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

• Published in: Atmospheric Measurement Techniques
• Main Authors: Witschas, Benjamin, Gisinger, Sonja, Rahm, Stephan, Dörnbrack, Andreas, Fritts, David C., Rapp, Markus
• Format: Text
• Language: English
• Published: 2023
• Subjects: Gisinger; Kiruna
• Online Access: https://doi.org/10.5194/amt-16-1087-2023; https://amt.copernicus.org/articles/16/1087/2023/

In the course of the GW-LCYCLE II campaign, conducted in Jan/Feb 2016 from Kiruna, Sweden, coherent Doppler wind lidar (2 µ m DWL) measurements were performed from the DLR Falcon aircraft to investigate 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 µ m DWL. This allows us to measure the vertical wind and the horizontal wind along the flight track simultaneously with a high horizontal resolution of ≈800 m and hence enables us to derive the horizontal MF profile for a broad wavelength spectrum from a few hundred meters to several hundred kilometers. The functionality of this method and the corresponding retrieval algorithm is validated using 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 µ m DWL observations are determined. Further, the measurements performed on that day are used to reveal significant changes in the horizontal wavelengths of the vertical wind speed and of the leg-averaged momentum fluxes in the tropopause inversion layer (TIL) region, which are likely to be induced by interfacial waves as recently presented by Gisinger et al. ( 2020 ) .