Extended Abstract (260K)P6.8
Turbulent transfer efficiency of momentum, heat, vapor, and CO2 measured in the urban surface layer over a densely built-up canopy
Ryo Moriwaki, Tokyo Institute of Technology, Tokyo, Japan; and M. Kanda and T. Watanabe
The field observation over a densely built-up residential area in Tokyo, Japan, is performed using a tower. The plan area index of the buildings in the observation site is 0.48. The nature of the turbulent transfer of momentum, heat, vapor, and CO2 is investigated using the correlation coefficients and wavelet analysis. In this study, turbulence data, i.e. the fluctuations of three dimensional wind velocity, temperature, vapor density, and CO2 concentration, sampled with 8 Hz and measured at the height z/h=4.0 (with z=29 m as the sensor height and h=7.3 m as the average height of buildings) for 8 months are analyzed. Following conclusions are obtained.
(1) The ratio of transfer efficiency of heat and momentum, rwT/ruw , as a function of the atmospheric stability, z'/L , agrees well with existing function form provided in other cities.
(2) The transfer efficiency ratio of vapor for momentum, rwq/ruw , is smaller than provided function form. The ratio of CO2 for momentum, rwc/ruw , is much smaller, and its dependence on the atmospheric stability is not found.
(3) Wavelet analysis shows the contribution of various scale of turbulence to the each scalar tranport (heat, vapor, and CO2). In the morning, the thermally convective large-scale motions are dominant. In such an unstable condition, water vapor is transferred effectively. On the other hand, in the dattime, the heat and vapor are similarly transferred by small-scale turbulence (organized structure and wake), but, in thermal-scale, vapor and CO2 are not or adversely transferred while heat is effectively transferred.
Poster Session 6, BLs over Heterogeneous Surfaces; Coupled Surface - BL Studies
Thursday, 18 July 2002, 2:00 PM-2:00 PM
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