Abstract
The simulated quasi-biennial oscillation (QBO) in the Energy Exascale
Earth System Model version 2 (E3SMv2) is characterized by a shorter
period and stronger amplitude compared with its predecessor E3SMv1. This
is primarily attributed to updates to the deep convection
parameterization which makes convection more intense but less frequent
while leaving the time-mean convective heating tendency almost
unchanged. Amplitudes of momentum fluxes associated with parameterized
gravity waves, which are determined by the square of convective heating
tendency, are consequently intensified. In addition, stronger planetary
waves, another contributor to the QBO driving, are simulated in E3SMv2
in part due to tropospheric processes. Furthermore, there is evidence
that planetary wave generation is present in the stratosphere due to
dissipation of amplified parameterized gravity waves. These factors are
found to be responsible for the stronger and faster QBO simulated in
E3SMv2.