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On the Atmospheric Potential Gradient at the Top of the Hill, "Kakioka Fujiyama"
From Nov. 2600 to Mar. 2601, the writer carried out a measurement of the potential gradient near the earth's surface at the top of the hill so-called“Fujiyama". The observing point is located about 1km. southward from this observatory. This hill stands alone at somewhat south from the center of the Kakioka basin. The top of the hill is flat and forms the circular ground about 30 m.
in diameter, surrounded with pine trees excepting for northside, their height being nearly equal to the level of the top. The observing point is at an elevation of 128 m. above the sea level and about 100 m higher than this observatory.
As the measuring apparatus, a Benndorff's selfrecording electrometer was used with a ratio thorium collector which was apart 103cm. from the wall and 198 cm. above the ground. Its reduction factor to a flat place is 1.23. 0N the other hand, at this observatory a water dropper col1ector is used which is 135 cm. apart from the wall and 200 cm. above the ground. Its reduction factor is 1.32.
From the results of the simultaneous observations we obtained, as an average value, 186.5V/m at the hill and 150.5 V/m at this observatory. The former is 1.29 times as large as the latter, but the hourly ratios between them change considerably and the average ratio from 11 h to 16 h is 1.65.
It must be noticed that the value of the morning maximum at the hill is rather smaller than that at this observatory.
The diurnal variation in a fine weather shows the double maxima-type at both places, but there are some differences as below mentioned;
(1) The amplitude at the hill is smaller than that at the observatory ,that is, in the latter the morning maximum develops predominantly than evening maximum, while in the former these maxima being nearly equal.
(2) The time of maximum in the morning at the hill is tending to retard about one hour than that at this observatory, while the evening maximum occurs almost the same time at both places.
Such differences may be attributed to those of the meteorological conditions at both places, especially to that the reversed state in the atmosphere near the top of the hill breaks earlier than that at this observatory.
The writer also discussed the diurnal variations on cloudy days and the potential variations
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