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• Air near Earth’s surface generally flows from the poles toward the equator. • Air moves from high-pressure regions to low-pressure regions • high pressure regions form where cold air sinks toward Earth’s surface • poles • Low-pressure regions form where warm air rises away from Earth’s surface • equator • The circulation of the atmosphere and the oceans is affected by the rotation of Earth on its axis •The air flows faster and over a farther distance at the equator •When air moves to the poles, it travels faster than the land beneath it rotates • Causes air to flow in a curved path • Coriolis Effect • The tendency of a moving object to follow a curved path rather than a straight path because of the rotation of the Earth • Examples: wind and water • Objects deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere • The faster an object travels, the greater the deflection • The air that flows from the poles toward the equator does not flow in a single strait line •Each hemisphere contains three looping patterns of flow called convection cells • Each cell correlates to an area on Earth’s surface known as a wind belt • Types of wind belts • Trade Winds • Names according to the direction from which they flow • Both trade wind belts meet along the equator in an area known as the doldrums • Air moves towards the equator from east to west (easterly) • Westerlies • air moves away from the equator from west to east (westerly) • Polar Easterlies • Strongest in Antarctica • Often stormy where it meets with the Westerlies • Air moves towards the equator from the pole in an easterly direction • Jet Streams • Narrow bands of highspeed winds that blow in the upper troposphere and lower stratosphere • Types • polar jet stream • Subtropical jet stream • Impacts weather patterns in North America • If the stream undulates further north it results in high temperatures • Ex: In June 2013, McGrath Alaska had a record high of 94 degrees. A few weeks earlier they had a record low of 15 degrees • If the stream undulate further south, it results in much lower temps and usually brings storms • Ex: the snow the northeast has gotten in February is because of the cold air from Canada interacting with the moisture of the Atlantic • Local Winds • Winds can also exist on a smaller, more local scale • Not a part of the wind belts • Land vs Sea Breezes • As the land heats up during the day, its temperature rises above that of the ocean • Results in hotter air over land • As the hot air rises, the cool ocean air moves inland creating a seabreeze • As the land cools off at night, the air descends creating a sea bound breeze known as a land breeze • There are two basic wind measurements direction & speed • Direction is determined by where the wind is coming from • Ex: a north wind is blowing from north to south • Instruments • Direction is most commonly determined using a wind vane • Speed is determined by an anemometer • If a wind blows more often from one direction, it is known as a prevailing wind • In the U.S., the westerlies consistently move weather from west to east across the continent