Impact of the Polar Vortex on Sub-Seasonal O/N 2 Variability in the Lower Thermosphere Using GOLD and WACCM-X

We find strong positive correlations between the Northern Annular Mode (NAM) index and subseasonal (10-90 days) Global Observations of the Limb and Disk (GOLD) O/N-2 perturbations at low to mid-northern latitudes, with a largest value of +0.55 at similar to 30.0 degrees N when anomalously strong or weak (NAM >2.5 or < -2.1) vortex times are considered.

Strong agreement for O/N-2 variability and O/N-2-NAM correlations is found between GOLD observations and the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) simulations, which is then used to delineate the global distribution of O/N-2-NAM correlations. We find negative correlations between subseasonal variability in WACCM-X O/N-2 and NAM at high northern and southern latitudes (as large as -0.54 at similar to 60.0 degrees S during anomalous vortex times).