

Z S '4- -y 6 7 



Fig. 6. — Correlation of air tem- 

 perature in January with 

 pressure difierential between 

 Nikolsk and Asahigawa. 



summer rises due to the air current from the. low latitude zone revolving 

 with the North Pacific High on its right. Using the ledgers of weather 

 charts published at Kobe Marine Observatory, I have investigated the 

 change of the five-year means of pressures of the area within the 

 rectangle, bounded by longitude 180° E. to 130° W. and latitude 25° N. 

 to 50° N. for the period from 1911 to 1935. As shown in Fig. 7, the curve 

 of the secular change of intensity of pressures within the rectangular 

 area, which is obtained by averaging the data of each, section divided 

 by every longitude 5° and latitude 5°, is in good harmony with that of 

 summer air temperatures as well as precipitations at Hushiki. 



The curves of secular trend of the amount of precipitation observed 

 in central part of the Japan Proper are shown in Fig. 7 ; with the increase 

 of the intensity of the North Pacific High, the high-pressure zone extends 

 over the Japan Proper and diminishes the amount of precipitation in the 

 said district, by pushing the isobar-curves northwards, along which 

 depressions tend to proceed (4). 



The above-described various facts seem to lead us to the conclusion 

 that the Siberian High in winter as well as the Pacific High in summer 

 have been heightened, since around 1900 a. d., in other words, the 



114 



