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STATUS:
10.13.2014
Instrument Status
The AIM spacecraft continues to perform well. All subsystems are operational.
CIPS:
The CIPS instrument continues to perform well, with no health issues. We have seen an increasing number of out-of-season false detections, and are investigating the cause of these. They are believed to be due to issues associated with our changing beta angle. The investigation of the correlation between the cold air outbreak (CAO) in the northeastern United States in January 2014 and PMC variations observed by AIM over Antarctica has confirmed a link between the CAO, PMCs, and planetary wave (PW) activity in the Arctic stratosphere. This strongly suggests a causal relationship, whereby wintertime PW activity in the stratosphere affects atmospheric circulation, leading to changes in both tropospheric weather in the winter hemisphere and mesospheric weather in the summer hemisphere. Previous observational studies of interhemispheric coupling have shown correlations between PMCs and wintertime stratospheric winds. This is the first observational study to show the link between PMCs and PW activity, which is the driver of variability in the winds. It is also the first study to suggest a direct link between the polar summer mesosphere and the surface in the winter hemisphere.
SOFIE:
AIM data helps to provide a quantitative benchmark for long-term PMC trends
AIM satellite instruments have measured Polar Mesospheric Clouds (PMCs) continuously with unprecedented precision since the mission was launched in 2007, thereby compiling over seven years of data on critical aspects and properties of the clouds. PMCs occur 50 miles above the surface during summer in the polar regions and satellite observations indicate they have been increasing with time for reasons that are not fully understood. Hervig and Stevens [2014] have used AIM SOFIE data to improve and validate PMC retrievals from the 35-year SBUV satellite measurement record (1979-2013). The results yielded SBUV retrievals that account for non-spherical particles, retrievals of particle size from SBUV, and retrievals of the vertical ice column mass (or IWC) from SBUV that use SBUV particle size information. Comparisons of SOFIE and SBUV for collocated measurements (2007 - 2013) indicate good agreement on PMC particle size and IWC, as shown in the Figure below. Note that SOFIE is much more sensitive than SBUV, and thus the SBUV detection threshold (IWC > 40 g/km2) was applied to the SOFIE measurements for the comparisons. This study provides an improved interpretation of the SBUV data, and through the validation against SOFIE gives confidence in understanding long-term trends derived from SBUV. AIM data will continue to play an important role in investigations to quantify links between mesospheric change and multi-decadal climate change, and the Hervig and Stevens [2014] results provide a crucial quantitative benchmark in these studies.
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