Observation And Simulation Study On Atmospheric Boundary Layer Over Inhomogeneous Underlying Surface In Nanjing During Summer

The environment of human subsistence has a close relation with atmospheric Boundary layer processes. As an important carrier of the human population living in, dynamic and thermodynamic characteristics of urban atmospheric boundary layer and its interaction mechanism has become an important issue that affects human’s life. By using the data of2010Nanjing Summer turbulent character three-dimensional observation test in Nanjing and its causes were analyzed in methods of data analysis and numerical simulation. The results showed that:(1) During daytime, mixed layer in urban developed faster and higher than that in suburb. During nighttime, unstable stratification of the urban atmosphere was easy to form a mixed layer. The strong convective mixing in urban atmosphere exacerbated the development of boundary layer, so that the night inversion layer and gale area uplifted. Urban mixed layer height was estimated as300m in nighttime and1300m in daytime in summer2010in Nanjing. The top height of city mixed layer continues lifting along with urban development. Urban and suburban low-level winds are subject to urban overlay, inversion layer in city at night and windy areas with urban development and uplift along with urban development, and rapid wind appear at the top of the inversion layer, highly consistent with the development of the mixed layer at night.(2) Integrated studies on turbulence vertical structure of Nanjing UBL suggest:Under unstable condition, the normalized turbulent wind standard deviation (σu/u*,σv/u*,σW/u*) follow the Monin-Obukhov similarity theory and its normalized functions are given out as well. Horizontal normalized turbulent wind standard deviation reduce with the increase of the underlying surface roughness.The horizontal turbulent Decimalized standard deviations over the urban surface are always less than those over the suburban area.(3)WRF model applied to the Nanjing urban boundary layer meteorological characteristics is feasible, the result further reveals a significant impact on the structure of the urban boundary layer due to the special urban surface. In the summer time when the weather was fine, heat island took shape in boundary layer all day in Nanjing. At the daytime, TKE in city can reach the higher value of1,2m2/s2in200-700m, twice as that in suburbs. At night in the city heat storage release heat, TKE is still greater than the suburbs.