Pathways and processes leading to the warming of air masses in northern hemispheric summer anticyclones

Summer anticyclones are known for their strong connection to extreme near-surface temperatures, potentially leading to severe natural hazards in the mid-latitudes. Although our understanding of the processes causing these heat extremes is growing, the causal relationship between soil conditions, near-surface air temperature and the synoptic systems above them is still far from being fully understood.
The aim of this work is to provide insight into the interaction between near-surface air masses and heat-generating mid-tropospheric summer anticyclones. Using Lagrangian analyses and a temperature change decomposition method, we illustrate the contributions from advection, diabatic and adiabatic heating in air streams during different phases of the anticyclone life cycle from a composite perspective. Moreover we look for coherent trajectory patterns that could contribute to the coupling of near-surface temperature extremes and the mid-tropospheric flow.
We demonstrate that the role of diabatic warming increases in the southeast of the mid-level anticyclone during more intense heat waves over land. In contrast, the areas in the west of the anticyclone, where the heat waves occur, are primarily affected by advection and adiabatic warming. We also provide evidence for the occurrence of coherent air streams injected from the outflow of dry intrusions or post frontal subsidence in troughs adjacent to the anticyclone and explore their implications for the life cycle of the anticyclone.