Wind Patterns on Earth
What causes air to move? Air pressure differences causes air to move. These differences in air pressure at the same altitude is caused by uneven heating of the Earth s surface. With this, wind is formed. Wind is the horizontal movement of air. It is parallel to the ground. Amount of sunlight and heat from the sun differs on our planet. The equator regions have the most constant amount of sunlight. The poles have the least amount of sunlight.
How does wind form? Sun warms the ground unevenly and high and low pressures are formed. Low pressure is formed because the sun warmed the ground strongly and warm air rises up. High pressure is formed when the ground is heated less strongly. Cool, dense air sinks. Cool air sinking Warm air rising High pressure moves towards lower pressure in the form of wind.
Coriolis Effect Global winds begin at the poles (high pressure to low pressure) towards the equator. If Earth did not rotate, the winds would go straight towards the equator. Coriolis effect- influence of Earth s rotation. This causes winds to curve from the poles. Noticeable with long distance winds.
Calm Regions Calm Regions Doldrumsabout 5⁰ N and S of equator Low pressure zone Warm air rises to top of troposphere Air spreads out toward the poles Weather: moist, produces clouds (storms during summer) Horse Latitudesabout 30⁰ N and S of equator High pressure zones Warm air from equator sinks in these regions Weather: clear and dry
Global Wind Belts Trade Winds- between equator and 30⁰ N and S Blow from east from horse latitudes to equator Strong, steady winds that calm down near the equator Calm Regions & Global Winds
Global Wind Belts Trade Winds- between equator and 30⁰ N and S Blow from east from horse latitudes to equator Strong, steady winds that calm down near the equator Westerlies- blow from west Move from horse latitudes towards the poles Bring storms to most of US Calm Regions & Global Winds
Global Wind Belts Trade Winds- between equator and 30⁰ N and S Blow from east from horse latitudes to equator Strong, steady winds that calm down near the equator Westerlies- blow from west Move from horse latitudes towards the poles Bring storms to most of US Easterlies- blow from east Move from the poles to horse latitudes When easterlies and westerlies meet, stormy weather often occurs Calm Regions & Global Winds
Air Currents: Sailing Around the World Parts 1 and 2 While you watch this video, pay attention to the regions and wind belts she has sailed through and what happened while she was there. DISCUSSION: What were her experiences in the doldrums and horse latitudes? What happened in the polar easterlies? How did she use the trade winds to help her? Video: Discovery Education
How does wind affect travel? How does wind affect sailors? -wind belts can help them move along the ocean -calm regions give them safety How does the jet stream affect those flying in airplanes? -flights can be longer or shorter, depending on the jet stream
Jet streams o Formed by uneven heating of Earth s surface o Flow from west to east o Flow in upper troposphere (or in the tropopause- boundary between stratosphere & troposphere) o Flow about 10-15 km (6-9 miles) above Earth s surface o Speeds are greater than 200 km/hr or 124 miles/hr o In each hemisphere, there are usually two jet streams- polar and subtropical and they loop north and south o Scientists need to know where the jet streams are to make accurate weather predictions (they don t stay in the same place) o Affect the weather- they can pull cool air from the poles and warm air from mid-latitudes and cause storms
Local Winds Local winds blow in small areas, are predictable, and can change daily in a pattern. The sun warms the land or water, and higher pressure moves toward lower pressure to create wind or a breeze. Sea breeze- During the day, land warms up more than the water during the day. Low pressure forms over the land, and high pressure over the water. High pressure moves from the water to the land in the form of a cool sea breeze. Land breeze- At night, land cools faster than water. Low pressure forms over the water and high pressure over the land. High pressure moves from the land to the water in the form of a land breeze.
Local Winds Local winds blow in small areas, are predictable, and can change daily in a pattern. The sun warms the land or water, and higher pressure moves toward lower pressure to create wind or a breeze. Mountain breezes go down to the valley at night. Valley breezes go up during the day.
Monsoons Winds the change direction with the seasons Caused by different heating and cooling rates of land and sea Flow longer distances than local winds and affect much larger areas Winter monsoons- land is much cooler than the sea. High pressure over the land blows dry air out to the sea. Summer monsoons-land is warmer than the sea. High pressure over the sea blows moist air to the land. Produces rain and storms.