Atmospheric HazardsAtmospheric Hazards

Thunderstorms, Tornadoes, Thunderstorms, Tornadoes, High Winds, and FogHigh Winds, and Fog

Session 7Session 7

Pure AirPure Air

InvisibleInvisible ColorlessColorless OdorlessOdorless TastelessTasteless

Atmospheric CompositionAtmospheric Composition

GasesGases Liquid and Solid MatterLiquid and Solid Matter

Atmospheric GasesAtmospheric Gases

Nitrogen 78% of volumeNitrogen 78% of volume Oxygen 21%Oxygen 21% Others combined approximately 1%Others combined approximately 1% Includes Argon, Neon, Helium, Includes Argon, Neon, Helium,

Methane, Krypton, and HydrogenMethane, Krypton, and Hydrogen

Variable-Amount GasesVariable-Amount Gases

Water VaporWater Vapor Carbon dioxideCarbon dioxide Carbon MonoxideCarbon Monoxide OzoneOzone Sulfur dioxideSulfur dioxide Nitrogen dioxideNitrogen dioxide

Atmospheric CompositionAtmospheric Composition

Liquid and Solid MatterLiquid and Solid Matter

Liquid: WaterLiquid: Water < 1% by volume< 1% by volume Solids: Ice CrystalsSolids: Ice Crystals < 1% by volume< 1% by volume Particulate matterParticulate matter < 1% by volume< 1% by volume

Particulate MatterParticulate Matter

Tiny solids such as dust, smoke, soil, Tiny solids such as dust, smoke, soil, ash, salt spray, and pollutantsash, salt spray, and pollutants

May be suspended in the atmosphere May be suspended in the atmosphere for long periods of time (years)for long periods of time (years)

Most particulate matter close to Most particulate matter close to source of origin but can travel great source of origin but can travel great distances both horizontally and distances both horizontally and verticallyvertically

Affects on WeatherAffects on Weather

Hygroscopic (absorb water) so water Hygroscopic (absorb water) so water vapor condenses around particulates vapor condenses around particulates affecting cloud formationaffecting cloud formation

Absorb or reflect insolation changing Absorb or reflect insolation changing the amount of solar radiation the amount of solar radiation reaching the surfacereaching the surface

Atmospheric PressureAtmospheric Pressure

Atmosphere has weight, pressing Atmosphere has weight, pressing downwarddownward

Molecules of air create air pressure Molecules of air create air pressure through their motion, size, and through their motion, size, and numbernumber

Pressure exerted on all surfaces in Pressure exerted on all surfaces in contact with the aircontact with the air

Same pressure inside us pushing Same pressure inside us pushing outward so we are not crushedoutward so we are not crushed

More PressureMore Pressure

Average force 14.7 lb/in.Average force 14.7 lb/in.2 2

Normal pressure 1013.2 mb (29.92”)Normal pressure 1013.2 mb (29.92”) Density decreases with altitudeDensity decreases with altitude 50% of molecules are below 3.5 50% of molecules are below 3.5

miles and 90% in 10 milesmiles and 90% in 10 miles

Thermal LayersThermal Layers

TroposphereTroposphere StratosphereStratosphere MesosphereMesosphere ThermosphereThermosphere ExosphereExosphere

Layers of the AtmosphereLayers of the Atmosphere

TroposphereTroposphere

Lowest region of the atmosphereLowest region of the atmosphere Name implies vertical mixing of airName implies vertical mixing of air Usually a steady decrease in Usually a steady decrease in

temperature with an increase in temperature with an increase in altitudealtitude

3.53.5° per 1000’ (6.4°/1000m)° per 1000’ (6.4°/1000m) Lapse RateLapse Rate

InversionsInversions

Increase in air temperature with Increase in air temperature with increase in altitudeincrease in altitude

Can trap air pollutionCan trap air pollution

Tropospheric CharacteristicsTropospheric Characteristics

Most moisture and heat located hereMost moisture and heat located here Most weather occursMost weather occurs Depth an average of 11 miles from Depth an average of 11 miles from

surface at equator and 5 miles at the surface at equator and 5 miles at the polespoles

Fluctuates during seasonsFluctuates during seasons

StratosphereStratosphere

Roughly 11 miles to 31 miles above Roughly 11 miles to 31 miles above the surfacethe surface

Strong inversion exists due to Strong inversion exists due to absorption of uv radiation from the absorption of uv radiation from the Sun Sun

Contains ozone (OContains ozone (O33) layer to absorb ) layer to absorb this radiationthis radiation

