Abstract

Clear-air turbulence (CAT) is hazardous to aircraft and is projected to intensify in response to future climate change. However, our understanding of past CAT trends is currently limited, being derived largely from outdated reanalysis data. Here we analyze CAT trends globally during 1979–2020 in a modern reanalysis data set using 21 diagnostics. We find clear evidence of large increases around the midlatitudes at aircraft cruising altitudes. For example, at an average point over the North Atlantic, the total annual duration of light-or-greater CAT increased by 17% from 466.5 hr in 1979 to 546.8 hr in 2020, with even larger relative changes for moderate-or greater CAT (increasing by 37% from 70.0 to 96.1 hr) and severe-or-greater CAT (increasing by 55% from 17.7 to 27.4 hr). Similar increases are also found over the continental USA. Our study represents the best evidence yet that CAT has increased over the past four decades.

Key Points

• Clear-air turbulence (CAT) diagnosed from reanalysis data has increased over the satellite era
• The increases are largest over the USA and North Atlantic, which are both busy flight regions
• Severe-or-greater CAT increased the most, becoming 55% more frequent in 2020 than 1979

Plain Language Summary

Turbulence is unpleasant to fly through in an aircraft. Strong turbulence can even injure air passengers and flight attendants. An invisible form called clear-air turbulence (CAT) is predicted to become more frequent because of climate change. Here we analyze modern atmospheric data based on four decades of observations (1979–2020) to investigate whether CAT has already started to increase. We use 21 different turbulence calculations to ensure our results are as reliable as possible. We find clear evidence of large CAT increases in various places around the world at aircraft cruising altitudes since satellites began observing the atmosphere. For example, at a typical point over the North Atlantic, the upward trend is such that the strongest category of CAT was 55% more frequent in 2020 than 1979. Our study represents the best evidence yet that CAT has increased over the past four decades, consistent with the expected effects of climate change.

Read the full study here:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL103814