“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Aviation WeatherAviation WeatherAviation WeatherAviation WeatherDynamically SpeakingDynamically Speaking

Written for the Notre Dame Pilot Initiative By the Pilots of the University of Notre Dame

Written for the Notre Dame Pilot Initiative By the Pilots of the University of Notre Dame

QuoteQuoteQuoteQuote

Just remember, if you crash because of weather, your funeral will be held on a sunny day. –Layton A. Bennett

Just remember, if you crash because of weather, your funeral will be held on a sunny day. –Layton A. Bennett

Lesson PlanLesson PlanLesson PlanLesson PlanWill learn

Atmosphere & Global Circulation Weather & Climate Clouds & Stability Weather Forecasting

Will be able to recite Air Mass Types Lapse Rates Stages of Thunderstorm Development Types of Fog & Clouds

Will be able to distinguish Pictures of different cloud types

Will learn Atmosphere & Global Circulation Weather & Climate Clouds & Stability Weather Forecasting

Will be able to recite Air Mass Types Lapse Rates Stages of Thunderstorm Development Types of Fog & Clouds

Will be able to distinguish Pictures of different cloud types

“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

The AtmosphereThe Atmosphere&&

Global CirculationGlobal Circulation

The AtmosphereThe Atmosphere&&

Global CirculationGlobal Circulation

Atmospheric CompositionAtmospheric CompositionAtmospheric CompositionAtmospheric Composition

Earth's atmosphere has a unique composition of gases when compared to that of the other planets in the solar system.

Earth's atmosphere has a unique composition of gases when compared to that of the other planets in the solar system.

Nitrogen78%

Oxygen21%

Argon1% Other

0%

At greater altitudes, the same volume of air contains fewer molecules of the gases that make it up. This means that the density of air decreases with increasing altitude.

At greater altitudes, the same volume of air contains fewer molecules of the gases that make it up. This means that the density of air decreases with increasing altitude.

The earth's atmosphere thins rapidly with increasing altitude and is much closer to the earth than most people realize.

The earth's atmosphere thins rapidly with increasing altitude and is much closer to the earth than most people realize.

Thermal Model of the AtmosphereThermal Model of the AtmosphereThermal Model of the AtmosphereThermal Model of the Atmosphere

Sunlight AngleSunlight AngleSunlight AngleSunlight Angle

On a global, yearly basis, the equatorial region of the earth receives more direct incoming solar radiation than the higher latitudes. As a result, average temperatures are higher in the equatorial region and decrease with latitude toward both poles. This sets the stage for worldwide patterns of prevailing winds, high and low areas of atmospheric pressure, and climatic patterns.

On a global, yearly basis, the equatorial region of the earth receives more direct incoming solar radiation than the higher latitudes. As a result, average temperatures are higher in the equatorial region and decrease with latitude toward both poles. This sets the stage for worldwide patterns of prevailing winds, high and low areas of atmospheric pressure, and climatic patterns.

Global Wind PatternsGlobal Wind PatternsGlobal Wind PatternsGlobal Wind Patterns

Hot air rises over the equator due to the fact that it is less dense.

This is called the intertropical convergence zone

This rising air cools as it rises resulting in precipitation in the region of the ITCZ.

The air then travels north and south at high altitude.

Hot air rises over the equator due to the fact that it is less dense.

This is called the intertropical convergence zone

This rising air cools as it rises resulting in precipitation in the region of the ITCZ.

The air then travels north and south at high altitude.

Global CirculationGlobal CirculationGlobal CirculationGlobal Circulation

With Globe, Coriolis Seasons – Have kid

stand on table as sun Chris Columbus -

trades With Fan,

demonstrate orthographic lifting

With Globe, Coriolis Seasons – Have kid

stand on table as sun Chris Columbus -

trades With Fan,

demonstrate orthographic lifting

Global Wind PatternsGlobal Wind PatternsGlobal Wind PatternsGlobal Wind Patterns

Hot air rises over the equator due to the fact that it is less dense.

The cooled air descends to reach the surface at about 24 ON and 24 OS of the equator.This forms a high pressure areaThe great deserts of the world are

located in this high pressure area

Hot air rises over the equator due to the fact that it is less dense.

The cooled air descends to reach the surface at about 24 ON and 24 OS of the equator.This forms a high pressure areaThe great deserts of the world are

located in this high pressure area

Coriolis EffectCoriolis EffectCoriolis EffectCoriolis Effect

An object in motion in the northern hemisphere appears to turn to the right.

An object in motion in the northern hemisphere appears to turn to the right.

An object in motion in the southern hemisphere appears to turn to the left.

An object in motion in the southern hemisphere appears to turn to the left.

Global Circ PixGlobal Circ PixGlobal Circ PixGlobal Circ Pix

Part of the generalized global circulation pattern of the earth's atmosphere. The scale of upward movement of air above the intertropical convergence zone is exaggerated for clarity. The troposphere over the equator is thicker than elsewhere, reaching a height of about 12 mi.

