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G. Langer

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G. Langer

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A detailed examination was made of the variables affecting the operation of the National Center for Atmospheric Research (NCAR) ice nucleus counter. The design criteria for proper flow control to achieve consistent cloud formation were established. The loss of ice crystals by settling to the bottom of the cloud chamber instead of exiting to the ice crystal counter was found to be constant. The most important variable is the concentration of the cloud condensation nuclei added to the sample stream to control cloud supersaturation. The rate of activation for AgI can be increased considerably by increasing the super-saturation by the new method of combining the AgI particles with NaCl particles serving as low supersaturation condensation centers. This also gives a much faster nucleation rate of potential importance in cloud seeding. The response of kaolin and phloroglucinol under varying supersaturation was found to be in agreement with previous studies, the former being responsive to high and the latter to low supersaturation for activation. The counter provided normal temperature spectra for AgI and compared well to the Colorado State University (CSU) isothermal chamber.

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G. Langer

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The Second International Workshop on Condensation and Ice Nuclei, held at Ft. Collins, Colo., in 1970, provided approximately 10,000 measurements by ice nucleus counters of natural and artificial aerosols, with the counters operating under well-defined conditions. Relevant data on nucleus aerosol size and concentration, and the properties of related condensation nuclei were provided. A first review of the data showed a number of serious discrepancies between the various instruments. This paper gives a detailed analysis of data from ten instruments and makes clear the origin of the discrepancies, which are related to the degree of supersaturation and its relationship to the concentration of condensation nuclei during cloud formation. Different instruments respond differently to these variables but the present results make it evident that meaningful results can be obtained with the counters now available.

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B. G. Mendonca and Gerhard Langer

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G. Cooper, G. Langer, and J. Rosinski

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Aluminized Mylar bags are used by many researchers to store aerosol samples for later analysis. Our results show that the rate of deposition of unipolar unit-charged aerosols to the walls can be extremely high and is unpredictable for different bags that by inspection appear to be in identical condition. Filling losses and the rate of decay of monodispersed unit-charged aerosols smaller than 0.2 μm in aluminized Mylar bags were shown to be strongly dependent on the electrostatic charges existing on the bags' surfaces despite the aluminum coating; for monodispersed charge-equilibrated aerosols the rate of deposition was much lower. Application of antistatic agents to the bags' interior or exterior surfaces increased the lifetimes of aerosols stored within. But the application of the antistatic agent tested did not completely neutralize the charges residing on the surfaces of the bags. A paper bag with an interior aluminum foil coating was shown to be far superior to the aluminized Mylar bag in handling convenience and for aerosol storage. A method for estimating aerosol deposition rate limits in the absence of electrostatic fields was deduced.

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C. T. Nagamoto, J. Rosinski, and G. Langer

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J. Rosinski, G. Langer, and C. T. Nagamoto

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J. Rosinski, G. Langer, and R. Bleck

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The concentrations of both deuterium and water-insoluble particles in snow collected during snowstorms in the mountains of Colorado were found to be proportional to the size of snowflakes. Large snowflakes were associated with high particle concentration and high deuterium content. Small snow crystals appear to have originated in deuterium and aerosol-particle depleted air. The small snow crystals appeared at times of highest ice-forming nuclei concentration in air. The ratios of concentrations of different sized particles present in snow collected during a brief snowshower in March reveal that the predominant particles within small snow crystals are indeed those corresponding to the size range of ice nuclei. The relationship between the number of different sized particles present in a single snow crystal and the mass of snow crystals is given. Analyses of trajectories of moisture-bearing air parcels explained the large difference between the deuterium content of snow from the two snowfalls.

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G. Langer, C. Biter, and A. Dascher

An aircraft instrumentation system for cloud nucleation studies has been developed. It continuously measures and records ice nucleus concentration, aerosol concentration and size distribution in the 0.5–9 μ range, temperature, dew point, static pressure (altitude), dynamic pressure, magnetic heading, ground speed, and drift angle.

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G. Langer, A. Lieberman, and J. Rosinski

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