The ice-nucleating abilities of various rock-forming minerals which exist commonly on the surface of the earth were determined in laboratory. The most effective minerals as ice nuclei among the minerals tested are magnetite, hypersthene, kaolinite and sanidine. Quartz, amphibole, olivine, calcite and orthoclase are found to be less effective. As for the volcanic ejecta, the degree of weathering to which they have been subjected seems to give significant effect on their ice-nucleating abilities. The temperature spectra of atmospheric ice nuclei observed in Tokyo were compared with those of materials which were considered to have arrived in the air over Tokyo, and fair agreements were seen between them. It is suspected that meteoritic dust particles which contain magnetite or minerals similar to it might act as effective ice nuclei.
It is shown that two-parameter geostrophic models are not consistent system for certain type of disturbance in view of baroclinic development. Static stability field as a third parameter has significant roles on dynamical properties such as wave velocity, growth rate, meridional and vertical heat transport and instability of the wave disturbances in a baroclinic atmosphere.
The motion of ice-area composed of ice of any size when the thickness of individual ice constituting it is comparatively small may be determined by the surface current where it is floating and the drift current caused by wind. In the present study the transition of ice-limit and the increase of ice-thickness of drift-ice on the Okhotsk Sea during the so-called early drift-ice season are estimated theoretically using the equations based on the theories by Ekman and Zubov, etc. The estimated results are in general in good agreement with the actual states obtained from the weather messages from the ships of U.S.S.R. in 1956/57 to 1956/59. Thus, it is verified that the synoptic forecasting of ice-edge is certainly possible using the given transition chart of ice-limit (Fig. 1).