Trends and Difference Analyses of Temperature Extremes in Rural and Urban Areas in Beijing
北京地区城郊极端温度事件的变化趋势及差异分析

The frequency and intensity of temperature extremes in Beijing was studied by using the standardized weather station data from 1979 to 2008. The differences between rural and urban areas and their relationship to the urban heat island intensity are discussed. The analysis results show that the decrease in the minimum temperature events over the urban area -5.94 d (10 a)-1] was slightly higher than that over rural areas -5.28 d (10 a)-1] over the 30-a period, while the difference of maximum temperature changes between the urban 4.33 d (10 a)-1] and rural 4.42 d (10 a)-1] areas were much smaller. The authors also found that the frequencies of extreme events between the urban and rural areas were very small. The investigation of the intensity revealed similar trends. Although the temperature extremes over the urban area were clearly stronger than over the rural areas, in the urban area the decreasing trend of minimum temperature extremes was slightly greater 0.042 °C (10 a)-1] than the increasing trend of the maximum temperature extremes, while in the rural area the deceasing trend of the minimum temperatures was slightly less 0.052 °C (10 a)-1] than the increasing trend of the maximum temperatures. The study on the differences between the urban and rural areas suggested that the intensity of the temperature extremes was stronger over the urban area than that over the rural area. The difference in temperature extremes ship between the urban and rural areas was generally a positive value (except for the negative difference in maximum high temperature in 1982 and 1885). On the other hand, statistical analysis showed no correlationship between the intensity of the urban heat island and the rural-urban difference of extreme temperature events, indicating that the impact of the urban heat island on the urban and rural areas is mainly coincident for a super-city like Beijing.