Convection in Our Atmosphere Credit to: Burnett Middle School 8th Grade Science

Previous Knowledge What do you already know about convection?

Vocabulary Convection and Winds Vocabulary - give as notes.

CONVECTION is the transfer of heat by the movement of warmed matter (air or liquid)

The Sun provides the energy that drives convection within the atmosphere and oceans, producing winds and ocean currents.

Hot Air is Less Dense!

What is most dense SINKS! Atmospheric Density What is most dense SINKS!

CONVECTION

CONVECTION

CONVECTION CURRENTS move the air in our atmosphere! We have global winds that blow because of these large convection currents

CONVECTION Wind over the shore changes direction because of EARTH’S UNEVEN WARMING & COOLING! We can these local winds

Click the Video button to watch a movie about convection currents. - Winds Convection Currents Click the Video button to watch a movie about convection currents.

CONVECTION DEMOS! Tea bag http://www.youtube.com/watch?v=7xWWowXtuvA http://www.youtube.com/watch?v=YsCXw2bQU50&feature=youtu.be Colored Water http://www.youtube.com/watch?v=7xWWowXtuvA

Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Why are the heating elements placed beneath hot water tanks in people’s homes? Hot water rises. So when the element heats the water, and the hot water rises, the water tank is filled with hot water.

Wind

Wind is the movement of air from an area of high pressure to an area of low pressure. This is caused by the unequal heating of the Earth’s surface. As air is heated, it becomes less dense and rises. The air pressure is also lower . Cooler, more dense air, has a higher pressure, and moves under the warmer air. This causes a convection current, creating wind The greater the pressure difference, the faster the air moves, and the stronger the wind blows.

How is Wind Measured? Wind direction is measured with a wind vane, which points in the direction the wind is coming from. This is how the wind is named. A western wind is blowing from the west. This means a northern wind actually blows toward the south. Wind speed is measured with an instrument called an anemometer.

Why We have Global Winds Since the air near the equator is less dense, it rises forming areas of low pressure. The cold air near the poles sinks because it is more dense, forming areas of high pressure. The air moves in large circular patterns called convection currents. The change in density is due to the unequal heating of Earth’s surface

L H 90 30 60 Cold Moist Air Rises Cool Dry Air Sinks 60 90 Warm Moist Air Rises Very Cold Air Sinks Cold Moist Air Rises Cool Dry Air Sinks Cool Dry Air Sinks Cold Moist Air Rises Very Cold Air Sinks

Wind Moves from HIGH to LOW 30 60 90 Wind Moves from HIGH to LOW

Objects are deflected to the RIGHT in the Northern Hemisphere 30 60 90 Objects are deflected to the RIGHT in the Northern Hemisphere But why?

The Coriolis Effect As Earth rotates, the Coriolis effect turns winds in the Northern Hemisphere toward the right.

Northern Global Wind Patterns Polar Easterlies 90 – 60 latitude from the east Prevailing Westerlies 60 – 30 latitude from the west Trade winds 30 – 0 latitude from the East

Global Winds Polar Easterlies are the wind belts that extend from the poles to 60° latitude in both hemispheres. They form as cold, sinking air moves away from the poles. They can carry cold arctic air over the U.S. which can produce snow and freezing weather. Westerlies are the wind belts found between 30° and 60° latitude in both hemispheres. They blow toward the poles from west to east. These winds can carry moist air of the U.S. producing rain and snow. Trade Winds are the winds that blow from 30° latitude almost to the equator in both hemispheres. They curve to the West as they blow toward the equator.

Global Winds, continued The Doldrums The trade winds of the Northern and Southern Hemispheres meet in an area around the equator called the doldrums. there is very little wind because the warm, rising air creates an area of low pressure. The name doldrums means “dull” or “sluggish.”

Global Winds Sailing the global winds activity

Jet Streams Narrow belts of high-speed winds that blow in the upper troposphere and lower stratosphere. Knowing the path of a jet stream is important not only to pilots but also to meteorologists. Because jet streams affect the movement of storms, meteorologists can track a storm if they know the location of a jet stream.

Jet Streams Jet Streams form at latitudes where wind systems come together High speed westerly winds form high above the surface

Local Winds Sea Breeze Land Breeze Local winds move over a short distance Caused by the heating of a small area of Earth’s surface Sea Breeze The sun warms the land faster than the water, so the air above the land becomes warmer. The cooler air over the water moves inland Land Breeze At night, the land cools faster than the water, so the air above the land becomes cooler. The cooler air over the land moves out to the water.

Local Winds Local winds generally move short distances and can blow from any direction. Mountain and valley breezes are examples of local winds caused by an area’s geography. Sea and land breezes are affected by temperature.

Air Currents United streaming video – 11 minutes

Ocean Currents

Major Ocean Currents An Ocean Current is a large volume of water flowing in a certain direction. Wind-driven currents are called surface currents. Surface currents carry warm or cold water horizontally across the ocean’s surface

Major Ocean Currents Surface currents extend to about 400 m below the surface, and they move as fast as 100 km/day. Earth’s major wind belts, called prevailing winds, influence the formation of ocean currents and the direction they move.

Coriolis Effect The Coriolis Effect is the movement of wind and water to the right or left that is caused by Earth’s rotation. It causes fluids such as air and water to curve to the right in the Northern hemisphere, in a clockwise direction. The Coriolis effect also cases fluids to curve to the left in the southern hemisphere, in a counterclockwise direction.

Coriolis Effect The shapes of continents and other land masses affect the flow and speed of currents. Currents form small or large loops and move at different speeds, depending on the land masses they contact.

Impacts of Weather and Climate Warm-water currents and cold-water currents affect weather and climate in different ways Regions near warm-water currents are often warmer and wetter than regions near cold-water currents

Impacts on Weather and Climate The Gulf Stream is a warm-water current that affects coastal areas of the southwestern United States by transferring lots of thermal energy and moisture to the surrounding air. The cold California Current affects coastal areas of the southwestern United States.

Video Ocean Currents and weather You can show whole video (27 minutes) or just the section on ocean currents (5ish minutes) Planet Water – Water cycle, oceans, and weather – 20 minutes

Puff Mobile

Answer the following questions using complete sentences. Explain in detail how the wind affected the movement of your car. Incorporate factors such as intensity, duration, and direction in your explanation. Using the same factors, explain how wind affects air masses which in turn impact our weather.