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Earth’s atmosphere supports a variety of internal wave motion which are responsible for spatio-temporal changes in temperature, winds, density, and chemical constituents. One of the most striking dynamical features of the upper atmosphere (i.e. mesosphere and lower thermosphere [MLT], 50-120 km) are atmospheric tides. In particular, the eastward-propagating nonmigrating diurnal tide with zonal wave number 3 (DE3), originating from tropical deep convection, introduces a large longitudinal and local time variability in temperature, wind and density in the MLT region. The DE3 is thus key to understanding how tropospheric weather influences space weather. However, DE3 short-term tidal variability is not well understood and part of the motivation for constellation missions. Single satellites such as TIMED nevertheless provide a pathway to identify multi-timescale tidal variability from days to years. We utilize 16 years of SABER (an instrument onboard the TIMED satellite) DE3 “tidal deconvolution” diagnostic that provides a unique opportunity to investigate interannual changes in short-term (days to weeks) tidal variability on various planetary wave time scales. The approach is based on information-theoretic techniques using Bayesian statistics, time dependent probability density functions and Kullback-Leibler divergence followed by multiple linear regression analysis. In this presentation, we focus on interannual changes in short-term DE3 variability on a 10-day planetary wave timescale and how it changes as a function of the quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO) and the solar cycle.

Observations from the recently launched Global-Scale Observations of the Limb and Disk (GOLD) instrument on the geostationary SES-14 communications satellite provide the first observational proof for the impact of stratospheric weather, that is, polar vortex dynamics during a Sudden Stratospheric Warming (SSW), on the composition of the thermosphere. During the early January 2019 SSW, GOLD observes a >10% O/N2 column density ratio depletion in both hemispheres unrelated to geomagnetic activity. The data and supporting TIE-GCM and WACCM-X simulations show that enhanced global-scale wave activity during the SSW causes an enhanced wave driving of the lower thermosphere zonal mean circulation that leads to a reduction in lower thermosphere atomic oxygen, which then propagates through molecular diffusion into the upper thermosphere. The observed composition changes will likely impact Earth's ionospheric plasma environment as well and imply another pathway for SSW impacts on space weather, in addition to dynamo processes.