Abstract
The freezing of freely suspended, supercooled water drops by contact nucleation has been studied. Water drops were balanced in an updraft of a large vertical wind tunnel and allowed to supercool to the ambient temperature. Ice crystals introduced into the updraft were, as expected, the most effective nucleants in freezing the drops at ambient temperatures colder than and up to 0C. The results of this experiment using silver iodide and clay as contact nucleants closely agree with earlier work performed with a constant rate of cooling apparatus. The effective temperature for 100% nucleation efficiency in the case of AgI particles was −4 to −5C and for silicate particles −7 to −10C.
