Effects of Sudden Stratospheric Warming on the Light H and O Species in the Upper Thermosphere

Abstract

Sudden stratospheric warming (SSW) is a significant type of meteorological disturbance that occurs in the winter polar atmosphere. Previous studies have shown that rapid warming of the polar stratosphere can induce electrodynamic and thermodynamic variabilities in the upper atmosphere over the entire globe. However, the effects of SSW on the light neutral species (e.g., H and O) remain poorly understood. Here we report coincident H and O variations in the upper thermosphere during SSW events, based on observations from the Global Ultraviolet Imager (GUVI) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. The GUVI observations indicate rapid increase of the H abundance and reduction of the O abundance at low latitudes within $\sim 30°$S–30$°$N in the upper thermosphere ($\sim$200–500 km) following the onset of an Antarctic and an Arctic SSW event that occurred under high solar condition in September 2002 and January 2003, respectively. Moreover, we found that the effects of SSW on the H variations are barely discernible from the GUVI observations that were acquired in 2004–2006 under relatively low solar condition. We used the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) to simulate the effects of SSW on the H and O abundance. The modeling results under both high and low solar conditions are consistent with the GUVI observations, indicating that solar activity modulates the effects of SSW on vertical coupling between the lower and upper atmosphere.