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A rapidly travelling planetary‐scale instability in the atmosphere
Author(s) -
Lynch Peter
Publication year - 1983
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl010i012p01176
Subject(s) - baroclinity , atmosphere (unit) , instability , zonal flow (plasma) , troposphere , mean flow , atmospheric sciences , geostrophic wind , physics , primitive equations , wavenumber , energy flux , geology , mechanics , environmental science , meteorology , nonlinear system , turbulence , plasma , optics , quantum mechanics , numerical partial differential equations , astronomy , tokamak
The hydrodynamic instability of the zonally averaged circulation of the atmosphere is investigated using a primitive equation model on a global domain. The classical baroclinically unstable modes are examined and a new mode of instability is found. This mode has phase‐speed greater than the maximum zonal flow velocity (such a solution is impossible within the framework of quasi‐geostrophic theory). It draws energy from the mean flow in the troposphere through baroclinic conversion and it penetrates deeply into the middle atmosphere, its growth there being supported by convergence of vertical wave energy flux. With zonal wavenumber one it has a period of two days and an e‐folding time of six days. Such instabilities may play an important role in the dynamics of the middle atmosphere.