Composition and Structure of Composition and Structure of AtmosphereAtmosphereWeather Patterns and ForecastingWeather Patterns and ForecastingFactors Influencing ClimateFactors Influencing ClimateSevere WeatherSevere Weather

Weather vs. ClimateWeather vs. Climate Weather- constantly changing, refers to the Weather- constantly changing, refers to the

state of the atmosphere at any given time and state of the atmosphere at any given time and placeplace

Climate- based on observations that have been Climate- based on observations that have been collected over many years and describes a collected over many years and describes a place or regionplace or region

Both measure- air temperature, humidity, Both measure- air temperature, humidity, precipitation, air pressure, wind (speed and precipitation, air pressure, wind (speed and direction)direction) What is the climate of the Las Vegas valley?What is the climate of the Las Vegas valley? What is the weather today in the Las Vegas valley?What is the weather today in the Las Vegas valley?

Composition and Structure Composition and Structure of Earth’s Atmosphereof Earth’s Atmosphere

A mixture of gases A mixture of gases with some suspended with some suspended solids (dust, salt, ice) solids (dust, salt, ice) and liquids (water and liquids (water droplets in clouds).droplets in clouds).

Extends from surface Extends from surface to outer space – to outer space – hundreds of km’s.hundreds of km’s.

Very thin layer Very thin layer around Eartharound Earth

Earth Science Reference Table

Major ComponentsMajor Components

99% of 99% of atmosphere is 2 atmosphere is 2 gases- nitrogen gases- nitrogen and oxygenand oxygen

.93% - Argon.93% - Argon .039% Carbon .039% Carbon

DioxideDioxide

Variable ComponentsVariable Components Water vapor- source of Water vapor- source of

clouds and clouds and precipitationprecipitation Absorbs solar energyAbsorbs solar energy

Ozone- OOzone- O3 3 10-50km 10-50km above earth. Absorbs above earth. Absorbs UV radiation from sun UV radiation from sun

Dust – fine grained Dust – fine grained particles can stay particles can stay suspended for some suspended for some timetime

Changes in Earth’s Changes in Earth’s AtmosphereAtmosphere

Earth’s atmosphere Earth’s atmosphere thins as you travel thins as you travel from Earth until from Earth until there are too few there are too few gas molecules to gas molecules to detect- this is spacedetect- this is space

As gas molecules As gas molecules decrease air decrease air pressure decreasespressure decreases

Layers of the AtmosphereLayers of the Atmosphere

Troposphere

Stratosphere

Mesosphere

Thermosphere

TroposphereTroposphere

Contains 75% of atmospheric gases, Earth’s surface – 12 kilometers

Weather, clouds, and smog found here

Temperature TrendsTemperature Trends Temp decrease Temp decrease

with altitude in the with altitude in the TroposphereTroposphere

- Temp rises in the - Temp rises in the Stratosphere Stratosphere Why?Why?

- Ozone layer occurs Ozone layer occurs in stratospherein stratosphere- Remember Ozone Remember Ozone

absorbs UV absorbs UV radiationradiation

- Being destroyed by Being destroyed by Clorofluorocarcbons Clorofluorocarcbons (CFCs)(CFCs)

Pressure TrendsPressure TrendsGases in the atmosphere, like all matter, have mass.

Atmosphere is a sea of air – the deeper you are in it, the heavier it feels (more force exerted)

Sea level pressure is 1013 mb at STP

Denver pressure is 550 mb (1600 m)

Mt Everest pressure is 315 mb (8800 m)

Types of heat transferTypes of heat transfer Radiation (no molecules needed)Radiation (no molecules needed)

transfer of energy without the involvement of a transfer of energy without the involvement of a physical substance in the transmission.physical substance in the transmission.

Allows solar radiation to reach Earth as it travels Allows solar radiation to reach Earth as it travels through spacethrough space

Convection (air movement)Convection (air movement) transmits heat energy by transporting groups of transmits heat energy by transporting groups of

molecules from one place to another within a molecules from one place to another within a substancesubstance- warmer less dense portions of the medium will - warmer less dense portions of the medium will rise while colder more dense areas will sinkrise while colder more dense areas will sink

Conduction (direct contact)Conduction (direct contact) Transfer of energy between molecules until an Transfer of energy between molecules until an

even temperature is reachedeven temperature is reached

What happens to solar What happens to solar radiation?radiation?

When radiation strikes an object 1 of When radiation strikes an object 1 of three things can happenthree things can happen

1)1) Energy is absorbed by the object Energy is absorbed by the object (temperature of object increases)(temperature of object increases)

2)2) Energy is transmitted by object Energy is transmitted by object (temperature of object does not (temperature of object does not increase) air and water transmit some increase) air and water transmit some radiationradiation

3)3) Energy bounces off object without Energy bounces off object without being absorbed or transmittedbeing absorbed or transmitted

Weather Patterns and Weather Patterns and ForecastingForecasting

Sun is the external heat engine for Sun is the external heat engine for our planet.our planet.

