Characteristics of Temperature Variation over the Past 53 Years in Hefei

Based on the daily average temperature, the maximum temperature and the minimum temperature data during the period of January, 1953 to December, 2005 in Hefei, the characteristics of temperature variation in Hefei are analyzed by least squares method and wavelet analysis method. The results show that the annual mean temperature, the annual mean maximum temperature and the annual mean minimum temperature present alternant characteristics among cold period and warm period, and the cold period is much longer than the warm period over the past 53 years in Hefei. The average values of temperature in spring, autumn and winter present increasing characteristics, however, the rates of warming are different. The warming rate in winter is larger than that in spring and autumn. And the summer temperature has a weak downward trend. The yearly extreme maximum temperature has a weak downward trend, while the yearly extreme minimum temperature has an obvious upward trend. The cold accumulated temperatures tend to ascend remarkably, while the hot accumulated temperatures tend to descend slightly. The annual mean temperature, the annual mean maximum temperature and the annual mean minimum temperature vary periodically, they present almost the same large-scale period oscillation (about 30-years) but different medium and small-scale period oscillations.