Article Type:
Research Article

Static Stability—An Update

Roland B. Stull Boundary Layer Research Team, Department of Meteorology, University of Wisconsin, Madison, Wl 53706-1695

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Online Publication:
01 Oct 1991
Print Publication:
01 Oct 1991
DOI:
https://doi.org/10.1175/1520-0477(1991)072<1521:SSU>2.0.CO;2
Page(s):
1521–1530
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Static stability should not be evaluated from the local lapse rate. There is a growing body of observations, such as within portions of mixed layers and forest canopies, showing that the whole sounding should be considered to evaluate stability. Air parcels can move across large vertical distances to create turbulence within regions that would otherwise have been considered stable or neutral according to classical local definitions. A nonlocal determination of static stability is presented that accounts for both the local lapse rate and for convective air parcels moving across finite distances. Such a method is necessary to properly estimate turbulence, dispersion, and vertical fluxes that affect our weather and climate forecasts. Teachers of introductory meteorology courses and textbook authors are encouraged to revise their static stability discussions to follow air parcel displacements from beginning to end.

Static stability should not be evaluated from the local lapse rate. There is a growing body of observations, such as within portions of mixed layers and forest canopies, showing that the whole sounding should be considered to evaluate stability. Air parcels can move across large vertical distances to create turbulence within regions that would otherwise have been considered stable or neutral according to classical local definitions. A nonlocal determination of static stability is presented that accounts for both the local lapse rate and for convective air parcels moving across finite distances. Such a method is necessary to properly estimate turbulence, dispersion, and vertical fluxes that affect our weather and climate forecasts. Teachers of introductory meteorology courses and textbook authors are encouraged to revise their static stability discussions to follow air parcel displacements from beginning to end.

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Cover Bulletin of the American Meteorological Society
Bulletin of the American Meteorological Society