Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Global Circulation and Winds (Stewart Cap. 4) Outline 1. 2. 3. 4. Atmospheric pressure Winds Global circulation patterns Ocean circulation patterns 1. Atmospheric Pressure Atmospheric Pressure Density of the atmosphere decreases with altitude Earth Atmospheric Pressure: Force exerted by the atmospheric per unit area Measuring Atmospheric Pressure At sea level: • 101,320 Pascals (101 kPa) • 1013.2 millibars • 76 cm Hg (30 in Hg) Atmospheric Pressure Atmospheric Pressure Isobar map Differences in atmospheric pressure cause air to move … 820 820 830 830 840 840 850 860 850 870 880 860 weak pressure gradient 890 strong pressure gradient Winds are named for the direction they originate from Local winds Land – sea breezes Daytime: sea breeze Night time: land breeze 3. Global circulation patterns http://www.bergonia.org/History/Hist-maps/columbusmap.gif Cold High Pressure 90oN Solar radiation creates variation in heating / atmospheric pressure 60oN 30oN SUN 0o 30oS 60oS 90oN Earth Warm Low Pressure 90oN 60oN 30oN L 0o 30oS 60oS 90oN Warm air rises at equator and flows towards the poles 90oN Cold air sinks at 30o N and S latitude creating high pressure 60oN 30oN 0o 30oS 60oS 90oN H L H Low pressure at 0o , 60o latitude high pressure at 30o , 90o latitude Doldrums: strong vertical uplift, little horizontal wind Hadley cells: well developed low pressure cells in the tropics H 90oN 60oN L 30oN H 0o L 30oS 60oS 90oN H H L Pressure gradients influence development of global wind patterns Easterly winds 90oN 60oN 30oN 0o 30oS 60oS 90oN H L Westerly winds Easterly winds (trade winds) H Westerly winds Easterly winds 4. Ocean circulation patterns Ocean currents • large continuously moving loops (gyres) • produced by winds, Coriolis effect and land masses Ocean circulation exposes east coasts of continents to warm currents, west coasts to cold currents Ocean upwelling Summary • Variation in heating causes variation in atmospheric pressure conditions • Variation in atmospheric pressure causes air to move (H L) • Local-scale wind patterns occur with variation in heating, pressure Summary (continued) • Direction of air movement affected by pressure gradient, Coriolis effect, and friction • In No. Hemisphere L pressure systems (cyclones) circulate counterclockwise in, H pressures systems (anticyclones) circulate clockwise out Summary (continued) • Global variation in heating produces L pressure at 0o and 60o, H pressure at 30o and 90o • H and L pressure systems drive global wind patterns (easterlies between 30o N and 30o S; westerlies between 30-60o N and S) Summary (continued) • Ocean currents influenced by winds, Coriolis effect and land masses • Ocean circulation exposes east coasts of continents to warm currents, west coasts to cold currents