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

Abstract

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.

Validation of the Aeolus L2B wind product with airborne wind lidar measurements in the polar North Atlantic region and in the tropics

“…The 2 µm DWL has been operated by DLR for more than 20 years and has been deployed in several ground and airborne field campaigns for measuring, for instance, aircraft wake vortices (Köpp et al, 2004), aerosol optical properties (Chouza et al, 2015(Chouza et al, , 2017, horizontal wind speeds over the Atlantic Ocean as input data for assimilation experiments (Weissmann et al, 2005;, and horizontal as well as vertical wind speeds to study the life cycle of gravity waves (Witschas et al, 2017(Witschas et al, , 2022. In addition, the system was applied in several Aeolus pre-launch campaigns conducted within the last 10 years (e.g., Marksteiner et al, 2018;Lux et al, 2018).…”