Observational Evidence for the Monin-Obukhov Similarity under All Stability Conditions

Data collected in the surface layer in a northern suburban area of Nanjing from 15 November to 29 December 2007 were analyzed to examine the Monin-Obukhov similarity for describing the turbulent fluctuations of 3D winds under all stability conditions and to obtain the turbulence characteristics under different weather conditions. The results show that the dimensionless standard deviations of turbulent velocity components (σu/u*, σv/u*, σw/u*) and dimensionless turbulent kinetic energy (TKE) can be well described by ``1/3'' power law relationships under stable, neutral, and unstable conditions, with σu/u*>σv/u*>σw/u*. Land use and land cover changes mainly impact dimensionless standard deviations of horizontal component fluctuations, but they have very little on those of the vertical component. The dimensionless standard deviations of wind components and dimensionless TKE are remarkably affected by different weather conditions; the deviations of horizontal wind component and dimensionless TKE present fog day > clear sky > overcast > cloudy; the trend of the vertical wind component is the reverse. The surface drag coefficient at a Nanjing suburban measurement site during the observation period was obviously higher than at other reported plains and plateau areas, and was approximately one order larger in magnitude than the reported plains areas. Dimensionless standard deviation of temperature declined with increasing |z'/L| with an approximate ``-1/3'' slope in unstable stratification and ``-2/3'' slope in stable stratification.