geostrophic wind


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geostrophic wind

[¦jē·ō¦sträf·ik ′wind]
(meteorology)
That horizontal wind velocity for which the Coriolis acceleration exactly balances the horizontal pressure force.

Geostrophic Wind

 

a horizontal, even, and straight movement of air with no force of friction and with balance in the gradient of pressure and the deflecting force of the earth’s rotation; the simplest theoretical scheme of air movement of the rotating earth. The actual wind in atmospheric layers higher than 1 km above the earth’s surface is close to the geostrophic wind. The geostrophic wind is directed along the isobar, with an area of low pressure remaining to the left of the stream in the northern hemisphere and to the right in the southern. The velocity of the geostrophic wind is proportional to the magnitude of the horizontal gradient of pressure. With equal gradients it is inversely proportional to the density of the air and the sine of geographic latitude and therefore increases with elevation and with increasing nearness to the equator.

geostrophic wind

geostrophic wind
Pressure-gradient force causes air parcel to accelerate. Coriolis begins deflecting air to the right. Coriolis increases as speed increases. Coriolis eventually balances pressure gradient forces.
That horizontal wind velocity for which the Coriolis acceleration exactly balances the horizontal pressure or gradient force.
References in periodicals archive ?
If ' the isobars are at four-mb intervals and they're spaced about 100 NM apart at the latitude of Chicago, the geostrophic wind equals 40 knots.
In these cases, accounting for the influence of the larger-scale pressure distribution (prevailing geostrophic wind direction) leads to the distinction between corkscrew and backdoor breezes.
We reasonably owe to use these equations since the horizontal temperature gradient in the thermal wind equation tend to induce the vertical shear to geostrophic wind [52], while the DFCE will help to ascertain reasons on how the vertical shear (i.e., increased/decreased in wind speed) will lead into divergence/convergence, a necessary mechanism for convective processes.
In particular, the abrupt change in the air flow, evaluated from geostrophic wind fields (Soomere and Raamet, 2014), signals a major change in the air pressure and upper-level wind system over the southern Baltic Sea in 1988.
The wave model was forced with wind data corresponding to an elevation of 10 m above the sea surface, constructed from the Swedish Meteorological and Hydrological Institute (SMHI) geostrophic wind database.
Figure 6 shows the 500/1000 thickness advection by geostrophic wind of 1000 hpa level in the selected case studies to represent.
a) The exponent a is constant all over the thickness of the atmospheric boundary layer, up to [z.sub.g = [delta]], where the velocity is equal to the geostrophic wind velocity G.
where u, v, and [theta] are, respectively, the wind components and the air temperature, [u.sub.G], [v.sub.G] are the components of the geostrophic wind, [bar.u'w'] and [bar.v'w'] are the components of the moment flux, and [bar.w'[theta]'] is the sensible heat flux.
This is a consequence offriction entering into the geostrophic wind equation; since Coriolis is velocity dependent it reduces its effect in the balance between Coriolis and pressure gradient, which acts toward the right, so instead of blowing south to north, it becomes increasingly southwest to northeast and so on.
The most popular way consists in the use of geostrophic wind fields that are adjusted to the 10 m level by means of a simplified procedure in which the geostrophic wind speed (usually retrieved from the Swedish Meteorological and Hydrological Institute database) was multiplied by 0.6 and the direction turned 15[degrees] counter-clockwise (Bumke & Hasse 1989).
The wind forcing at a 10 m level was derived from geostrophic winds as recommended by Bumke and Hasse (1989): the geostrophic wind speed was multiplied by 0.6 and the direction turned by 15[degrees] to the left.
The direction of the geostrophic wind relative to the slope was incremented by 45[degrees] in each successive run.