Air Currents in the Atmosphere

Why is it warmer at the equator?

Draw the circles that the flashlight makes on the globe on the circles in your notes.

More direct rays mean more heat.

What is Wind? Wind is the movement of air from an area of higher pressure to an area of lower pressure. Warmer air expands, becoming less dense than colder air. This causes air pressure to be lower where air is heated H → L

The Coriolis Effect

The Coriolis Effect - The tendency for any moving body on or above the earth's surface, such as an air or water current, to drift sideways from its course because of the earth's rotation. This affects Earth’s winds and water movement. Air moves to the right in the Northern Hemisphere. In the Southern Hemisphere, they move to the left.

Warm Moist Air Rises

Cool Dry Air Sinks

Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises

Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks

Warm Moist Air Rises Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks H L H H H L L

H L H H H L L Wind Moves from HIGH to LOW

Objects are deflected to the RIGHT in the Northern Hemisphere

Global Winds Global Winds - Wind gets its name from the direction it is blowing FROM!

Winds in the Upper Troposphere The jet stream is a current of fast moving air found in the upper levels of the troposphere.

The polar jet stream forms at the boundary of cold, dry polar air to the north and warmer, more moist tropical air to the south.

The jet stream moves faster in the winter because the difference between cold air and warm air is greater. The jet stream helps move storms across the country.

Land Breeze vs. Sea Breeze

Land Breeze – movement of air from land to sea at night; created when cooler, denser air from the land forces up warmer air over the sea.

Sea Breeze – movement of air from sea to land during the day when cooler air from above the water moves over the land, forcing the heated, less dense air above the land to rise.

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GLOBAL FORCES The following global forces can affect the formation of surface currents.

Equator Earth’s Rotation Continental Deflection Global Forces

Continental Deflection Since the Earth’s surface is not fully covered by water, currents cannot move freely around the world. So when surface currents meet continents, they deflect, or change direction Predict what will happen with each labeled area.

Equator Earth’s Rotation Continental Deflection Coriolis Effect Global Forces

Coriolis Effect The Earth’s rotation causes surface currents to move in curved paths rather than in a straight line. North Pole Earth’s Rotation

Equator Earth’s Rotation Continental Deflection Coriolis Effect Global Forces Global Winds

Global winds are affected by their latitude and the Coriolis Effect. In the tropics winds blow from the east to the west. In more temperate areas, the winds blow from the west to the east. Near the poles the winds blow from the east to the west. Tradewinds Westerlies Polar Easterlies

Equator Earth’s Rotation Continental Deflection Coriolis Effect Global Forces Transparency Global Winds Deep Ocean Currents

Deep cold currents move water toward the equator. Cold water rises to replace warm water leaving. Warm water travels near the surface toward polar regions. Warm water replaces cold water.

Equator Earth’s Rotation Continental Deflection Since the Earth’s surface is not fully covered by water, currents cannot move freely around the world. So when surface currents meet continents, they deflect, or change direction. Coriolis Effect The Earth’s rotation causes surface currents to move in curved paths rather than in a straight line. Global Forces Global Winds Global winds are affected by their latitude and the Coriolis Effect. In the tropics winds blow from the east to the west. In more temperate areas, the winds blow from the west to the east. Near the poles the winds blow from the east to the west. Deep Ocean Currents Deep cold currents move water toward the equator. Cold water rises to replace warm water leaving. Warm water travels near the surface toward polar regions. Warm water replaces cold water.