In our papers(1) on the interpretation of the anomalous propagation of sound waves. especially at a short distance, we have studied the effect of the current of the air, on an idealized assumption that there is an uniform current in each of the two layers of the air respectively. In the present short note, we studied the sound waves which is transmitted through the air with current varying as the height, on the assumption that the velocity of the current is small compared with the sound velocity and that the temperature is constant. If we define P such that the variable part of the density ρ'=DP, the fundamental equation can be written in the form (D2=c2Δ)P=O, where D=∂/∂t+U ∂/∂x, c is the velocity of sound when there is no current and ΔLaplacian, the z-axis being taken vertically upwards and x-, y- axes horizontally. U is the velocity of the current and a function of z. In the case in which U varies linearly as the height z, In the case in which U varies linearly as the height z, we obtain a solution which involves a cylindrical function of degree 1/3. It corresponds to the plane waves when the current is uniform. The ray of sound bends in the course of its propagation, as one can expect from the outset. Our former idealized theory must be filled up in this respect, but the essential idea is not affected because the bend is small as the present investigation shows.
It is well known that atmospherics have an intimate relation with thunder storms. The writers tried to construct a mechanically self-recording apparatus of atmospherics in order to obtain some data for the warning or prediction of thunderstorms which are carried on in the summer seson at the Oosaka Branch of Central Met. Observatory. The apparatus is consisted of three parts, an antenna, magnifier and self-recording part. The antenna of ordinary vertical type was about 40m high. The magnifier is also nothing but an ordinary receiving set with capacity feed-back and its tuned wave length is 10km_??_15km. But it is designed so as to be convenient to get mechanical recording. Its wiring is shown in Fig. 1. The recording part is consisted of two, a recording galvanometer and moving cylinder. The former is a moving-coil galvanometer with a long straw stem bearing a pen at its end. This pen draw the continuous record of atmeospherics on the smoked paper wound round a metal cylinder. The cylinder is continually driven by a synchronous motor and at the same time horizontally shifted by the “twisted method” as was used in Mainka's Seismograph. (Fig. 2 and Plate I fig. 1). This apparatus is now working in good order day by day and giving complete data of atmospherics. Some examples of recorded atmospheriecs are shown in Plate II fig. 3 and 4. Discussions on the observed data in connection with meteorological phenomena especially with thunderstorm will be made in the next report.
In this paper is investigated the Typhoon of Sep. 11th 1937 from the point of view of the storm prediction for the Oosaka district. The results obtained are as follows;- 1. The weakening factor of wind velocity is defined by(1-V/Vg), where V is the observed wind velocity and Vg that calculated from the pressure gradient using the Humphreys' tables. This quantity has a distinct feature, influenced partly by the ground resistance, as its value decreases with time in the case of veering wind, while on the contrary increasing in the case of backing wind. That is to say, the wind velocity is in general accelerated gradually in the case of veering wind but the reverse is observed in the case of backing wind. It may be wonderful to see the distribution and variation of the weakening factor obtained in the neighbourhood of the Typhoon center of Sept. 11th 1937 as is seen in Fig. 6, showing the large wind velocity in the SE-ern quadrant. It may be perhaps partly due to the superposition of the Werly general current, so-called “Field wind” in this quadrant. Therefore, the value of weakening factor at any place on the East side of the Typhoon track decreases generally according as the center comes nearer and takes the minimum value when it arrives there and then increasing gradually in the rear. But on the western side (in the left front)the change is quite different from those above mentioned. In the city of Oosaka, its mean value is obtained as about 0.76 for the NE-erly wind and 0 28 for the SW-erly wind. These values and their deviations from the mean value in the individual cases may be useful to expect the variation of wind velocity with time when a storm attacked the city. 2. For the relation between wind velocity and atmospheric pressure gradient, a characteristic distinction between veering wind and backing wind is found. The writer tried to explain this fact theoretically that the wind should blow stronger in the Eastern side of the cyclone path (veering wind) than in the Western side (backing wind) for the places of the same pressure gradient. 3. Concerning the Typhoon of Sept. 11th 1937, the writer investigated the wind directions and velocities as was done by Mr. Goldie, and found no discontinuity line nor secondary low pressure and diverging line in the region of the Typhoon. Perhaps this Typhoon had still a symmetrical structure of tropical cyclone as was presented by Dr. Y. Horiguti even after it landed on Japan Proper. 4. The relation between the maximum wind velocity and the minimum pressure, both observed at Oosaka, is investigated statistically by the data of some violent Typhoons which had attacked this district in recent years. The maximum wind velocity is approximately in inverse ratio to the minimum air pressure and is usually occurred about one hour or more late after the occurrence of the minimum air pressure. 5. Characteristic equation showing the distribution off wind velocity at the height of 50m above the mean sea level in this city is obtained as follows:- R=υ/V=e-0.088. D where υ is the wind velocity at a place being distant D km. from the west edge of the harbour where the wind velocity is V (m/s). This empirical formula may be applicable when a SW-erly strong gale predominated over the city. In the last, the author expresses his best thanks to Dr. K. Wadati under whose guidance this paper was made.
In this paper has been reported the result which the evaporating power of atmosphere close to the ground in the growing space of crops was measured with the new filter's atmometer by Daigo which was previously reported. Measurement of the evaporating power was carried out in the following 6 places: open place, glass house, paddy field, corn field, maize field. and bean field. Process of change and difference of amount of relative evaporation: (amount of evaporation in every place/amount of evaporation in open place×100) based upon the growth and difference of sort of crops in every place is as shown in Fig. 1. On and after the last decade of July the amount of relative evaporations were maintained constantly as follows: paddy field 20%, glass house 40%, bean field 70%, corn field 75%, maize field 80%. Relations between amount of evaporation in open place and amount of relative evaporation in every place are shown in Fig. 2.
In this first paper, the influences of viscosity upon the wave motions were investigated in the case of isothermal change of air condition applying the first appoximation. The results are as follows:- The effects on amplitude of waves are classified in three cases; damped, stable, and unstable oscillations according to the wave length. The effects on period of wave are also divided into three parts; longer or shorter than where no viscosity, and independent of viscosity. The effects above mentioned are very trivial if we consider the viscosity as molecular except in very short waves, but if we consider it as eddy these effects are very remarkable particularlly in short waves.