High Resolution Simulations of the Chemistry and Dynamics of the Mesosphere and Lower Thermosphere During the 2018-2019 Sudden Stratosphere Warming

The 2018–2019 sudden stratospheric warming (SSW) is simulated using a high-resolution whole atmosphere model that includes interactive chemistry and constrained meteorology. The simulations are performed using a high-resolution (∼0.25 (Formula presented.)) configuration of the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) with the meteorology constrained up to ∼10 hPa using ECMWF Reanalysis v5 (ERA5). The high-resolution WACCM-X simulations are compared to satellite and ground-based observations as well as two whole atmosphere data assimilation systems. Based on these comparisons, the high-resolution WACCM-X simulations are shown to alleviate two long-standing biases in low-resolution (∼2 (Formula presented.)) WACCM-X: a westward wind bias in the mesosphere and lower thermosphere (MLT) at wintertime high-latitudes, and insufficient downward transport of nitric oxide (NO) following SSWs. The high-resolution simulations are also able to capture much of the day-to-day variability in MLT winds seen in meteor radar observations. The simulations represent the first meteorologically constrained high-resolution whole atmosphere simulations with fully interactive chemistry, and demonstrate that high-resolution whole atmosphere model simulations can significantly improve representation of dynamical and chemical variability in the middle and upper atmosphere during SSWs.