Longitudinal Variations of Tropical Winds in the UTLS: Aeolus and Strateole measurements of Equatorial Waves and the Walker Circulation

Tropical atmospheric waves often have fine vertical scales that are difficult to resolve in models and cannot easily be observed using existing satellite or ground-based instruments. These waves are known to strongly influence the driving of the quasi-biennial oscillation (QBO), which is an important source of seasonal predictability in the lower stratosphere, and have important interactions with dynamical mechanisms such as the Walker Circulation. As the first Doppler wind lidar in space, Aeolus provides high resolution measurements of wind on a global scale, including in the hard-to-observe upper-troposphere lower-stratosphere (UTLS) region of the atmosphere. It is therefore a uniquely capable platform for studying these phenomena. Here, we sample ERA5 as Aeolus to produce like-for-like comparisons of resolved and observed wind structures, and co-locate measurements with stratospheric superpressure balloon observations from the Strateole-2 campaign. We analyse Kelvin waves and their interaction with the QBO, including the 2019/20 QBO disruption for which a special Aeolus scanning mode was implemented. We also compare our results with wave spectra from outgoing long-wave radiation (OLR) measurements, and highlight how Aeolus and future Doppler wind lidar satellites can deepen our understanding of the tropical UTLS more generally.