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13 Cards in this Set
- Front
- Back
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Explain why atmospheric pressure alwaysdecreases with increasing altitude. |
Atmosphericpressure always decreases with increasing altitude, because there is lessatmosphere above to provide weight, which is responsible for the pressure atany point. |
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What is considered standard sea-levelatmospheric pressure in millibars? In inches of mercury? In hectopascals |
Standardsea-level pressure in millibars is 1013.25 mb. In inches of mercury it is29.92in. In hectopascals (same as millibars) it is 1013.25 hPa |
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How does sea-level pressure differ fromstation pressure? Can the two ever be the same? Explain. |
Stationpressure is the actual barometric pressure measured at a weather station, withno correction for altitude applied. Sea level pressure is the adjusted pressureafter applying a correction (about 10 mb per 100 m) for the station's altitudeabove sea level. The two would be the same for a station located right at sealevel. |
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Why will Denver, Colorado always have a lowerstation pressure than Chicago, Illinois. |
Denver willalways have a lower station pressure than Chicago because it is located at aconsiderably higher elevation, and the difference in pressure in the twostations due to elevation will overshadow any horizontal pressure differences |
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What are isobars. |
Isobars arecontour lines of pressure on a weather map; that is, lines of constantpressure. The contour interval is typically 4 mb. |
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What do Newton's first and second laws of motiontell us? |
Newton's First Law of Motion (Law of Inertia)tells us that a body at rest will remain at rest, and a body in motion willremain in motion (with the same speed and direction), unless acted upon by aforce. Newton's Second Law of Motion, which can be expressed F=m x a, statesthat a force applied to a body will be equal to the mass of the body times theacceleration (change in speed or direction) achieved by the body. Theimplication is that a body will always accelerate in the direction of the total(or net) force acting on it |
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What does a steep (or strong) pressure gradientmean? |
A steep (orstrong) pressure gradient means that for a given distance, the pressuredifference over that distance is large, OR that for a given pressure change,the distance over which that change occurs is small (or BOTH). dy> |
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What is the name of the force that initiallysets the air in motion, and hence causes the wind to blow? |
Closely spacedisobars or contours indicates a strong pressure gradient, thus a strongpressure gradient force to start and maintain air motion. Widely spaced isobarsindicate a weak pressure gradient force, and weak air movement. |
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What does the Coriolis force do to moving airlow? |
(a) inthe Northern Hemisphere? The Coriolis force deflects moving air to theright of its original path. (b) inthe Southern Hemisphere? The Coriolis force deflects moving air to theleft. |
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Explain how each of the following influences theCoriolis force: |
(a) windspeed -- The Coriolis force increases as the wind speed increases. (b) latitude-- The Coriolis force increases as the latitude increases (i.e., as you moveaway from the Equator). |
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What is geostrophic wind? On an upper levelchart, how does it blow. |
Geostrophicwind is the name given to wind flowing parallel to straight isobars or contourlines as a result of an equal and opposite force balance between the pressuregradient force and the Coriolis force. On an upper level chart, it will blow ina direction parallel to the isobars, with lower pressure on the left (in theNorthern Hemisphere). |
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On asurface map, why do surface winds tend to cross the isobars and flow fromhigher pressure toward lower pressure? |
Surface windstend to cross the isobars at an angle toward low pressure because at theEarth's surface, friction tends to slow the wind speed, which in turn decreasesthe Coriolis force such that it no longer equals the pressure gradient force.The stronger pressure gradient force (always directed toward low pressure)causes the deflection of the flow at an angle across the isobars. |
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Since there is always an upward-directedpressure gradient force, why doesn't air rush off into space? |
Our atmospheredoesn't rush off into space because the upward-directed pressure gradient forceis balanced (on the average) by the downward force of gravity, in what is called the hydro-static balance. |
