“Christmas Storm” known to Christian Fishers in Japan

Abstract

A small group of Kirisitan (Christian) has miraculously survived in Japan despite the severe oppression in Tokugawa Period. While the majority of Japanese used a lunar calendar, only these Kirisitan fishers knew Gregorian Calendar introduced by Portugese missionaries. During the oppression time their christianity has transformed into a polytheistic religion. Even so they have kept and used their calendar until today for their services with a day's delay from the Gregorian Calendar.Through this solar calendar, they have experienced that on their Christmas Eve, 23 rd of December, heavy storms often began, followed by calm days on 26th and 27th. These storms are confirmed by Fig. 1 to be the winter monsoon from Siberia and the calm days to be the result of the weakening of the Siberian High (Fig. 2).A problem arises whether these Kirisitans have discovered this “Christmas Storm” by themselves or they have learnt it from Portugese missionaries four hundred years ago. For it is possible that the Portugese missionaries knew something about the Portugese weather on these days of which equivalent is known in Germany as Wheinachtstauwetter (Christmas Bad Weather).Such a oversea spread of weather knowledge seems to be possible through a case study on the west coat of South America, where fishers know Viento de San Juan (Wind of St. John) etc which are not supported by the local meteorogical observations. In this case a spread from Spain seems to be probable.On the other hand, some of Japanese fishers have used a lunar calendar even until today with several knowledges on lunar singularities such as “8 th's Storm” etc. Against my working hypothesis that such knowledges reflect local weather differences, the distributions of lunar weather knowledges are almost uniform throughout Japan except “Daishiko Storm” and “Daishiko Calm” on 23rd of XI Month (Fig. 3 and 4).This uniformity may indicate that a spreading played more important role in the aquirment of weather knowledges than discovery. Since some similarities in lunar weather knowledges are found in Korea and Taiwan a spread from the mainland of China is possible.By such considerations a spread of “Christmas Storm” from Portugal still remains a possible guess. Informations from Portugal are most welcomed.