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High resolution observations of small scale gravity waves and turbulence features in the OH airglow layer

Sedlak, Rene and Hannawald, Patrick and Schmidt, Carsten and Wüst, Sabine and Bittner, Michael (2016) High resolution observations of small scale gravity waves and turbulence features in the OH airglow layer. Atmospheric Measurement Techniques (AMT), 9, pp. 5955-5963. Copernicus Publications. DOI: 10.5194/amt-2016-292 ISSN 1867-1381

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A new version of the Fast Airglow Imager (FAIM) for the detection of atmospheric waves in the OH airglow layer has been set up at the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) in Oberpfaffenhofen (48.09° N, 11.28° E), Germany. The spatial resolution of the instrument is 16m in zenith direction with a field of view (FOV) of 11.1 km x 9.0 km at the OH layer height of ca. 87 km. Since November 2015, the system has been in operation in two different setups (zenith angles 46° and 0°) with a temporal resolution of 2.5 to 2.8 s. In a first case study we present observations of two small wave-like features that might be attributed to gravity wave instabilities. In order to spectrally analyse harmonic structures even on small spatial scales down to 550 m horizontal wavelength, we made use of the Maximum Entropy Method (MEM) since this method exhibits an excellent wavelength resolution. MEM further allows analysing relatively short data series, which considerably helps to reduce problems such as stationarity of the underlying data series from a statistical point of view. We present an observation of the subsequent decay of well-organized wave fronts into eddies, which we tentatively interpret in terms of an indication for the onset of turbulence. Another remarkable event which demonstrates the technical capabilities of the instrument was observed during the night of 4th to 5th April 2016. It reveals the disintegration of a rather homogenous brightness variation into several filaments moving in different directions and with different speeds. It resembles the formation of a vortex with a horizontal axis of rotation likely related to a vertical wind shear. This case shows a notable similarity to what is expected from theoretical modelling of Kelvin-Helmholtz instabilities (KHIs). The comparatively high spatial resolution of the presented new version of the FAIM airglow imager provides new insights into the structure of atmospheric wave instability and turbulent processes. Infrared imaging of wave dynamics on the sub-kilometre scale in the airglow layer supports the findings of theoretical simulations and modellings.

Item URL in elib:https://elib.dlr.de/109574/
Document Type:Article
Title:High resolution observations of small scale gravity waves and turbulence features in the OH airglow layer
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Sedlak, ReneRene.Sedlak (at) dlr.deUNSPECIFIED
Hannawald, Patrickpatrick.hannawald (at) physik.uni-augsburg.deUNSPECIFIED
Schmidt, CarstenCarsten.Schmidt (at) dlr.deUNSPECIFIED
Wüst, Sabinesabine.wuest (at) dlr.deUNSPECIFIED
Bittner, MichaelMichael.Bittner (at) dlr.deUNSPECIFIED
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
DOI :10.5194/amt-2016-292
Page Range:pp. 5955-5963
Publisher:Copernicus Publications
Keywords:Airglow Imager, Gravity Waves, Atmospheric Instability, Turbulence, OH Airglow, KHI
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Datenprodukte für Klima- und Atmosphärenanwendungen (old)
Location: Oberpfaffenhofen
Institutes and Institutions:German Remote Sensing Data Center > Atmosphere
Deposited By: Sedlak, Rene
Deposited On:14 Dec 2016 13:52
Last Modified:08 Mar 2018 18:10

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