The Effective Static Stability Experienced by Eddies in a Moist Atmosphere
Water vapor directly affects the dynamics of atmospheric eddy circulations through the release of latent heat. But it is difficult to include latent heat release in dynamical theories because of the associated nonlinearity (precipitation generally occurs where there is upward motion). A new effect...
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| Format: | Article |
| Language: | en_US |
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American Meteorological society
2011
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| Online Access: | http://hdl.handle.net/1721.1/65826 https://orcid.org/0000-0003-1748-0816 |
| Summary: | Water vapor directly affects the dynamics of atmospheric eddy circulations through the release of latent heat.
But it is difficult to include latent heat release in dynamical theories because of the associated nonlinearity
(precipitation generally occurs where there is upward motion). A new effective static stability is derived that
fundamentally captures the effect of latent heat release on moist eddy circulations. It differs from the usual dry
static stability by an additive term that depends on temperature and a parameter measuring the up–down
asymmetry of vertical velocity statistics. Latent heat release reduces the effective static stability experienced by
eddies but cannot reduce it to zero so long as there are nonprecipitating regions of the eddies. Evaluation based
on reanalysis data indicates that the effective static stability in the lower troposphere ranges from ;80%of the
dry static stability at high latitudes to ;25% in the tropics.
The effective static stability provides a solution to the longstanding problem of how to adapt dry dynamical
theories to the moist circulations in the atmosphere. Its utility for climate change problems is illustrated based
on simulations with an idealized general circulation model. It is shown to help account for changes in the
thermal stratification of the extratropical troposphere, the extent of the Hadley cells, the intensity of extratropical
transient eddies, and the extratropical eddy length. |
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