  We analyze the robust character against non-static noise of clock transitions
implemented via a method of continuous dynamical decoupling (CDD) in a
hyperfine Zeeman multiplet in ^{87}\textrm{Rb}. The emergence of features
specific to the quadratic corrections to the linear Zeeman effect is evaluated.
Our analytical approach, which combines methods of stochastic analysis with
time-dependent perturbation theory, allows tracing the decoherence process for
generic noise sources. Working first with a basic CDD scheme, it is shown that
the amplitude and frequency of the (driving) field of control can be
appropriately chosen to force the non-static random input to have a
(time-dependent) perturbative character. Moreover, in the dressed-state
picture, the effect of noise is described in terms of an operative random
variable whose properties, dependent on the driving field, can be analytically
characterized. In this framework, the relevance of the spectral density of the
fluctuations to the performance of the CDD technique is precisely assessed. In
particular, the range of noise correlation times where the method of
decoherence reduction is still efficient is identified. The results obtained in
the basic CDD framework are extrapolated to concatenated schemes. The
generality of our approach allows its applicability beyond the specific atomic
system considered.
