Atmosphere, Weather, & Climate

Ch. 15, 16, 17, & 18

Earth’s Atmosphere

Gases in Earth’s Atmosphere

Atmospheric Pressure

Air pressure

Since air has mass, it is affected by gravity

Air pressure - the result of the weight of a column of air pushing down on an area

Measured with a barometer

2 kinds: aneroid and mercury

Barometers

Aneroid

Mercury

Standard Atmospheric Pressure

Units of pressure (numbers represent standard air pressure at sea level):

1013 millibars

14.7 psi (pounds per square inch)

29.92 inHg (inches of Mercury)

760 mmHg (millimeters of Mercury)

Air Pressure and Wind

Wind blows from areas of high pressure to areas of low pressure

Air Masses

Air mass - A huge body of air that has similar temperature, humidity, and pressure throughout

Fronts

Front - The boundary where air masses meet

Water in the Atmosphere

Precipitation

Humidity

Humidity is the measure of the amount of water vapor in the air

- Depends on temperature (warm air holds more water vapor than cool air)

Heat index

How Clouds Form

Clouds form when water vapor in the air condenses to form liquid water or ice crystals (due to cooling of air)

Water vapor needs particles in the atmosphere to adhere to

Core Four Clouds

Cumulus - Thick, puffy clouds

Cirrus - High, featherlike clouds

Stratus - Layers of clouds

Nimbus - Rain clouds

Cloud Types

Weather instruments

Thermometer - measures temperature

Barometer - measures air pressure

Psychrometer - measures relative humidity

Wind vain - measures wind direction

Anemometer - measures wind speed

Rain gauge - measures amount of precipitation