DOI: 10.1175/JCLI-D-17-0644.1
Scopus记录号: 2-s2.0-85049728354
论文题名: Eddy lifetime, number, and diffusivity and the suppression of eddy kinetic energy in midwinter
作者: Schemm S. ; Schneider T.
刊名: Journal of Climate
ISSN: 8948755
出版年: 2018
卷: 31, 期: 14 起始页码: 5649
结束页码: 5665
语种: 英语
英文关键词: Atmosphere
; Extratropical cyclones
; Kinetic energy
; Lagrangian circulation/transport
; Seasonal cycle
; Storm tracks
Scopus关键词: Diffusion
; Earth atmosphere
; Kinetic energy
; Kinetics
; Lagrange multipliers
; Storms
; Baroclinic instability
; Eddy kinetic energy
; Extratropical cyclones
; Lagrangian circulation/transport
; Midwinter minimums
; Potential vorticity
; Seasonal cycle
; Storm track
; Fighter aircraft
; atmospheric circulation
; atmospheric transport
; baroclinic instability
; climate prediction
; eddy
; extratropical cyclone
; kinetic energy
; Lagrangian analysis
; potential vorticity
; seasonal variation
; storm track
; winter
; Pacific Ocean
; Pacific Ocean (North)
英文摘要: The wintertime evolution of the North Pacific storm track appears to challenge classical theories of baroclinic instability, which predict deeper extratropical cyclones when baroclinicity is highest. Although the surface baroclinicity peaks during midwinter, and the jet is strongest, eddy kinetic energy (EKE) and baroclinic conversion rates have a midwinter minimum over the North Pacific. This study investigates how the reduction in EKE translates into a reduction in eddy potential vorticity (PV) and heat fluxes via changes in eddy diffusivity. Additionally, it augments previous observations of the midwinter storm-track evolution in both hemispheres using climatologies of tracked surface cyclones. In the North Pacific, the number of surface cyclones is highest during midwinter, while the mean EKE per cyclone and the eddy lifetime are reduced. The midwinter reduction in upper-level eddy activity hence is not associated with a reduction in surface cyclone numbers. North Pacific eddy diffusivities exhibit a midwinter reduction at upper levels, where the Lagrangian decorrelation time is shortest (consistent with reduced eddy lifetimes) and the meridional parcel velocity variance is reduced (consistent with reduced EKE). The resulting midwinter reduction in North Pacific eddy diffusivities translates into an eddy PV flux suppression. In contrast, in the North Atlantic, a milder reduction in the decorrelation time is offset by a maximum in velocity variance, preventing a midwinter diffusivity minimum. The results suggest that a focus on causes of the wintertime evolution of Lagrangian decorrelation times and parcel velocity variance will be fruitful for understanding causes of seasonal storm-track variations. © 2018 American Meteorological Society. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/111497
Appears in Collections: 气候减缓与适应
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作者单位: Geophysical Institute, University of Bergen, Bergen, Norway; Bjerknes Centre for Climate Research, University of Bergen, Bergen, Norway; Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland; California Institute of Technology, Pasadena, CA, United States
Recommended Citation:
Schemm S.,Schneider T.. Eddy lifetime, number, and diffusivity and the suppression of eddy kinetic energy in midwinter[J]. Journal of Climate,2018-01-01,31(14)