Transition zone called stratopauseTransition zone called stratopause

MesosphereMesosphere

Temperature decreases with heightTemperature decreases with height Due to distance from ozone layerDue to distance from ozone layer Approximately 31 to 50 miles above Approximately 31 to 50 miles above

the Earth’s surfacethe Earth’s surface Top of layer bounded by an Top of layer bounded by an

isothermal layer called the isothermal layer called the MesopauseMesopause

ThermosphereThermosphere

Dramatic decrease in heat energy contentDramatic decrease in heat energy content BUT very high temperature (2200BUT very high temperature (2200° F)° F) Due to lack of massDue to lack of mass Approximately 50 to 300 miles above the Approximately 50 to 300 miles above the

Earth’s surface (lower in less active solar Earth’s surface (lower in less active solar activity, 155 miles) activity, 155 miles)

Isothermal layer called the ThermopauseIsothermal layer called the Thermopause

ExosphereExosphere

300 miles out to 20,000 miles from 300 miles out to 20,000 miles from the surfacethe surface

Outer spaceOuter space Atmosphere is rarefied, practically a Atmosphere is rarefied, practically a

vacuumvacuum Few hydrogen and helium atoms Few hydrogen and helium atoms

weakly bound by gravityweakly bound by gravity

What is Weather?What is Weather?

WeatherWeather

Short term atmospheric conditions that Short term atmospheric conditions that exist for a given time in a specific locationexist for a given time in a specific location

Can be sum of variables such as Can be sum of variables such as temperature, cloudiness, humidity, temperature, cloudiness, humidity, precipitation, wind, storms, and pressureprecipitation, wind, storms, and pressure

Temporal parameters can be moment, Temporal parameters can be moment, day, week, season, year, or decadeday, week, season, year, or decade

What is Climate?What is Climate?

ClimateClimate

Aggregate of day-to-day weather Aggregate of day-to-day weather conditions over a long period of timeconditions over a long period of time

Includes both average characteristics Includes both average characteristics along with the variations and along with the variations and extremesextremes

Normally 30 years for climate studiesNormally 30 years for climate studies

Major Elements of Weather and Major Elements of Weather and ClimateClimate

TemperatureTemperature PressurePressure WindWind Moisture ContentMoisture Content

Principal Climate and Weather Principal Climate and Weather ControlsControls

LatitudeLatitude Land and water distributionLand and water distribution General circulation of the General circulation of the

atmosphereatmosphere General circulation of the oceansGeneral circulation of the oceans ElevationElevation Topographic barriersTopographic barriers StormsStorms

LatitudeLatitude

Latitude influences temperature Latitude influences temperature Positional relationship between Earth Positional relationship between Earth

and Sunand Sun Varying amounts of radiant energyVarying amounts of radiant energy

Land and Water DistributionLand and Water Distribution

Moisture content and temperatureMoisture content and temperature Continental versus maritime climatesContinental versus maritime climates Oceans heat and cool slower than Oceans heat and cool slower than

landmasseslandmasses Source of moistureSource of moisture Uneven distribution of land and Uneven distribution of land and

waterwater

General Circulation of the General Circulation of the AtmosphereAtmosphere

Semipermanent pattern of wind and Semipermanent pattern of wind and pressure systems in the tropospherepressure systems in the troposphere

Local wind to regional patternsLocal wind to regional patterns Winds in the tropics from east while Winds in the tropics from east while

midlatitudes from westmidlatitudes from west

General Circulation of the General Circulation of the OceansOceans

Heat transfer with currentsHeat transfer with currents Warm water poleward and cool water Warm water poleward and cool water

towards the equatortowards the equator Warm currents off east coasts of Warm currents off east coasts of

continentscontinents Cool currents off west coasts of Cool currents off west coasts of

continentscontinents

ElevationElevation

Temperature, pressure, and moisture Temperature, pressure, and moisture content decrease with increase in content decrease with increase in elevationelevation

Influence in mountainous areasInfluence in mountainous areas

Topographic BarriersTopographic Barriers

Mountains and hills have effects on Mountains and hills have effects on climate elementsclimate elements

Lake effect snowLake effect snow Windward and leeward side of Windward and leeward side of

mountainsmountains

StormsStorms

Local thunderstormLocal thunderstorm TornadoTornado HurricaneHurricane MonsoonMonsoon BlizzardBlizzard Mid Latitude CycloneMid Latitude Cyclone

What are the Characteristics What are the Characteristics of a Thunderstorm?of a Thunderstorm?

