[en] It is shown that cold dense condensations of interstellar gas originating at a nonlinear stage of thermal instability may have a form of thin pancakes which may be curved. It reminds origin of Zeldovich's pancakes owing to the development of the longwave gravitational instability

[en] The influence of aerosols serving as cloud condensation nuclei (CCN) on the production of droplets in mixed-phase cloud systems is an ongoing research problem that influences their optical and microphysical properties. During February and March 2019, the Role of Aerosols and CLouds Enhanced by Topography on Snow (RACLETS) field campaign collected unique and detailed airborne and ground-based in-situ measurements of cloud and aerosol properties over the Swiss Alps. This study presents analysis of the observed CCN activity of the aerosol, which combined with observed aerosol size distributions, can be introduced into a cloud droplet activation parameterization to investigate the drivers of droplet variability in these clouds. The implications for secondary ice production are then discussed.

[en] Alpha clustering and α condensation in lighter nuclei are presently strongly and increasingly discussed in the literature both from the experimental and from the theoretical side. A discussion of the present status of the theory as well as outlooks for future developements will be presented.

[en] A test set-up for ultra-microscopic detection of condensation nuclei according to the Aitken-method is described, and it is shown that due to the delay of a video camera tube the video-technique allows to store flashlight shots of condensation particles such as they occur in an expansion cloud chamber. The possibilities resulting from that technique are stated. (orig.)

[en] Cloud microphysics affects cloud albedo precipitation efficiency and the extent of cloud feedback in response to global warming. Compared to other cloud parameters, microphysics is unique in its large range of variability and the fact that much of the variability is anthropogenic. Probably the most important determinant of cloud microphysics is the spectra of cloud condensation nuclei (CCN) which display considerable variability and have a large anthropogenic component. When analyzed in combination three field observation projects display the interrelationship between CCN and cloud microphysics. CCN were measured with the Desert Research Institute (DRI) instantaneous CCN spectrometer. Cloud microphysical measurements were obtained with the National Center for Atmospheric Research Lockheed Electra. Since CCN and cloud microphysics each affect the other a positive feedback mechanism can result

[en] The solar wind disturbances result in the emergence of condensation structures in plasma comet tail. Most of them are correlated with plasma vortex flow. In this paper, we analyze the features of condensations basing on the theories of MHD and force-free field. Specifically, we discuss the construction and the distribution of magnetic field and its energy in condensations. We also analyze in detail the coupling process between an unsteady plasma motion and a magnetic field. The coupling effect will let the energy in comet tail change into the force-free field in condensations, so that the magnetic field energy in the condensations increases constantly. Many phenomena observed in comet tail can be explained with the model. (author). 22 refs

[en] Calculations and experimental results exhibit a good agreement. Thus the model develop seems to give an accurate description of the phenomena occuring in the Continuous Flow CNC's. For concentrations larger than 10⁴ p.cm^-3, the final droplets size decreases and a significant vapor's reduction occurs. This result explains the irregular shape of the factory calibration curve for the large concentrations range. Furthermore, for a concentrated polydisperse aerosol, a dilution technique must be used for meaningful measurements. (orig.)

[en] Aerosol particles that act as cloud condensation nuclei (CCN) inuence cloud albedo and lifetime and thereby affect the planetary radiative balance. The indirect aerosol effect on climate is still one of the largest uncertainties and especially the role of biological particles is not yet well described. Pollen grains are primary biological particles that become airborne during the blooming season of plants. Pollen from wind pollinated plants represent a seasonally signifficant portion of the organic aerosol in the atmosphere. Intact pollen grains are rather large (10-100 µm) but under conditions of high humidity pollen grains have been shown to rupture and release cytoplasmic material including a large number of particles much smaller in size (0.5-5 µm). In this study we extract soluble and insoluble material from several pollen samples (Phleum, Betula, Artimesia, Poa, Corylus and Ambrosia) and investigate the CCN activity of the extracts in a laboratory study. The main component of the experiment is the continuous-flow streamwise thermal-gradient cloud condensation nuclei counter (CCNC) from Droplet Measurement Technologies (DMT). The CCNC was calibrated with (NH4)2SO4. The activation behavior of (NH4)2SO4 is theoretically well described by Kohler equation. For particles which consist of a multitude of organic components it is convenient to represent the chemical composition through the hygroscopicity parameter κ. In the first part of the experiment, we determine the activation diameter at 5 different supersaturations and calculate the kappa parameter for all pollen samples. We find that the values fall in the range from 0.1-0.2. which is typical for particles composed of organic substances. Extracts from Betula pollen show the highest hygroscopicity (κ = 0.18), while extracts from Artimesia exhibit the lowest hygroscopicity (κ = 0.13). In the second part of the experiment we will also investigate the CCN activity of the insoluble material.

[en] Measurements of alpha and beta radiations carried out in Ibadan (Nigeria) are presented. Activity of alpha radiation in the air is much lower than that of beta. The mean daily activity (Bq) ranged from 0.013 to 0.075 for alpha and from 1.475 to 76.136 for beta throughout the periods of investigation which include wet, dry and harmattan periods. The highest activity occurred during harmattan followed by wet period and the least was during the dry period. The harmattan dust originating from the Sahara desert is found to be radioactive. During wet period the aerosols and the condensation nuclei present in the atmosphere were also found to be radioactive to some extent. Background beta (β) and alpha (α) activities were found to have increased greatly over those earlier reported in the period between 1986/1987-2001/2002. Beta activity has two peaks at 19 and 6hLT while the peak time of alpha activity varies randomly throughout the periods of observation. The minima activities of alpha and beta occur throughout the day. The results showed that ambient α and β activities were highly correlated to atmospheric potential gradient

[en] CN and radon concentrations have been measured at coastal and island sites in programs measuring 'baseline' concentrations of atmospheric trace constituents. It is shown that addition of CN and radon concentrations to meteorological criteria for characterisation of an air mass, substantially improves the objectivity of 'baseline' selection. Wind direction and CN concentration are both useful for indicating likelihood of pollution from sources within a few km. Beyond that the fetch over land is enough for radon to be useful. For sources more than a thousand km away, wind direction and CN become poor indicators, whereas radon concentrations still yield reliable indications of land contact. (author) 24 refs.; 7 figs.; 1 tab