Energy Events in the Atmospheric Boundary Layer

Abstract

Turbulent velocity fluctuations in the atmospheric boundary layer are analysed using the VITA technique, with a view to understand the relation of the special events detected by the technique with turbulent bursts at high Reynolds numbers. Utilising data acquired under conditions of neutral stability at the Boulder Atmospheric Observatory, it is found that the “energy events” so detected are qualitatively similar in many respects to the turbulent bursts observed at much lower Reynolds numbers in the laboratory, but last longer and occur less frequently, in a manner not inconsistent with outer scaling. It is concluded that high Reynolds number flows reveal bursts tending to scale on outer variables — a conclusion that is considered particularly significant as wall parameters are of the same order in the atmospheric boundary layer as in the laboratory flows that have been widely studied.