Using aviation meteorology to improve aircraft safety

Aviation meteorology is the science of understanding, predicting, and minimizing the risks from these hazards, to improve flight safety. There is evidence that both lightning and turbulence will become more common because of climate change, increasing the need to improve our understanding of these hazards.

Many helicopters working in the North Sea oil and gas sector have been struck by lightning, some encountering positive strikes that are especially destructive. In a typical winter season, there are about 10 cold-air outbreaks in the North Sea operating area, each lasting around three days, meaning there are typically 30 strike risk days per season. Lightning strikes can cause substantial damage, immediately prompting an emergency and requiring the helicopter to be taken out of service for maintenance and repairs. The detailed relationship between atmospheric conditions and lightning strikes is currently poorly established.

In addition, thousands of planes encounter potentially hospitalizing severe turbulence globally each year. As well as injuring passengers and crew, turbulence can also cause structural damage to aircraft. The economic cost of turbulence is several hundred million dollars annually. Encounters with vertical and horizontal high-altitude wind shear - which is associated with turbulence - sometimes currently infringe aircraft certification envelopes, according to accident and incident investigations. Existing operational turbulence prediction algorithms generate a significant fraction of missed events and false positives. This reflects our poor understanding of the causes of turbulence and its relationship to atmospheric conditions, suggesting considerable scope to improve the accuracy of the forecasts through targeted research.

This project will improve our scientific understanding of aviation-affecting turbulence and lightning and their relationship to atmospheric conditions. The Civil Aviation Authority's (CAA's) database of several hundred-thousand accidents and incidents since the 1970s will be mined to isolate events involving turbulence or lightning. For each event, the atmospheric conditions at the time, date, and location will be determined from reanalysis data (e.g. ERA-Interim). Various proposed diagnostics of clear-air turbulence (e.g., Ellrod's index, potential vorticity, Richardson number), convective turbulence (e.g., convective available potential energy (CAPE) and other convective diagnostic products), and lightning (e.g., maximum cloud height to the fifth power, CAPE multiplied by precipitation rate) will be calculated. Their ability to represent the observed event will be tested by identifying which percentile they correspond to, in a histogram of the statistical climatology of the particular diagnostic.

A second strand to the project will be to consider the effects of climate change. Having identified which diagnostics are most skillful at diagnosing events in the CAA database using the gridded reanalysis data, those diagnostics will be calculated from gridded climate model simulations. Under a suitable greenhouse gas scenario, long-term trends in the diagnostics will be identified at different altitudes and geographic regions and in different seasons.

The project will result in an improved understanding of (i) the relationship of aviation-affecting turbulence and lightning to large-scale atmospheric conditions, and (ii) the response of aviation-affecting turbulence and lightning to climate change.