The coming decade is expected to bring a continuing decline in the impact of ozone-depleting substances on the composition of the middle atmosphere, concurrent with an increasing influence of changes in greenhouse gases. A sustained and reliable observing system is essential for quantification of these changes and their impacts in the middle atmosphere and more broadly. The future evolution of the current observing system, and its suitability for meeting high-priority scientific needs, both long-standing and newly emerging, is the focus of this session.
The last 10–15 years arguably represent a "golden age" for spaceborne observations of the middle atmosphere, with at peak 12 limb or occultation sounding instruments operating on eight satellites. These years have also witnessed a significant increase in the number and capabilities of operational nadir sounding instruments providing radiance observations that inform meteorological reanalyses, and the emergence of new temperature profile observations from GNSS radio occultation. Although prospects for future nadir and GNSS sounders are clear and robust, the future for limb and occultation sounders is less assured, with the only confirmed upcoming instrument, from any country or agency, being the ultraviolet OMPS-Limb instruments planned for the JPSS 2 and 3 missions, mainly measuring ozone and aerosol. This looming "gap" in limb sounding observations has received much attention within the community, and concerns about it have been raised in several international reports and studies.
At the same time, there now exist diverse capabilities for making in situ and airborne or ground-based remote sounding observations of the middle atmosphere. A rich database of such measurements continues to grow, both in the form of sustained long-term observations and more episodic measurement campaigns. However, as with the spaceborne observations, increasing pressure on funding agency budgets, particularly in the light of increasing focus on Earth science issues beyond atmospheric composition, has placed some of these observations in jeopardy.
This session will provide an opportunity to air the multifaceted issues surrounding future evolution of the observing system, the possibilities for filling looming gaps, and the routes to turning those possibilities into reality. In the case of spaceborne observations, the recent release of the 2018 NASA Earth Science Decadal Survey, which listed such measurements as one of the potential foci for a new "Earth Explorer" program, makes this a particularly timely session for the AMS Middle Atmosphere meeting.
We solicit papers covering all aspects of this topic, including papers assessing the potential scientific impacts of observation gaps, those articulating quantified objectives that require new or continued observations in order to be met, and those outlining potential new measurement approaches or instruments (especially instruments enabled by newly developed technologies). Papers describing OSSE-like quantification of measurement requirements are particularly welcome.
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