Observations of Aerosols Attached to Falling Snow Crystals, Part I, Utilizing an Optical Microscope

The size distribution of aerosols attached to falling snow crystals was measured, utilizing optical microscopic photographs of sublimated traces of the snow crystals in Sapporo where the air is highly polluted, in March 1973. The resolution power of the microscope was insufficient to measure the size distribution of submicron aerosols, and the movement of aerosols towards the center of the snow crystals was recognized. However, within the resolution power, the following results were obtained. 1. In the size distribution of aerosols attached to the snow crystals, the frequency increased smoothly as their size decreased down to I (.t. 2. Several thousand aerosols were attached to one snow crystal. 3. The area number density of aerosols in a rimed snow crystal of needle type was much greater than in those of plane type. This difference is related to the difference in the thickness of the snow crystals. 1