A laboratory study of the turbulent velocity characteristics in the convective boundary layer |
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| Authors: | Sun Jianning Jiang Weimei Chen Ziyun Yuan Renmin |
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| Institution: | Department of Atmospheric Sciences, Nanjing University, Nanjing 210093,Department of Atmospheric Sciences, Nanjing University, Nanjing 210093,Department of Atmospheric Sciences, Nanjing University, Nanjing 210093,Department of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 |
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| Abstract: | Based on the measurement of the velocity field in the convective boundary layer (CBL) in a convection water tank with the particle image velocimetry (PIV) technique, this paper studies the characteristics of the CBL turbulent velocity in a modified convection tank. The experiment results show that the velocity distribution in the mixed layer clearly possesses the characteristics of the CBL thermals, and the turbulent eddies can be seen obviously. The comparison of the vertical distribution of the turbulent velocity variables indicates that the modeling in the new tank is better than in the old one. The experiment data show that the thermal's motion in the entrainment zone sometimes fluctuates obviously due to the intermittence of turbulence. Analyses show that this fluctuation can influence the agreement of the measurement data with the parameterization scheme, in which the convective Richardson number is used to characterize the entrainment zone depth. The normalized square velocity w2i/w2* at the top of the mixed layer seems to be time-dependent, and has a decreasing trend during the experiments. This implies that the vertical turbulent velocity at the top of the mixed layer may not be proportional to the convective velocity (w*). |
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| Keywords: | convective boundary layer (CBL) convection water tank turbulent velocity entrainmentzone |
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