Weather Weather ConditionsConditions

What Makes up Earth’s What Makes up Earth’s Atmosphere?Atmosphere?

The layer of air surrounds our The layer of air surrounds our planet is called the atmosphere.planet is called the atmosphere.

Layers of the Atmosphere Layers of the Atmosphere

TroposphereTroposphere StratosphereStratosphere MesosphereMesosphere ThermosphereThermosphere

TroposphereTroposphere

Layer closes to the Layer closes to the earthearth

Weather happens in Weather happens in this layerthis layer

Live and breathe air in Live and breathe air in this layerthis layer

Air temperature Air temperature decreases as you go decreases as you go higherhigher

StratosphereStratosphere

Airplanes travel in this Airplanes travel in this layer to avoid bad weatherlayer to avoid bad weather

Contains most of the Contains most of the atmosphere’s ozoneatmosphere’s ozone

Ozone protects living Ozone protects living things from harmful rays of things from harmful rays of the sunthe sun

Temperature increase with Temperature increase with heightheight

MesosphereMesosphere

Temperature decrease Temperature decrease with heightwith height

Coldest layer of the Coldest layer of the atmosphereatmosphere

ThermosphereThermosphere

Hot, outermost layerHot, outermost layer Temperature increase Temperature increase

quickly with heightquickly with height

How Do Air Masses Affect the How Do Air Masses Affect the WeatherWeather

Greenhouse EffectGreenhouse Effect

Air MassesAir Masses

What happens when to air masses What happens when to air masses meet?meet?

When two air masses meet, they form a When two air masses meet, they form a border called a frontborder called a front

A front is the area where two air masses A front is the area where two air masses meet and weather happensmeet and weather happens

Cold FrontCold Front

A cold air mass A cold air mass catches up with a catches up with a warm air masswarm air mass

The cold air mass The cold air mass forces the warm air up forces the warm air up in the atmospherein the atmosphere

As warm airAs warm air

Cold FrontCold Front

As warm air pushes As warm air pushes upward, it cool and upward, it cool and forms cloud. forms cloud.

Rain develops.Rain develops. Thunderstorm often Thunderstorm often

occur along a cold occur along a cold front.front.

Cold FrontCold Front

Generally move from northwest Generally move from northwest to southeastto southeast

Air behind a cold front is colder Air behind a cold front is colder and drier than the air ahead of and drier than the air ahead of it.it.

When a cold front passes When a cold front passes through, temperatures can drop through, temperatures can drop more than 15 degrees within the more than 15 degrees within the first hour.first hour.

Represented by a solid lines Represented by a solid lines with triangles along the front with triangles along the front pointing towards the warmer air pointing towards the warmer air and in the direction of and in the direction of movementmovement

Warm FrontWarm Front

Forms when a warm air Forms when a warm air mass catches up with a mass catches up with a cold air masscold air mass

Warm air slides up over Warm air slides up over the colder, denser airthe colder, denser air

Generally move from Generally move from southwest to northeast southwest to northeast

Air behind a warm Air behind a warm front is warmer and front is warmer and more moist than the air more moist than the air ahead of itahead of it

Represented by a solid Represented by a solid line with semicircles line with semicircles pointing towards the colder pointing towards the colder air and in the direction of air and in the direction of the movementthe movement

Steady rain or snow may Steady rain or snow may fall as the front fall as the front approaches and passesapproaches and passes

Common Characteristics of Warm Fronts

Before PassingWhile Passing After Passing

Winds South-southeast

Temperatures

Pressure

Clouds

Precipitation

Visibility

Dew Point

Clouds and WeatherClouds and Weather Weather scientists classify a cloud based on its shape, its Weather scientists classify a cloud based on its shape, its

color, and where it forms in the atmospherecolor, and where it forms in the atmosphere

CirrusCirrus

A wispy white cloudA wispy white cloud Fair weatherFair weather

CumulusCumulus

Puffy cotton-ball Puffy cotton-ball cloudsclouds

Begins to form when Begins to form when water droplets water droplets condense at middle condense at middle altitudesaltitudes

CumulonimbusCumulonimbus

Dense cumulus cloud Dense cumulus cloud with a hazy outlinewith a hazy outline

Usually producing Usually producing heavy rain, heavy rain, thunderstorms, or thunderstorms, or hailstormshailstorms

StratusStratus

Dark gray clouds that Dark gray clouds that form a low layerform a low layer

Sometimes bring rain Sometimes bring rain or snow showersor snow showers

What is a Cycle?What is a Cycle?

A sequence of events A sequence of events that repeat themselvesthat repeat themselves

EvaporationEvaporation

The sun heats up water in The sun heats up water in rivers, lakes, or oceanrivers, lakes, or ocean

The water changes from a liquid The water changes from a liquid into a gas, vapor, or steam.into a gas, vapor, or steam.

The water vapor leaves the The water vapor leaves the rivers, oceans, or lakes and rivers, oceans, or lakes and goes into the atmosphere.goes into the atmosphere.

CondensationCondensation

Water vapor in the air Water vapor in the air gets cold and changes gets cold and changes back into liquidback into liquid

forming cloudsforming clouds

TranspirationTranspiration

Is the process by which plants Is the process by which plants return water to the atmosphere.return water to the atmosphere.

After absorbing water from the After absorbing water from the ground, plant release water ground, plant release water through their leaves.through their leaves.

This helps plants stay cool.This helps plants stay cool.

Precipitation Precipitation

Occurs when so much Occurs when so much water has condensed that water has condensed that the air cannot hold it the air cannot hold it anymore.anymore.

Clouds get heavy and Clouds get heavy and water falls back to earth in water falls back to earth in the form of rain, sleet, hail, the form of rain, sleet, hail, or snowor snow

What instruments do meteorologist What instruments do meteorologist use to forecast weather?use to forecast weather?

AnemometerAnemometer

Measures wind speedMeasures wind speed The cups catch the The cups catch the

wind, turning a dial wind, turning a dial attached to the attached to the instrument.instrument.

The dial shows the The dial shows the wind speed.wind speed.

BarometerBarometer

Measures air pressureMeasures air pressure

Psychrometer Psychrometer

Measures relative Measures relative humidity, using the humidity, using the cooling effect of cooling effect of evaporationevaporation

HygrometerHygrometer

Measures the amount Measures the amount of humidity in the air.of humidity in the air.