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Review geographical variation in temperature. Station A. Station B. Elevation 1608 ft (490 m) 13,461 ft (4103 m). Concepci ó n is station: A B. Station A. Station B. Station Verkhoyansk, Russia Trondheim, Norway Elevation 450 ft (137 m) 377 ft (115 m)
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Station A Station B Elevation1608 ft (490 m) 13,461 ft (4103 m) Concepción is station: A B
Station A Station B Station Verkhoyansk, Russia Trondheim, Norway Elevation450 ft (137 m)377 ft (115 m) Latitude 67o 35’ N 63o 25’N Longitude 135o 23’ E 10o 27’ E Verkhovansk is station: A B
Atmospheric Pressure and Winds Geog 096: Weather, Climate & Landscapes
Arbogast, Fig. 6.4 Atmospheric Pressure with altitude Atmospheric Pressure: Force exerted by the atmospheric per unit area
Measuring atmospheric pressure • At sea level: • 76 cm Hg (30 in Hg) • 1013.2 millibars • 101,320 Pascals (101 kPa) Arbogast, Fig 6.3
Factors influencing air pressure • Air density (gravity) • Air temperature • Lifting of air (local heating & convection, fronts, topography) Arbogast, Fig. 6.2
820 830 840 850 860 820 830 840 850 860 870 880 890 differences in atmospheric pressure cause air to move … weak pressure gradient strong pressure gradient
Factors affecting wind movement Arbogast, Fig. 6.10 1. Pressure gradient force Air moves perpendicular to isobars
Factors affecting wind movement 2. Coriolis effect Air is deflected; moves parallel to isobars deflection: right in no. hemisphere left in so. hemisphere Arbogast, Fig. 6.11
Factors affecting wind movement Arbogast, Fig. 6.13 3. Friction Drag on air as it moves across the earth’s surface (reduced with altitude)
Combined effects of pressure gradient, Coriolis effect and friction Image: Christopherson 2001, Elemental Geosystems
Geostrophic Winds Operate in the upper atmosphere Not affected by friction Image: Christopherson 2001, Elemental Geosystems
The Jet Stream ( a geostrophic wind) Image: Christopherson 2001, Elemental Geosystems
Rossby Waves Undulations in polar air flow created by temperatures differences between polar and tropical air masses Arbogast, Fig. 6.21
Remote Sensing of Weather Systems The Weather Channel (www.weather.com) “Seeing the Big Picture” http://link.brightcove.com/services/link/bcpid823503751/bclid877032959/bctid877032779 Image source: www.kidsgeo.com
Image pair from October 21, 2007 shows how quickly the fires grew in just a few hours. Plumes of smoke being blown offshore indicate the intensity of the Santa Ana winds
Witch Fire, S. California: 196,420 acres Destroyed : 1,609 homes, Charred 695 sq miles, Insurance costs of $1 billion
Which of the following statements is NOT true • Air tends to move from High to Low pressure • Low pressure systems circulate counterclockwise inward in the northern hemisphere • Low pressure systems are called “anticyclones”