Sodium Layer Responses to the Sudden Stratospheric Warming

This study investigates the response of the mesospheric and lower thermospheric (MLT) sodium (Na) layer to the 2002 Southern Hemisphere sudden stratospheric warming (SSW) event using model simulations. Simulations from the Whole Atmosphere Community Climate Model (WACCM) metal layer dataset reveal a marked decrease in sodium number density occurring during the SSW. The latitudinal evolution of sodium number density displays a distinct northward propagation toward near-equatorial regions. Furthermore, ground-based sodium lidar observations at 23°S in Brazil record a significant reduction in sodium number density approximately 10 days following the SSW onset. Planetary wave components derived from WACCM simulations of Na density and temperature are closely associated with the observed modulation in the Na layer. These findings indicate that SSWs can induce cross-hemispheric responses in the sodium layer, likely mediated by enhanced planetary wave activity.