%X The Holton–Lindzen–Plumb (HLP) model of the quasi-biennial oscillation (QBO) is
investigated in order to assess the impact of introducing intermittency in the wave forcing.
Intermittency is introduced to HLP by allowing the amplitude of the waves which force the
QBO to evolve according to a stationary random process, driven by a stochastic differential
equation (SDE) with an associated time scale Ï„ . Provided that Ï„ is much shorter than
the QBO period, it is shown that the impact on the QBO of the intermittent forcing is
captured by a single intermittency parameter λ, and the value of λ is proportional to τ and
otherwise depends upon the details of the SDE. Numerical simulations, using a family of
mean-reverting Ornstein–Uhlenbeck processes as the choice of SDE, show that the effect
of increasing the intermittency parameter is invariably to decrease the QBO amplitude
and increase its period. Changes to the QBO amplitude and period are indeed found to
collapse onto a single curve controlled by λ, as predicted by the theory, provided that τ is
small enough for the approximations used to be valid. The extension to broadband forcing
is discussed in the context of stochastic gravity wave parameterisation, with the eventual
goal of developing a representation of source intermittency in the most general situation
with close fidelity to the physics
%K Atmospheric flows, internal waves
%I CAMBRIDGE UNIV PRESS
%T The effect of intermittency in wave forcing on the quasi-biennial oscillation
%L discovery10194544
%V 988
%J Journal of Fluid Mechanics
%A M Ewetola
%A JG Esler
%D 2024
%O © The Author(s), 2024. Published by Cambridge University Press. This is an Open Access article,
distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/
licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original
article is properly cited.