  Data of skewness $S$ and kurtosis $K$ of vertical velocity in the convective
boundary layer from different datasets have been analysed. Vertical profiles of
$S$ were found to be grouped into two classes that display different slopes
with height: one is nearly constant and the other is increasing. This behaviour
can be explained using a simple model for the PDF of vertical velocity and
assuming two distinct vertical profiles of updraft area fraction from
literature. The possibility of describing the explicit dependence of $K$ on $S$
was revised critically, also considering the neutral limit as well as the limit
for very small non-dimensional height. It was found that the coefficients of
the relationship depends on both the Obukhov length scale $L$ and inversion
height $z_i$.

Atmospheric and Oceanic Physics