Lecure 5 Outline - Pressure and Wind

# Lecure 5 Outline - Pressure and Wind - Chapter 5...

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Sheet1 Page 1 Chapter 5: Atmospheric Pressure and Wind CHAPTER OUTLINE I. The Impact of Pressure and Wind on the Landscape A. Humans not as sensitive to air pressure as they are to other three climate elements (heat, air movement, and humidity). B. Air pressure acts and responds to other three climate elements, but most intimately with wind. C. Spatial variations in pressure create air movements. II. The Nature of Atmospheric Pressure 3. Force drops with increasing altitude because actual number of gas molecules also drops. C. Factors Influencing Atmospheric Pressure 1. The pressure of a gas is proportional to its density and temperature. 2. This cause-and-effect relationship between these three variables is explained by the ideal gas law. other two. a) Relationship is very complex, so difficult to make exact predictions of how change in one changes the others. 4. Density and Pressure a) Density is the mass of matter in a unit of volume. Density of gas changes easily because gas expands as far as the environmental pressure will allow. b) The denser the gas, the greater the pressure it exerts. 5. Temperature and Pressure a) If air is heated the molecules become more agitated and they exert greater pressure. (1) Therefore an increase in temperature equals an increase in pressure and a decrease in temperature equals a decrease in pressure. A. Pressurehthe force a gas exerts on some specified area of the container walls. B. Atmospheric pressurehthe force exerted by gas molecules in the atmosphere. 1. Affects Earthhs surface as well as any other body on Earth. 2. Omnidirectional forcehexerted equally in all directions. 3. Variations in any onehpressure, density, and temperature of atmospherehaffect the

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Sheet1 Page 2 b) If a mass of air is not confined, it will expand when heated and may actually lead to a decrease in pressure as temperature increases. 6. Dynamic Influences on Air Pressure a) Surface air pressure may also be influenced by dynamic factors such as the movement of air. (1) i.e., upper atmosphere convergence can cause higher pressure at the surface. b) Generalizations regarding high and low pressure at the surface: dynamic high. (2) Very cold surface conditions are often associated with high pressure at the dynamic low. d (4) Very warm surface conditions are often associated with relatively low D. Mapping Pressure with Isobars bar, or 1000 dynes per square centimeter a) Average sea-level pressure is 1013.25 millibars. the pressure of the adjoining areas. (1) Strongly descending air is associated with high pressure at the surfaceha surfaceha thermal high. (3) String rising air is often associated with low pressure at the surfaceha pressure at the surfaceha thermal low. 1. Barometerhinstrument for measuring atmospheric pressure.
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## This note was uploaded on 04/21/2008 for the course GEOG GEOG-1114 taught by Professor Dung during the Spring '08 term at Oklahoma State.

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Lecure 5 Outline - Pressure and Wind - Chapter 5...

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