Abstract: Based on the data collected at a 255 m tower during an atmospheric boundary layer experiment in Tianjin, the micro-structures of turbulence and characteristics of energy transfer during an advective fog process in February 2006 are analyzed. Combined with the cold front passage, clear and weak wind condition, and light fog, the characteristics of turbulent kinetic energy during the fog process are discussed. The results show that the peak frequencies of energy spectral density for all directions are at the higher frequency part during the fog occuring, while being at the lower frequency part before the fog formation and after the fog dissipation. Compared with the velocity spectra, the peak frequency change of temperature spectra is larger than that of velocity spectra before the fog formation. As the fog dissipates, the peak frequency of temperature spectra is lower than that of velocity spectra. During the fog, the mean kinetic energy shows a smaller value, while the turbulent disturbance is active, and the vertical turbulent momentum transfer is dominant. The abrupt rising of mean and turbulent kinetic energy before the fog formation may be regarded as the starting signal of advective fog.

Key words: advective fog, energy transfer, turbulent energy spectra, meteorological tower

摘要： 利用天津255m气象塔大气边界层实验资料, 分析了2006 年2 月一次平流雾过程湍流微结构及能量输送的演变特征, 并结合冷锋过境、晴朗小风及轻雾等天气条件, 讨论了雾过程中湍流动能特征。得到:雾中各向风速能谱密度峰值频率偏于高频段, 雾前和雾后风速能谱峰值频率偏向于低频段; 与速度能谱相比较, 雾形成前期, 温度谱峰值频率的变化大于速度谱; 雾消散期间, 温度谱峰值频率比速度谱峰值频率更偏向于低频; 雾过程中, 平均动能较小, 但湍流扰动活跃, 湍流动量输送以垂直方向为主; 平均动能和湍流动能在雾前 出现异常增强, 这可能是平流雾的启动信号。

关键词: 平流雾, 能量输送, 湍流能谱, 气象塔