气候变化领域集成服务门户(CCPortal): Orographically induced spontaneous imbalance within the jet causing a large-scale gravity wave event

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DOI	10.5194/acp-21-10393-2021
	Orographically induced spontaneous imbalance within the jet causing a large-scale gravity wave event
	Geldenhuys M.; Preusse P.; Krisch I.; Zülicke C.; Ungermann J.; Ern M.; Friedl-Vallon F.; Riese M.
发表日期	2021
ISSN	1680-7316
起始页码	10393
结束页码	10412
卷号	21 期号:13
英文摘要	To better understand the impact of gravity waves (GWs) on the middle atmosphere in the current and future climate, it is essential to understand their excitation mechanisms and to quantify their basic properties. Here a new process for GW excitation by orography-jet interaction is discussed. In a case study, we identify the source of a GW observed over Greenland on 10 March 2016 during the POLSTRACC (POLar STRAtosphere in a Changing Climate) aircraft campaign. Measurements were taken with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) instrument deployed on the High Altitude Long Range (HALO) German research aircraft. The measured infrared limb radiances are converted into a 3D observational temperature field through the use of inverse modelling and limited-angle tomography. We observe GWs along a transect through Greenland where the GW packet covers ≈1/3 of the Greenland mainland. GLORIA observations indicate GWs between 10 and 13km of altitude with a horizontal wavelength of 330km, a vertical wavelength of 2km and a large temperature amplitude of 4.5K. Slanted phase fronts indicate intrinsic propagation against the wind, while the ground-based propagation is with the wind. The GWs are arrested below a critical layer above the tropospheric jet. Compared to its intrinsic horizontal group velocity (25-72ms-1) the GW packet has a slow vertical group velocity of 0.05-0.2ms-1. This causes the GW packet to propagate long distances while spreading over a large area and remaining constrained to a narrow vertical layer. A plausible source is not only orography, but also out-of-balance winds in a jet exit region and wind shear. To identify the GW source, 3D GLORIA observations are combined with a gravity wave ray tracer, ERA5 reanalysis and high-resolution numerical experiments. In a numerical experiment with a smoothed orography, GW activity is quite weak, indicating that the GWs in the realistic orography experiment are due to orography. However, analysis shows that these GWs are not mountain waves. A favourable area for spontaneous GW emission is identified in the jet by the cross-stream ageostrophic wind, which indicates when the flow is out of geostrophic balance. Backwards ray-tracing experiments trace into the jet and regions where the Coriolis and the pressure gradient forces are out of balance. The difference between the full and a smooth-orography experiment is investigated to reveal the missing connection between orography and the out-of-balance jet. We find that this is flow over a broad area of elevated terrain which causes compression of air above Greenland. The orography modifies the wind flow over large horizontal and vertical scales, resulting in out-of-balance geostrophic components. The out-of-balance jet then excites GWs in order to bring the flow back into balance. This is the first observational evidence of GW generation by such an orography-jet mechanism. © Copyright:
语种	英语
scopus关键词	air temperature; gravity wave; inverse analysis; jet stream; middle atmosphere; orographic effect; stratosphere; wind; Arctic; Greenland
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/246744
作者单位	Forschungszentrum Jülich, Institute of Energy and Climate Research, Stratosphere (IEK-7), Jülich, Germany; South African Weather Service, Private Bag X097, Pretoria, 0001, South Africa; Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany; Leibniz Institute of Atmospheric Physics, University of Rostock, Kühlungsborn, Germany; JARA, Forschungszentrum Jülich GmbH, Jülich, Germany; Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing (IMK-ASF), Karlsruhe, Germany
推荐引用方式 GB/T 7714	Geldenhuys M.,Preusse P.,Krisch I.,et al. Orographically induced spontaneous imbalance within the jet causing a large-scale gravity wave event[J],2021,21(13).
APA	Geldenhuys M..,Preusse P..,Krisch I..,Zülicke C..,Ungermann J..,...&Riese M..(2021).Orographically induced spontaneous imbalance within the jet causing a large-scale gravity wave event.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(13).
MLA	Geldenhuys M.,et al."Orographically induced spontaneous imbalance within the jet causing a large-scale gravity wave event".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.13(2021).