Evaluation of the mesospheric polar vortices in WACCM

Mesospheric altitudes are where high-top models underestimate the concentration of nitrogen oxides produced by energetic particle precipitation. For this reason, we seek to determine the extent to which the observed mesospheric vortex size and frequency of occurrence is reproduced by the model.

We compare 13 years (2005-2017) of "specified dynamics" Whole Atmosphere Community Climate Model (where meteorology in the troposphere and stratosphere is constrained by observations) to Sounding of the Atmosphere using Broadband Emission Radiometry and Mesospheric Limb Sounder observations. Near 75 km, the model reproduces observed winter mesospheric vortex frequency of occurrence rates and size reasonably well. The simulated Antarctic mesospheric vortex is displaced toward the Pacific longitude sector, and the Arctic mesospheric vortex is present 10-20% less often over the pole but similar to 5% more often in midlatitudes, particularly over the continents.