Study GuideTest 12/16

Topics Include:Relative Humidity

Dew PointCloud Formation

Air MassesFronts

Make Sure You Understand:Relative humidity is the amount of moisture (water vapor) in the air compared to the amount of moisture the air can hold at that temperature.

When the air is Saturated, it has 100% relative humidity.

Dew Point is when air cools to the temperature at which air is saturated.

Assuming the amount of water vapor in the air stays the same…

•If the temperature increases, then the relative humidity decreases.

•If the temperature decreases, then the relative humidity increases.

What is a cloud?• A cloud is made of water droplets.• Clouds form when warm air rises and cools

Be able to answer the following:Name of Cloud Appearance Effect

 1. Cumulus

 White, puffy, cotton ball clouds

 Fair weather. Nice day outside.

 2. Cirrus

 Feathery, wispy clouds.  Made of ice crystals!

 Fair at present, BUT rain in 24 – 48 hours (a day or two).  Warns of a warm front approaching.

 3. Stratus  

 Flat layers of gray clouds Brings gentle steady rain.

 Forms in a warm front. 

 4. Cumulonimbus  

 Thunderhead!

Dark flat bottoms building into anvil shaped tops

 Thunderstorms! Heavy rain, thunder, lightning, and possible hail. Forms in cold front.

Key Terms

• Precipitation - water that falls to the Earth’s surface as rain, snow, sleet, or hail

• Condensation - process in which water vapor cools and turns to liquid

• Weather- condition of the atmosphere at a certain time and place

• Humidity- the amount of moisture in the air

Key Terms, continued

• Anticyclone- area of high pressure where air moves apart and sinks

• Cyclone- area of low pressure where air masses meet and rise

• Dew Point- the temperature at which a gas condenses into a liquid

Measuring Weather

• Anemometer - measures wind speed

• Barometer - measures air pressure

• Radar - locates precipitation

• Thermometer - measures air temperature

• Windsock - measures wind direction

Air MassesA. mPB. cP and/or cAC. mPD. cTE. mTF. mT

G. What is the origin of each of the 3 mT air masses?

The Pacific Ocean, the Gulf of Mexico, and the Atlantic Ocean

Air MassesAn air mass is named for it’s temperature and moisture level.

When two air masses meet the warm air mass will rise and the cool air mass will sink.

Continental

Maritime

Polar

Tropical

Dry

Wet

Cold

Warm

Air MassesAn air mass is a body of air.

•A Continental Polar (cP) air mass brings cold, dry weather.

•A Maritime Polar (mP) air mass brings cold, moist (wet) weather.

•A Continental Tropical (cT) air mass brings dry and warm weather.

•A Maritime Tropical (mT) air mass brings warm, moist (wet) weather.

FrontsFronts are the boundary between different air masses.

• Cold fronts create short, heavy, violent periods of rain followed by cool fair weather

• Warm fronts occur when warm air rises and condenses into long areas of clouds which bring gentle rain or snow followed by warmer weather

• Stationary fronts create clouds and fog at the site of the front and can bring days of rain or snow

• Occluded fronts occur when warm air is cut off from the ground which can bring heavy wind and precipitation

Warm front

(red)

Make sure you know:

1. Which symbol belongs to which front.2. The color of each front symbol.3. The type of weather does each front bring.

Occluded front

(purple)

Cold front

(blue)

Stationary front

(red and blue)

Topics to Review• Dew Point Lab

– Words to know: Dew Point, Saturated, Condensation, Water Vapor

• High Pressure System

• Low Pressure System