宇宙線と氣團

新氣象要素としての宇宙線, I

抄録

Blackett⁽¹⁾ has suggested that the “temperature effect” of cosmic rays is due to the vertical shift of the layer in which mesotrons are formed, and he has further suggested that it may be possible to correlate cosmic-ray data with the structure of depressions. Loughridge and Gast⁽²⁾ have pointed out that cosmic-ray data in America indicate a noticeable change in intensity at the fronts which separate different air-masses.
The polar continental (Pc) air-mass⁽³⁾ originates in Manchuria and Siberia and comes to Japan proper as the northwest monsoon in the colder half of the year. The tropical maritime (Tm) air-mass flowing from the North Pacific subtropical high pressure belt comes to Japan proper as the southerly tropical air mainly in the warmer half of the year. The polar maritime (Pm) air-mass originates in the Okhotsk Sea and sea to the east of Japan and comes to Japan proper as the mild northeast wind in the rainy season. The Pm air-mass found in Japan is shallow, but plays an important weather rôle. The Pm air-mass is seldom thicker than 2000 m and is usually overrun by a Tm air-mass; the interaction of these two air-masses results in forming a stationary front and is responsible for the gloomy, rainy weather during the Bai-u period of Japan. There are two other modified polar continental air-masses, which lose their original coldness and dryness in the lower layers. One comes to Japan proper by the sea route from the northwest, and the air-mass type is transformed from the fresh one into the modified one (NPc 1). The other arrives in North and Central China by the land route and then comes to us by the sea route, with the general westerly wind (NPc 2).
These air-masses were identified, using the synoptic charts analysed by the Forecasting Division of the Central Meteorological Observatory, Tõkyõ. Cosmic-ray intensities measured with a Steinke cosmic-ray meter and their barometer effects under various air-ma s conditions prevailing in Tokyo during the year 1937 are shown in the annexed table. We find thus: (1) both the correlation coefficient and the barometric coefficient are relatively high in the fresh Pc air-mass and Tm air-mass, and show a gradual decrease as the air-mass type is transformed from the fresh one into the modified one; (2) the correlation coefficient and the barometric coefficient are very low in a Pm air-mass which is shallow and is overrun by a Tm air-mass; (3) the reduced cosmic-ray intensity is relatively low in warm air (Tm and Pm), but is high in cold air (Pc).