长沙城市化进程对局地气候的影响

利用1961—2010年湖南省长沙及周边郊县共5个气象站的逐日气温、降水和相对湿度观测数据,在对各气象要素资料序列进行均一性检验和订正的基础上,以郊县站作为背景场,系统地分析了长沙城市化不同阶段对城市气候的影响。结果表明:受城市化的影响,近50年长沙市区地面气温及其上升速率远高于郊县的,城市热岛效应明显,热岛效应对市区年平均气温的增温贡献率达30%,且主要出现在20世纪90年代之后,四季中城市化贡献率的最大值出现在夏季,秋季和春季的次之,冬季的最小。50年来长沙市区和郊县年降水量差值序列呈显著增加趋势,长沙城市雨岛效应较为显著,且主要发生在春季和夏季,城市化带来的雨岛效应加速了长沙降水结构两极分化,使城市内涝发生的概率进一步增大。50年来长沙市区和郊县年平均相对湿度及其差值的变化趋势均不显著,就全年平均而言,长沙的城市干岛效应并不明显,但近20年来干岛效应显著增强;分季节来看,近50年干岛效应主要发生在夏季。

Effect of Urbanization Process on Local Climate in Changsha City

Using daily air temperature, precipitation and relative humidity observation data of Changsha and 4 nearly suburban county weather stations from 1961 to 2010, preprocessing with homogeneous adjustment and correction, the climate impact of urbanization on different stages in Changsha is analyzed through suburban stations as background field. The results are as follows. For the influence of urbanization, the increasing trend of surface air temperature in urban is much higher than suburban in recent 50 years. The urban heat island effect is significant, which contribute 30% of the annual mean air temperature increasement in the urban area, and mainly appeared after 1990s. Among the four seasons, summer has the most contribution of urbanization, following autumn and spring, and winter has the least. The differences of precipitation between urban and suburban have an obviously increasing trend over the last 50 years. The rain island effect is significant, particularly in spring and summer. The rain island effect accelerates the polarization of precipitation structure in Changsha and increases the probability of urban waterlogging. Neither the relative humidity in urban and suburban or the differences between them show any significant trend in recent 50 years. For annual average, the dry island effect of Changsha in recent 50 years is unremarkable but significantly enhanced in recent 20 years. For seasonal, the dry island effect mainly occurs in summer in recent 50 years.