On the Measurement of the Total Amount of Radiation from the Whole Sky and the Atmospheric Taransmission's Coefficient

Abstract

The actinographs of Gorcainsky's type were used for the measurement of the total amount of radiation from the whole sky. The observed records used in this investigation are those taken in the interval from April 1937 to February 1940. The chief part of the apparatus is a thermopile. The elements which form this thermopile are extremely thin fo_??_ls of manganin and constantan. The thermopile is composed of 14 elements and has electric resistance of 12.11±0.015Ω, and it needs about 9 sec till the full electro-motive force caused by the constant radiation is measured. It is laid on a circular disk of brass having a diameter of 22mm. Each element is 0.8mm broad, 12mm long and 10 microns thick, and is blackened with soot of camphor and is exposed to the radiation all over the whole length Owing to the good heat conduction of the junctions and to the small capacity of the active junction, it reaches its equilibrium of temperature instantaneously.
The recording part of the apparatus is a recording millivoltmeter of ordinary type. made by the Shimazu Mauufacturing Factory. The portion which gives motion to the needle is just the same as the usual millivoltmeter with moving coil. In front of this part there is a drum rotating around a horizonatal axis by clock-work. The recording sheet is rolled up to this drum. The needle marks the values of the thermo-electric voltage generated in the thermopile every four minutes In this investigation, we used the records of clear days only.
On clera days a beautiful sinusoidal curve is recorded. In this sheet we must obtain the time corresponding to the sun's altitudes of 10°, 20° and so on. It is possible to obtain the hour angle from the fundamental formulae of spherical astronomy giving the sun's altitude and declination and the latitude at the observing place. But, for convenience'sake, we used the graphical method of nomograph.
To determine the scale value of this actiongraph, it is necessary to observe the absolute value of total radiation. In our case the new apparatus of direct measurement of the absolute value of the total amount of radiation from the whole sky was used. We can easi_??_y get the reduction factor of the actinograph by comparing the reading value r with the observed absolute value of the total radiation Q. The (Q. r) curve thus obtained is nearly a straight line. This fact indicates that the Berlage's formulae are in accord with our observation, and so we will be able to obtain conversely the coefficient of atmospheric transmission by comparing the recording sheet with the claculated value from the theoretical formulae given by Berlage. Thus we obtained the averaged annual variation of the transmission comefficient.
In July and August the transmission coefficient of the sky is very small. This is of course attributed to the vast amount of the atmospheric water vapour in these months.
The above investigations support, contrary to Reitz's objection, the formulae given by Berlage