Scaling of turbulence inurban surface layer using boundary layerheight

本文研究的主要内容是边界层高度与城市地表湍流和能量平衡的关系。我们利用夏季观测的云基面、太阳辐射、地表热通量、气温和湿度等数据，研究了土地利用的差异对云形成的影响。主要研究结果如下：在土地利用突变的边缘地区，当风吹过时，城市地区的云基准面高于农村地区。在晴天的下午，城市地区的太阳辐射往往比农村地区的小。水汽的空间分布和由地表热通量估算的混合层的发展证明了这一点。与农村地区相比，城市地区的绝对湿度有降低的趋势。因此，城市露点温度也变得低于农村。因此，城市的抬升冷凝层(LCL)也较低。LCL的空间差异与观测到的边界层的空间差异定性一致。这表明地面水汽分布影响了高空云的形成。此外，还利用地面热通量的累积估算了混合层高度。估算结果表明，对流在LCL以外的区域向上发展，这在市区更为突出。这一估计支持了城市地区云发展趋势高于农村地区的观察结果。

The main interest in this study is the relationship between boundary layer height and the urban surface turbulence and energy balance. We investigated the effects of differences in land use on the formation of clouds, using the summer time datasets from the observations of cloud base level, solar radiation, surface heat flux, air temperature and humidity. The followings are main outcomes.Cloud base level over urban area was higher than that over rural area when wind blew along the border of the abrupt change of land use. Solar radiation over urban area tended to be smaller than that over rural area in the afternoon of sunny days. This was demonstrated by the spatial distribution of water vapor and the development of mixing layerestimated from surface heat flux. Absolute humidity in urban area tended to be lower in comparison with that in rural area. Therefore, the urban dew-point temperature also became lower than that in rural area. As a result, the urban lifted condensation level(LCL) was also lower. The spatial difference of LCL qualitatively coincided with that of observed boundary layer. This indicates that the surface water vapor distribution affected the formation of cloud aloft. In addition, the mixing layer height was estimated from the accumulation of surface heat flux. The estimation shows that the convection developed upward beyond LCL and this is more prominent in urban area. The estimation supports the observation where cloud in urban area tended to develop higher than rural area.