ThunderstormsThunderstorms

Heavy rainHeavy rain LightningLightning Flash FloodingFlash Flooding HailHail WindWind TornadoesTornadoes

What is a Severe Thunderstorm?What is a Severe Thunderstorm?

Severe ThunderstormsSevere Thunderstorms

Winds > 50 kts (58 mph)Winds > 50 kts (58 mph) Hail Hail ≥ 1”≥ 1” TornadoTornado

Life CycleLife Cycle

Three Main StagesThree Main Stages InitialInitial MatureMature DissipationDissipation

Initial StageInitial Stage

Towering Cumulus StageTowering Cumulus Stage Persistent updraft and rapidly Persistent updraft and rapidly

growing vertical cloudgrowing vertical cloud Expanding cloud diameterExpanding cloud diameter

Mature StageMature Stage Updraft strength reaches maximum Updraft strength reaches maximum

heightheight Some storm tops over 25,000’-60,000’ aglSome storm tops over 25,000’-60,000’ agl Lightning at beginning of mature stageLightning at beginning of mature stage Rainfall begins and forces downdraftRainfall begins and forces downdraft MicroburstsMicrobursts HailHail Gust frontGust front Pool of cool air at surfacePool of cool air at surface

Dissipation StageDissipation Stage

Dome of cool air cuts off updraft at Dome of cool air cuts off updraft at surface and causes storm to die outsurface and causes storm to die out

Edge of dome is now in outflow Edge of dome is now in outflow boundary, potential for new boundary, potential for new thunderstorms to formthunderstorms to form

Possible tornado formation due to Possible tornado formation due to enhanced low-level horizontal shearenhanced low-level horizontal shear

Thunderstorm StagesThunderstorm Stages

Types of ThunderstormsTypes of Thunderstorms

Forms of ThunderstormsForms of Thunderstorms

Squall Line: organized line of individual Squall Line: organized line of individual cells (downbursts, straight-line winds)cells (downbursts, straight-line winds)

Multicell Cluster (MCC): strong updrafts Multicell Cluster (MCC): strong updrafts (hail, heavy precipitation); can exist for (hail, heavy precipitation); can exist for hourshours

Supercell: strong updrafts and vertical Supercell: strong updrafts and vertical wind shear (potential mesocyclones and wind shear (potential mesocyclones and tornadoes); large hail and downburststornadoes); large hail and downbursts

Supercell Supercell

Thunderstorm DistributionThunderstorm Distribution

Lightning FatalitiesLightning Fatalities

Thunderstorm Case StudiesThunderstorm Case Studies

Nashville, TennesseeNashville, Tennessee Ouachita National Forest, ArkansasOuachita National Forest, Arkansas

Nashville, TennesseeNashville, Tennessee

May 1-2, 2010May 1-2, 2010 13+” rain13+” rain 29 fatalities in southern United 29 fatalities in southern United

StatesStates http://www.srh.noaa.gov/ohx/?n=ma

y2010epicfloodevent

Ouachita National ForestOuachita National Forest

June 11, 2010June 11, 2010 5+” rain5+” rain River estimated to rise 8’/hourRiver estimated to rise 8’/hour 20 fatalities20 fatalities

TornadoesTornadoes

Rapidly rotating column of air that Rapidly rotating column of air that extends from cloudbase to ground extends from cloudbase to ground

InvisibleInvisible Primarily produced by mesocyclonesPrimarily produced by mesocyclones

Tornado LifecycleTornado Lifecycle

Dust WhirlDust Whirl OrganizingOrganizing MatureMature WeakeningWeakening RopeRope

Tornado FormationTornado Formation

Tornado DistributionTornado Distribution

Tornadoes by MonthTornadoes by Month

Tornadoes by Time of DayTornadoes by Time of Day

Enhanced Fujita Scale Enhanced Fujita Scale

F F ScaleScale

Wind SpeedWind Speed EF-EF-ScaleScale

Wind Wind SpeedSpeed

F0F0 45-7845-78 EF0EF0 65-8565-85

F1F1 79-11779-117 EF1EF1 86-10986-109

F2F2 118-161118-161 EF2EF2 110-137110-137

F3F3 162-209162-209 EF3EF3 138-167138-167

F4F4 210-261210-261 EF4EF4 168-199168-199

F5F5 262-317262-317 EF5EF5 200-234200-234Wind speeds in mph, 3-second gust

Number of Tornadoes by F-ScaleNumber of Tornadoes by F-Scale

F5 Tornadoes in the U.S.F5 Tornadoes in the U.S.

