Weather Patterns Mr. Latzos

Starter Match the word with the definition Densityatmospherealtitude The distance above sea level The amount of mass in a given volume of substance The whole layer of air that surrounds Earth

Key Concepts

Key Terms

Explore Air Pressure What does air do to the balloon? What happened? What can your observations tell you about the air in the bottle?

Weather Patterns The atmosphere is a layer of air that surrounds Earth. The atmosphere supports and protects life. Air molecules bounce of each other and anything they touch using force. Air pressure is the force of air molecules pushing on an area. The greater the force, the higher the air pressure.

Altitude and Density Altitude is the distance above sea level. As you move higher into the atmosphere (above sea level), air pressure decreases. Density is the amount of mass in a given volume of a substance. At higher altitudes density decreases also because there are not as many air molecules pushed together.

Pressure and Air Motion Sometimes air pressure can be different at places that have the same altitude. If air pressure were the same in all locations, air would not move. Air in areas of high pressure moves to areas of lower pressure. –For example when you open a bottle of soda you hear a hissing sound. That is because the air pressure inside the bottle is lower than the air pressure outside the bottle. When the bottle is open, the air outside the bottle moves to the inside of the bottle.

Barometers A barometer is any instrument that measures air pressure.

The Atmosphere has Wind Patterns

Starter True or False? Differences in pressure cause the horizontal movement of air. Air pressure and air density increase with altitude. The sun supplies most of the Earth’s energy.

Key Concepts

Key Terms

The Atmosphere has Wind Patterns Weather is the condition of the Earth’s atmosphere at a particular time and place. Wind is air that moves horizontally, or parallel to the ground.Wind –Uneven heating of the Earth’s surface causes pressure differences, setting air in motion. –Wind moves from areas of higher pressure to areas of lower pressure.

Wind Air circulation (wind) is caused by uneven heating of the Earth’s surface. 1.Sunlight heats an area of the ground that warms the air. The warm air rises, creating an area of low pressure. 2.Sunlight heats an area of the ground less strongly. The cooler, dense air sinks slowly creating an area of high pressure. 3.Air moves wind across the surface of the Earth, from higher pressure to lower pressure.

Global Winds Global winds travel thousands of kilometers in steady patterns. Global winds last for weeks. Global winds are caused by uneven heating between the equator and north and south poles. Global winds travel in routes called global wind belts.

Coriolis Effect Global winds curve because of the Earth’s Rotation. The Coriolis Effect is the influence of the Earth’s rotation on wind. If the Coriolis Effect did not exist, winds would blow directly from the poles to the equator. In the Northern Hemisphere, winds curve to the right, and in the Southern Hemisphere winds curve to the left.

How does Earth’s Rotation Affect Wind? How did the rotation affect the lines that were drawn? How does this demonstrate the Coriolis effect? How might changing the speed at which the balloon rotates affect the results?

Global Wind Belts and Calm Regions The Earth’s rotation and it’s uneven heating cause patterns of wind belts to be separated by calm regions. Calm regions are zones of either high pressure or low pressure where winds stay calm. Each wind belt and the calm regions that border it form a giant loop of moving air called circulation cells.

Calm Regions There are two types of calm regions: 1.The Doldrums are a low-pressure zone near the equator. Air rises in these regions producing clouds and heavy rain. Heavy evaporation in these areas fuel tropical storms. 2.The horse latitudes are high-pressure zones located 30 degrees above and below the equator. Warm air traveling away from the equator cools and sinks in these regions.

Wind Belts Three global wind belts are located in each hemisphere: 1.The trade winds blow from the east, moving from the horse latitudes toward the equator. 2.The westerlies blow from the west. They bring storms across much of the US. 3.The easterlies blow from the east, moving from the polar regions. Stormy weather often occurs when the cold air of the easterlies meets the warmer air of the westerlies.

Jet Streams A jet stream does not travel on the Earth’s surface. Instead, it flows in the upper troposphere from west to east. Jet streams do not flow in a straight line, they loop north and south. There are two jet streams in each hemisphere.

Monsoons Monsoons are winds that change direction with the seasons. In the winter, the land is cool creating high pressure and winds blow out toward the sea. In the summer, the land is warmer than the sea. Winds blow from the sea onto land, often bringing heavy rains.