Upward propagation of turbulence bursts in the nocturnal boundary layer

It is well known that during nights with clear skies and weak winds the turbulence mixing is almost completely suppressed by the thermal stratification caused by the radiative cooling of the surface. Such conditions generally favor the appearance of bursts of intense turbulent activity, which occur in an apparently unpredictable manner in time and space. Despite the common association of many nonlocal physical phenomena to the generation of intermittent bursts, there is no commonsense regarding the surface-atmosphere interaction as a mechanism which is able to generate these intermittent events near the ground, by shear instabilities, as well as their upwards propagation in the surface layer. Under the optics of dynamical systems, such a scenario could imply that these events are a natural state of the very stable boundary layer. In order to characterize this kind of intermittent event in experimental data, allowing subsequently investigation of its role as a transport phenomena, we propose a method to identify and characterize the vertical propagation of the turbulence bursts. This novel method is applied on multi-level atmosphere data collected at a very stable site, which permits us to assess how distinct events are connected. Results are compared with model simulations that support that this special type of turbulent bursts promote sequential decreasing of the temperature in upper boundary layer levels, as it propagates upwards.