城市水泥下垫面／郊区下垫面湍流统计特征分析

为探讨城市水泥下垫面和郊区下垫面上的无量纲速度方差及温度方差与稳定度的关系,对2006年2月18日至3月10日南京市委党校楼顶和南京大学浦口校区观测站三层高度上的湍流资料的统计特征进行了对比分析,发现在不稳定层结下,城市水泥下垫面上的无量纲水平速度方差σu/u*和垂直速度方差σw/u*比郊区下垫面小,两者随稳定度z/L的变化基本符合1/3次律,但不能直接用Panofsky等提出的乡村下垫面条件下的经验关系式来表示。城市水泥下垫面上的无量纲温度方差σT/T*大于郊区下垫面。同时,在郊区30m高度附近的无量纲水平速度方差σu/u*和垂直速度方差σw/u*满足1/3次律,2m高度则不满足1/3次律。40m以下高度σT/T*与-z/L之间满足-1/3次律。

Comparison and Analysis on the Statistical Characteristics of the Turbulence over the Urban Concrete/Suburban Underlying Surface

To figure out whether velocity components and temperature variances with the stability in the surface layer under unstable stratification satisfy the Monin-Obukhov similarity theory, the statistical characteristics of the turbulent data observed in the winter at the top of the Dangxiao Building in the urban area of Nanjing city and at three heights on the meteorological tower in the Pukou campus of Nanjing University, which lies in the suburban area, are analyzed and compared. The analysis on the data shows that the horizontal and vertical turbulent Decmalized standard deviations over the urban surface are always less than those over the suburban area. The variances with the stability in the surface layer under unstable stratification satisfy the Monin-Obukhov similarity theory. But they cannot be expressed as the empirical formula Panofsky proposed for rural underlying surface. However, the temperature turbulent Decmalized standard deviations in the urban area are larger than that over the suburban area. Meanwhile, the analysis on the suburban data at different heights shows that velocity components and temperature variances with the stability in the surface layer under unstable stratification satisfy the Monin-Obukhov similarity theory at the height of 30 m and 40 m. The temperature variances at the height of 2 m follow the same theory.