Part of the generalized global circulation pattern of the earth's atmosphere. The scale of upward movement of air above the intertropical convergence zone is exaggerated for clarity. The troposphere over the equator is thicker than elsewhere, reaching a height of about 12 mi.

Pressure Pressure AreasAreas

Pressure Pressure AreasAreas

Air sinks over a high-pressure center that moves away from the center on the surface, veering to the right in the Northern Hemisphere to create a clockwise circulation pattern.

Air moves toward a low-pressure center on the surface, rising over the center. As air moves toward the low-pressure center on the surface, it veers to the left in the Northern Hemisphere to create a counterclockwise circulation pattern.

Air sinks over a high-pressure center that moves away from the center on the surface, veering to the right in the Northern Hemisphere to create a clockwise circulation pattern.

Air moves toward a low-pressure center on the surface, rising over the center. As air moves toward the low-pressure center on the surface, it veers to the left in the Northern Hemisphere to create a counterclockwise circulation pattern.

“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Weather and ClimateWeather and ClimateWeather and ClimateWeather and Climate

DefinitionDefinitionDefinitionDefinition

Weather is a description of the changeable aspects of the atmosphere, the temperature, rainfall, pressure, and so forth, at a particular time. These changes usually affect your daily life one way or another, but some of them seem more inconvenient than others.

Weather is a description of the changeable aspects of the atmosphere, the temperature, rainfall, pressure, and so forth, at a particular time. These changes usually affect your daily life one way or another, but some of them seem more inconvenient than others.

Air MassesAir MassesAir MassesAir Masses

Polar air massAn air mass that moves from a cold

regionTropical Air Mass

An air mass that moves from a warm region

Continental Air MassMoves in from a land mass

Maritime Air MassMoves in from over an ocean

Polar air massAn air mass that moves from a cold

regionTropical Air Mass

An air mass that moves from a warm region

Continental Air MassMoves in from a land mass

Maritime Air MassMoves in from over an ocean

Air Mass TypesAir Mass TypesAir Mass TypesAir Mass Types

Temperature/Moisture

Hot Cold

Wet Tropical Maritime

Polar Maritime

Dry Tropical Continental

Polar Continental

Current WeatherCurrent WeatherCurrent WeatherCurrent Weather

“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Clouds and StabilityClouds and StabilityClouds and StabilityClouds and Stability

Types of CloudsTypes of CloudsTypes of CloudsTypes of Clouds

Cumulus (heaped)Stratus (layered)Cirrus (curled)Nimbus (rain)

Cumulus (heaped)Stratus (layered)Cirrus (curled)Nimbus (rain)

How a Cloud FormsHow a Cloud FormsHow a Cloud FormsHow a Cloud Forms Temperature and Dewpoint Converge Water Condenses on Particles (Dirt, Dust, Smoke) Fog is a cloud very near to the surface

Temperature and Dewpoint Converge Water Condenses on Particles (Dirt, Dust, Smoke) Fog is a cloud very near to the surface

PrecipitationPrecipitationPrecipitationPrecipitation

Precipitation is water in the liquid or solid form that returns to the surface of the earth. The precipitation you see here is liquid, and each raindrop is made from billions of the tiny droplets that make up the clouds. The tiny droplets of clouds become precipitation by merging to form larger droplets or by the growth of ice crystals that melt while falling.

Precipitation is water in the liquid or solid form that returns to the surface of the earth. The precipitation you see here is liquid, and each raindrop is made from billions of the tiny droplets that make up the clouds. The tiny droplets of clouds become precipitation by merging to form larger droplets or by the growth of ice crystals that melt while falling.

This figure compares the size of the condensation nuclei to the size of typical condensation droplets. Note that 1 micron is 1/1,000 mm.

This figure compares the size of the condensation nuclei to the size of typical condensation droplets. Note that 1 micron is 1/1,000 mm.

Condensation Nucleus (0.2 microns)

Average Cloud Droplet (20 microns)

Large Cloud Droplet (100 microns)

Drizzle Droplet (300 microns)

Average Rain Drop (2000 microns)

StabilityStabilityStabilityStability

Air may be:Unstable (vertically)

Cumulus cloudsStable (vertically)

Stratus clouds

Air may be:Unstable (vertically)

Cumulus cloudsStable (vertically)

Stratus clouds

CumulusCumulusCumulusCumulus

Fair weather

0

500

1000

1500

2000

19 21 23 25 27 T(°C)

Alti

tud

e (f

t.)

