Past trends in near-cloud turbulence diagnosed from reanalysis data

Turbulence is the principal cause of in-flight bumpiness at cruise level, causing economic loss and threatening passenger safety. Following the growth of aviation transport, the impact of turbulence has become critical, making it necessary to investigate its response to climate change. This study will examine the historical frequencies of near-cloud turbulence (NCT), which is difficult to avoid because it is invisible to radar and satellites. Previous research has been scarce because cloud boundaries are ill-defined and multiple influencing mechanisms are involved. In this study will use the latest ERA5 reanalysis (1979-2024) and a dedicated parameterization. We examine global NCT climate trends across seven regions, four diagnostics, five turbulence-intensity bins and four seasons. At typical cruise altitudes, diagnosed NCT probabilities have risen in the mid-latitudes, most notably along heavily trafficked corridors over Europe, the North Atlantic, the North Pacific, and the south-western United States, with local relative increases reaching 100%. Conversely, probabilities have fallen in the tropics—especially over long-standing hotspots such as Southeast Asia and the Caribbean Sea. A lower occurrence rate, however, may signal fewer but deeper and more vigorous convective events, increasing the risk to commercial aviation. These findings in the tropics differ from earlier climate-model projections and should help refine future NCT forecasts, providing a fuller basis for assessing aviation exposure in a warming climate.