouds.However, these nuclei exist in the atmosphere, and they can be of importance in other processes in the air; for example, they can be partners for annihilation of small air ions there. Therefore, a direct investigation of the interaction between the condensation nuclei and the small air ions may be of interest. For this purpose an, ionometric counter for condensation nuclei is designed, in which the air under examination is mixed in a mixing chamber with small air ions produced by a tritium ion-generator, and the presence of condensation nuclei is measured by the decrease of the concentration of air ions recorded with an aspiration ion counter as compared to the concentration recorded when filtered air was originally sucked through the mixing chamber.Comparatively rapid variations of the concentration of nuclei can be continuously recorded. The electrical properties of the aerosol particles destroying air ions can be investigated by inserting an electrical filter. By the ionometric counter condensation nuclei can be investigated without adding water particles to them.     

Role of condensation nuclei as carriers of radioactive particles

Summary The effect on the deposition of thoron and radon decay products of attachment to condensation nuclei is described. Methods are suggested of using these decay products as markers for condensation nuclei and comparison is made between radioactive and non radioactive determinations of the diffusion coefficients of marked nuclei. The spontaneous production of condensation nuclei by irradiation of clean air by alpha and beta particles and by X-rays is described.     

Influence of sunlight on atmospheric condensation nuclei

I has been shown that irradiation of air by sun-rays leads to a formation of atmospheric condensation nuclei, as measured with the automatic nucleus counter (1).To control the influence of the material, experiments were done in a gasometer where a rubber balloon was built in, also in a metal container covered either with uviol glass or window glass, or with air in a polyethylene balloon. The same influence of sunrays was observed in each case.Similar experiments were then done with compressed air from a metal container, or with oxygen gas, nitrogen gas or nitrous oxide all from metal containers. In all cases sun-rays produced condensation nuclei; the effect was present both at 1800 m and at 270 m altitude. Diffuse sunlight with high clouds also had an effect. Infra-red radiation and mechanical shaking were without result, but ultraviolet rays from a quartz-mercury lamp increased the nucleus count of the balloon whether it contained air or one of the above-mentioned gases.As yet it has not been possible to decide the mechanism of formation of these nuclei and what their meteorological and biological role might be.The detailed paper will appear later in «Geofisica pura e applicata».     

Towards the production of a reproducible aerosol by radiolytic methods

Summary A convenient constant reproducible aerosol has been a long-felt need for satisfactory research and development purposes in the field of Aitken nucleus studies. An account is given of a recent attempt to produce such an aerosol by radiolytic methods. It consists of the introduction of -particle sources of different activities into nucleus-free air in aerosol containers. Condensation nuclei in the Aitken size-range are produced by radiolytic reactions in the air. The concentration, size and size-distribution of the particles have been measured for sources of various activities and the results are sufficiently consistent to allow us to state that radiolytic production seems a promising approach to the problem of providing aerosols of particles lying in the lower Aitken nucleus size range.     

Variations in atmospheric transparency under the action of galactic cosmic rays as a possible cause of their effect on the formation of cloudiness

The possible mechanism by which cosmic rays affect the formation of neutral water droplets and ice crystals in the Earth’s atmosphere has been considered. This mechanism is based on changes in atmospheric transparency and vertical temperature distribution. It has been indicated that a change in the optical thickness for visible and IR radiation by several percents, which can take place when cosmic-ray particles penetrate into the atmosphere, results in a change in the temperature vertical distribution, affecting the growth of water droplets, concentration of active condensation nuclei, and the formation of ice particles. This mechanism makes it possible to explain the correlation between the intensity of galactic cosmic rays at low altitudes and the absence of this correlation at middle altitudes.     

Some airborne observations of condensation nucleus concentration

Summary The measurement of condensation nucleus concentration from an aircraft is considered and preliminary observations made with a photo-electric condensation nucleus counter discussed. It is concluded that at heights up to 6000 ft concentrations of condensation nuclei vary, from 200 cm^–3 in clean maritime air to 5 × 10³ cm^–3 generally over large industrial areas and 35 × 10³ cm^–3 downwind of specific industrial sources. It appears that sea spray makes a contribution to the nucleus population.Mr. G. J.Day, B. Sc., Meteorological Research Flight, Royal Aircraft Establishment,Farnborough, Hants. (Great Britain).     

