We proposed a new height parameter which explicitly and uniquely specifies the potential range of surface layer regardless of daytime mixed layer, nocturnal stable layer, or indoor free stream topped on it. This parameter is defined as the level where the momentum flux becomes zero by extrapolating the momentum flux profile within the surface layer to the top. We conducted multi-point Doppler lidar observations in Tokyo to test this parameter. Two Doppler lidars were used to measure the vertical distribution of the momentum flux at two locations to test the new parameter proposed in this study. The other one is used to measure the height of the atmospheric boundary layer for comparison. When the mixed-layer is well developed, the height of surface layer reached about 15% of the mixed layer height, which is consistent with the conventional estimates. It is also observed that the diurnal variations of the height of surface layer and mixed layer are negatively correlated.
