Abstract
This study analyzes the long-term temperature trends and the occurrence frequency of temperature extreme climate observations for yearly surface air temperature since 1909 at Seoul, Daegu, Busan and Mokpo. We devised three DESIGNs for reference state to determine the long-term mean and trends, which are the measures of normal climate. DESIGN 1 uses the 70-years-mean of the yearly mean as a long-term norm for the leading 70 years. DESIGN 2 uses the linear regression function fitted by the perturbations at each station of DESIGN 1 as the long-term trend. DESIGN 3 uses the long-term trend of Mokpo for the leading 70 years as the natural trend because Mokpo's temperature may not be affected by urbanization. It was found that Mokpo's increasing trend was the lowest among the cities under our study. The quasi-extreme and extreme climate, which are defined as the yearly air temperature exceeding ±1.5 standard deviation and ±2 standard deviation respectively, so they show the different aspect dependent on the each DESIGN. The temperature anomaly histogram in Seoul and Daegu have the broad frequency distribution about mean relative to Busan and Mokpo. Especially the extreme climate for climate change in which a trend with urban effect is permitted is overestimated by more frequency than that without urban effect.