WeatherWeather

Atmosphere and Air Atmosphere and Air TemperatureTemperature

insolationinsolation – the amount of the – the amount of the Sun’s energy that reaches Earth at Sun’s energy that reaches Earth at a given time and placea given time and place

When the sun is directly overhead When the sun is directly overhead its shadow is shortest. As the angle its shadow is shortest. As the angle decreases, the shadow lengthens.decreases, the shadow lengthens.

The angle of insolation affects The angle of insolation affects temperature. temperature.

It takes more heat to raise the It takes more heat to raise the temperature of water than it temperature of water than it takes to raise the temperature of takes to raise the temperature of land.land.

In winter, warm water warms In winter, warm water warms the air and in the summer, the the air and in the summer, the cooler water cools the air.cooler water cools the air.

atmosphereatmosphere – the – the blanket of gases that blanket of gases that surround the earthsurround the earth

TroposphereTroposphere – the – the layer of the layer of the atmosphere that is atmosphere that is closest to the Earth’s closest to the Earth’s surfacesurface

The higher the The higher the altitude, the colder altitude, the colder the air temperature!the air temperature!

air pressureair pressure – the force put on – the force put on a given area by the weight of a given area by the weight of the air above itthe air above it

Air has weight.Air has weight. As altitude increases, air As altitude increases, air

pressure decreases.pressure decreases.

weatherweather – what the – what the lower atmosphere is lower atmosphere is like at any given place like at any given place and time and time

Weather includes a number of Weather includes a number of conditions at any one timeconditions at any one time

barometerbarometer – a device for – a device for measuring air pressure measuring air pressure

Barometers help to predict Barometers help to predict the weather the weather Example: When air pressure falls, rain Example: When air pressure falls, rain

is likelyis likely

Water in the AirWater in the Air

water vaporwater vapor – water in the form of gas – water in the form of gas humidityhumidity – the amount of water vapor – the amount of water vapor

in the air in the air evaporationevaporation – the changing of a – the changing of a

liquid into a gas liquid into a gas Evaporation requires heat and Evaporation requires heat and

in places where in places where evaporation evaporation takes place become cooler as takes place become cooler as a result. a result.

relative humidityrelative humidity – a comparison – a comparison between the actual amount of water between the actual amount of water vapor in the air and the amount the air an vapor in the air and the amount the air an hold at a hold at a given temperature.given temperature.

condensationcondensation – the changing of – the changing of a gas into a liquid a gas into a liquid

Molecules in water vapor move Molecules in water vapor move more quickly than more quickly than molecules in molecules in cold water. cold water.

Heat causes water to change to Heat causes water to change to water vapor. water vapor.

How can warm air become How can warm air become cool?cool? Warm air can be pushed upward Warm air can be pushed upward

by windsby winds Warm air can be pushed Warm air can be pushed

up by cool air up by cool air Warm air can cool by rising and Warm air can cool by rising and

expandingexpanding

Clouds of Water and IceClouds of Water and Ice

Stratus CloudsStratus Clouds stratus cloudsstratus clouds – a cloud that forms – a cloud that forms

in a blanket like layerin a blanket like layer

Cumulus CloudsCumulus Clouds

cumulus cloudcumulus cloud – a puffy cloud that – a puffy cloud that appears to rise up from a flat bottomappears to rise up from a flat bottom

Cirrus CloudsCirrus Clouds

cirrus cloudcirrus cloud – a high – a high altitude cloud with a altitude cloud with a featherlike shape, featherlike shape, made of ice crystalsmade of ice crystals

FogFog

fogfog – a cloud that forms at ground – a cloud that forms at ground levellevel

PrecipitationPrecipitation precipitationprecipitation – any form of water particles – any form of water particles

that falls from the atmosphere and reaches that falls from the atmosphere and reaches the groundthe ground

The larger the cloud the more water it The larger the cloud the more water it holds, so it may produce more holds, so it may produce more precipitation.precipitation.

The Water CycleThe Water Cycle water cyclewater cycle – the continuous – the continuous

movement of water between Earth’s movement of water between Earth’s surface and the air, changing from surface and the air, changing from liquid to gas to liquid.liquid to gas to liquid.

Air Pressure and WindAir Pressure and Wind Warming molecules speed up and Warming molecules speed up and

spread out. This lowers air pressure.spread out. This lowers air pressure. Molecules of water vapor weigh less Molecules of water vapor weigh less

than oxygen and nitrogen in the air, than oxygen and nitrogen in the air, and thus exert less pressure.and thus exert less pressure.

The direction a barometer is changing The direction a barometer is changing can be a clue to future weather. can be a clue to future weather. A falling barometer may be a sign A falling barometer may be a sign

that a storm is on its waythat a storm is on its way A rising barometer may be a sign A rising barometer may be a sign

that fair weather is approachingthat fair weather is approaching

windwind – air that moves horizontally – air that moves horizontally updraftupdraft – air that rises – air that rises

Air that is warmed risesAir that is warmed rises downdraftdowndraft – air that sinks – air that sinks

Air moves down when air pressure above is Air moves down when air pressure above is higher and the moves down to an area of higher and the moves down to an area of lower pressurelower pressure

convection cellconvection cell – part of – part of the atmosphere the atmosphere where air where air moves in a circular pattern moves in a circular pattern because of unequal heating because of unequal heating and cooling. and cooling.