Bildung von Kondensationskernen durch UV-Strahlung in verschiedenen Gasen

Zusammenfassung Die Erzeugung von Kondensationskernen durch UV-Licht wurde mittels eines automatischenPollakschen Kernzählers und einerWilsonkammer aus Glas untersucht. Da die UV-Kerne von einem Schwebstoffilter zurückgehalten werden, ließ sich durch Verwendung zweier Bestrahlungsgefäße mit dazwischengeschaltetem Filter die Spurengashypothese bestätigen. Bestrahlungsversuche in Luft, Stickstoff, Sauerstoff, Argon und Wasserstoff ergaben, daß durch längere Bestrahlung eines abgeschlossenen Gasvolumens die kernbildende Substanz allmählich verbraucht wird. Durch Zugabe definierter Mengen gasförmigen Ammoniaks in den Bestrahlungsraum zeigte sich, daß die von verschiedenen Autoren geäußerte Ansicht, gasförmiges Ammoniak sei die kernbildende Substanz, nicht haltbar ist. Die Untersuchung des Einflusses von Schwefelwasserstoff bzw. Schwefeldioxyd ergab, daß die atmosphärische Konzentration von H₂S zur Erklärung des UV-Effektes nicht ausreicht, während dies bei SO₂ der Fall ist. Das Ergebnis, daß SO₂ maßgebend an der Bildung der UV-Kerne in atmosphärischer Luft beteiligt ist, wird dadurch gestützt, daß der UV-Effekt einen ähnlichen Tagesgang zeigt wie das atmosphärische SO₂.

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Summary The production of condensation nuclei by UV light was investigated by means of an automaticPollak nucleus counter and aWilson glass-chamber. As the UV nuclei can be removed by an aerosol filter, the trace gas hypothesis could be confirmed by using two irradiation tubes separated by an aerosol filter. Irradiation experiments in air, nitrogen, oxygen, argon and hydrogen in a closed volume had the result that the nucleogenic substance gradually disappears after sufficiently long irradiation. By adding definite quantities of ammonia vapour into the irradiation tube it could be shown that ammonia is not the nucleogenic substance, as was supposed by some authors. The investigation of the influence of sulphur dioxide and hydrogen sulfide showed that the atmospheric concentration of H₂S is not sufficient to explain the UV effect in atmospheric air, whereas this is true with SO₂. The result that SO₂ takes part in the formation of the UV nuclei is supported by the fact that SO₂ and the UV effect show a similar diurnal variation.

     

The approach to charge equilibrium in a stored aerosol during aging

Summary The approach during natural aging to charge equilibrium of an aerosol produced and stored in a polyester «Mylar» balloon gasometer with metallized internal surface and 4200 litres content is studied. The number of charged condensation nuclei at any instant is related to the number of charged nuclei present at the same moment in electrical equilibrium produced by alpha-irradiation of the aerosol.It is shown that a stored aerosol consisting of small nuclei of moderate concentration is not later than 15 minutes after their birth in electrical equilibrium. With increasing size and concentration of the nuclei it takes longer and longer until the stored aerosol attains charge equilibrium. Stored large nuclei appear not to reach exact charge equilibrium even after several days.The reasons for replacing the rubber balloon gasometer, used previously, by the Mylar balloon for this investigation are given.In connection with the ionizing radiation required for producing charge equilibrium, the generation of condensation nuclei by alpha-radiation in stagnant and moving nucleus-free air has been investigated. It has been found that no condensation nuclei are being produced in filtered (nucleus-free) air for air-flows of between 0.1 and 20 litres/min in a tube of 4.2 cm diameter by the alpha-rays of Polonium 210 of about 125 c.

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Zusammenfassung Es wurde die während natürlicher Alterung stattfindende Annäherung an das elektrische Gleichgewicht eines Aerosols, welches in einem «Mylar» Ballon-Gasometer aus Polyester mit metallisierter Innenfläche und von 4200 Litern Inhalt erzeugt und gespeichert wurde, studiert. Die in jedem Augenblick vorhandene Anzahl der geladenen Kondensationskerne wurde zu der Zahl der geladenen Kerne im elektrischen Gleichgewicht für den gleichen Moment in Beziehung gesetzt, welches durch Bestrahlung des Aerosols mit Alpha-Teilchen erzeugt wurde.Es wird gezeigt, dass ein gespeichertes Aerosol, welches aus kleinen Kernen von mässiger Konzentration besteht, nicht später als 15 Minuten nach der Geburt der Teilchen im elektrischen Gleichgewicht ist. Mit zunehmender Grösse und Konzentration der Kerne dauert es länger und länger bis das gespeicherte Aerosol sein Gleichgewicht erreicht. Gespeicherte grosse Kerne scheinen selbst nach mehreren Tagen nicht das volle Gleichgewicht zu erreichen.Die Gründe für die Einführung des Mylar Ballons statt des früher benützten Gummiballons werden gegeben.In Zusammenhang mit der radioaktiven Bestrahlung, welche für die Erzeugung des Ladungsgleichgewichtes gebraucht wird, wurde die Produktion von Kondensationskernen durch Alpha-Teilchen in stagnierender und bewegter kernfreier Luft untersucht. Es wurde festgestellt, dass keine Kondensationskerne erzeugt werden, wenn kernfreie Luft, welche sich mit 0.1 bis 20 Litern per Minute durch ein Rohrsystem mit 4.2 cm Durchmesser bewegt, von Polonium 210 mit 125 c bestrahlt wird.

