Gravity wave activity during recent stratospheric sudden warming events from SOFIE temperature measurements

Abstract

Stratospheric Sudden Warmings (SSWs) followed by the formation of an elevated stratopause at ~70–80 km occurred in four of the five recent Arctic winters (2009–2013). We use global high-latitude temperature measurements from the Solar Occultation for Ice Experiment (SOFIE) to analyze the gravity wave (GW) activity in the upper stratosphere and mesosphere (30–90 km) during different phases of the SSW events. We characterize GW activity in terms of temperature fluctuations and the growth of GW potential energy with altitude. At both 40 and 60 km, compared to the non-SSW year of 2011, the GW activity in the SSW years of 2009, 2010, 2012, and 2013 was reduced after the warming, during the occurrence of an isothermal atmosphere and an elevated stratopause. In contrast, at 80 km the GW activity was highly variable between the individual stratospheric warming events. A case study of GW activity during the 2013 warming event and coincident SOFIE observations of water vapor (H2O) from ~40 to 90 km indicate a correlation between increase in wave activity at each altitude and the time of descent of dry air. This study supports previous modeling studies' findings that enhanced GW activity is responsible for the downward transport of trace species from the mesosphere to the stratosphere following an SSW event.