Air moves from an area with higher Air moves from an area with higher pressure to an area of pressure to an area of lower pressurelower pressure

sea breezesea breeze – wind that blows from – wind that blows from sea to landsea to land When the air over the land gets hotter When the air over the land gets hotter

than the air over the waterthan the air over the water land breezeland breeze – wind that blows from – wind that blows from

land to sealand to sea When the air pressure over the sea is When the air pressure over the sea is

higher than the air pressure over the higher than the air pressure over the land.land.

Coriolis effectCoriolis effect – – the curving of the the curving of the path of a moving path of a moving object caused by object caused by Earth’s rotating.Earth’s rotating.

If the Earth did not If the Earth did not rotate, air would rotate, air would travel away from travel away from the equator the equator towards the poles. towards the poles. At the poles, the At the poles, the air would move air would move back towards the back towards the equator.equator.

air massair mass – a large region of the – a large region of the atmosphere where the air has similar atmosphere where the air has similar properties throughoutproperties throughout

frontfront – a boundary between air – a boundary between air masses with different temperaturesmasses with different temperatures

Cold FrontCold Front

cold frontcold front - cold - cold air moves in under air moves in under a warm air massa warm air mass

What kind of weather would you expect a cold front to produce?

Cold fronts can produce short, heavy rains, often thunderstorms with heavy winds, followed by clear skies and cooler, drier weather.

Warm FrontWarm Front

warm frontwarm front – – warm air moves in warm air moves in over a cold air over a cold air massmass

What kind of weather does a warm front produce?

A warm front can cause steady rain or snow that may last for days and light winds, followed by warmer and more humid weather.

Occluded FrontOccluded Front

occluded frontoccluded front – – a front formed a front formed where a warm where a warm front and cold front and cold front meetfront meet

Stationary FrontStationary Front stationary frontstationary front – –

an unmoving front an unmoving front where a cold air where a cold air mass and a warm mass and a warm air mass meetair mass meet

What Do Fronts Look Like What Do Fronts Look Like from Space?from Space?

Satellites Satellites show large show large weather weather patterns, patterns, such as such as fronts and fronts and storms storms which help which help weather weather scientists.scientists.

ThunderstormThunderstorm thunderstormthunderstorm – –

the most common the most common severe storm, severe storm, formed in formed in cumulonimbus cumulonimbus cloudsclouds

What causes lightning?

Air from updrafts rubs against air from downdrafts, creating static electricity. The static electricity builds up, until lightning sparks.

TornadoTornado

tornadotornado – a violent whirling wind that – a violent whirling wind that moves across the ground in a narrow moves across the ground in a narrow pathpath

HurricaneHurricane

hurricanehurricane – a very large, swirling storm – a very large, swirling storm with very low pressure at the centerwith very low pressure at the center

Hurricane Fran

Storm SurgeStorm Surge

storm surgestorm surge – a – a great rise of the great rise of the sea along a shore sea along a shore caused by low caused by low pressurepressure

A shallow slope off the coast (above) will allow a greater storm surge.

A steeper continental shelf (below) will not see as much of a storm surge.

Doppler RadarDoppler RadarDoppler radar bounces sound waves off the Doppler radar bounces sound waves off the

storm clouds.storm clouds.

Doppler radar can tell if raindrops are Doppler radar can tell if raindrops are moving toward or away from observers, moving toward or away from observers, and it can spot spinning movements in and it can spot spinning movements in clouds. This helps scientists predict clouds. This helps scientists predict which way storms will travel.which way storms will travel.

ClimateClimate

climateclimate – the – the average weather average weather pattern of a pattern of a regionregion

Factors That Affect Factors That Affect TemperatureTemperature

Distance from the equatorDistance from the equator

Air pressure and windsAir pressure and winds

AltitudeAltitude

Distribution of waterDistribution of water

radiative balanceradiative balance – a balance – a balance between energy lost and energy between energy lost and energy gainedgained

The Earth is constantly radiating The Earth is constantly radiating energy into the atmosphere, which energy into the atmosphere, which lowers temperature.lowers temperature.

Greenhouse EffectGreenhouse Effect

greenhouse greenhouse effecteffect – the – the ability of the ability of the atmosphere atmosphere to let in to let in sunlight but sunlight but to not let to not let heat escapeheat escape

What causes climate What causes climate change?change?

The Sun (sunspots)The Sun (sunspots)

Ocean CurrentsOcean Currents

VolcanoesVolcanoes

isobarisobar – a line on a weather map – a line on a weather map connecting places with equal air connecting places with equal air pressurepressure Show patterns better than numbersShow patterns better than numbers

wind vanewind vane – a device that – a device that indicates wind indicates wind directiondirection

anemometeranemometer – a device – a device that that measures wind speedmeasures wind speed

Exploring Weather – The Exploring Weather – The Atmosphere In MotionAtmosphere In Motion