Abstract
Deciding the position of the Pacific Polar Frontal Zone in January from 1952 to 1957 by the frontal frequencies on daily synoptic weather maps, two different movements of the zone are found: 1. While the zone off the eastern side of Japanese Islands is apt to go up north, it has a tendency to run southward off the western coast of North America. 2. A quite reversal movement to above mentioned also takes place in each area. (Fig. 1)
Correlation ratio of given point at the Japanese Pacific side with other places around the North Pacific in regard to monthly mean temperature and total precipitation in January is calculated to seek the regional differences in the climatic fluctuation of there. For the tempera-ture, while high ratio areas expands from the northern part of the Korean Peninsula to the inland part of Asian continent, the low ratio areas covers northeastern Siberia and the west coast of U.S.A. (Fig. 2) For the precipitation, high ratio area covers the Korean Peninsula, inland of Asia, the northeastern Siberia and the west coast of U.S.A., the low ratio area covers the northern part of the Sea of Japan and Alaska. (Fig. 3)
Observing secular variation of the mean temperature and total precipitation in January on both sides of the North Pacific, the author finds a regularity that the warm rainy season of the Japanese Pacific side coinsides with the cold rainy season of western coast of the U.S.A. and cold dry season of the former coinsides with the warm dry season of the latter. (Tab. 1 and Fig. 4)
Making a composite map of frontal frequencies according to the pattern of temperature anomaly, he finds that the movement of the frontal zone is usefull to explain the climatic fluctu-ation above mentioned. Seesaw-like movement of the frontal zone is seen also on another map (Pig. 5) in accordance with the pattern of temperature anomaly on both sides of the ocean. Adequate movements of frontal zone is recognized by the strong westerlies on the com-posite maps of east-west components of geostrophic wind at 500mb level. (Pig. 6)
To make sure of relationship between atmospheric circulation pattern and the temperature anomaly pattern, a model of atmospheric circulation which is expected to show the negative anomaly of mean monthly temperature over both regions is made ref Bring to the conditions of above mentioned results. The model shows us three movements: 1. Southward movement of the polar frontal zone along the both side of the ocean. 2. South and eastward expansion of easterly wind area over the north west Pacific at 500mb level. 3. Strengthening of westerlies over the east coast of Asia and southward movement of westerlies axis over the west coast of U.S.A. at 500mb level. Applying this model to actual case of January 1963 when the mean monthly temperature shows negative anomaly on both sides of the ocean, they coincide with each other. Then, he conclude that the seesaw-like movement of the frontal zone and ade-quate changes of upper atmospheric circulation for that of frontal zone might be taken as a decisive factor to provide the regional differences of climatic fluctuation on both sides of the Pacific Ocean.
