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Baroclinic instability at the winter stratopause
Author(s) -
Simmons A. J.
Publication year - 1974
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710042603
Subject(s) - stratopause , baroclinity , instability , stratosphere , atmospheric sciences , thermal wind , wind shear , geology , mesosphere , climatology , environmental science , meteorology , mechanics , physics , wind speed
Baroclinic instability is examined in an idealized model of the winter stratopause. The upper stratosphere is more stably stratified than the lower mesosphere, and instability can occur when the zonal flow has westerly shear., Using representative parameter values, a maximum doubling time of 2 days is found for a disturbance with zonal wavelength 4000 km and vertical scale 10 km, moving with a velocity within 2ms −1 of that of the zonal wind at the stratopause. Newtonian cooling reduces growth‐rates by some 80% of the damping rate, and becomes important for relaxation times of less than 7 days.