Dec.19,2018 You need: Clean paper / pencil Water cycle filled in Warm Up: Start with evaporation and list the steps of the water cycle. I CAN: determine how heat, water, and air interact to create air masses and fronts. Dec.19,2018

Water in the Atmosphere

Earth is called the “Water Planet” 71% of the earth’s surface is covered by water. Water is essential for LIFE on earth.

Water on earth’s surface is easy to see… Oceans Lakes Rivers Glaciers But what about water in earth’s atmosphere???

Water in the atmosphere It’s less obvious than surface water, but there are many signs of water in the atmosphere: Rain, Snow, Drizzle Clouds & Fog Hot days that feel “muggy” or “humid” Dew on the grass in the morning

Water Cycle The movement of water between the atmosphere and earth’s surface is the water cycle.

How does water get into the air? EVAPORATION – is the process where liquid water molecules escape into the air as water vapor. 3 things affect how quickly water evaporates: 1) Temperature 2) Wind 3) Humidity of the air

How much water can air hold? HUMIDITY is the measure of how much water vapor is in the air. TEMPERATURE affects how much water vapor the air can hold… Warm Air Cold Air holds MORE water vapor. holds LESS water vapor. That’s why air feels more “HUMID” on hot days!

What is the “Dew Point”? As air cools, the amount of water vapor it can hold decreases. At a certain temperature, the water vapor in the air will CONDENSE back into water droplets or ice. This temperature is the “DEW POINT”.

What is the “Dew Point”? So, when the air temperature equals the “Dew Point” temperature, the air cannot hold any more water. That means relative humidity is 100%!

Ever wondered about why the grass (or a car windshield) is wet in the morning? Overnight, the temperature dropped below the “dew point” temperature, and the water in the air condensed into water droplets on the grass.

Climate vs Weather Global vs Local winds LARGE scale = overall pattern, trend small scale = daily, weekly, small times Global vs Local winds LARGE scale = Over the entire Earth small scale = tiny area…usually land beside water.

Global winds 1 2 3 4 5 Polar easterlies Prevailing westerlies Horse latitudes 4 Trade winds 5 Equator / Doldrums

United States of America

Coriolis Effect – the effect on the air caused by the rotation of the earth.

Watch the BrainPop video on “Humidity”. Write down 3 things you learned.

Air Masses & Fronts

What is an AIR MASS? WARM COLD WET DRY An air mass is a huge body of air that influences weather. Scientists classify air masses based on: TEMPERATURE and HUMIDITY WARM COLD WET DRY

Air Masses are named based on where they FORMED… = TROPICAL = POLAR = MARITIME (means sea… wet) = CONTINENTAL (means land… dry) WARM COLD WET DRY

How are Air Masses named? WET DRY MARITIME TROPICAL CONTINENTAL TROPICAL WARM MARITIME POLAR CONTINENTAL POLAR COLD

North American Air Masses MARITIME POLAR CONTINENTAL POLAR MARITIME POLAR MARITIME TROPICAL MARITIME TROPICAL CONTINENTAL TROPICAL

How do these air masses move? MARITIME POLAR CONTINENTAL POLAR MARITIME POLAR Jet Stream That’s why weather generally moves WEST to EAST in the U.S. Jet Stream Prevailing Westerlies Prevailing Westerlies MARITIME TROPICAL MARITIME TROPICAL CONTINENTAL TROPICAL

What happens when air masses meet? Air masses don’t mix easily. The line between air masses is called a front.

COLD FRONTS

WARM FRONTS

Watch the BrainPop video on “Weather” and write down 2 things you learned.

Use your textbook (pg.133-135) to fill out the chart.

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front Stationary Front Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Cold and warm air meet, but neither can move the other. Creates “standoff” Rain, snow, clouds, or fog that may last for days. Occluded Front

Compare/Contrast Chart - Types of Fronts How it Forms Type of Weather Cold A fast-moving cold air mass overtakes a warm air mass. Clouds form. If warm air is humid, rain/snow may fall. Possible thunderstorms. Warm Front A warm air mass overtakes a slow-moving cold air mass. Scattered clouds. Light rain or snow. May last several days. Stationary Front Cold and warm air meet, but neither can move the other. Creates “standoff” Rain, snow, clouds, or fog that may last for days. Occluded Front A warm air mass is caught between 2 cooler air masses. Warm air mass is pushed up. Temperature gets cooler. Clouds and rain may form.

Surface Map (Fronts & Precipitation) Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front

Temperature Map

H L What will happen to the weather in Little Rock? Which direction is the warm front moving? L H 12°C 19°C 14°C 20°C 25°C Tuesday Weather Little Rock, AR Clouds & Rain Warmer = 21°C Wednesday Weather Little Rock, AR Partly Sunny Warmer = 26°C Monday Weather Little Rock, AR Sun & clear skies Cool = 15°C 28°C 21°C 26°C 15°C 30°C Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front

Which direction is the cold front moving? What will happen to the weather in Nashville? 10°C 8°C 18°C 10°C 11°C Thursday Weather Nashville, TN Partly Sunny Warm = 20°C Saturday Weather Nashville, TN Sunny Cool = 10°C Friday Weather Nashville, TN Thunderstorms Cooler = 15°C 10°C 20°C 15°C Warm Front H High Pressure Occluded Front L Low Pressure Cold Front Stationary Front

BrainPop Log in: carrington1 Password: cougars Watch the WEATHER video and write what you learn. Watch WIND, HUMIDITY, CLOUDS – video for each. Write two things you learn from each.