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Four‐Dimensional Quantification of Kelvin‐Helmholtz Instabilities in the Polar Summer Mesosphere Using Volumetric Radar Imaging
Author(s) -
Chau J. L.,
Urco J. M.,
Avsarkisov V.,
Vierinen J. P.,
Latteck R.,
Hall C. M.,
Tsutsumi M.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl086081
Subject(s) - geology , stratification (seeds) , buoyancy , mesosphere , radar , turbulence , froude number , atmospheric sciences , geophysics , physics , meteorology , mechanics , stratosphere , seed dormancy , telecommunications , breakup , botany , germination , dormancy , computer science , biology
We present and characterize in time and three spatial dimensions a Kelvin‐Helmholtz Instability (KHI) event from polar mesospheric summer echoes (PMSE) observed with the Middle Atmosphere Alomar Radar System. We use a newly developed radar imaging mode, which observed PMSE intensity and line of sight velocity with high temporal and angular resolution. The identified KHI event occurs in a narrow layer of 2.4 km thickness centered at 85 km altitude, is elongated along north‐south direction, presents separation between billows of ∼ 8 km in the east‐west direction, and its billow width is ∼ 3 km. The accompanying vertical gradients of the horizontal wind are between 35 and 45 m/s/km and vertical velocities inside the billows are ± 12 m/s. Based on the estimated Richardson ( < 0.25), horizontal Froude ( ∼ 0.8), and buoyancy Reynolds ( ∼ 2.5 × 104) numbers, the observed event is a KHI that occurs under weak stratification and generates strong turbulence.