High resolution simulations of the chemistry and dynamics in the mesosphere and lower thermosphere during the 2018-2019 sudden stratosphere warming

We present analysis of the chemical and dynamical variability in the mesosphere and lower thermosphere (MLT) during the 2018-2019 sudden stratospheric warming (SSW) as simulated by the high resolution (~25 km horizontal and 0.1 scale height vertical resolution) version of the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X). The WACCM-X simulations make use of new capabilities, including the spectral element dynamical core and the ability to constrain the lower atmosphere meteorology in WACCM-X at high-resolutions. Compared to standard resolution (~200 km horizontal and 0.25 scale height vertical resolution) WACCM-X simulations, the high-resolution simulations are in better agreement with Thermosphere Ionosphere Mesosphere Energetics Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED-SABER) and Atmosphere Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) observations. In particular, the high-resolution simulations better reproduce the Northern Hemisphere middle-high latitude winds in the MLT. The downward transport of nitric oxide (NO) following the SSW is also better reproduced in the high-resolution simulations. The results demonstrate the importance of capturing mesoscale processes for accurately simulating the chemistry and dynamics of the MLT.