  Characterising the stratosphere as a turbulent system, temporal fluctuations
often show different correlations for different time scales as well as
intermittent behaviour that cannot be captured by a single scaling exponent. In
this study, the different scaling laws in the long term stratospheric
variability are studied using Multifractal de-trended Fluctuation Analysis. The
analysis is performed comparing four re-analysis products and different
realisations of an idealised numerical model, isolating the role of topographic
forcing and seasonal variability, as well as the absence of climate
teleconnections and small-scale forcing. The Northern Hemisphere (NH) shows a
transition of scaling exponents for time scales shorter than about one year,
for which the variability is multifractal and scales in time with a power law
corresponding to a red spectrum, to longer time scales, for which the
variability is monofractal and scales in time with a power law corresponding to
white noise. Southern Hemisphere (SH) variability also shows a transition at
annual scales. The SH also shows a narrower dynamical range in multifractality
than the NH, as seen in the generalised Hurst exponent and in the singularity
spectra. The numerical integrations show that the models are able to reproduce
the low-frequency variability but are not able to fully capture the shorter
term variability of the stratosphere.
