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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The mobile SOUSY VHF Radar was operated inthe summer of 1987 during the MAC/SINE campaign in northern Norway to study thepolar mesosphere summer echoes (PMSE). Measurements of the spectral widthindicate that two types of structures occur. In general mesospheric layers arebifurcated exhibiting a narrow spectral width and a well-defined aspectsensitivity. However, for about 10% of the observation time cells of enhancedturbulence characterized by extremely broad spectral widths appear predominantlyin the upper sublayer above 86 km. Identification and separation of beam andshear broadening allows a determination of the turbulence-induced component ofthe spectral width. This case study reveals that during several events thesecloud-like structures of enhanced turbulence move with an apparent velocity ofseveral tens of meters per second which is almost identical with the phase tracevelocity of simultaneously observed waves. Since, at that time, the Richardsonnumber was less than a quarter, it was concluded that these turbulent cells weregenerated by a Kelvin-Helmholtz mechanism. The horizontal extent of thesestructures was calculated to be less than 40 km. A general relation betweenspectral width and echo power was not detected. The turbulent component of thespectral width was used to calculate typical values of the energy dissipationrate at times where narrow spectral width dominates and during periods ofenhanced turbulence. In addition, the outer scale of the inertial subrange(buoyancy scale) was estimated. For the first time the occurrence and motion ofthis type of structures of enhanced spectral width is analyzed and discussed indetail

VHF radar observations of turbulent structures in the polar mesopause region