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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
The region of confluence at the upwind extremity of a jet stream; the opposite of exit region.
Industry:Weather
A layer of intermittent turbulence and overshooting thermals at the top of the convective mixed layer where the free atmosphere is entrained into the top of the boundary layer. The entrainment zone is thinner when a stronger temperature inversion caps the boundary layer and thicker when turbulence and thermals are more vigorous.
Industry:Weather
The volume of entrained air per unit area per unit time, which has units of velocity. It is a measure of dilution of an entity, such as a rising smoke plume, or of a whole layer, such as the atmospheric boundary layer. For a growing atmospheric mixed layer, the rate of rise of the top of the mixed layer zi equals the entrainment velocity we minus any large-scale subsidence ws that is imposed at the top of the boundary layer. During sunny days over land, the entrainment velocity is proportional to the heat flux from the surface divided by the potential temperature change across the entrainment zone (i.e., the strength of the capping inversion). On windy days, the entrainment velocity is proportional to the turbulence kinetic energy at the top of the boundary layer and is inversely proportional to the potential temperature change across the entrainment zone. See entrainment rate.
Industry:Weather
An image that has had processing (e.g., contrast stretching, pseudocoloring, unsharp masking) applied to improve information presentation.
Industry:Weather
The rate at which entrainment proceeds. In the absence of advection effects, the entrainment rate is equal to the rate of deepening of the mixed layer.
Industry:Weather
The ratio of lateral entrainment velocity to plume-rise velocity of a smoke plume. Smoke plumes that rise through the environment due to buoyancy or momentum become diluted with environmental air, where the rate of dilution is proportional to the rise rate of the plume. The entrainment coefficient is this constant of proportionality. This concept of lateral entrainment does not work well for convective thermals in the atmospheric boundary layer. One reason is that boundary layer thermals are part of a large overturning circulation involving the whole boundary layer during statically unstable conditions of free convection, rather than being thin currents of rising smokestack air.
Industry:Weather
1. In meteorology, the mixing of environmental air into a preexisting organized air current so that the environmental air becomes part of the current; the opposite of detrainment. Entrainment of air into clouds, especially cumulus, is said to be inhomogeneous when the timescale for mixing of environmental air is very much greater than the timescale for drop evaporation. Under these conditions, which are often found when environmental air is first entrained into cumulus, regions of cloud and entrained air are intertwined, with evaporation occurring only on the edges of the interface between the cloudy and entrained environmental air. 2. The process by which turbulent fluid within a mixed layer incorporates adjacent fluid that is nonturbulent, or much less turbulent; thus entrainment always proceeds toward the nonturbulent layer. In the absence of advection effects, this tends to deepen the mixed layer.
Industry:Weather
An idealization of cloud mixing where parcels of cloudy and noncloudy air move with no dilution to their respective levels of neutral buoyancy within a cloud, after which they mix with the environment.
Industry:Weather
One-half the square of the relative vorticity. The term was popularized by C. Leith and is based on the modern Greek στωφη, meaning “act of turning. ” Enstrophy is a conservative quantity in two-dimensional inviscid flow. However, when viscosity is finite, enstrophy tends to be selectively decayed relative to more rugged integrals such as energy and angular momentum.
Industry:Weather
Acronym for El Niño–Southern Oscillation, coined in the early 1980s in recognition of the intimate linkage between El Niño events and the Southern Oscillation, which prior to the late 1960s had been viewed as two unrelated phenomena. The global ocean–atmosphere phenomenon to which this term applies is sometimes referred to as the “ENSO cycle. ” See also El Niño, La Niña, Southern Oscillation.
Industry:Weather