Fatalities by DecadeFatalities by Decade

Decade Tornadoes/Year Fatalities/Year

1950-59 480 148

1960-69 681 94

1970-79 858 100

1980-89 819 52

1990-99 1,220 56

2000-07 1,319 52

Note: 2000-2007 is less than a decade.

Tornado Cases StudiesTornado Cases Studies

Tristate Tornado OutbreakTristate Tornado Outbreak Xenia, OhioXenia, Ohio Moore, Oklahoma (Oklahoma City)Moore, Oklahoma (Oklahoma City)

Tristate TornadoTristate Tornado

Xenia, OhioXenia, Ohio

April 3, 1974April 3, 1974 34 fatalities34 fatalities 1150 injuries1150 injuries 2000+ homes 2000+ homes

Moore, OklahomaMoore, Oklahoma

Adjacent to Oklahoma CityAdjacent to Oklahoma City May 3, 1999May 3, 1999 38 fatalities38 fatalities 800 injuries800 injuries

Horizontal Movement of AirHorizontal Movement of Air

Wind: Horizontal movement of airWind: Horizontal movement of air Larger spatial area than vertical Larger spatial area than vertical

motionmotion ““Air in a hurry”Air in a hurry”

Ultimate Cause of Wind?Ultimate Cause of Wind?

AnswerAnswer

InsolationInsolation Unequal heating of EarthUnequal heating of Earth Temperature and pressure gradients Temperature and pressure gradients

put air in motionput air in motion Nature’s way to move air pressure to Nature’s way to move air pressure to

form an equilibriumform an equilibrium

Main Causes of Wind DirectionMain Causes of Wind Direction

Pressure GradientPressure Gradient Coriolis EffectCoriolis Effect FrictionFriction

Pressure GradientPressure Gradient

Coriolis EffectCoriolis Effect

Wind Direction VariablesWind Direction Variables

Wind DirectionWind Direction

Direction from which wind is blowingDirection from which wind is blowing Measured in degreesMeasured in degrees 00°=North°=North 90°=East90°=East 180°=South180°=South 270°=West270°=West

Wind SpeedWind Speed

Knots (1 nautical mile per hour)Knots (1 nautical mile per hour) MPH (1kt = 1.15 mph)MPH (1kt = 1.15 mph) m/s (1 kt = 0.51 m/s)m/s (1 kt = 0.51 m/s) Average wind speed in U.S. 6.9-13.8 Average wind speed in U.S. 6.9-13.8

mph mph

Wind Case StudiesWind Case Studies

Schmidlin articleSchmidlin article Santa Ana winds and wildfires in Santa Ana winds and wildfires in

CaliforniaCalifornia

FogFog

According to international definition, According to international definition, fog reduces visibility below 1 km fog reduces visibility below 1 km (0.62 miles)(0.62 miles)

Fog differs from a cloud only in that Fog differs from a cloud only in that the base of fog is at the Earth’s the base of fog is at the Earth’s surface while clouds are above the surface while clouds are above the surfacesurface

Fog FormationFog Formation

CoolingCooling Evaporation and mixingEvaporation and mixing

Major Fog TypesMajor Fog Types

RadiationRadiation AdvectionAdvection UpslopeUpslope

Types of Fog in U.S.Types of Fog in U.S.

Days with Heavy FogDays with Heavy Fog

Fog HazardsFog Hazards

Problems due to reduced visibilityProblems due to reduced visibility Transportation sector: vehicle, Transportation sector: vehicle,

maritime, and aviation accidentsmaritime, and aviation accidents Health issues: smog and acid fogHealth issues: smog and acid fog

Fog Case StudiesFog Case Studies

Maritime: Andrea Doria, 1956, 46 Maritime: Andrea Doria, 1956, 46 fatalitiesfatalities

Aviation: B-25 crash into Empire Aviation: B-25 crash into Empire State Building, 1945, 14 fatalitiesState Building, 1945, 14 fatalities

Vehicles: Calhoun, Tennessee, 1990, Vehicles: Calhoun, Tennessee, 1990, 99 vehicles, 12 deaths, 42 injuries99 vehicles, 12 deaths, 42 injuries

Fog AccidentsFog Accidents

40,000+ fog-related crashes per year40,000+ fog-related crashes per year 600 fatalities and 19,000+ injuries 600 fatalities and 19,000+ injuries

annuallyannually