Ch. 5 Flashcards
(29 cards)
atmospheric pressure
the force exerted by the weight of these gas molecules on a unit of area of earths surface or any other body
temp and pressure relationships
an increase in temp creates a decrease in density and thus a decrease in pressure and vise versa
dynamic high
strongly descending air is usually associated with high pressure at the surface
thermal high
very cold surface conditions are often associated with high pressure at the surface
dynamic low
strongly rising air is usually associated with low pressure at the surface
thermal low
very warm surface conditions are often associated with relatively low pressure at the surface
barometers
measure atmospheric pressure
millibar
most common unit of measure for atmospheric pressure
isobars
once pressure in millibars is plotted on a weather map, it is possible to draw isolines of equal pressure called isobars
ridge
elongated area of relatively high pressure
trough
an elongated area of relatively low pressure
pressure gradient
the abruptness of the pressure change over a distance
wind
horizontal movement of air. unequal heating of different parts of earths surface brings about temp gradient that generate pressure gradients that set air into motion. flows from higher pressure to lower pressure
anti cyclone
a high pressure centered wind pattern
cyclones
low pressured centered wind pattern
coriolis effect
because earth rotates, everything near the surface appears to deflect to the right in the northern hemisphere and to the left in the southern hemisphere
friction
in the lowest portions of the troposphere a third force that influences wind direction is friction. the frictional drag of earths surface slows the wind movement and so the influence of the coriolis effect is reduced
friction layer
of the atmosphere extends to only about 1000 meters (3300 feet) above the surface
hadley cells
low latitude cells, one north and one south of the equator are gigantic convection systems. these are the two prominent convection cells. warm air rises producing areas of low pressure, this air cools and spreads to the poles and descends at 30 degrees where is has cooled the most. here there are bands of high pressure formed.
seven components of general circulation
(1) intertropical convergence zone ITCZ (2) Trade winds (3) suntropical highs (4) Westerlies (5) Polar front, sub polar lows (6) Polar easterlies (7) Polar highs
subtropical high
30 degrees. anticyclone. develop fro descending air from the hadleys. azores high: north atlantic. hawaiian high: North Pacific. intensified cell of high pressure. clear warm and calm weather.
trade winds
cover most of earth between 25N and 25S. predominantly easterlies. commerce winds. very consistent. warming drying winds capable of holding an enormous amount of water. they don’t usually release the moisture unless forced to by being uplifted by a topographic barrier or a pressure disturbance
intertropical convergence zone
the area where the air from the northern hemisphere and southern hemisphere come together, doldrums. warm surface conditions, low pressure with high rainfall instability and rising air.
the westerlies
flow from west to east between 30 and 60 degrees.
