Early Warning Signals for Regime Transition in the Stable Boundary Layer

Early Warning Signals for Regime Transition in the Stable Boundary Layer: A Model Study

van Hooijdonk, I.G.S. (Eindhoven University of Technology)
Moene, A. F. (Wageningen University & Research)
Scheffer, M. (Wageningen University & Research)
Clercx, H. J H (Eindhoven University of Technology)
van de Wiel, B.J.H. (TU Delft Atmospheric Remote Sensing)

2017-02-01

The evening transition is investigated in an idealized model for the nocturnal boundary layer. From earlier studies it is known that the nocturnal boundary layer may manifest itself in two distinct regimes, depending on the ambient synoptic conditions: strong-wind or overcast conditions typically lead to weakly stable, turbulent nights; clear-sky and weak-wind conditions, on the other hand, lead to very stable, weakly turbulent conditions. Previously, the dynamical behaviour near the transition between these regimes was investigated in an idealized setting, relying on Monin–Obukhov (MO) similarity to describe turbulent transport. Here, we investigate a similar set-up, using direct numerical simulation; in contrast to MO-based models, this type of simulation does not need to rely on turbulence closure assumptions. We show that previous predictions are verified, but now independent of turbulence parametrizations. Also, it appears that a regime shift to the very stable state is signaled in advance by specific changes in the dynamics of the turbulent boundary layer. Here, we show how these changes may be used to infer a quantitative estimate of the transition point from the weakly stable boundary layer to the very stable boundary layer. In addition, it is shown that the idealized, nocturnal boundary-layer system shares important similarities with generic non-linear dynamical systems that exhibit critical transitions. Therefore, the presence of other, generic early warning signals is tested as well. Indeed, indications are found that such signals are present in stably stratified turbulent flows.

Critical regime transition
Early warning signals
Maximum sustainable heat flux
Minimum wind speed
Nocturnal boundary layer

http://resolver.tudelft.nl/uuid:66ff62ce-0213-40e0-8d13-61aed4bf0fad

https://doi.org/10.1007/s10546-016-0199-9

0006-8314

Boundary-Layer Meteorology: an international journal of physical and biological processes in the atmospheric boundary layer, 162 (2), 283-306

Institutional Repository

journal article

© 2017 I.G.S. van Hooijdonk, A. F. Moene, M. Scheffer, H. J H Clercx, B.J.H. van de Wiel