Abstract
Freezing experiments of freely falling water drops of diameter 45-765 μm were made by usinga large cloud chamber 14.7 meters in height. Frequent shattering of freezing water drops is observed not only when water drops are nucleated by silver iodide in suspension but also when they are nucleated by collision with ice crystals after attaining thermal equilibrium with the environment. The frequency of shattering depends considerably on the nucleation temperature (Tn) and the drop size (d). The frequency of shattering is especially high in the size range d=75-135 μm when water drops are nucleated at temperatures between -14 and -20°C. Spikes are formed when water drops are nucleated at temperatures higher than the air temperature (Ta) and are scarcely formed when Tn_??_Ta. In the case of Ta_??_-27°C, the frequency of spike formation increases with the rise of the nucleation temperature and the increase of the drop size.
