The characteristics and occurrence conditions of large-scale turbulence structures in the atmospheric boundary layer (ABL) are investigated above the suburbs of Kyoto City, Japan. An extensive observational set-up, including sonic anemometers–thermometers mounted on a tower, Doppler lidar, and radiosondes, was used to examine the turbulence structures and vertical profiles of the ABL downwind from the city. In near-neutral situations, large-scale turbulence structures with temporal scales of 100‒300 s are detected by the wavelet analysis in the time series of the streamwise velocity component measured in the surface layer. A shift towards unstable conditions is found to be favourable for the emergence of large-scale turbulence structures. Furthermore, the existence of these structures is seen to be related to the development of the ABL and the change of the turbulence situation in the daytime. On average at this site, wind speed in the lower ABL increases in the afternoon. From the intensive observations, we can infer that the downward transfer of momentum via turbulent mixing and other mechanisms extends a high-speed layer at the upper levels towards the surface. Intermittent occurrence of the further increase of wind speed in an interval of several tens of minutes is also found. Turbulence structures are clearly identified in these periods of higher wind speed.

研究了日本京都市郊区上空大气边界层（ABL）中大尺度湍流结构的特征和发生条件。广泛的观测装置，包括安装在塔上的声波风速计、温度计、多普勒激光雷达和无线电探空仪，用于检查城市顺风 ABL 的湍流结构和垂直剖面。在近中性情况下，通过小波分析在表层测量的流向速度分量的时间序列中检测到时间尺度为100-300 s的大尺度湍流结构。发现向不稳定条件的转变有利于大规模湍流结构的出现。此外，这些结构的存在被认为与ABL的发展和白天湍流形势的变化有关。平均而言，在该站点，下午 ABL 下部的风速增加。从密集的观察中，我们可以推断出，通过湍流混合和其他机制的动量向下传递将上层的高速层延伸到地表。还发现风速进一步增加以几十分钟为间隔的间歇性发生。在这些风速较高的时期可以清楚地识别出湍流结构。我们可以推断，通过湍流混合和其他机制的动量向下传递将上层的高速层延伸到地表。还发现风速进一步增加以几十分钟为间隔的间歇性发生。在这些风速较高的时期可以清楚地识别出湍流结构。我们可以推断，通过湍流混合和其他机制的动量向下传递将上层的高速层延伸到地表。还发现风速进一步增加以几十分钟为间隔的间歇性发生。在这些风速较高的时期可以清楚地识别出湍流结构。