Turbulent diffusions of matter (gas, minute particles or heat) emitted from a point source are classified into the following four types, and interrelations among them are discussed: (1) the instantaneous source type, (2) the continuous fixed source type in a fluid flow, (3) the continuous fixed source type in a fluid at rest (4) the continuous floating source type. As an extension of this research, the turbulent diffusion of matter from a body source in an isotropic turbulent field is discussed in the latter part of this paper. Furthermore, some remarks are made on the interrelation between the so-called Eulerian and Lagrangian correlation functions, and the equation expressing the wind velocity profile near the ground is derived by making use of the Lagrangian correlation.
It is known that photographic paper is coloured without development and fixing when it is exposed to the daylight or a light source of relatively short wave length. When the precipitation elements fall on a photographic paper and melt on it, the areas wet by the precipitation elements are coloured a different colour from the other unwet areas as shown in photos. 5_??_10. The coloured areas are stable if the paper is protected from the direct rays of the sun. By the use of this phenomenon, the size or shape of the precipitation elements (rain drop, snow crystal, snow flake, sleet, graupel) which fell on _??_ photographic paper are simply recorded on the photographic paper. In this work, the relation between the volume of individiual precipitation elements and the records coloured by them on the photographic paper, was investigated. a) Rain drop. From the calibration of the water drops at terminal velocity, the following relation was obtained d=10-1/3D2/3 where d=equivalent diameter of rain drops in mm, D=mean diameter of wet areas by rain drops on the photographic paper in mm. b) Snow crystal and snow flake. As the outline of the horizontal shape of the snow crystals or snow flakes in falling state is coloured and recorded on the photographic paper, we obtain d=2-1/3D where d=diameter of the snow crystals or snow flakes assumed to be spherical in falling state, D=mean diameter of areas coloured by them on the photographic paper due to their fall on the paper. in mm. c) Sleet (partially melted snow flake) The particles of sleet collapse and spread on the photographic paper when they fall on it, but their depths are roughly uniform, so their volumes are calculated from the records on the paper and the increase of the weight of the paper due to their fall. d) Graupel. The graupels melt to semispherical drops on the paper, so their diameters, equivalent to the ones of spherical water drops are also calculated as follows, d=2-1/3D where D=diameter of circles by the graupels in mm. Some examples of the volume distribution of great precipitation elements are shown in figs. 4_??_10.