Phase and amplitude relationships between ozone, temperature and
circulation in the Quasi-biennial Oscillation
Abstract
The phase and amplitude relationships between dynamical quantities and
ozone within the Quasi-biennial Oscillation (QBO) are explored. An
initial assessment of this is done by applying a Principal Oscillation
Pattern analysis to observations (SWOOSH for Ozone) and reanalysis data
(ERA5). This analysis highlights features of the ozone and temperature
variability including two peaks in amplitude in the QBO region as well
as more subtle phase differences that cannot be explained by a simple
QBO theory. We also quantify the sizes of the ozone and temperature
advection terms and show that the contribution of background upwelling
on variations in ozone gradient is not negligible (~25%).
A radiative-convective equilibrium and photochemical equilibrium model,
with the imposed ERA5 QBO variation in upwelling and OSIRIS NOx
variations, is used to further understand ozone and temperature changes.
The results show that photochemistry and transport are important at all
levels and it is misleading to divide the QBO into separate regimes.
Prominent aspects of the variability can be reproduced if ERA5 upwelling
is reduced by ~60% between 15 and 50 hPa where ERA5 is
likely over-predicting the strength of the secondary meridional
circulation. Finally, we demonstrate that non-locality in the vertical
plays a major role in QBO dynamics. This arises from ozone transport,
the dependence on column ozone of photochemical production and radiative
transfer between layers.