Unit 4 Notes - Weather

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Unit 4 Notes Weather

Weather is the study of the Earth’s atmosphere and a person who studies weather is a meteorologist. Overall most of the weather storms that happen in the US come from the west and travel to the east. This is because of upper wind patterns.

Earth’s atmosphere made up of 21% oxygen, 78% nitrogen 1% other

Air Pressure- measure of the force with which air molecules push and an area of a surface. As you claim up into the layers of the atmosphere the air pressure (the number of air molecules) decreases.

Barometer - Instrument used to measure air pressure

      Layers of the Atmosphere

The layers of the atmosphere are classified by their air pressure.

Thermosphere – absorbs high-energy solar radiation.

Mesosphere – protects us from meteorites this is the layer that they begin to burn up in

Stratosphere – contains the ozone layer that protects us from UV radiation

Troposphere – layer where all the weather talks place 80% of the atmosphere’s gases are found here

Energy Budget – is a way to keep track of energy transfers into and out of the earth system.

Greenhouse effect- gases in the atmosphere like water vapor and co2 adsorb and give off infrared radiation.

Heat – energy that is transferred between objects that are at different temperatures

Convection – is the transfer of energy due to the movement of matter.

Radiation – is the transfer of energy as electromagnetic waves. (from the sun)


The continuous movement of water between the atmosphere, the land, the oceans and living things affects the patterns of weather.

In order to form clouds, water vapor must condensate. Condensation can only take place if water vapor has something to condensate on such as a small piece of dust, salt, smoke particles and even bacteria. The object is referred to as the cloud condensation nuclei. These water drops then come together to form Clouds. 

Cloud – is a collection of small water droplets

The sun causes the atmosphere to heat up, the heated air rises and creates winds, these winds blow across the oceans and land. Over the ocean it causes ocean currents.

Wind – the movement of air caused by differences in air pressure.

Coriolis Effect – curving of the path of a moving object from an otherwise straight path due to Earth’s rotation. (hurricanes, ocean gyres)

GLOBAL WINDS – created by the heating of the earth by convection. These winds produce convection cells. The major winds are

 Polar Easterlies – move from the poles to about 600 latitude on both hemispheres

Westerlies – move from 300-600 latitude on both hemispheres

Trade Winds – move 300 to the equator on both hemispheres

Jet Stream – narrow belts of high-speed winds that blow from west to east in US

Local wind – the movement of air over short distances


Sea breezes – move from large bodies of water toward the land

Land breezes – move from the land to the ocean.

Weather – is the condition of the earth’s atmosphere at a certain time and place.

Humidity – the amount of water vapor in the air

Relative humidity – is the amount of water vapor in the air compared to the amount of water vapor needed to reach saturation. This tells you how sticky it’s outside.

Dew point – the temperature at which more condensation than evaporation occurs

Precipitation – water falling to earth as rain snow hail or sleet

There are three basic cloud shapes:

Stratus – thin flat low clouds that are often gray in color. Fog is a type of stratus cloud that forms near the Earth’s surface.

Cumulus – thick puffy clouds, normally associated with fair weather.

Cirrus – feathery white clouds that are high

Nimbus – means rain, low clouds

Alto – means middle height clouds

Cirro –high clouds

Cumulonimbus – huge towering clouds that can produce severe weather

Air Pressure- how many air molecules are in a given volume.

Air mass – is a large volume of air which temperature and moisture content are nearly the same throughout

Fronts – are a boundary that forms between two air masses. The main types of fronts are cold, warm and stationary.

Cold Front – cold air mass pushes under a warm air masses cause’s quick heavy rain

Warm front – warm air mass that follows a retreating cold air mass, causes drizzly rain that can last long with warmer air temperatures after the rain.

Stationary front – two air masses meet and neither is strong enough to move the other.

Pressure Systems

High-pressure system – air sinks downward or moves down associated with clear weather

Low-Pressure system – air rises associated with precipitation weather.

READING WEATHER MAPS (images not available)

Thunderstorm – is an intense local storm that forms strong winds, heavy rain, lightning, thunder and sometimes hail.

Lightning – is an electric discharge that happens between a positively charged area and a negatively charged area.

Thunder – is the sound created by the rapid expansion of air along a lightning strike.

Hurricane -  tropical low-pressure system with winds blowing at speeds of 74 miles per hour or more in the western pacific ocean they are called typhoons, and cyclones over the Indian ocean.

Tornado – rotating column of air


Most climate predictions are based on computer models.