The authors compare the mixing depths in the daytime convective boundary la
yers that were observed remotely by wind profilers and an airborne lidar du
ring the 1995 Southern Oxidants Study. The comparison is used to determine
whether the mixing depths deduced from radar reflectivity profiles measured
by the wind profilers are the appropriate mixing depths to use in air poll
ution applications. The profiler mixing depth!: are based on evidence that
the profile of the refractive index structure function parameter exhibits a
peak at the boundary layer capping inversion. The lidar mixing depths are
determined from the gradient in aerosol backscatter at the top of an aeroso
l mixing layer. The results of linear regression analysis show that the mix
ing depths measured by the wind profiler and lidar are in good agreement, p
articularly in the absence of scattered clouds forming at the top of the co
nvective boundary layer. When significant cumulus convection occurs, the de
finition of mixing depth from both experimental and theoretical points of v
iew is ill defined.