Vertical characteristics of heat waves at sub-daily scales in ERA5 over Europe

Heat waves are considered among the greatest hazards associated with climate change. Defined as prolonged periods of anomalously high temperatures during summer, they are linked to substantial impacts on both natural ecosystems and human societies. However, projections of heat waves under future climate scenarios are laden with uncertainties, largely due to limitations in climate models' ability to accurately simulate the underlying physical mechanisms. This study aims to enhance our understanding of the processes governing heat waves by investigating them as three-dimensional (3D) phenomena on sub-daily temporal scales. Lhotka and Kyselý (2024) demonstrated that different driving mechanisms are driving near-surface and various tropospheric heat wave types. We utilize hourly data from the ERA5 reanalysis to examine the evolution of temperature anomalies across different vertical atmospheric levels. The 3D structure of temperature anomalies is linked primarily to atmospheric circulation, surface energy budget, precipitation, and cloud cover. Although the effect of land–atmosphere coupling on near-surface temperatures is relatively well established, its role in the sub-daily development of the planetary boundary layer remains less understood. Therefore, we also focus on features such as nocturnal temperature inversion and residual layers, and their contributions to the vertical development of heat waves under various synoptic conditions. We employ the ERA5 reanalysis over the selected European regions for the 1950–2024 period. Heat waves are identified based on positive temperature anomalies exceeding high percentiles of their distributions at the near surface and across 14 vertical levels, from 950 hPa to 300 hPa, with an added temporal persistence criterion.

 

Lhotka, O., Kyselý, J. Three-dimensional analysis reveals diverse heat wave types in Europe. Commun Earth Environ 5, 323 (2024). https://doi.org/10.1038/s43247-024-01497-2