Three possibilitiesThree possibilities1)Reflect to space1)Reflect to space

AtmosphereAtmosphereLand (Albedo)Land (Albedo)

2)Absorbed by atmosphere2)Absorbed by atmosphere3)Absorbed by land or 3)Absorbed by land or

absorbed/transmitted by water absorbed/transmitted by water surfacessurfaces

Albedo of Earth SurfacesAlbedo of Earth Surfaces

WeatherWeather The present state of the atmosphereThe present state of the atmosphere Describes current conditionsDescribes current conditions

Air PressureAir Pressure WindWind Air TemperatureAir Temperature Amount of MoistureAmount of Moisture

Water CycleWater Cycle

Evaporation/transpirationEvaporation/transpiration CondensationCondensation PrecipitationPrecipitation

Air MassesAir Masses A large body of air that has the same A large body of air that has the same

properties as the surface over which properties as the surface over which it develops.it develops.

When you witness a change When you witness a change

in the weather from one day to in the weather from one day to

the next, it is due to the move-the next, it is due to the move-

ment of air masses.ment of air masses.

Prevailing Winds across Prevailing Winds across U.S.U.S.

Winds tend to move towards the right Winds tend to move towards the right due to the Coriolis effectdue to the Coriolis effect Coriolis effect created by the rotation of Coriolis effect created by the rotation of

the earththe earth Surface winds across U.S. consist of Surface winds across U.S. consist of

prevailing westerlies prevailing westerlies Winds blow from southwest to northeastWinds blow from southwest to northeast These winds are responsible for movement These winds are responsible for movement

of weather across the U.S. and Canadaof weather across the U.S. and Canada

FrontsFronts Boundary between two air massesBoundary between two air masses

Cold FrontCold Front Warm FrontWarm Front Occluded FrontOccluded Front Stationary FrontStationary Front

HumidityHumidity Refers to the water vapor content in the atmosphereRefers to the water vapor content in the atmosphere Relative Humidity is the ratio of the amount of water vapor Relative Humidity is the ratio of the amount of water vapor

in air to the maximum amount it can hold at that in air to the maximum amount it can hold at that temperature. (expressed as percentage) *Varies with temperature. (expressed as percentage) *Varies with temperature changetemperature change

Dew PointDew Point Temperature at which air is saturated and condensation occurs.Temperature at which air is saturated and condensation occurs.

Point where saturated vapor pressure equals actual vapor pressurePoint where saturated vapor pressure equals actual vapor pressure Point where relative humidity equals 100%Point where relative humidity equals 100%

CloudsClouds Classified mainly on shape and heightClassified mainly on shape and height Form when warm air is forced upward, Form when warm air is forced upward,

expands, and cools.expands, and cools. At the dew point, condensation occursAt the dew point, condensation occurs Aided by nuclei (dust, salt, smoke…)Aided by nuclei (dust, salt, smoke…)

Classification of CloudsClassification of Clouds

Weather MapsWeather MapsCloud Cover and Cloud Cover and

PrecipitationPrecipitation

Weather MapsWeather MapsIsobar and IsothermIsobar and Isotherm

Weather Map SymbolsWeather Map Symbols

Weather MapWeather Map

Five Factors Influencing Five Factors Influencing ClimateClimate

Factors Influencing ClimateFactors Influencing Climate

Climate is an average of the weather Climate is an average of the weather over a long period of time.over a long period of time.

Influenced by: Influenced by: Global wind patternsGlobal wind patternsLatitudeLatitudeTopographic FeaturesTopographic FeaturesLarge bodies of waterMountainsLarge cities

Global WindGlobal Wind

Uneven heating of the latitudes Uneven heating of the latitudes produces major convection currents.produces major convection currents.

Deflect to the right in N.H.Deflect to the right in N.H. Coriolis EffectCoriolis Effect

Topographic FeaturesTopographic Features

Severe WeatherSevere Weather

TornadoTornado HurricaneHurricane LightningLightning

TornadoTornado

Violent, whirling wind that moves in a Violent, whirling wind that moves in a narrow path over the land, usually in a narrow path over the land, usually in a direction from southwest to northeast.direction from southwest to northeast.

Typically form along a frontTypically form along a front Local storm, short durationLocal storm, short duration Spin counterclockwiseSpin counterclockwise Vortex extends from cloudVortex extends from cloud Why can we see it?Why can we see it?

Tornado OccurrenceTornado Occurrence

< 1% of all thunderstorms

~ 770 per year

April - June

Tornado Category ScaleTornado Category Scale

Fujita ScaleFujita Scale

Tornado SummaryTornado Summary LightningLightning Damaging HailDamaging Hail High WindsHigh Winds Torrential RainTorrential Rain

Hurricane Hurricane (Typhoon/Cyclone)(Typhoon/Cyclone)

Is a low pressure system that forms over Is a low pressure system that forms over tropical oceans. tropical oceans.

The greatest storms on Earth – several 100 The greatest storms on Earth – several 100 miles across!miles across!

