Using high-resolution climate models to predict increases in atmospheric turbulence

Atmospheric turbulence is the leading cause of in-flight injuries to air travellers and flight attendants.
Tens of thousands of aircraft encounter severe turbulence annually, injuring hundreds of people and
causing structural damage to planes. For example, a typical airline loses over 7,000 working days
annually, due to flight attendants being injured by turbulence and unable to work. Turbulence
contributes to the fear of air travel (aviophobia), which reportedly affects up to 40% of the population
to some degree. Turbulence is estimated to cost the global aviation sector around one billion dollars
annually.
Climate change is thought to be strengthening clear-air turbulence, which is a particularly hazardous
form, because it is undetectable by on-board radar. However, our current knowledge of this trend is
based on climate model simulations whose spatial resolution is (a) too coarse to resolve individual
patches of turbulence and (b) an order of magnitude coarser than the resolution at which the
diagnostics have been shown to be skilful. Furthermore, the response of turbulence in clouds
(convective turbulence) to climate change has not previously been studied, even though convective
turbulence is also hazardous and likely to depend on climate.
This project will use high-resolution climate models for the first time to investigate how clear-air
turbulence and convective turbulence respond to climate change. There are many benefits of using
an atmospheric grid resolution of ~20 km, rather than the ~200 km used in previous studies. First, the
small-scale processes that generate turbulence (such as wind shear and convective updrafts) will be
resolved in much finer detail. Second, operational forecasts of aviation turbulence are done at ~20 km
resolution and have high skill scores when verified against aircraft measurements, demonstrating
confidence in the calculations. And third, because the median length of a patch of turbulence is
60 km, we will be resolving individual patches of turbulence for the first time. This opens up the
possibility of asking new scientific questions that were previously unanswerable.
This PhD project will consider the following research questions:
- How well do high-resolution climate models simulate the processes generating clear-air
turbulence, compared to newly available high-resolution reanalysis data (ERA5)? How does
clear-air turbulence respond to climate change in these models?
- How does convective turbulence (diagnosed using skilful proxies such as the convective
precipitation rate and convective available potential energy) respond to climate change in high-
resolution climate models?
- How do the turbulence patch size distributions change? Will there be twice as many patches
of the same size, or the same number of patches but each doubled in size? These opposite
possibilities have different implications for future aircraft operations.
The student will work closely with the NCAS high-resolution climate modelling group, and will thereby
gain access to a set of high-resolution climate simulations, such as those recently prepared for CMIP6
as part of the PRIMAVERA project. As well as the results being of great academic interest from an
atmospheric dynamics perspective, they will also be of direct interest to the commercial aviation
sector, leading to a high non-academic impact.