  We consider the effects of a shear on velocity fluctuations in a flow. The
shear gives rise to a transient amplification that not only influences the
amplitude of perturbations but also their time correlations. We show that, in
the presence of white noise, time correlations of transversal velocity
components are exponential and that correlations of the longitudinal components
are exponential with an algebraic prefactor. Cross correlations between
transversal and downstream components are strongly asymmetric and provide a
clear indication of non-normal amplification. We suggest experimental tests of
our predictions.
