Atmospheric Circulation

Target #1- I can explain the direction in which air flows across Earth’s surface 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 Target #2- I can summarize the impact the Coriolis effect has on wind patterns in the atmosphere

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 Target #3- I can describe how air moving through convection cells make up Earth’s windbelts

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

Target #4- I can describe jet streams Narrow bands of high-speed winds that blow in the upper troposphere and lower stratosphere Types polar jet stream Subtropical jet stream

Target #5- I can describe how fluctuations in the jet stream can cause weather phenomena in the United States 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

Target #6- I can compare land and sea breezes 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

Target #7- I can state how wind is measured 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

Target #8- I can describe prevailing winds 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