Evaluation of the E3SM Version 3 Stratosphere Performance

Abstract

The interactions between the stratosphere and the troposphere have significant impacts on human activities and Earth system variability. In the third release version of the low‐resolution Energy Exascale Earth System Model (E3SMv3), the representation of the stratosphere is improved through vertical grid refinement in the lower stratosphere and the implementation of the linearized ozone scheme version 3 (Linozv3). In this study, we conduct a comprehensive evaluation of the dynamics and chemistry of E3SMv3's stratosphere using reanalysis data and satellite observations. E3SMv3 simulates an overall realistic stratosphere, capturing the basic temperature and circulation structures, including the Brewer–Dobson circulation (BDC) and the polar vortex, as well as reasonable distributions and transport of key trace gases such as ozone and water vapor. The model also reproduces a quasi‐biennial oscillation (QBO) with a realistic amplitude and wave forcing compared to a reanalysis data set, with a slightly faster period of 25 months. However, notable biases remain: weak upward‐propagating wave activities near the tropopause during boreal winter and slightly stronger wave activities during boreal summer lead to an overall slow‐biased deep branch of the BDC, which affects trace gas transport. Additionally, the polar vortex is overly strong and stable during boreal winter, resulting in fewer sudden stratospheric warming events and a weak teleconnection between the QBO and polar vortex, while it is slightly weaker and less stable during austral winter. Overall, E3SMv3 demonstrates good fidelity for stratosphere‐related studies, though opportunities remain to reduce key dynamical and chemical biases.