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The research reported in this article has been supported in part by the Geophysics Research Directorate of the Air Force Cambridge Research Laboratories, through the European Office of the Air Research Division, United States Air Force under Contract AF 61 (052)-26 and by the Instrumentation Engineering Physics & Analysis Laboratory of the General Electric Co., Schenectady, New York under Retainer Agreement.     

Vertical profiles of condensation nuclei in the stratosphere

An automatic condensation nuclei counter was developed for the concentration range of about 1 to 400 particles per cubic centimeter. After expansion, the water droplets are photographed when they are still suspended in the air so that the counter can be considered an absolute one. The volume in which the droplets are counted is determined by the size of the picture of the droplets as a function of their distance from the focal plane. To eliminate any effect of decreasing pressure with altitude, the cloud chamber is filled with clean air prior to expansion to about half an atmosphere above ambient pressure. This counter was used to obtain vertical profiles of condensation nuclei up to altitudes of 27 km with high altitude balloons. A total of seven profiles was obtained over a period of about one year at 47° N over the United States. Because of the restrictions in the range of the meter no data could be obtained below 5 km. The profiles show the following main features:

1. 1.
   Although there are pronounced fluctuations in the individual flights the average nuclei concentration of 200 to 300/cm³ remains fairly constant from 5 km to the tropopause.     
   
   

Electron-microscope study of snow crystal nuclei: II

Summary Experimental work was conducted in an igloo, half way up Mt. Taisetsu (1050 m), Mt. Tokachi (1030 m) and Mt. Okuteine (820 m) in Hokkaido. One solid nucleus (center nucleus) was observed almost always in the central portion of a snow crystal. From their electron micro-diffraction patterns, the materials of the nuclei were classified into three kinds; a single crystal, polycrystalline or amorphous substances. The patterns of the single crystal gave a hexagonal cross grating, the atomic arrangement in their basal plane had some similarity to that of an ice crystal. Some polycrystalline center nuclei were small sea salt, particles. Their shape was similar to that of the nuclei of sea sprays, and their patterns coincide with that of the sea salt. Some amorphous center nuclei were observed which looked like a liquid droplet under the operating condition of the electron-microscope. It seemed that they are chemical components in the sea salt such as KCl or MgCl particles.In the other parts of snow crystal, many smaller nuclei (condensation nuclei) were observed. These nuclei are also aerosols in the atmosphere; their size was 0.10.01 in diameter. They gave the Debye-Scherrer ring; their patterns were different in each specimen. Their materials consist of various substances. From these data, the origin of nuclei and the mode of action of center nucleus were discussed.     

Sur les aérosols intéressants la Météorologie

Summary The lecture is a critical survey of the studies regarding the particles in suspension in atmospheric air and which interest in the phenomenon of water vapor condensation and generally in cloud formation and in the ensuing precipitation.A part of the lecture is devoted to the manifold technics of study introduced, above all, in the last decade, in addition to the method ofAitken counting gear. It dwells particularly on the use of Millipore filter used byLodge and his collaborators for the gathering of the condensation nuclei and of the successive chemical analysis with specific reagents to make evident the nature of the nuclei.The review ends underlining the necessity that the measures of the atmospheric aerosol may be systematically carried on by the synoptical meteorological observatories and the necessity that the experiments in this field may be made with a more and more increasing care and critical mind.     

Charged meteoric particles as ice nuclei in the mesosphere: Part 2: A feasibility study

Recondensed meteoric material, so-called meteoric smoke, has long been considered the main candidate for condensation nuclei for mesospheric ice formation. Recently however, model studies have shown that meteoric smoke particles are transported away from the polar region, where ice phenomena such as noctilucent clouds occur, before they can grow large enough to serve as ice condensation nuclei. In the accompanying paper it is argued that charging of the meteoric smoke particles may solve this dilemma by significantly altering the efficiency of the particles as condensation nuclei. In the present paper, the feasibility of this idea is investigated more quantitatively, by analysing the time scales of processes such as charging, recombination, and particle growth. Despite large uncertainties, especially in the charging efficiency of the smallest smoke particles, we show that reasonable assumptions yield number densities of charged condensation nuclei that are consistent with what is expected for mesospheric ice phenomena.     

