Air Pressure Chapter 2, Section 1

Air Pressure The force of air molecules pushing on an area. Depends on the weight of the air above it The greater the force, the greater the pressure. Molecules push in all directions

Air Pressure and Altitude Air pressure decreases as altitude increases With less air above you (i.e. at the top of a mountain), the pressure is lower.

Air Pressure and Density Remember, density is the mass of an object divided by its volume. Since the pressure is greater nearer to sea level, the air’s density is also greater. More pressure = tightly packed air molecules

Air Pressure and Air Motion Air moves from areas of higher air pressure to lower air pressure

Air Pressure and Barometers A barometer is any instrument that measures air pressure.

Air Pressure and Weather If a high pressure system is on its way, often you can expect cooler temperatures and clear skies. H If a low pressure system is coming, then look for warmer weather, storms and rain. L

Wind Chapter 2, Section 2

Brain Break Seat mix up. 2 minutes to find a new seat for the day… make smart choices!

Wind and Weather Weather: the condition of Earth’s atmosphere at a certain time or place Wind: the air that moves parallel to the ground Wind moves from high pressure to low pressure

Wind Movement Sun heats ground, ground heats air. Warm air rises, low pressure forms. Sun heats new ground less strongly. Cold air is more dense, sinks, and a high pressure forms. Air moves from the high pressure to the low pressure.

Wind Movement Some winds die quickly. Some winds travel thousands of kilometers in patterns Global winds They last for weeks. Caused by uneven heating between the poles (cooler) and the equator (warmer).

Earth’s Rotation and Wind The Coriolis effect causes global winds to curve as they move from the poles to the equator. They move in three curved paths, called the global wind belts.

Calm Regions The Doldrums The Horse Latitudes Low pressure zone near the equator Warm air rises and spreads out to poles, causing clouds and heavy rain The Horse Latitudes high pressure zones located 30 degrees north and south of the equator Warm air traveling from equator cools and sinks

Wind Belts 3. The Trade Winds 4. The Westerlies 5. The Easterlies Blow from the east toward the equator Die out as they come near equator 4. The Westerlies Blow from the west toward the poles Bring storms across the US 5. The Easterlies Blow from the east, moving from the poles to the mid-latitudes Stormy weather occurs when they meet the westerlies

Eye Witness Part 1 Eye Witness Part 2

Chapter 2, Notes 3 Clouds

What is a cloud? A cloud is a large group of water droplets that join together during the process of condensation. You can write: cloud = group of droplets joined by condensation

Types of Clouds There are three main categories that clouds are grouped into: High clouds = cirrus Middle clouds = alto Low clouds = stratus

Cirrus clouds Cirrus means “curl of hair”. thin and wispy. high clouds mostly made of ice crystals. found above 18,000 feet. indicate fair/pleasant weather.

Altostratus clouds A type of alto cloud. Gray or blue colored cloud. Made of ice crystals. Usually form before a rain or snow storm.

Altocumulus clouds A type of alto cloud. Gray puffy masses. Can indicate thunderstorms.

Stratus clouds Gray clouds that usually cover the entire sky. Looks like fog. Sometimes a light precipitation comes from them.

Nimbostratus clouds Dark gray, wet looking clouds Light to moderate continuous rain fall or snow.

Note Break! 5 minute vocab review

Cumulus clouds White, puffy clouds that look like cotton. “fair-weather clouds” Flat bottoms with rounded tops.

Cumulonimbus clouds Thunderstorm clouds High winds flatten the clouds Heavy rain, snow, hail, lightning, and tornadoes.

Fog Cloud on the ground.

Contrails Trails left behind jet aircrafts. Hot air from exhaust mixes with cold atmosphere.

Green Clouds Severe weather likely to produce hail and tornadoes. The green color is not understood yet.

Brain Break! 3 minute break.

Chapter 2, Notes 4 Precipitation

How it forms… By several water droplets combining About 1 million By growth of ice crystals

How is it measured? Rain: we use a rain gauge to collect the rain and it has measurements on the side. Snow: ruler or a special type of gauge

Types of Precipitation Rain/drizzle Most common type Drizzle: light rain from stratus clouds

Types of Precipitation Freezing Rain Freezes when it lands on Earth’s surface

Types of Precipitation Sleet Freezes in the air and turns into small pellets of ice.

Types of Precipitation Snow Ice crystals grow and combine in the clouds They have 6 sides

Types of Precipitation Hail Lumps of ice fall from cumulonimbus clouds

Acid Rain Rain that mixes with sulfur and nitrogen in the air to form acid. Dangerous to living organisms.