To discuss more precisely cloud formation or precipitation caused by the ascending of warm air over cold air it would be required to introduce a new conception of mixing of warm and cold airs into the treatment of this problem. In this case a frontal su_??_face will change its form with time by mixing of warm and cold airs, so that it would be diffcult to treat this problem mathematically. The principle of our calculation, however, lies in treating successively in turn the ascent of warm air over cold air and their mixing for each short time. Here surface of discontinuity shall be defined by the boundary where warm and cold airs are mixed equally. The mixing of warm and cold airs and the change of distribution of heat and water vapour contents might be calculated by “the Graphical Solution of Eddy Diffusion” suggested before by the present author.
When κρ2u, in the equations of motion, is replaced by-ku, there may be the following correspondence: where n is any positive integer. This correspondence is found from two solutions, one. of which is from κρ2u-type equation and the other from ku-type equation, when expanded in infinite seies.
At the same time and place with the previous report (Jour. Met. Soc. Japan: Vol. 24 No.1_??_12), another party has executed some observations to examine the relation between the visibility and some other optical elements in meteorology which were not touched in the previous paper. In the first place, the relation between the visibility _??_nd the intensity of the. ultra-violet rays was examined. The former was observed with the Wigand's visibility-meter, and the latter with Dr. Miyake's dosimeter. The results of observations show that as shown in Fig. 2, the seeing is better as the intensity of ultra-violet rays becomes stronger, just as was expected from the beginning. This better seeing seems to be more remarkable for white objects than for red objects. In the second place, they have examined the efficiency of the red glass colour filter for improving the visibility for white and red marks, and found that as shown in Tab. 4, in which S0 and SR, are the visibility without and with the red filter respectively, the red filter rather diminishes the seeing of white objects, but it increases the seeing for red objects very remarkably. Especially, we have frequently experienced the fact that, when the fog covered the _??_ield and the objects can no more be perceived these re-appeared using the red filter, though the quantitative relation could not be de termined, because we had no method of classifying the mean density of the fog in the sight line as a whole. The difference of seeig without and with filter seems to _??_e large when the weather is bad compared with those of clear weather. Perhaps it is due to the change of contrast bet- ween the object and its background. The daily variation of the difference between the eastern and western visibility SE-SW is very clear (Fig. 5). i. e. SE-SW is very small in the early morning, and very large in the evening. Both visibility SE, SW coincide at about noon when the position of the sun became symmetry with respect to these eastern and western marks. Further, examining the Fig. 2 in detail, we can find the seeing for southern objects are always smaller than those of the other directions for the same condition of the weather. The reason of which can not be easily explained, but it seems to be perhaps due to, one part at least, the instrumental causes, because the visibility in the case when the ground glass was shaded with hand n_??_ are remarkably large compared with those when the direct sunshine is incident upon the ground glass of the Wigand's meter n_??_ Tab. 5). It seems that this phenomena are the similar ones as the flre for the lenses. The ratio n-/n0 is very large in the early morning and approaches to unity at about . 10_??_30m when the sun's altitude is about 45°. Thus the Wigand's meter is only useful when the incident angle of the solar beam upon the ground glass exceeds 45°, for the small incident angle it must be used shading the ground glass by any means. It was a remarkable fact also that the seeing is better when the direct sunshine illuminates the field between the observer and the marks than when sunshine is shaded with cloud (Tab. 8). As to the effect of contrast, numerious observations of visibility for mountain peaks were made, the background of these mountain peaks being always the free sky. For the classification of the blueness of the sky standard tint classes in 20 steps extending the Linke's 14 steps were made. The observation shows that when the weather is bad and the sky is appearing in grey colour, the visibility is sometimes very large and sometimes is very small, and it seems to be at random. Then, as the blueness of the sky increases the visibility increas s proportionally, but when the blueness becomes very thick, the rate of incr_??_ses becomes small and approaches asymptotically to some finit_??_ value.
Turusi-cloud, formed over Mt. Fuji, was investigated, using the observational data of 10 years during 1934-1944. In the 10 years the total frequencies of observation is 459, and the annual variation shows the maximum in July, the minimum in Feb., while the diurnal variation is larger in A. M. than in P. M. Turusi-cloud is mostly formed when a depression or a discontinuiy line is produced on the Japan Sea and the lower wind direction is WNW_??_NW, while that of upper wind is W_??_SW. The duration of Turusi is mostly 2 hours and is longer than that of lenticular-cloud. The probability of rainfall within 24 hours after the formation of Turusi-cloud is on an average 66% and in April it becomes 87%. Consequently, Turusi-cloud is useful for weather forecast as the symptom of rainfall.
The comparative observations of the black and the white thermometer s_??_reens provided with the dry-bulb and the wet-bulb thermometers in them were made at the Central Meteorological Observatory, Tokyo during one year from Dec. 1942 to Nov. 1943. The same comparative observations were also made from Jan. 22nd to Feb. 25th, 1942 with the other thermometers and another white thermometer screen of the same type. The results are summarized as follows: (a) Air temperature. The remarkable difference occurs a ab ut 14h. The maximum difference is +1.2°C and in fine weather it is controlled by several elements except solar radiation. (b) Wet-bulb temperature. Compared with the case of air temperature, the difference is generally small, showing almost the same results at night. (c) Water vapour tension. When air temperature is above 25°C, the difference ranges from +4.5 to -1.8mm Hg_??_ Its ratio, however, is almost the same both in summer and winter, the fluctuation being 4% or so, while, when air temperature is below 25°C, the difference is trivial in spring and at night. (d) Relative humidity. The mean difference is the smallest of the present results throughout the year, showing the fluctuation of 2% or so. No marked diurnal variation is found.