Condensation of water vapor and carbon dioxide in the jet exhausts of rocket engines: 1. Heterogeneous condensation of combustion products

Condensation of water vapor and carbon dioxide in the jet exhausts of rocket engines during last stages of Proton, Molniya, and Start launchers operating in the upper atmospheric with different types of fuels is considered. Particle heating is taken into account with emission of latent heat of condensation and energy loss due to radiation and heat exchange with combustion products. Using the solution of the heat balance and condensed particle mass equations, the temporal change in the temperature and thickness of the condensate layer is obtained. Practically, no condensation of water vapor and carbon dioxide in the jet exhaust of a Start launcher occurs. In plumes of Proton and Molniya launchers, the condensation of water vapor and carbon dioxide can start at distances of 120–170 m and 450–650 m from the engine nozzle, respectively. In the course of condensation, the thickness of the “water” layer on particles can exceed 100 Å, and the thickness of carbon dioxide can exceed 60 Å.     

On the condensation nuclei about the time of sunrise

Summary Some marked variations of the content of condensation nuclei in the air deserve to be considered individually. it is shown that by simultaneous measurements of phenomena other condensation nuclei, especially atmospheric electrical, a more complete insight into all the processes involved could be obtained, when investigating the condensation nuclei during the time about sunrise.

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Zusammenfassung Einzelne ausgeprägte Variationen des Gehaltes an Kondensantionskernen in der Luft verdienen individuell behandelt zu werden. Es wird gezeigt, dass mit gleichzeitig ausgeführten Messungen anderer, besonders luftelektrischer Erscheinungen, neben jenen der Kondensationskerne eine vollständigere Einsicht in alle in Betracht kommenden Prozesse erhalten wird, wenn die Kondensationskerne vor und nach dem Sonnenaufgang untersucht werden.

     

A new aspect of condensation theory

This paper examines the effects of the mixing of dry air into a cloud top from the point of view of the droplet spectra. It is shown theoretically that the resulting cycling of the air up and down in the cloud, as seems to be the essential mechanism by which cumuli have been diluted to their observed liquid water mixing ratio, can double the largest drop radius and generate cloud parcels containing drops of all sizes up to this maximum. These changes in the droplet distribution with size occur by a process which is not greatly influenced by the cloud condensation nuclei or the details of droplet growth since maritime like spectra can develop in continental type cumuli. It shows that large numbers of cloud condensation nuclei should not have much effect in inhibiting the rainforming process by reducing coalescence growth. On the contrary, the controlling parameters which determine precipitation efficiency and times seem to be those which control the mixing.     

Die Bedeutung der Kondensationskerne in der hygienischen Forschung

Zusammenfassung Eine erschöpfende Beurteilung des Verunreinigungsgrades der Luft ist nur auf Grund von Registrierungen der wichtigsten gasförmigen und korpuskulärne Beimengungen möglich. Eine grobe Aussage wird in vielen Fällen bereits auf Grund gleichzeitiger Messungen des Kern- und Staubgehalts der Luft gemacht werden können.Eine Aussage über die schädigende bzw. belästigende Wirkung einer Luftheimengung nur auf Grund einer Kernzahlbestimmung, wird nur in wenigen besonderen Fällen möglich sein. Als Beispiel sei angeführt, daß bei der Verunreinigung der Luft mit Tabakrauch die Kernzahl ein grobes Maß für den Nikotingehalt und die Kernzahl in Verbindung mit der Staubzahl ein Maß für den Gehalt der Luft an Tabakteeren darstellt.Auf Grund eigener Untersuchungen und den bisher in der Literatur veröffentlichten Meßergebnissen werden maximale Mittelwerte für den Kern- und Staubgehalt der Luft für verschiedene Orte angegeben. Somit wird es den Gesundheitsämtern möglich sein, durch einfache Kern- und Staubmessungen den geforderten Reinheitsgrad der Luft zu kontrollieren. Eine Vorraussetzung hierfür ist die Schaffung einheitlicher, leicht transportabler und einfach zu bedienender Meßgeräte.

