选取纬度相近、发展规模类似的近海(济南)与内陆(西安)城市为研究对象,对比分析了1956—1998年间济南和西安气温与热岛效应的变化趋势.结果表明:1956—1978年间,除济南年均最低气温以0.37℃.10a^-1的速率上升外,2个城市的气温指标均无明显变化趋势;1979—1998年间,2个城市则表现出显著的增温趋势,其中西安年均最高气温和年均气温的增加速率大于济南,济南年均最低气温的增加速率大于西安.1956—1978年间,2个城市均存在城市热岛效应但无显著增加趋势,1979—1998年间的热岛效应明显强化,以西安在年均气温(0.22℃.10a^-1)和年均最低气温(0.32℃.10a^-1)上表现的热岛效应的增加趋势更为明显.济南热岛效应强度和年际波动均大于西安,但其增加速率却小于西安.济南年均最高气温、年均气温和年均最低气温的增温速率和热岛效应强度明显不同,西安则较接近.3个气温指标中以年均最低气温的增加趋势最明显,同时对热岛效应的响应最显著,年均最高气温的波动性最大.地理位置不但影响城市增温的幅度,而且也深刻影响着城市增温的形式与热岛效应强度.
Temporal changes in air temperature and urban heat island (UHI) effects during 1956-1998 were compared between a coastal city,Ji'nan,and an inland city,Xi'an,which were similar in latitude,size and development. During 1956-1978,except that the annual mean minimum temperature in Ji'nan increased by 0.37 ℃·10 a^-1,the temperature variables in the two cities did not display any apparent trend. During 1979-1998,all temperature variables of the two cities showed an increasing trend. Comparing with that in Ji'nan,the increasing rate of annual mean maximum temperature and annual mean temperature in Xi'an was greater,but that of annual mean minimum temperature was smaller. In the two cities,heat island effect occurred during 1956-1978 but without any apparent trend,whereas during 1979-1998,this effect increased with time,especially in Xi'an where the annual mean minimum temperature and annual mean temperature increased by 0.22 ℃·10 a^-1 and 0.32 ℃·10 a^-1,respectively. Both the level and the inter-annual variation of the heat island effect were much greater in Ji'nan than in Xi'an,but the increasing rate of this effect was greater in Xi'an than in Ji'nan. Obvious differences were observed in the increasing rate of annual mean maximum air temperature,annual mean air temperature,and annual mean minimum temperature as well as the heat island effect in Ji'nan,whereas negligible differences were found in Xi'an. Among the three temperature variables,annual mean minimum temperature displayed the most obvious increasing trend and was most affected by heat island effect,while annual mean maximum temperature was most variable inter-annually. Geographical location not only affected the magnitude of urban warming,but also affected the mode of urban warming and the strength of heat island effect.