It is well known that the factor of the cup-anemometer varies with the wind velocity. It increases with decreasing wind velocity. Why the anemometer factor varies with the wind velocity? How the angular velocity of rotation of the anemometer depends on the true wind velocity? These are the subjects of the present memoir. Let us suppose that the couple of forces due to the winds which compel to rotate the anemometer is composed of two components due to viscosity and inertia of air. Their intensities are proportional to the velocity of wind and its square respectively. In the same way we can suppose two terms of the first and second powers of the speed of the anemometer rotation. In this case however we have to take the friction between the rotating part and the fixed one of the instrument into account, in addition to the resistance of air. Hence for stationary state of rotation of the anemometer we can assume the relation between the true velocity of winds V and the speed of rotation of the cup u as follows: aρV2+bV=cρu2+du where ρ is the density of air and a, b, c, d are constants. In practice of the ordinary observation of wind speed by the cup-anemometer, it is assumed that v=kuwhere is the scale value of the wind speed, and k is the ordinary anemometer factor. Then we have If we express the wind velocity which satisfies the last equation with V', we obtain If we put k' for the variable anemometer factor, then it is clear that These equations show the relations between the true wind velocity or the variable anemometer factor and the scale value of wind velocity of the anemometer. As an example, let us take the experimental data for the 9-inch cup-anemometer in the Observer's Handbook of the Meteorological Office, London. Then we get the following numerical values for the constants of the anemometer:- α=0.7277, β=2.9193, m=0.3543. and accordingly for the true wind velocity and the variable anemometer factor we obtain The calculated values of them by these formulae show fair coincidence with the observed ones in the Handbook.
This short note gives the results of comparison of the solar radiation intensity observed at the central meteorological observatory of Japan with that at the Tiba Hygenic Colledge situated at a marginal part of Tiba, a country town some 30km distant from Tokyo due northeast. The comparisons have been made only for the total radiation in the cases when there was no spec of cloud over the sun's disk. The series of the simultaneous observations taken in this investigation extends over the three months, August, September and November of 1931. The radiation intensity at Tokyo was found to be remarkably below that at Tiba, with a few exceptions. The extinction came out, in the mean, 0.44 for Tokyo and 0.34 for Tiba. The general tendency is the same throughout day time, but the contrast is most marked in the later morning hours and afternoon being temporarily diminished by noon. Medium wind velocity at Tokyo tends to diminish the contrast of the atmospheric conditions of the two stations. No definite relation of the contrast to the wind direction has been found to exist, but there seems to be a slight tendency that northerly winds at Tokyo favour greater contrast.
The vertical structure of the typhoon was investigated from the pilot-balloon observations. A circular area of 1750km radius around the center of typhoon was taken as the domain of typhoon. This area was divided into 112 segments with six concentric circles and with sixteen radii. The results of observations in each segment were collected together and vectorial means of wind velocities, which were used for representing the mean state in that segment of the ordinary typhoon, were calculated. Then the distribution of cyclonic winds was investigated, disregarding general currents. And the ascending or descending currents were calculated from the convergence or divergence of winds near the ground and at higher levels.
The effect of air on water waves is treated hydrodynamically, taking into account the viscosity of water and air, both assumed as incompressible fluids. The velocity of propagation of waves and the damping of motion are proved to be almost the same with those in single layer of water.