English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We investigate the decay of planetary boundary layer (PBL) turbulence in theafternoon, from the time the surface buoyancy flux starts to decrease untilsunset. Dense observations of mean and turbulent parameters were acquiredduring the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) fieldexperiment by several meteorological surface stations, sounding balloons,radars, lidars and two aircraft during the afternoon transition. We analysed a case study based on some ofthese observations and large-eddy simulation (LES) data focusing on theturbulent vertical structure throughout the afternoon transition.  The decay of turbulence is quantified through the temporal and verticalevolution of (1) the turbulence kinetic energy (TKE), (2) the characteristiclength scales of turbulence and (3) the shape of the turbulence spectra. Aspectral analysis of LES data, airborne and surface measurements is performedin order to characterize the variation in the turbulent decay with height andstudy the distribution of turbulence over eddy size.  This study highlights the LES ability to reproduce the turbulence evolutionthroughout the afternoon. LESs and observations agree that the afternoontransition can be divided in two phases: (1) a first phase during which theTKE decays at a low rate, with no significant change in turbulencecharacteristics, and (2) a second phase characterized by a larger TKE decayrate and a change in spectral shape, implying an evolution of eddy sizedistribution and energy cascade from low to high wave number.  The changes observed either in TKE decay (during the first phase) or in thevertical wind spectra shape (during the second phase of the afternoontransition) occur first in the upper region of the PBL. The higher within thePBL, the stronger the spectra shape changes

Turbulence vertical structure of the boundary layer during the afternoon transition