Atmosphere and Climate

Objective and Key Concepts How does uneven heating of Earth's surface result in air movement? How are air currents on Earth affected by Earth's spin? What are the main wind belts on Earth?

THE SUN! Global Winds Wind patterns can be global or local. There are great wind belts that circle Earth. The energy that causes this large movement of air comes from.... ? THE SUN!

Unequal Heating of Earth's Surface Not all areas on Earth receive the same amount of energy from the sun because it depends on the sun's angle.

light Areas near the equator are known as the tropics. Sunlight strikes Earth's surface there at a 90 degree angle all year-round. They receive more sunlight, which causes the land, water, and air at the equator to be warm. Near the poles, sunlight strikes Earth at a low angle. It is spread over more surface area and it is colder.

Air Density Warm air rises and cold air sinks. Warm air is less dense than cold air, just like warm water is less dense than cold water.

Wind Knowing that warm air is less dense than cold air, which do you think puts more pressure on Earth? Air pressure is usually low over the tropics because it's warm there... Air pressure is high over colder areas such as the poles. This difference in pressure creates wind. WIND- movement of air from areas of high pressure to areas of low pressure.

Coriolis Effect Because the Earth spins, wind does not move in perfectly straight lines!

Earth’s Rotation Affects Wind Direction Because Earth rotates, scientists are able to tell the directions wind will flow. The Coriolis Effect is the influence of Earth’s rotation on wind patterns. Global winds curve as the Earth turns beneath them. Winds in the northern hemisphere curve right and winds in the southern hemisphere curve left.

Prevailing Wind Types Trade winds Steady winds that flow east to west polar easterlies Cold winds that blow from east to west near the poles prevailing westerlies Steady winds that flow west to east

Jet Streams Near the top of the troposphere is a narrow band of high winds called the jet stream. Jet streams flow around Earth from west to east and influence weather. They move cold air toward the equator, and warm air toward the poles as fast as 300 km/hour, and have a strong influence on our weather.

Sea and Land Breezes Sea breeze- wind that blows from the sea to the land due to local temperature and pressure differences. Because land warms faster than water, the differences in pressure over the warm land and the cooler water results in a cool wind that blows from the sea onto land.

Land Breezes Land breeze- wind that blows from the land to the sea due to local temperature differences. At night, the land cools more quickly than the water. An area of low pressure forms over the warm water. Cool air over land moves toward low pressure over the water.