Spatial Dependence of Stably Stratified Nocturnal Boundary-Layer Regimes in Complex Terrain

• Published in: Boundary-layer meteorology 2020-10, Vol.177 (1), p.19-47
• Main Authors: Abraham, Carsten, Monahan, Adam H.
• Format: Article
• Language: English
• Subjects: Analysis; Atmospheric boundary layer; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Boundary layers; Computational fluid dynamics; Dependence; Earth and Environmental Science; Earth Sciences; Markov chains; Markov processes; Meteorology; Planetary boundary layer; Probability theory; Research Article; Sequences; Terrain; Towers; Turbulence; Wind direction; Windows (intervals)
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-020-00532-x

The stably stratified atmospheric boundary layer (SBL) has been found in previous studies to display distinct regimes of behaviour. In particular, a contrast is often drawn between the weakly (wSBL) and very (vSBL) stable boundary layers. Time series of SBL regime affiliation obtained from hidden Markov model analyses of data from three different towers at the Los Alamos National Laboratory are used to investigate the spatial dependence of SBL regime occupation and SBL transitions. The local topography influences the flow such that south-west to north-east flow prevails, for which wSBL and vSBL conditions respectively are more likely to occur. Joint probabilities of shared regime occupation at the three towers (with and without conditioning on wind direction) are much larger than would be expected from statistically independent regime sequences at the different locations. Very persistent wSBL nights (without any transitions to the vSBL) have a higher probability of occurring across the entire tower network domain than very persistent vSBL nights. Many regime transitions occur within a narrow time window between the different towers; occurrence probabilities of such events are much higher than would be expected from statistically independent regime transitions. Of such events, transitions occurring at exactly the same time across the tower network occur most often. Many co-occurring turbulence recovery events can be associated with high-intensity intermittent turbulence events. Our results imply that the scale on which the SBL regime occupation and transitions are dependent exceeds 10 km in this region of complex terrain.