Is There a Spatial Link Between Ice Supersaturation and Aviation Turbulence?

Contrail cirrus contributes significantly to aviation’s climate warming impact. To limit this impact, flight trajectories can be climate-optimised by minimising both CO₂ and non-CO₂ emissions. Operationally, safety is often an overriding consideration that must be accounted for before a climate-optimised flight trajectory can be undertaken. Since atmospheric turbulence is the leading cause of commercial aviation accidents, it is vital to establish if and how ice supersaturated regions (ISSRs) are spatially related to region with moderate-or-greater (MOG) turbulence. This link is motivated by the role of vertical air motions, which promote ice supersaturation through adiabatic cooling and are also a defining characteristic of atmospheric turbulence.

Using European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data and the most relevant clear air turbulence (CAT) diagnostics, we first examine whether ISSRs and MOG turbulence occur concurrently and whether they are correlated. Preliminary results indicate a weak relationship exists between the two regions. Analysis of the instantaneous plots indicate that, while co-occurrence is uncommon, the two regions often occur adjacent to each other. This adjacency is particularly evident in three-dimensional reconstructions of regions where an intersection had occurred. We quantified this spatial relationship via the Euclidean distance from an ISSR to a MOG CAT region and aggregated these distances (e.g., mean distance) to identify regions that frequently exhibits this behaviour. Finally, this measure is used to establish whether ISSRs that originate from large scale vertical movements and MOG CAT are related. These insights provide a foundational step toward establishing whether this underlying relationship between the two regions can be leveraged to improve forecast confidence and the implications on the operational complexity of safe, climate-optimised flight trajectories.