Abstract
The influence of the time lag in the activation of ice nuclei on the number of ice crystals in cloud was numerically studied. Following conclusions were obtained from computation ; (1) the increase in the number of activated atmospheric ice nuclei with cooling-time is remarkable, particularly under the cooling at lower temperature than -25°C. The total number of atmospheric ice nuclei activated for a few hours under the cooling at -30°C to -40°C becomes 10 times as large as that for 1 minutes, while the number of activated atmospheric ice nuclei in the case of the cooling at the temperature warmer than -20°C is at most 3 times as large even after 10 hours as that for 1 minute, (2) The number of atmospheric ice nuclei activated in the upward air-current with vertical velocity of the order of 10cm/s is 5 to 10 times as large as that in the air-current of the order of 10m/s, if the numbers in both cases are compared at the same level.
