Novel Applications of Aeolus Wind Lidar Observations to Atmospheric Dynamics

: (Alternative Format Thesis)

Abstract

With a changing climate, it is more important than ever to understand how the atmosphere works and how we can forecast the weather events which define its relationship with us. The field of atmospheric dynamics is at the forefront of this effort and aims to study the physical processes and phenomena which form the global circulation that keeps the atmosphere in motion. This involves both observational and theoretical analyses and has critical applications ranging from aviation to disaster relief. Observing the atmospheric state with as much accuracy and completeness as possible is an age-old problem, but has seen significant recent advances due to the introduction of satellites. With the technological advances which have allowed for supercomputers to run state-of-the-art numerical weather models, it is important that the global observing system keeps pace and provides the high-quality real-time measurements that are required.

In this thesis, we investigate the impact of novel observations made by a new type of satellite, the Doppler wind lidar, to the field of atmospheric dynamics. The Aeolus satellite carries the first of these instruments, which gives measurements of wind speed on a global scale for the very first time. It therefore provides a unique opportunity to examine the phenomena that drive the Earth's atmospheric circulation in ways not previously explored. This thesis gives us new insights into a wide range of atmospheric processes, demonstrates the impact of assimilating Aeolus data into numerical weather prediction models, and paves the way for future research using both Aeolus and the next generation of space-borne Doppler wind lidars.

In particular, this thesis focuses on the application of Aeolus observations to atmospheric gravity waves, the quasi-biennial oscillation in the tropics and sudden-stratospheric warmings of the polar vortex. Crucially, these phenomena all play an important role in atmospheric dynamics, and are topics of a great deal of recent research, particularly due to the lack of existing observations. The often neglected upper-troposphere lower-stratosphere region of the atmosphere is explored in great detail here, resulting in several important discoveries and first observations of their kind.

Here, we present the first observations of atmospheric gravity waves using a Doppler wind lidar satellite, using Aeolus. We show direct global wind measurements of a disruption to the quasi-biennial oscillation for the very first time, and demonstrate Aeolus' capability to capture regions of sharp vertical wind shear in tropical equatorial waves. We also reveal a lagged relationship between El Nino and gravity wave amplitudes in aircraft measurements, and an increasing prospect of further disruptions to the quasi-biennial oscillation as a consequence of climate change. Ultimately, the main goal of this thesis is to provide a baseline for research into atmospheric dynamics using Doppler wind lidar satellites, like Aeolus; especially with a view to improving the numerical weather prediction models of the future.

Date of Award	22 May 2023
Original language	English
Awarding Institution	University of Bath
Sponsors	Engineering and Physical Sciences Research Council
Supervisor	Corwin Wright (Supervisor), Neil Hindley (Supervisor) & Nicholas Mitchell (Supervisor)