西安城市化对气温变化趋势的影响

The Impact of Urbanization on the Surface Temperature in Xi'an

利用1951-2006年西安及周围3站点的气象数据分析了城市气温变化和周围台站温度变化的差异,给出了4个测站不同阶段、不同季节城市化影响气温变化的趋势系数及线性变化趋势。结果表明:城市化对气温的影响具有明显的阶段性和季节性。1980年以前,无论平均气温还是月最低气温和最高气温,西安与其周围站点的线性趋势系数及线性变化趋势相差不大;但在1980年以后,城市站的线性趋势系数明显大于周围站点的趋势系数,特别是在1993年以后,西安站的平均气温、最高和最低气温线性趋势系数远大于其周围站点的趋势系数,是周围站点的1.6～3.5倍,说明城市的热岛效应不但提高了城市的温度同时也改变城市的增温率,使得城市气温增温率加大。西安及其周围站的线性增暖趋势在春季最大,其中西安达到2.20oC/10a,是其它季节的2～4倍;秋季的线性增暖幅度次之,夏季最小。热岛效应对最高气温的最大贡献在春季,对最低气温的最大贡献在冬季。

Based on the observational data in Xi＇an and three other sites surrounding it from 1951 to 2006,this paper analyzes the impact of urbanization on surface air temperature change,including mean surface air temperature （Tm）,maximum surface air temperature （Tmax） and minimum surface air temperature （Tmin）. To get a better understanding of the influence of urban heat island （UHI） effect on warming trend,we study the differences of Tm,Tmax and Tmin between the city site and the other sites in different periods and at different time scales,respectively. The results show there are distinct seasonal differences in urban heat island effects on Tm trend,and different UHI effects are observed in different time periods. There is little difference in linear trend coefficient in annual mean surface temperature,maximum surface temperature and minimum surface temperature between the city site and the surrounding sites before 1980,and the linear trend coefficients of annual mean surface temperature （Tm）,maximum surface temperature （Tmax） and minimum surface temperature （Tmin） at the city station are larger than those of the other three sites after 1980. Especially after 1993,the linear trend coefficients of Tm,Tmax and Tmin in the city are much larger than those of the surrounding sites,and the linear trend coefficient of annual mean Tm is 1.6 to 3.5 times that of the surrounding sites,indicating that the urban heat island effect increases with the increase of both the surface air temperature and the warming rate. We also found that the most significant warming trend occurs at all the four sites in spring,with a rate of 2.20 oC/10a in Xi＇an in spring,which is 2-4 times that in the other three seasons,followed by autumn,and the least significant warming occurs in summer. The maximal influence of UHI effect on Tmax is observed in spring,but on Tmin in winter.