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Christian E. Junge

Abstract

A total of seven vertical profiles of Aitken nuclei in the upper troposphere and stratosphere are discussed. Average values are presented and compared with tropospheric data by other authors. The main features of the vertical profiles are explained by processes of washout, coagulation and eddy diffusion.

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Christian E. Junge

The field of atmospheric chemistry, which is defined as the chemistry of trace substances in the troposphere, is reviewed. Trace substances can be present as aerosols or as gases. Major sources of aerosols are the ocean and industrial activities. The chemical composition of the aerosol particles is not only determined by their source but also by various processes in the atmosphere—notably, reactions with gas traces.

Only little is known about trace gases like SO2, H2S, NH3 or NO2. Of special importance for meteorology is CO2 and its long-term fluctuations. The facts and possible reasons for its 10 per cent increase during this century are discussed.

The last part of the discussion is concerned with the physical processes by which the trace substances are removed from the atmosphere, primarily the role of precipitation.

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Christian E. Junge

Abstract

New data concerning the chemical composition of atmospheric aerosol particles in two radial size-ranges, 0.08 < r < 0.8 µ and 0.8 < r < 8 µ, were obtained during a four-week period on the Atlantic coast. The samples were analyzed for the five components, Na+, Cl, SO4 −−, NH4 +, NO3 , and later also for NO2 , ClO3 and Mg++. The large particles, with 0.08 < r < 0.8 µ, consisted nearly entirely of sulfate and ammonia, as was found in previous investigations in central Europe. Besides these substances, the giant particles, with 0.8 < r < 8 µ, contained variable, though sometimes considerable, amounts of nitrate and sodium chloride. Up to wind speeds of at least Beaufort 5, the production of sea-salt particles seems thus to be limited to radii above 0.8 µ. The components NO2 , ClO3 and Mg++ were not found to be present above the limit of detection.

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Peter Winkler and Christian E. Junge

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Charles W. Chagnon and Christian E. Junge

Abstract

An aircraft-borne impactor-filter system for the collection of tropospheric aerosols of natural and fission-product origin is described. The system has been used in studies of the size distribution of atmospheric particles as a function of altitude within the troposphere. Preliminary results indicate a size distribution in mid-troposphere as being intermediate between ground level and lower stratosphere and support the possibility that high level particles undergo a change in size on their descent through the atmosphere.

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Charles W. Chagnon and Christian E. Junge

Abstract

The vertical distribution of stratospheric particles with an average radius of 0.15 micron is presented in the form of five vertical profiles. These show a broad maximum in numerical concentration between 15 and 23 km, and are remarkably consistent throughout the one-year period of observations from November, 1959 to October, 1960. It is suggested that this “aerosol layer” is identical to the particles responsible for the “purple light” phenomenon, and the haze layers observed in the stratosphere. Some pertinent details of the balloon-borne collection instruments are included.

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Christian E. Junge and R. T. Werby

Abstract

The distribution of yearly averages of the concentration of various inorganic ions in rain water over the United States is discussed. The major source of Clis the ocean. The Cl/Na+ ratio, however, is considerably less than that in sea water. It is very likely that this is caused by excess Na+ from the soil. A similar distribution of excess material from the soil is observed with K+. In contrast to Na&plus: and K+, which are rather uniformly distributed over the United States, Ca+ shows highest values over the Southwest, in agreement with the occurrence of dust storms.

Most of the SO4 over the ocean originates from sea spray. The source of additional SO4 is the land. Budget considerations indicate that about 30 per cent of this additional SO4 on a global scale is due to human activities.

On the basis of the data presented, the average global residence time of SO2 is estimated to be 40 days. This value is compared with available data on residence times of other constituents which are also primarily controlled by washout.

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Christian E. Junge, Charles W. Chagnon, and James E. Manson

Abstract

A first report is presented on a comprehensive study of stratospheric aerosols up to 30 km altitude. Information was obtained on the vertical profiles as a function of particle size, on the size distribution of these particles and on their physical structure and chemical composition.

Vertical concentration profiles are first considered theoretically on the basis of equilibria between eddy diffusion, sedimentation, subsidence and coagulation. The results are compared with two sets of data: (1) vertical profiles obtained with a recording Aitken nuclei counter which measures the size range of 0.01 to 0.1 microns radius and (2) vertical profiles obtained with impactors over the size range of 0.1 to 1.0 microns radius. The first of these indicates a decrease in concentration from the tropopause to nearly zero at 20 km, whereas the second shows a maximum at about 20 km.

The size distributions of these particles were found to be quite constant with time. There is a maximum between 0.01 and 0.1 μ radius, the concentration varying inversely with the square of the radius between 0.1 and 1.0 μ. Very few data could be obtained for particles larger than 1.0 μ because of the low concentration. Large fluctuations seem to be indicated for this size range.

The particles between 0.1 and 1.0 μ were collected in sufficient concentration to permit detailed investigation. They were found to be very hygroscopic and, by electron microprobe analysis, were found to contain sulfur as a major constituent, with traces of iron and silicon.

From these observations, it is tentatively concluded that there are three major populations of particles present in the stratosphere. Those smaller than 0.1 μ are of tropospheric origin. Those between 0.1 and 1.0 μ are most likely formed within the stratosphere, possibly by oxidation of SO2 and H2S gas traces. Fall speed considerations make it very likely that the majority of particles larger than one micron are of extra-terrestrial origin.

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