The AIM spacecraft continues to perform nominally. The AIM spacecraft autonomy has smoothly transitioned the CIPS imaging from the Northern Hemisphere to the Southern Hemisphere sequence. Also, we certified the AS3 antenna at the Alaska SAR Facility at the University of Alaska, providing more coverage options for AIM from Alaska.
The CIPS instrument continues to perform well, with no health issues. CIPS saw its last clouds in the Northern Hemisphere (NH) 2014 season on 25 August. Figure 1 compares PMC frequencies at 80°N for all NH seasons observed by CIPS. The end of the season was interesting in that the cloud frequency dropped steeply around July 31 (40 Days From Solstice, DFS). This followed, by one week, the 23 July peak of a minor stratospheric warming in the Southern (winter) Hemisphere. It has previously been shown that warming in the winter stratosphere can cause warming in the summer mesopause region through interhemispheric teleconnections. Figure 2 shows that the temperature near the summer mesopause at 80°N was anomalously warm; whether this was caused by interhemispheric teleconnections is being investigated. The PMCs recovered extensively after a week of decline before falling off at the season end.
Figure 1. CIPS PMC frequencies at 80°N latitude for all NH seasons observed by AIM.
Figure 2. Temperature anomalies near the summer mesopause at 80°N from the NASA Microwave Limb Sounder (MLS) instrument in years 2005-2014. Note the strong warming in 2014 near DFS 45, which corresponded to a significant drop in CIPS PMC frequency.
A multi tracer analysis of thermosphere to stratosphere descent triggered by the 2013 Stratospheric Sudden Warming
Arctic winter observations in 2013 by the Solar Occultation for Ice Experiment (SOFIE) show significant transport from the lower-thermosphere to the stratosphere of air enriched in nitric oxide, but depleted in water and methane [Bailey et al., 2014]. The transport is triggered by the Stratospheric Sudden Warming (SSW) on 11 January and is continuously tracked for over 3 months. Ultimately, evidence for lower thermospheric air is seen at 40 km in mid-April, as demonstrated in the Figure below which shows SOFIE NO during the first 140 days of 2013 (red line marks the SSW event). Area integrated nitric oxide (NO) fluxes are compared with previous events in 2004, 2006, and 2009, to show that this event is the second largest in the past 10 years. The SOFIE data are combined with a meteorological analysis to infer descent rates from 40 to 90 km. The descent profile initially peaks near 75 km, shifting downward by approximately 5 km per 10 days. Our work demonstrates the utility of SOFIE tracer measurements in diagnosing vertical transport from the stratosphere to the edge of space.