Classification of Seasons in Japan 



Weather Type. 



Spring 



Earlv suiiinier 

 Bain 



Earlv winter 



Higli and low pass cyclicly, 



weather variable 

 High belt forms, fair and mild . . 

 Tropical front forms south of 



Japan, rain 

 Southerh' monsoon prevails, hot, 



fair weather, stable 



Tm air mass replaced by Pc, 



raining 

 High and low pass cyclicly, weather 



changes cyclic 

 Cold air mass comes to Japan, 



occasional showery precipitation 

 Northerly monsoon prevails cold 



and fair on Pacific coast, snowy 



on Japan sea coast, stable 



Mar. X ± Id 



April 30 ± 8 

 June 5 ± 10 



July 18 ± 7 



Sept. 11 ± 6 

 Oct. 10 i 9 

 Nov. 20 ± 10 

 Dec. 18 ± 5 



Temperature rises suddenly after 

 passage of travelling anticyclone. 



Cyclic change of weather over. 



Temperature falls, rainy season 

 begins. 



Temperature rises suddenly, some- 

 times accompanied by heavy 

 rains. 



Temperature falls suddenly, some- 

 times accompanied by typhoons. 



Rainy weather over continental 

 high develops. 



Winter type pressure pattern begins 

 occasionally. 



Temperature falls suddenly after 

 passage of cyclone. 



In this table only an outline of the characters of every season are 

 shown. Studying further we may have results which would be useful 

 for long-range forecasting. The weather of Japan changes cyclically, 

 as a whole, and we found three or four days and seven or nine days 

 periodicit}^ The short period is caused by the passage of low, while the 

 long period is caused by the outflow of highs from high latitudes. In 

 summer and winter long periods predominate, and in spring and fall 

 short periods predominate. We experience also thirty-live days periodi- 

 city. Japanese forecasters know that the modes of the weather changes 

 have a yearly character, and similar weather situations appear very often 

 in one j^ear. This is proved statistically, and it is important for long- 

 range forecasting. 



ON SEA FOG OF ADVECTION TYPE OVER THE OYA SHIO 



By YosHiHiKO Takahashi, Central Meteorological Observatory, Japan 



Introduction 



In June- July fogs are frequently observed at sea along the Kuril Islands 

 and the Pacific coasts of Hokkaido, when- the wann and humid air from 

 the south moves in over the Oya Shio. 



The weather map in Fig. 1 shows a representative of the pressure 

 distribution favourable to the occurrence of such fog, and Fig. 2 shows 

 the distribution of the water temperature of sea surface averaged for the 

 first ten days of August, 1941. This year the period of the predominance 

 of the Oya Shio has been somewhat late. 



As frequently as sea fog of advection type another type of fog, or 

 frontal fog, occurs in the same season along the Kuril Islands and the 

 Okhotsk coasts of Hokkaido, when the cold wind from the anticyclone 

 over the Okhotsk Sea or the Bering Sea blows toward these districts. 



The present paper, however, will be concerned with sea fogs 

 of advection type only. 



As to the causes of sea fogs it has been known only that as the warm 

 and humid air moves over the colder water and is cooled from below so 

 that its dew point is reached, fog will be produced. But from the 

 physical point of view such a theory must confront many difficulties to 

 explain quantitatively the properties of sea fogs. If the theory be correct, 

 for example, sea fogs would not be much different in properties from 



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