While previous studies have examined the planetary boundary layer (PBL) and it's interactions during individual heat waves, a consistent assessment of the PBL behavior across multiple European heat waves remains lacking. Recent research identifies the PBL as an amplifier of heat waves via heat accumulation and surface feedback. We investigate whether this is reflected in general patterns in PBL height. Using reanalysis data and radiosonde observations, we investigate PBL height variations during heat waves compared to normal conditions. We apply a pattern-based heat wave definition and estimate boundary layer heights using the bulk Richardson number. Our analysis demonstrates significant increases in daily maximum PBL height during hot conditions. While the height of the PBL shows considerable fluctuations over time for individual heat waves, increasing height tendencies are more frequent than decreasing ones. Main drivers in the heat wave and corresponding height changes of the PBL are advection and preconditioning. However, the severity of a heat wave or the drivers are no sufficient predictors for the height of the PBL during a heat wave.
Fohrmann et al. (Fri,) studied this question.