Further Tests on the Ice Nucleation Potential of Meteoritic Material
SCHAEFER1 was unable to detect any trace of ice-crystal formation when he vaporized a sample of iron–nickel meteorite by electric spark in a supercooled cloud—even in clouds as cold as −25° C. Mason and Maybank2, who ground up and vaporized three samples of stony meteorites, and Mason3 with three further samples also reported that they were unable to detect any production of ice-crystals at temperatures above −17° C This communication records the results of tests on the nucleating properties of a further thirteen samples of meteoritic materials. These comprised iron–nickel types (siderites), stony type (aerolites), plus two samples of the intermediate (siderolite) variety (all obtained from the American Meteorite Laboratory, Denver).
The Role of Natural and Anthropogenic Pollutants in Cloud and Precipitation Formation
Since the resurgence of interest in cloud and precipitation physics, stimulated by the demonstration in 1946 of the possibility of cloud modification by artificial nucleation, an ever-increasing amount of research has been reported in the literature on the mechanisms which underlie the formation of clouds and precipitation in the atmosphere. This research has essentially been carried out along two lines of study: studies of the cloud microphysical processes including the phase change of water substance in the atmosphere and the growth of the formed cloud particles to precipitation particles, and studies of the cloud macrophysical processes including all those dynamic processes which govern the formation, growth, dimensions, shape, organization, lifetime, and vigor of the cloud as a whole. In recent years, it has been realized that the cloud dynamical and cloud microphysical processes have to be viewed in a combined manner for a complete understanding of the formation of clouds and precipitation. Thus, much work is currently being done with this aim in mind.
Comparison of model prediction with measurements of galactic background noise at L-band
The spectral window at L-band (1.413 GHz) is important for passive remote sensing of surface parameters such as soil moisture and sea surface salinity that are needed to understand the hydrological cycle and ocean circulation. Radiation from celestial sources (mostly galactic) is strong in this window, and an accurate accounting of this background radiation is often needed for calibration. This paper presents a comparison of the background radiation predicted by a model developed from modern radio astronomy measurements with measurements made with several modern L-band remote sensing radiometers. The comparison validates the model and illustrates the magnitude of the correction necessary in remote sensing applications.