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Wind

Wind. Chapter 6. Learning Targets. # 4-Define wind and describe the factors that affect wind. # 5-Explain the formation of a geostrophic wind. #7-Diagram winds associated with surface cyclones and anticyclones in both the northern and southern hemispheres. Wind.

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Wind

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  1. Wind Chapter 6

  2. Learning Targets • #4-Define wind and describe the factors that affect wind. • #5-Explain the formation of a geostrophic wind. • #7-Diagram winds associated with surface cyclones and anticyclones in both the northern and southern hemispheres.

  3. Wind • Wind-the result of horizontal differences in air pressure. • Ultimate source for most wind is solar radiation due to unequal heating of Earth’s surface (generates pressure differences) • Air flows from high to low pressure, but not directly. This would only happen if the Earth did not rotate and if there were no friction.

  4. Factors Affecting Wind • Isobars-lines that connect points that have the same sea level pressure. Similar to contour lines on a topographic map.

  5. Factors Affecting Wind • Pressure-Gradient Force • To get anything to accelerate requires an unbalance fore in one direction. • The force that generates winds results from horizontal pressure differences. • Temperature differences can generate a horizontal pressure gradient (creating winds)

  6. Factors Affecting Wind • Coriolis force • Earth rotates on its axis, causing the apparent rising and setting of the Sun. Due to this rotation, freely moving objects do not travel in perfectly straight paths. • The Coriolis force causes an apparent deflection in the path of a moving object. • Cannonball • Migrating birds • Aircraft • Wind

  7. Coriolis and Wind Influence of Coriolis on Wind Direction

  8. Factors Affecting Wind • Friction • A force that opposes motion. • Friction’s effect on air is negligible above a few kilometers.

  9. Geostrophic Winds

  10. Gradient Wind

  11. High Pressure System • When compared with low pressure systems, highs tend to cover a greater area, move more slowly and have a longer life. • When the high pressure system is located over land the weather will be typically dry and free of cloud.

  12. Low Pressure System • A low pressure system (cyclone) develops where relatively warm air ascends from the Earth's surface. • These are systems of counter-clockwise air movements • As the rising air cools, clouds will begin to form. The instability of the air will produce quite large vertical development of cumuliform clouds with associated rain showers. • An elongated extension of isobars away from a low pressure centre is known as a trough of low pressure. This trough usually contains one or more cold fronts

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