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In this study, the Lepage test, a nonparametnc 2-sample test, was used to statistically analyze annual and seasonal temperatures for the 344 climate divisions in the conterminous United States for the years 1895 through 1989 The objectives of the study were to (1) identify statistically significant changes in annual and seasonal temperatures, (2) determine durlng which seasons the most dramatic changes in temperature occurred, (3) d e t e r m~n e the spatial distribution of significant changes in temperature and (4) determine whether significant regional temperature changes represented gradual or abrupt changes The analysis ind~cated that abrupt and significant changes in annual a n d seasonal temperatures occurred near 1930 and 1958, and that these changes occurred over large parts of the conterminous United States Othei significant and abrupt changes in seasonal temperatures occurred d u n n g the summer near 1917 and 1943, and during the autumn near 1948 and 1964 Temperatures durIng the summer season exhibited the most frequent and widespread signlf~cant changes The results of this study suggest that s~gnificant changes in reg~onal temperature occur abruptly as opposed to giadual uniform changes In a d d~t~o n , the changes In temperature were spat~ally evtensive and appeal to be associated with changes in atmospheric c~r c u l a t~o n KEY WORDS: Temperature c h a n g e. Lepage test-United States. Climat~c change

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Regional changes in precipitation are studied by means of a statistical hypothesis test. Precipitation data used are records at 52 meteorological stations in Japan where observation has been carried out since before 1900. The test used is the Lepage test, which is a distribution-free two-sample test.The detection is made in the following way: Two data sets of precipitation records during N-year period till (Y-1) year and after Y year are statistically tested. The Y year is moved so as to cover the time series data at each station, and when the test rejects the null hypothesis of no difference with a 1% or 5% significance level, the change is determined.The time variation of the number of the stations where the change in the annual precipitation amount is detected with a 1 % significance level shows that the number of the stations sharply increases around 1924, 1949 and 1960 when N=25. This large number indicates that the change occurred in a wide area, and the sharp variation of the number indicates that these changes are discontinuous. A change in 1915 can be added to these by referring to a previous study.Spatial distributions of the difference between the means for 25-year periods prior to and from the years mentioned above illustrate that every change shows a trend of being consistent within one region but different among other regions. Thus, regional discontinuous changes are presented.The same test is applied to the seasonal data. The change in 1949 is strongly detected in the AprilJuly season when it falls on Baiu, an East Asian rainy season. The change in 1915 is also detected in the November-March season, an East Asian winter monsoon season. The changes in 1924 and in 1960 were dominant only in the annual precipitation amount. Dependence of the detection upon the sample size is also studied.Because a few papers reported that discontinuous climate changes occurred on a global scale in 1920s and around 1950, regional changes in precipitation corresponding to these global changes are shown in Japan.

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Power of the Lepage test, a distribution-free two-sample test, is studied by means of statistical simulation. The results show that the Lepage test detects such changes as long term trends, cyclic variations and step-like changes in different ways for each type of phenomenon. The Lepage test can be a very good tool for statistical researches in climate change.

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* 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.