The Long and Winding Road: Research on Stable Boundary Layers & Surface Coupling

In this presentation I will sketch my research journey through stably stratified and nocturnal boundary layers. I will reflect on gained insights and remaining unknowns. The usefulness and limitations of simplifications and conceptual models in stable boundary layer research is discussed. I will share personal experiences in searching for physical explanations of SBL phenomena such as ‘the collapse of turbulence’ and turbulence intermittency.

While observational insights and numerical simulations often complement each other, they may also show significant disagreement.  Although we learned from international model comparisons such as the GABLS initiatives, we still struggle in further translating local processes into generic weather forecast parameterizations. Realistic boundary layers are typically “non-ideal” and simplified assumptions (e.g., homogeneity and stationarity) are violated in practice. Fortunately, new observational and modelling techniques allow for fresh perspectives and conceptual progress.

Here, I will reflect on our recent research on the thermodynamic coupling between the lower atmosphere and the underlying surface. This coupling is becoming increasingly important under strongly stratified conditions, where the impact of turbulent fluxes on the surface temperature and energy budget is weak. New model parameterizations of the coupling must reflect this in order to accurately predict surface temperatures. In the future we therefore aim to further understand this coupling and its impact on near-surface cold extremes in this fascinating field of research