Abstract
The analyses of the meteorological surface data at Wajima, Matsumoto, and Nikko Weather Stations in Japan were made in order to examine the effect of relative humidity of air on melting of snowflakes below freezing level in the atmosphere. The results showed that the types of precipitations (rain or snow) observed on the ground were closely dependent on surface relative humidity as well as surface air temperature. When surface relative humidity was below a certain critical humidity, even at a higher surface air tempera- ture above 0°C precipitations were snow. Using the regression analysis, the relations of the critical relative humidity RHcri to surface air temperature T could be obtained at each Weather Station in the following forms, RHcri=-7.5T+93, ............... Wajima, RHcri=-7.3T+96, ............... Mtsumoto, RHcri=-6.2T+91, ............... Nikko.
The relations thus obtained agreed well with that obtained previously from the theoretical calculations by Matsuo and Sasyo (1981).
