17 Aug 2022
17 Aug 2022
Status: this preprint is currently under review for the journal AMT.

Airborne coherent wind lidar measurements of the momentum flux profile from orographically induced gravity waves

Benjamin Witschas1, Sonja Gisinger1, Stephan Rahm1, Andreas Dörnbrack1, David C. Fritts2, and Markus Rapp1 Benjamin Witschas et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Institut für Physik der Atmosphäre, 82234 Oberpfaffenhofen, Germany
  • 2GATS, Boulder, CO, USA

Abstract. In the course of the GW-LCYCLE II campaign, conducted in Jan/Feb 2016 from Kiruna, Sweden, coherent Doppler wind lidar (2-µm DWL) measurements were performed from the DLR Falcon aircraft to investigate small-scale gravity waves induced by flow across the Scandinavian Alps. During a mountain wave event on 28 January 2016, a novel momentum flux (MF) scan pattern with fore and aft propagating laser beams was applied to the 2-µm DWL. This allows to measure vertical wind and horizontal wind along the flight track simultaneously, and hence, enables to derive the horizontal momentum flux profile. The functionality of this method and the corresponding retrieval algorithm is validated by means of a comparison against in-situ wind data measured by the High Altitude and Long Range (HALO) aircraft which was also deployed in Kiruna for the POLSTRACC (Polar Stratosphere in a Changing Climate) campaign. Based on that, the systematic and random error of the wind speeds retrieved from the 2-µm DWL observations are determined. Further, the measurements performed on that day are used to reveal pronounced changes of the horizontal scales of the vertical velocity field and of the leg-averaged momentum fluxes in the tropopause inversion layer (TIL) region, which are induced by interfacial waves.

Benjamin Witschas et al.

Status: open (until 24 Oct 2022)

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Benjamin Witschas et al.

Benjamin Witschas et al.


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Short summary
In this paper, a novel scan technique is applied to an airborne coherent Doppler wind lidar, enabling to measure the vertical wind speed and the horizontal wind speed along flight direction simultaneously with a horizontal resolution of 800 m and a vertical resolution of 100 m. The performed observations are valuable for gravity wave characterization as they allow to calculated the leg-averaged momentum flux profile, and with that, the propagation direction of excited gravity waves.