Spring and Autumn Climate Change in Osaka City since Late 19th Century

543-0026, Japan Abstract This paper analyzed spring (April) and autumn (October) climate change in Osaka City, central Japan, during the period from 1883 (or 1890) to 2006. During these 124 (or 117) years, the April monthly means of daily mean, maximum, and minimum air temperature increased by 2.3°C, 1.9°C, and 3.2°C, respectively, while the relative humidity decreased by 16%. The relative humidity decreased at a low rate of 4.1% per 100 years in 1883-1940, but at a high rate of 17% per 100 years in 1941-2006. The October monthly means of daily mean, maximum, and minimum air temperature increased by 2.5°C, 1.8°C, and 3.6°C, respectively, while the relative humidity decreased by 12%. The relative humidity stayed at a higher level in 1883-1940, decreased at a high rate of 29% per 100 years in 1941-1980, then stayed again at a lower level in 1981-2006. An influence of urbanization on climate change from the middle of the 20th century was suggested by the April and most of the October data. No such influence was however indicated by the October monthly average of daily