摘要
利用WRF V3.2.1模式,分别在京津冀、长三角和珠三角进行城市区域扩展,通过改变城市扩展区域的城市化率,模拟研究不同城市化率对东亚季风气候的影响。结果表明:城市化使得夏季华北地区降水偏少、华南地区降水偏多,即阻挡东亚夏季风向北方推进,从而减弱东亚夏季风。对气温的影响来看,在京津冀、长三角和珠三角地区进行大规模城市化,分别对同一纬度带上的华北、江淮和华南地区的气温变化影响最大。在京津冀试验组中的华北或珠三角试验组中的华南地区,在同一城市化率试验中,无论冬季还是夏季,其最高温的增幅基本大于最低温幅增幅;无论最低温还是最高温,其夏季气温增幅总是大于冬季增幅。而长三角试验组中的江淮地区,在同一长三角城市化率试验中,无论最高温或最低温,其夏季的气温增幅总是大于冬季。除了近地面气温,城市化会影响城市区域上空的气温和垂直运动,城市化率越高,城市拓展区上空的低层升温强度越强,升温延伸高度越高,差值上升运动愈加明显。季节差异上,城市拓展区上空的夏季升温强度比冬季强,高度也比冬季高,伴随的差值上升运动总体上夏季亦比冬季强。而从850 h Pa高度层平均风场的差值结果来看,夏季华北地区大都盛行差值偏北风,说明城市化使夏季风向北推进到华北地区的偏南风分量比城市化前减小,影响夏季风向北推进的能力和强度,不利于给华北地区带来更多的降水,造成华北地区偏旱;冬季时,大部分试验中华南地区上空始终有反气旋性差值环流,该差值环流北部的差值偏南风较强,说明城市化使冬季风向南侵袭到华南地区的偏北风分量比城市化前减小,不利于冬季风影响华南地区,一定程度上减弱了冬季风。
By using mesoscale WRF model version 3.2.1,the impacts of urbanization on monsoonal climate in East Asia are studied with modified urban land cover in different locations of eastern China. The results show that the urbanization in eastern China have decreased the summer precipitation in northern China but increased that in southern China,indicating that the urbanization in eastern China has prevented the East Asia summer monsoon（EASM） advancing northward and thus the EASM is weakened. For temperature,the large-scale urbanizations in the Beijing-Tianjin-Hebei area,the Yangzte River Delta or the Pearl River Delta,exert most remarkable impacts on the temperature of the northern China,the Yangzte-Huaihe Valley and the southern China respectively. In the northern China of the Beijing-Tianjin-Hebei area urban tests or the southern China of the Pearl River Deltaurban tests,whether in summer or winter,the increase of the maximum temperature is almost more significant than that of the minimum temperature,and whether the maximum temperature or the minimum,its increase in summer is larger than that in winter.In the Yangzte-Huaihe Valley of the Yangzte River Delta tests,whether the maximum temperature or the minimum,its increase in summer is lager than that in winter. Besides the surface temperature,the urbanization influences on the temperature and the vertical motion above the urban areas. As the urban fraction gets higher,the warming effect in low-layer over the urban extending areas is stronger,the warming elevation is higher and the deviation ascending motion is more significant. When it comes to their seasonal difference,the warming effect in summer over the urban extending areas is more pronounced than that in winter,the same are the warming elevation and the deviation ascending motion in summer. Finally for the 850 h Pa deviation wind vectors,the urban extension causes that the deviation north wind prevails in the northern China during summer,which affects the EASM advancing northward and its intensity and reduces the precipitation in northern China. While during winter in most urbanization tests,the southern China is occupied by an anticyclone circulation and the deviation south wind from its northern part blow northward significantly,which is not benefit to the East Asia winter monsoon（EAWM）blowing southward to the southern China and may weaken the EAWM.
出处
《气象与减灾研究》
2016年第1期16-31,共16页
Meteorology and Disaster Reduction Research
基金
国家重点基础研究发展计划(973计划)项目(编号:2010CB428505)
国家自然科学基金项目(编号:41275012
41475069)
