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The spatial variability of both turbulent flow statistics in the roughness sublayer (RSL) and temperature profiles within and above the canopy layer (CL) were investigated experimentally in a densely built-up residential area in Tokyo, Japan. Using five towers with measuring devices, each tower isolated from the others by at least 200 m, we collected highfrequency measurements of velocity and temperature at a height z = 1.8 z H , where z H , the mean building height in the area, is 7.3 m. Also, temperature profiles were measured from z = 0.4 to 1.8 z H . The 'areal mean' geometric parameters that were obtained for the areas within 200 m of each tower were fairly homogeneous among the tower sites. The main results are as follows: (1) The spatial variability of all RSL turbulent statistics, except the sensible heat flux, was comparable to that reported in a pine forest. Also, the variability decreased with increasing friction velocity. (2) The spatial variability of the RSL sensible heat flux was larger than that reported in a pine forest. Also, the variability depended on the time of the day and became larger in the morning. The difference among the sites was well related to the areal fraction of vegetation. (3) The spatial variability of the CL temperature profile depended on the time of the day and became larger in the morning. Nevertheless, the spatial standard deviation of CL temperature was always below 0.7 K. (4) It is suggested that the "warming-up" process in the morning when heat storage is dominant increases the spatial variation of RSL sensible heat flux and CL temperature according to the local properties around each tower and the variation decreases once there is further convective mixing in the midday.

Large Eddy Simulations have been performed for fully developed turbulent flow within and above explicitly resolved simple cube arrays. The model (LES-CITY) was validated in comparison with laboratory experiments. The systematic influence of cubic density on turbulent flow characteristics was investigated through numerical experiments in a wide range of cubic area density (0 to 0.44).The following results were obtained. 1) The intermittency of flow: the temporally and spatially averaged flow structure confirms the existence of conventionally described canyon flow regime. However, the intermittency of the canyon flow for any cubic densities is large and the stream patterns are never persistent. 2) Turbulent Organized Structures (TOS): TOS are characterized by longitudinally elongated low speed streaks and corresponding streamwise vortices. The streaks in sparse and dense canopy flows are likely to be aligned to the street-line and to the roof-line, respectively.