Relations between the Temperature and the Rate of Evaporation of Fog, Cloud and Rain Drope: Fogs caused by the Evaporation of Rain Drops (Stuoies on Evaporation V)

[摘要] In the preceding investigations we have not touched with the temperature of cloud or rain drops, which is however very important on the evaporation. As the rate of fall of cloud and fog particles is very small we can assume the temperature and humidity of the surrounding air as constant through the fall. Therefore we can regard the rate of evaporation of them as stationary. By comparing the incoming and outgoing heat of particles their temperature was given as T0=T_??_+q(C0-C_??_) where, T_??_: air temperature; C0, C_??_, k, a: same as in the “Studies on Evaporation IV”; l: heat of vaporisation; λ: thermal conductivity of the air; α=μ0/2k; α=c_??_μ0/2λ μ0: rate of fall of the particle; Cμ: specific heat of the air at constant pressure; _??_: density of the air. The value of q is 2.48×106_??_2.24×106 for a=0_??_60μ and _??_o the temperature of cloud and fog particles is nearly the same as the wet bulb temperature of the surrounding air.As regards rain drops, however, only in the special case or in the stationary state its temperature is expressed by the same formula as that of cloud, the value of q being 2.24×106. In the non-stationary state its temperature changes as the drop falls in the air and so it depends on the temperature and humidity distributions of the atmosphere. Some example were shown diagrammatically in Fig. 3 and 4. Lastly the author calculated the increase of humidity of the atmosphere by the evaporation of rain drops and confirmed that fog or cloud can be not rarely formed by the evaporation of rain drops.

[学科分类] 大气科学