Discontinuous Climate Changes in Japan after 1900

[摘要] Because the statistical hypothesis test (the Lepage test) has successfully shown the regional abrupt changes in precipitation in Japan after 1900, changes of the temperature and sea-level air pressure are studied by means of the same method.The analysis shows that the temperature and sea-level pressure also presented discontinuous changes. Also, it is noted that the changes in the temperature were not fictitious ones caused by changes in observational methods, instrument changes or other factors.Referring to the previous study on the changes in precipitation, the climate changes which occurred in Japan after 1900 can be summarized as follows: (1) Changes detected were discontinuous ones and trends of temperature did not cause any significant changes. (2) Very noticeable abrupt warmings with a magnitude exceeding 1°C of the seasonal mean temperature occurred in 1914 and 1949, and the precipitation amount increased in the successive seasons. (3) The seasonal mean temperature also changed in 1957 and 1967. These recent changes were discontinuous ones, but were neither abrupt warmings nor abrupt coolings. The mean temperature for August-October fluctuated more after 1957 and for April-July it fluctuated less after 1967. (4) Cooling trends were noticed during periods between discontinuous changes but they did not cause any definite changes to be detected by the Lepage test. (5) The sea-level air pressure changed three times. Though the quality of the sea-level air pressure records is questionable, it may be worthy to note that one of the changes occurred in 1924 and in 1924 the annual precipitation amount decreased.The discontinuous changes support the idea that the climate system is a chaotic spontaneous dynamic system. Mechanisms of the regional discontinuous changes and the relations between the very noticeable abrupt warmings and the concentration of greenhouse effect gases should be the subjects of future studies.

[学科分类] 大气科学