Abstract:The atmospheric boundary layer height is a critical parameter for studies of weather, climate and air pollution. The entrainment process at the top of the Convective Boundary Layer (CBL) results in an increased vertical gradient of temperature and humidity, thus enhancing the refractive index structure constant Cn2 for this layer. This vertical distribution feature of Cn2 is often used to locate the CBL height Zi. In this paper, the CBL height Zi is deduced from the wind profile radar data of Grand Port District of Tianjin from July to August in 2010. For the multiple or unclear Cn2 peaks, this paper improves the measurement of Z, and discusses the applicability of the maximum backscattered intensity method and the method combining Cn2 and the vertical velocity variance σw2. The results show that:(1) When the Cn2 profile has a single peak, the maximum backscattered intensity method can correctly estimate the height of CBL. This situation often corresponds to a sunny day. The maximum backscattered intensity method may incorrectly estimate the height of CBL when the temperature and humidity fluctuation caused by the residual layer or the cloud layer in the CBL leads to a Cn2 profile with double peaks or even multiple peaks; (2) The method combining Cn2 and σw2 is not only consistent with the maximum backscattered method at sunny days, but also distinguishes the Cn2 peak caused by CBL from the Cn2 peak caused by the cloud layer, thus correctly estimating the CBL height; (3) In general, the method combining Cn2 and σw2 can well identify the Cn2 peak corresponding to CBL when there are obvious, broken or undisclosed clouds in the convective boundary layer. However, because the situation in the boundary layer is extremely complex, this method may also incorrectly estimate the CBL height for different reasons.