Abstract: The characteristics of horizontal temperature of the convective boundary layer (CBL) were analyzed using water tank simulation. Based on the geometric similarity, kinematic similarity and dynamic similarity, the initial and boundary conditions can be set for simulation. The dimension of the water tank is 1.5 m×1.5 m×0.6 m. The degassed water was first filled with inversion stratification, then the bottom was heated and the convection was generated. The generation and evolution of the CBL were simulated. Temperature profiles and fluctuations at several heights were measured using fast response temperature sensors; optical turbulence was retrieved from the record using scintillation effect. Several parameters, such as the CBL depth, can be calculated. The AR power spectrum estimate was used to obtain the peak frequency of temperature fluctuations at those heights, which corresponds to the scale of quasi two-dimensional structure. The results show that scales of quasi two-dimensional structure at the low part of CBL increase with the height, reaching the maximum scale at about 065 Zi, and then decrease with the height at the upper part of the CBL. The results show good agreement with the fields and the numerical simulation. At the upper part of CBL, the normalized scales decrease with stabilizations. Based on the results, a thermal pattern for the free CBL was proposed.

Key words: convective boundary layer, quasi two-dimensional structure, characteristic scale, convective water tank, physical simulation