Does sudden stratospheric warming induce meridional circulation in the mesosphere thermosphere system?

摘要

Oxygen dayglow emissions at multiple wavelengths that emanate from different heights (from around 130 km to peak altitude of the ionospheric F region) over a low-latitude location showed systematic enhancements in intensities throughout the daytime hours during four sudden stratospheric warming (SSW) events that occurred in the years 2010–2013. The lower thermospheric temperatures at 120 km obtained from the Sounding of the Atmosphere using Broadband Emission Radiometry instrument are found to be enhanced during SSW events at arctic latitudes and show a gradient with a decrease toward low-latitudes. During these events, the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics Doppler Interferometer measurements showed equatorward winds in the mesosphere lower thermosphere (MLT) altitudes over high-latitudes. Both the high-latitude lower thermospheric temperature enhancements and the MLT region equatorward winds occur nearly simultaneously with the observed enhancements in the atomic oxygen dayglow emission intensities at all the wavelengths over low-latitudes. Based on these measurements and other supporting information, it is proposed that a new cell of meridional circulation in the MLT winds is set up during SSW events, which enables transport of atomic oxygen from high-to-low latitudes. Such an additional contribution of oxygen density over low-latitudes interacts with lower thermospheric daytime dynamics in that region and is attributed to be the cause for the observed enhancement in the oxygen daytime optical emission intensities over low-latitudes. The results presented here provide experimental evidence to such circulation alluded to by earlier simulation studies.