Global & Local Winds Chapter 15, section 3:

Earth’s Atmosphere Quiz When you’re finished with your quiz: Keep your quiz on your desk & cover it. Sit quietly at your desk. Read, work on your Heating Earth’s Atmosphere Lab packet (you should hand this in TODAY). Earth’s Atmosphere Quiz

Name 3 pieces of info. you can figure out from this weather map.

Air exerts Pressure Air Pressure: the force of air molecules pushing on an area. The greater the force, the higher the pressure. How is air pressure related to wind? Air molecules are always moving. Each time a molecule bounces off an object, it pushes, or exerts a force upon that object. NSF North Mississippi GK-8 Air molecules are always moving.

Air Pressure is Related to Altitude and Density Air pressure decreases as you move higher in the atmosphere (less air above you) Density of air decreases as you move higher in the atmosphere. Air pressure at any area on Earth depends on the weight of the air above that area. Air Pressure is Related to Altitude and Density NSF North Mississippi GK-8

Pressure & Air Motion Differences in pressure causes movement of air. High Air Pressure Low Air Pressure Low Air Pressure Movement of Air Air pressure can vary at any two locations at the same altitude. Wind: the movement of air caused by differences in air pressure. NSF North Mississippi GK-8

Uneven Heating Causes Wind to Move Large pressure difference - strong wind Small pressure difference- slight wind Wind Wind: Air in motion. NSF North Mississippi GK-8

Uneven Heating of Earth: N/S poles: spread out sunlight, less of sun’s energy, cool & dense air, high pressure Equator: direct/strong sunlight, high temp. (warm air rises), low pressure Where on Earth would you expect > heating? Less heating? NSF North Mississippi GK-8

High and Low Pressure Areas High pressure- air sinks Usually results in several days of clear sunny skies Air rises in low pressure areas and forms water droplets Usually results in rain and storms NSF North Mississippi GK-8

Global Winds: long distance patterns of air circulation caused by convection cells & Coriolis effect Local Winds: caused by geography of an area 2 Main Types of Wind:

Earth’s Rotation Affects Wind Direction Coriolis Effect: The influence of Earth’s rotation on winds & objects moving on Earth. NSF North Mississippi GK-8

Global Winds Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles. NSF North Mississippi GK-8

Calm Regions & Global Wind Belts Doldrums “dull/sluggish”: Low pressure zone @ equator Warm air rises & spreads toward poles Rising moist air -->clouds & heavy rain (2) Horse Latitudes: (windless) High pressure zones @ 30˚ N/S Warm air from equator cools & sinks Clear & dry weather Air usually stays calm in high/low pressure zones. Winds are light & often change direction. NSF North Mississippi GK-8

Global Winds: Trade Winds: Blow East from Horse latitudes to Equator Strong & steady. Die out as they reach equator Westerlies: (blow from the West) Blow from Horse latitudes to poles Bring storms across U.S. Dense air (in horse latitudes & other high pressure zones) moves toward low pressure zones (like the doldrums) NSF North Mississippi GK-8

Polar Easterlies: (blow from East) Blow from polar regions to mid-latitudes NSF North Mississippi GK-8

Science Starter: Calm Areas and Wind Belts Name Characteristics (1) A low-pressure zone near the equator. (2) High-pressure zone at about 30° N and 30° S of the equator. (3) Winds that blow from the East from the horse latitudes to the equator. (4) Winds that blow from the West from the horse latitudes to the poles. NSF North Mississippi GK-8

Jet Streams Flow Near the Top of the Troposphere Not all long distance winds travel @ Earth’s surface. Jet Streams: Flow in a wavy pattern, move from W -->E, can pull cold air down into US, pull warm air up into Canada, flow faster than surface winds Each hemisphere has 2 jet streams: (1) Polar jet stream (2) Subtropical jet stream Jet Stream: Long distance wind that flows in the upper Troposphere. NSF North Mississippi GK-8

Local winds-sea/land breezes Local winds: change daily, flow within a small area, typically flow in a regular pattern How would this local wind pattern change at night? NSF North Mississippi GK-8

NSF North Mississippi GK-8

Local Winds-mountain/valley breezes During Day Local Winds-mountain/valley breezes

Local Winds-mountain/valley breezes During Night Local Winds-mountain/valley breezes

Measuring Air Pressure Barometer: an instrument that measures air pressure. NSF North Mississippi GK-8

Science Starter: How does the uneven heating of Earth’s surface cause winds to flow? NSF North Mississippi GK-8

Two barometers are placed one kilometer apart Two barometers are placed one kilometer apart. One shows higher pressure than the other. What will happen to the air between them? Science Starter: NSF North Mississippi GK-8