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Josef Stekl and Josef Podzimek

The foundation of the old mountain meteorological station Milesovka (Donnersberg) in western Bohemia and its operation since 1904 is described with special reference to its unique location in central Europe. The data presented might serve as important documentation of the intense industrialization of the surrounding region during the past 80 years.

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Josef Podzimek and James L. Kassner Jr.

Abstract

The recent article by Cadle et al. (1975) describes a comparison of different types of condensation nucleus counters. Some general remarks are made here on the terminology and calibration of the counters and on the interpretation of the results. A comparison of one of the calibrated instruments (SANDS) with the UMR Absolute Aitken Nuclei Counter (UMR-AANC) in Rolla just after the described workshop showed steadily lower counts by SANDS (about 30% lower). This enables one to compare indirectly the UMR-AANC with the other counters.

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Donald E. Hagen, Josef Podzimek, and Max B. Trueblood

Abstract

During the FIRE IFO II project, aircraft were available for airborne sampling in and around cirrus cloud. Aerosols can play a role in the cloud formation process through the heterogeneous nucleation mechanism, and in turn, once formed, cirrus clouds can impact the ambient aerosol through scavenging and other collection mechanisms. University of Missouri aerosol sampling facilities were employed on these aircraft for in situ collection and characterization of the particulates near cirrus cloud level. Tandem differential mobility analyzer and impactor techniques were used to measure aerosol size distribution, hydration capability, and particle composition information. Evidence of aerosol layering was observed near the tropopause, and there was a tendency toward depletion of the ambient aerosol at both ends of the condensation nuclei (CN) size distribution. A large variability in the fine particle CN concentration was found, ranging from several tens to several thousands per cubic centimeter. The size distribution of particles larger than 0.5 micro;m roughly followed a lognormal relationship and large particle concentrations varied between 0.127 and 1.70 cm−3. The particulates were found to be of mixed character, primarily inert with a small percentage of soluble material. A large variability in particulate concentrations was found.

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Adel N. Saad, Josef Podzimek, and John C. Carstens

Abstract

A numerical model has been developed to describe the early stage of cloud formation in a relatively small simulation chamber. The results for adiabatic expansion show a tendency for the cloud droplet spectrum to narrow, similar to the results obtained by other authors. The influence of updraft fluctuations is not as important as the fluctuation of temperature which depends upon the amplitude and frequency of the fluctuations, and the expansion rate of volume. Simple models of the sedimentation of the drops show that sedimentation might be a factor limiting the rate of expansion. Nuclei suddenly introduced into the cloud parcel indicate that the seeding effect depends significantly on the concentration and size of predominantly larger nuclei.

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