Wind speeds > 74 mphWind speeds > 74 mph Spin counterclockwiseSpin counterclockwise Average 6-10 per yearAverage 6-10 per year ““Season” July – SeptemberSeason” July – SeptemberProduces: Torrential rain,

Flooding, Damaging winds, Storm Surge

Anatomy of a HurricaneAnatomy of a Hurricane

Warm ocean water with a Warm ocean water with a minimum temp of 80° Fminimum temp of 80° F

Minimum ocean depth of 200 Minimum ocean depth of 200 mm

Converging winds near Converging winds near surfacesurface

Humid air rises and Humid air rises and condenses condenses

– – Latent heatLatent heatCondensation is a warming Condensation is a warming process, releasing stored heat. process, releasing stored heat. This heat warms the surrounding This heat warms the surrounding air, making it lighterair, making it lighter

Upper atmosphere high Upper atmosphere high pressure removes rising air in pressure removes rising air in stormstorm

Hurricane Category Hurricane Category ScaleScale

Winds greater than 155 mph have been Winds greater than 155 mph have been recordedrecorded Tropical storms have winds 39-74 mphTropical storms have winds 39-74 mph

Tracking HurricanesTracking Hurricanes MovementMovement

Storms gets Storms gets energy from warm energy from warm ocean waterocean water

Loses power when Loses power when it moves over landit moves over land

Difficult to predict Difficult to predict where it will make where it will make landland

Errors in prediction Errors in prediction and evacuation can be and evacuation can be costly!costly!

LightningLightning Polarization of + and – charges Polarization of + and – charges

within a storm cloud by within a storm cloud by frictional frictional chargingcharging and and freezingfreezing..

+ charges carried to upper portions + charges carried to upper portions of cloud and – portions gravitate to of cloud and – portions gravitate to bottom bottom of clouds.of clouds. Electric field from cloud induces Electric field from cloud induces

movement of electrons upon Earthmovement of electrons upon Earth Buildings, trees and people can Buildings, trees and people can

experience a build up of static experience a build up of static charge as electrons are repelled by charge as electrons are repelled by the cloud’s bottom.the cloud’s bottom.

Anatomy of LightningAnatomy of Lightning As static charge buildup As static charge buildup

increases, the electric field increases, the electric field becomes strongerbecomes stronger

Ionization of surrounding air Ionization of surrounding air makes it more conductivemakes it more conductive

Begins with development of a Begins with development of a stepstep leaderleader. Why zigzag?. Why zigzag?

Induces a strong positive Induces a strong positive charge on earth surface. This charge on earth surface. This charge begins migrating charge begins migrating upward (upward (streamerstreamer) through ) through buildings, trees and people buildings, trees and people into the air.into the air.

When step leader meets When step leader meets streamer, a complete streamer, a complete conductive pathway is mapped conductive pathway is mapped out and lightning begins.out and lightning begins.

Lightning RodsLightning Rods Pointed metal pole which extends Pointed metal pole which extends

upward above the building, is attached upward above the building, is attached by a copper cable to a grounding rod by a copper cable to a grounding rod buried in the Earth below.buried in the Earth below.

““leaks off” excess leaks off” excess

charges in the charges in the

atmosphere, thus atmosphere, thus

reducing the likelihood reducing the likelihood

of a sudden and of a sudden and

explosive discharge.explosive discharge.

Myths about LightningMyths about Lightning Never strikes the same place twiceNever strikes the same place twice Only strikes very tall objectsOnly strikes very tall objects Does not strike waterDoes not strike water Could be used as a power sourceCould be used as a power source Rubber shoes or boots insulate and Rubber shoes or boots insulate and

protect against a lightning strikeprotect against a lightning strike A metal vehicle is safe because of A metal vehicle is safe because of

rubber tiresrubber tires ““Heat lightning” is a strange Heat lightning” is a strange

phenomenon caused by hot water or phenomenon caused by hot water or occurs after very hot summer days and occurs after very hot summer days and poses no threat.poses no threat.

Lightning victims are electrifiedLightning victims are electrified

Facts about LightningFacts about Lightning The average flash could light a 100-Watt light bulb for The average flash could light a 100-Watt light bulb for

more than three monthsmore than three months Chances of being struck are estimated to be 1 in Chances of being struck are estimated to be 1 in

600,000600,000 Temperature of a flash is 5x hotter than sun’s Temperature of a flash is 5x hotter than sun’s

surfacesurface Can travel over and through the Earth’s surfaceCan travel over and through the Earth’s surface ~20 million cloud to ground lightning strikes occur in ~20 million cloud to ground lightning strikes occur in

the US per yearthe US per year ~2,000 thunderstorms active throughout the world at ~2,000 thunderstorms active throughout the world at

any given time, producing more than 100 any given time, producing more than 100 flashes/secondflashes/second

~26,400 lightning-induced fires/year in the US~26,400 lightning-induced fires/year in the US 80% of livestock deaths attributed to lightning strikes80% of livestock deaths attributed to lightning strikes Second largest storm killer in the US (#1 floods)Second largest storm killer in the US (#1 floods)

END OF PRESENTATION

Greenhouse EffectGreenhouse Effect

As heat is reflected back into the atmosphere it is absorbed by greenhouseGases. More gases in the atmosphere means more heat is absorbed.