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Weather Theory

Wind Patterns

Weather Theory

In the Northern Hemisphere, the flow of air from areas of high to low pressure is deflected to the right and produces a clockwise circulation around an area of high pressure. This is known as anticyclonic circulation. The opposite is true of low-pressure areas; the air flows toward a low and is deflected to create […]

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Altitude and the Human Body

Weather Theory

As discussed earlier, nitrogen and other trace gases make up 79 percent of the atmosphere, while the remaining 21 percent is life sustaining, atmospheric oxygen. At sea level, atmospheric pressure is great enough to support normal growth, activity, and life. By 18,000 feet, the partial pressure of oxygen is reduced and adversely affects the normal activities […]

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Altitude and Flight

Weather Theory

FlightAltitude affects every aspect of flight from aircraft performance to human performance. At higher altitudes, with a decreased atmospheric pressure, takeoff and landing distances are increased, as are climb rates. When an aircraft takes off, lift must be developed by the flow of air around the wings. If the air is thin, more speed is […]

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Measurement of Atmosphere Pressure

Weather Theory

Atmospheric pressure is typically measured in inches of mercury (“Hg) by a mercurial barometer. [Figure 11-6] The barometer measures the height of a column of mercury inside a glass tube. A section of the mercury is exposed to the pressure of the atmosphere, which exerts a force on the mercury. An increase in pressure forces […]

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Coriolis Force

Weather Theory

In general atmospheric circulation theory, areas of low pressure exist over the equatorial regions and areas of high pressure exist over the polar regions due to a difference in temperature. The resulting low pressure allows the high-pressure air at the poles to flow along the planet’s surface toward the equator. While this pattern of air circulation […]

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Atmosphere: Atmospheric Pressure

Weather Theory

The unequal heating of the Earth’s surface not only modifies air density and creates circulation patterns; it also causes changes in air pressure or the force exerted by the weight of air molecules. Although air molecules are invisible, they still have weight and take up space. Imagine a sealed column of air that has a […]

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Atmosphere: Atmospheric Circulation

Weather Theory

As noted earlier, the atmosphere is in constant motion. Certain factors combine to set the atmosphere in motion, but a major factor is the uneven heating of the Earth’s surface. This heating upsets the equilibrium of the atmosphere, creating changes in air movement and atmospheric pressure. The movement of air around the surface of the […]

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Atmosphere: Composition of the Atmosphere

Weather Theory

In any given volume of air, nitrogen accounts for 78 percent of the gases that comprise the atmosphere, while oxygen makes up 21 percent. Argon, carbon dioxide, and traces of other gases make up the remaining one percent. This cubic foot also contains some water vapor, varying from zero to about five percent by volume. […]

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