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34 terms

Chapter 6

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air pressure
the pressure exerted by the mass of air above a given point, usually expressed in millibars, inches of mercury, or in hectopascals
millibar
a unit for expressing atmospheric pressure
standard atmospheric pressure
A pressure of 1013.25 mb, 29.92 inHg, 760 mmHg, 14.7 lbpsi, or 1013.25 hectopascals
barometer
an instrument that measures atmospheric pressure.
mercury barometer
a type of barometer that uses mercury to measure atmospheric pressure. The height of the mercury column is a measure of atmospheric pressure.
aneroid barometer
an instrument designed to measure atmospheric pressure. Contains no liquid.
station pressure
the actual pressure computed at the observing sttion
sea-level pressure
the atmospheric pressure at mean sea level
isobar
a line connecting points of equal pressure
surface map
a map that shows the distribution of sea-level pressure with isobars and weather phenomena
anticyclone
an area of high atmospheric pressure around which the wind blows clockwise in the northern hemisphere and counterclock wise in the southern hemisphere
mid-latitude cyclonic storm
a cyclonic storm that most often forms along a front in middle and high latitudes
isobaric map
a chart showing variables such as temperature and wind, on a constant pressure surface
contour line
a line that connects points of equal elevation above a reference level, most often sea level
ridge
an elongated area of high atmospheric pressure
trough
an elongated area of low atmospheric pressure
pressure gradient
the rate of decrease of pressure per unit of horizontal distance
pressure gradient force
the force due to differences in pressure within the atmosphere that causes air to move and hence the wind to blow
coriolis force
an apparent force observed on any free moving object in a rotating system
geostrophic wind
A theoretical horizontal wind blowing in a straight path, parallel to the isobars or contours, at constant speed
gradient wind
a theoretical wind that blows parallel to curved isobars or contours
centripetal force
the radial force required to keep an object moving in a circular path. It is directed toward the center of that path
meridional wind flow
a type of atmospheric circulation pattern in which the north-south component of the wind is pronounced
zonal wind flow
a wind that has a predominate west to east component
friction layer
the atmospheric layer near the surface usually extending up to about 1 km where the wind is influenced by friction of the earth's surface and objects on it
hydrostatic equilibrium
the state of the atmosphere when there i a balance between the vertical pressure gradient force and the downward pull of gravity
onshore wind
a breeze that blows from the water onto the land
offshore wind
a breeze that blows from the land out over the water
prevailing wind
the wind direction most frequently observed during a given period
wind rose
a diagram that shows the percent of time that the wind blows from different directions at a given location over a given time
wind vane
an instrument used to indicate wind direction
anemometer
an instrument designed to measure wind speed
aerovane
a wind instrument that indicates or records both wind speed and wind direction
wind profiler
A doppler radar capable of measuring the turbulent eddies that move with the wind