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Clear Air Turbulence Observed Across a Tropopause Fold Over the Drake Passage—A Case Study

Rodriguez Imazio, Paola and Dörnbrack, Andreas and Urzua, Rodrigo Delgado and Rivaben, Nicolás and Godoy, Alejandro (2022) Clear Air Turbulence Observed Across a Tropopause Fold Over the Drake Passage—A Case Study. Journal of Geophysical Research: Atmospheres, 127 (4), pp. 1-24. Wiley. doi: 10.1029/2021JD035908. ISSN 0148-0227.

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Official URL: https://dx.doi.org/10.1029/2021JD035908

Abstract

An aircraft turbulence encounter over the Drake Passage is investigated by combining unique high-frequency flight level data, vertical profiles of a near-simultaneous radiosonde profile and numerical results from global and regional numerical weather prediction (NWP) models. Meteorological analysis reveals an intense polar low propagating from the Bellinghausen Sea toward the Drake Passage. A small and deep stratospheric intrusion formed a tropopause fold that promoted strong upper-level frontogenesis and enhanced shear and horizontal deformation of the upper tropospheric and lower stratospheric (UTLS) airflow. In this region, the Basic HALO Measurement and Sensor System (BAHAMAS) aboard the HALO research aircraft flying at FL450 detected large peak-to-peak variations in all meteorological parameters. The computed Energy dissipation rate (EDR) values (cubic root of the eddy dissipation rate) indicate moderate to severe turbulence. The location of this turbulence encounter was well-predicted by the clear air turbulence (CAT) indices derived from the NWP results. The enhanced CAT indices emphasize the large shear and horizontal deformation of the airflow as the cause of the turbulence. Horizontal and vertical energy spectra calculated from the 10 Hz BAHAMAS data show a well-defined energy cascade toward small scales with Kolmogorov scaling. Maximum EDR values of about 0.35 derived both from the spectra and structure functions for the wind speed agree quantitatively very well. In addition, the structure functions support the detection of turbulent atmospheric conditions with signatures of flow anisotropy generated by enhanced thermal stratification in the UTLS. The scales involved are between the buoyancy length scale LB ≈ 1,500 m and the Ozmidov scale LO ≈ 111 m.

Item URL in elib:https://elib.dlr.de/193578/
Document Type:Article
Title:Clear Air Turbulence Observed Across a Tropopause Fold Over the Drake Passage—A Case Study
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Rodriguez Imazio, PaolaConsejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, ArgentinaUNSPECIFIEDUNSPECIFIED
Dörnbrack, AndreasDLR, IPAhttps://orcid.org/0000-0003-0936-0216UNSPECIFIED
Urzua, Rodrigo DelgadoDirección Meteorológica de Chile, Santiago de Chile, ChileUNSPECIFIEDUNSPECIFIED
Rivaben, NicolásServicio Meteorológico Nacional, Buenos Aires, ArgentinaUNSPECIFIEDUNSPECIFIED
Godoy, AlejandroServicio Meteorológico Nacional, Buenos Aires, ArgentinaUNSPECIFIEDUNSPECIFIED
Date:2022
Journal or Publication Title:Journal of Geophysical Research: Atmospheres
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:127
DOI:10.1029/2021JD035908
Page Range:pp. 1-24
Publisher:Wiley
ISSN:0148-0227
Status:Published
Keywords:CAT, Drake Passage, Southern Hemisphere Transport
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Air Transportation and Impact
DLR - Research area:Aeronautics
DLR - Program:L AI - Air Transportation and Impact
DLR - Research theme (Project):L - Climate, Weather and Environment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Transport Meteorology
Deposited By: Ziegele, Brigitte
Deposited On:25 Jan 2023 11:25
Last Modified:30 Jan 2023 12:14

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