Scaling of turbulence inurban surface layer using boundary layerheight

本文主要研究边界层高度与城市地面湍流和能量平衡的关系。利用夏季云基准面、太阳辐射、地面热通量、空气温度和湿度观测资料，研究了土地利用差异对云形成的影响。主要结果如下：当风沿着土地利用突变边界时，城市地区云基础水平高于农村地区。晴天午后，城区太阳辐射量有小于郊区的趋势。水汽的空间分布和由地面热通量估算的混合层的发展证实了这一点。城市地区的绝对湿度与农村地区相比有较低的趋势。因此，城市的露点温度也变得低于农村地区。因此，城市的上升凝结水平（LCL）也较低。LCL的空间差异定性地与观测到的边界层一致。这表明地面水汽分布影响高空云的形成。此外，混合层的高度估计从地面热通量的积累。计算结果表明，对流在LCL之外向上发展，这在城市地区更为突出。该估计支持了城市地区的云往往比农村地区发展得更高的观察。

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.