Abstract: A new method for deriving the Lagrangian decorrelation time scales for inhomogeneous turbulence is described. The expression for the time scales here derived for the convective boundary layer are compared to those estimated by Hanna during the Phoenix experiment. Then the values of $C_0$, the Lagrangian velocity structure function constant, and of $B_i$, the Lagrangian velocity spectrum constant, were evaluated from the Eulerian velocity spectra and from the Lagrangian time scales derived, under unstable conditions, from Taylor's statistical diffusion theory. The numerical coefficient of the lateral and vertical Lagrangian spectra in the inertia subrange were found equal 0.21 in good agreement with the previous experimental estimates.