太原城市下垫面扩张对边界层特征影响的个例研究

通过高分辨率卫星夜间灯光数据获取最新的城市地表分布,并利用高分辨率数值模式对2013年8月14~16日太原区域的一次高温过程进行研究,探讨城市下垫面扩张对大气边界层的影响。结果表明：基于DMSP/OLS夜间灯光数据对模式中地表参数修正后,能够更准确地反映太原主城区和高速公路沿线小规模建筑群的扩张,有效改善了模式的预报性能,显著提高对近地面气温、地表温度的预报能力。城市下垫面的扩张,使城区夜间升温明显,热岛强度增强。与1992年的城市化状况相比,晴空天气条件下,2012年太原城区夜间气温上升5℃,热岛强度升高2~3℃。城市下垫面扩张,改变了地表能量分配关系,使得地表感热传输明显加强,潜热通量明显减弱,城市冠层作用下的储热能力增强。边界层内部湍流交换、水汽输送等的进一步研究表明：城市地表水汽输送减弱,边界层水汽含量减少,2~4 km高度的水汽含量增加,湍流动能的影响高度增高,湍流混合加剧;14：00,城区边界层高度抬高了800 m,城市上空混合层加深,持续时间更长。

A Case Study on the Effect of Urban Underlying Expansion on Atmosphere Boundary Layer Characteristics in Taiyuan

In order to understand the effect of urbanization on the local urban boundary layer,based on the light intensity at night from high resolution satellite,the latest spatial distribution of land use types in urban was obtained,firstly. And on this basis the impact of urbanization development on characteristics of atmosphere boundary layer（ ABL） over Taiyuan during a high temperature event which occurred on 14 to 16 August 2013 was conducted by introducing the high resolution land use of urban to numerical model. The results showed that the amended surface parameter in model with the nighttime light images from DMSP / OLS could not only accurately show the urban expansion in Taiyuan＇s main city zones and small scale buildings along highways,but also effectively improved the forecasting capability of model,especially on skin and surface temperature. The expansion of urban underlying has a significant influence on the increase of the urban heat island（ UHI） intensity and night temperature of urban areas. Compared with urban uderlying in 1992,the temperature at night of urban areas in Taiyuan increased by 5 ℃ under sunny weather condition,and the intensity of UHI increased by 2 ~ 3 ℃. The expansion of urban changed the distribution of earth surface energy,with a significant increase of sensible heat flux and decrease of latent flux,and then the heat storage capability under the effect of the urban canopy was enhanced. Further study on the turbulent exchange and the water vapor transfer in the boundary layer found that the water vapor transfer from the urban surface and the water vapor content in the boundary layer decreased,while the content over the height of 2- 4 km increased. The height influenced by turbulent kinetic energy increased,and the turbulence strengthened. The boundary layer over urban at 14： 00 BT was even lifted by800 m,and the mixing layer deepened and lasted longer.