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Summary An exhaustive assessment of the degree of contamination of the air is possible only from records of its most important gaseous and corpuscular admixtures. A rough assessment will be possible in many cases by using simultaneous measurements of the nuclei and dust content of the air.A statement on the injurious or annoying effect of an air admixture based only on the determination of the number of nuclei will be possible only in few special cases. As an example may be mentioned that with the contamination of the air due to tobacco smoke the number of nuclei represents a rough measure of the nicotine content and the number of nuclei together with the number of dust particles is a measure of the content of the tobaceo tars in the air.Based on personal investigations and on the results of measurements so far published highest averages of the nucleus and dust content of the air for various places are given. Thus, it will be possible for the health authorities by means of simple measurements of nuclei and dust concentration to check the prescribed purity of the air. A condition for this is the design of uniform measuring instruments which are very portable and simple to operate.

     

The vertical distribution of condensation nuclei near the ground

Summary Measurements have been made of the concentration of condensation nuclei, Z, at four heights between the ground and 300 cms in country air close to Cambridge. When the results are averaged over sufficiently long periods a systematic variation of Z with height is found and this variation itself has a diurnal variation. The results imply the production of nuclei in the atmosphere in this region. With the aid of simplifying assumptions, estimates of the rate of production are made for various periods of the day and night.     

Measurements of the effective attachment coefficient between RaA ions and condensation nuclei

Summary To clarify the interaction between RaA ions and condensation nuclei, simultaneous measurements of the concentration of RaA ions (n _A), radon-222, and condensation nuclei (Z) were carried out at several stations. In some occasions, the diffusion coefficients of nuclei (D) were also measured. It was found that the correlation among them may be well expressed by the simple formula;q _A = _A n_A Z. The correlation between _A andD (or radius of nuclei) was also obtained.The effective attachment coefficient of RaA ions was compared with that of small ordinary ions, and it was presumed that about one fourth of RaA atoms formed on the decay of radon-222 is positively charged, and the rest is neutral.     

Le teneur de l'air en petits et gros ions radioactifs

Résumé En assimilant à des petits ions les atomes RaA provenant de la désintégration du Radon présent dans l'air, on évalue par le calcul la fraction de ces particules fixées sur les poussières et les noyaux de condensation, ainsi que leur durée de fixation.Pour vérifier ces considérations, on compte les petits et gros ions radioactifs par la méthode deZeleny, en maintenant l'électrode axiale des tubes sous tension négative, les autres particules sont fixées par captation électrostatique ou avec un filtre papier et les activités des différents échantillons sont étudiées par comptage . On trouve une concentration de l'air en petits ions RaA de 1.5·10^–4 atome par cm³. Connaissant la teneur de l'air en Radon, et en admettant que l'équilibre radioactif est atteint entre le Radon et le Radium A qui en provient, on obtient par différence les concentrations de RaA fixée sur les autres particules.

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Summary The proportion and free life time of RaA atoms arising from the radioactivity of atmospheric radon, and catched by dust particles, large ions and condensation nuclei, is evaluated, with assumption that these atoms are identical to the ordinary small ions.Experimental verification of the calculation are made by catching small and large ions withZeleny tubes, axial electrode being negatively charged. Other particles being catched with electrical precipitation and filter paper, activities of different samples are measured by counting. 1.5·10^–4 per cm³ small ions RaA concentration is found. Knowing the air radon value concentration, and with the assumption of radioactive equilibrium only between radon and RaA in free air, it is possible to evaluate the concentration of RaA catched by other particles.

     

On the effect of emissions from aircraft engines on the state of the atmosphere

Emissions from aircraft engines include carbon dioxide, water vapour, nitrogen oxides, sulphur components and various other gases and particles. Such emissions from high-flying global civil subsonic air traffic may cause anthropogenic climate changes by an increase of ozone and cloudiness in the upper troposphere, and by an enhanced greenhouse effect. The absolute emissions by air traffic are small (a few percent of the total) compared to surface emissions. However, the greenhouse effect of emitted water and of nitrogen oxides at cruise altitude is potentially large compared to that of the same emissions near the earth’s surface because of relatively large residence times at flight altitudes, low background concentrations, low temperature, and large radiative efficiency. Model computations indicate that emission of nitrogen oxides has doubled the background concentration in the upper troposphere between 40○N and 60○N. Models also indicate that this causes an increase of ozone by about 5-20%. Regionally, the observed annual mean change in cloudiness is 0.4%. It is estimated that the resultant greenhouse effect of changes in ozone and thin cirrus cloud cover causes a climatic surface temperature change of 0.01-0.1 K. These temperature changes are small compared to the natural variability. Recent research indicates that the emissions at cruise altitude may increase the amount of stratospheric aerosols and polar stratospheric clouds and thereby have an impact on the atmospheric environment. Air traffic is increasing about 5-6% per year, fuel consumption by about 3%, hence the effects of the related emissions are expected to grow. This paper surveys the state of knowledge and describes several results from recent and ongoing research.