南京城市化对极端气温的影响

为了科学认识城市化对极端气温的影响,利用南京地区3个城区气象站和3个周边乡村站1961—2005年日最高、最低气温资料,对比分析城市站和乡村站17个极端气温指数的平均值和变化趋势,并定量估算极端气温变化趋势的城市化影响及贡献。结果表明:近45年南京地区暖事件均为增加趋势,而冷事件多为减少趋势,最高气温、最低气温的平均值和极值均为上升趋势。城市站与乡村站相比,暖事件更多,冷事件更少,最高气温、最低气温的平均值和极值更大。城市化对极端气温变化趋势的影响有两大特点:城市化加速了极端气温指数的变化速率,使得暖事件、平均值、极值的上升趋势和冷事件的下降趋势变得更大;基于最低气温的极端气温指数变化趋势比基于最高气温的极端气温指数受城市化影响更显著。城市化贡献表现为:暖事件大于冷事件,最低气温极值和平均值大于相应的最高气温极值和平均值。

The Impact of Urbanization on Extreme Air Temperature in Nanjing

The paper aims to scientifically understand the impact of urbanization on the extreme air temperatures. Based on the observed daily maximum air temperatures and minimum air temperatures at three urban stations and three rural stations in Nanjing during the period of 1961 to 2005, the average values and change trends of 17 extreme temperature indices for urban and rural stations were analyzed. The impact and contribution of urbanization on the variation trends of extreme temperature indices were also estimated. Results showed that warm events increased, while cold events decreased in Nanjing during 1961 to 2005. However, compared to rural stations, there were more warm events and less cold events for urban stations. Extreme value indices and mean value indices both exhibited increasing trend, and were larger at urban stations than that at rural stations. Impact of urbanization on the variation trends of extreme temperatures showed two characteristics. On one hand, urbanization accelerated the change rates of extreme temperature indices. The increasing rates of warm events, extreme value indices and mean value indices and the decreasing rates of cold events were both improved due to the urbanization. On the other hand, the trends of indices based on daily minimum temperature were more significant than that based on daily maximum air temperature. The contribution of urbanization on change trends was larger for warm events than that for cold events, and larger for extreme value indices and mean value indices of minimum air temperature than that for extreme value indices and mean value indices of maximum air temperature.