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Momentum fluxes from airborne wind measurements in three cumulus cases over land

Koning, Ada Mariska and Nuijens, Louise and Mallaun, Christian and Witschas, Benjamin and Lemmerz, Christian (2022) Momentum fluxes from airborne wind measurements in three cumulus cases over land. Atmospheric Chemistry and Physics (ACP), 22 (11), pp. 7373-7388. Copernicus Publications. doi: 10.5194/acp-22-7373-2022. ISSN 1680-7316.

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Official URL: https://dx.doi.org/10.5194/acp-22-7373-2022

Abstract

Measurements of wind and momentum fluxes are not typically at the centre of field studies on (shallow) cumulus convection, but the mesoscale organization of convection is likely closely tied to patterns in wind. This study combines in situ high-frequency turbulence measurements from a gust probe onboard a Cessna aircraft with downward profiling Doppler wind lidar (DWL) measurements onboard a Falcon aircraft to study variability in the wind profile and momentum fluxes in regions of convection. The dual-aircraft measurements were made during three prototype flights in shallow convective regimes over German agricultural areas (two of which had hilly topography, one flat) in late spring 2019, including forced cumulus humilis under weak winds and “popcorn” cumuli during stronger wind and wind shear after front passages. All flights show pronounced meso-gamma (2–20 km) scale variability in the wind, with the largest wind variance (on the order of 2–4 m2 s−2) towards cloud base and in the cloud layer on flights with large vertical wind shear. The wind and wind variance profiles measured in situ and by lidar compare very well, despite the DWL’s coarse (∼ 8 km) horizontal footprint. This highlights the presence of wind fluctuations on scales larger than a few kilometres and that wind lidars can be used more deliberately in field studies to map (mesoscale) flows. Cloudy transects are associated with more than twice the momentum flux compared with cloud-free transects. The contribution of the updraft to the total momentum flux, typically one-third to two-thirds, is far less than the typical contribution of the updraft to buoyancy flux. Even on the same flight day, momentum flux profiles can differ per track, with one case of counter-gradient momentum transport when the updraft does carry substantial momentum flux. Scales beyond 1 km contribute significantly to the momentum flux and there is clear evidence for compensating flux contributions across scales. The results demonstrate that momentum flux profiles and their variability require understanding of motions across a range of scales, with non-negligible contributions of the clear-sky fluxes and of mesoscales that are likely coupled to the convection

Item URL in elib:https://elib.dlr.de/198369/
Document Type:Article
Title:Momentum fluxes from airborne wind measurements in three cumulus cases over land
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Koning, Ada MariskaUniv. Delft, Niederlandehttps://orcid.org/0000-0001-7218-0504UNSPECIFIED
Nuijens, LouiseUniv. Delft, NiederlandeUNSPECIFIEDUNSPECIFIED
Mallaun, ChristianUNSPECIFIEDhttps://orcid.org/0009-0004-6501-6457UNSPECIFIED
Witschas, BenjaminDLR, IPAhttps://orcid.org/0000-0001-7993-1470UNSPECIFIED
Lemmerz, ChristianDLR, IPAhttps://orcid.org/0009-0002-8587-7436UNSPECIFIED
Date:8 June 2022
Journal or Publication Title:Atmospheric Chemistry and Physics (ACP)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:22
DOI:10.5194/acp-22-7373-2022
Page Range:pp. 7373-7388
Publisher:Copernicus Publications
ISSN:1680-7316
Status:Published
Keywords:Wind lidar, airborne, momentum flux, turbulence
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Project ADM III cont., R - Wind lidar technology development
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Flugexperimente > Mess- und Sensortechnik OP
Deposited By: Witschas, Dr. Benjamin
Deposited On:23 Oct 2023 09:06
Last Modified:24 Oct 2023 12:23

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