In thermal3 deg/1000 ft

Std. Conditions2 deg/1000 ft

Lapse RateLapse RateLapse RateLapse Rate

The average lapse rate (rate of cooling) is 2° C per 1,000 feet or 3.5° F per 1,000 feet

In order to calculate the base of thermal driven cumulus clouds, divide the temperature / dewpoint spread by the lapse rate (4.4 ° F per 1,000 feet )

The average lapse rate (rate of cooling) is 2° C per 1,000 feet or 3.5° F per 1,000 feet

In order to calculate the base of thermal driven cumulus clouds, divide the temperature / dewpoint spread by the lapse rate (4.4 ° F per 1,000 feet )

AltocumulusAltocumulusAltocumulusAltocumulus

Mackerel sky

Altocumulus at SunriseAltocumulus at SunriseAltocumulus at SunriseAltocumulus at Sunrise

0

2000

4000

6000

8000

10000

12000

14000

16000

0 2 4 6 8 10

T (°C)

Alt

itu

de

(ft.

)Temperature InversionTemperature InversionTemperature InversionTemperature Inversion

Fog is a cloud very near to the surfaceFog is a cloud very near to the surfaceFog is a cloud very near to the surfaceFog is a cloud very near to the surface

Types of FogTypes of FogTypes of FogTypes of FogRadiation (ground) fogAdvection fog

Requires windWarm air over cold land or water

Upslope (orographic) fogRequires wind

Steam fogLake or ocean source of waterCold air over warm water

Precipitation fog (rain fog)

Radiation (ground) fogAdvection fog

Requires windWarm air over cold land or water

Upslope (orographic) fogRequires wind

Steam fogLake or ocean source of waterCold air over warm water

Precipitation fog (rain fog)

Radiation FogRadiation FogRadiation FogRadiation Fog

From the AirFrom the AirFrom the AirFrom the Air

Advection FogAdvection FogAdvection FogAdvection Fog

Upslope FogUpslope FogUpslope FogUpslope Fog

Upslope FogUpslope FogUpslope FogUpslope Fog

Most types of fog form in stable atmospheric conditions. The exception is steam fog,shown in this picture of Maligne Lake, Alberta, Canada, just after sunrise in latesummer. The land cools off overnight while the water retains heat from the summer. Asthe cooled air slips over the lake, heat and moisture are added from below, resulting in afog that twists and writhes-- hence the term "steam fog".

Steam FogSteam FogSteam FogSteam Fog

OrchardOrchardOrchardOrchard

Fans like this one are used to mix the warmer, upper layers of air with the cooling air in the orchard on nights when frost is likely to form.

Fans like this one are used to mix the warmer, upper layers of air with the cooling air in the orchard on nights when frost is likely to form.

StratocumulusStratocumulusStratocumulusStratocumulus

Ice possible in the topsIce possible in the tops

Stratocumulus from aboveStratocumulus from aboveStratocumulus from aboveStratocumulus from above

StratocumulusStratocumulusStratocumulusStratocumulus

Red sky in the morning, sailors take warning

Red sky at night, sailors’ delight—only applies in the tropics

Red sky in the morning, sailors take warning

Red sky at night, sailors’ delight—only applies in the tropics

Types of CloudsTypes of CloudsTypes of CloudsTypes of Clouds

Cumulus (piled up)Stratus (layered)Cirrus (curled)Nimbus (rain)

Cumulus (piled up)Stratus (layered)Cirrus (curled)Nimbus (rain)

CirrusCirrusCirrusCirrus

Overrunning moistureOverrunning moisture

CirrostratusCirrostratusCirrostratusCirrostratus

Moisture increasingMoisture increasing

CirrostratusCirrostratusCirrostratusCirrostratus

Hazy circle round the moon

Means that rain is coming soon!

CirrostratusCirrostratusCirrostratusCirrostratus

Condensation Trails (Contrails)

CirrocumulusCirrocumulusCirrocumulusCirrocumulus

ThunderstormsThunderstormsThunderstormsThunderstormsThunderstorms require

Unstable air Moisture Lifting mechanism

T-storms always have lightning Thunder is the sound of lightning T-storms are reported when thunder is heard

Only true for manned observation posts Automatic Reporting (AWOS) detects lightning

discharge

Thunderstorms require Unstable air Moisture Lifting mechanism

T-storms always have lightning Thunder is the sound of lightning T-storms are reported when thunder is heard

Only true for manned observation posts Automatic Reporting (AWOS) detects lightning

discharge

Three stages in the life of a thunderstorm cell. (A) The cumulus stage begins as warm, moist air is lifted in an unstable atmosphere. All the air movement is upward in this stage.

Three stages in the life of a thunderstorm cell. (A) The cumulus stage begins as warm, moist air is lifted in an unstable atmosphere. All the air movement is upward in this stage.

(B) The mature stage begins when precipitation reaches the ground. This stage has updrafts and downdrafts side by side, which create violent turbulence.

(B) The mature stage begins when precipitation reaches the ground. This stage has updrafts and downdrafts side by side, which create violent turbulence.

(C) The final stage begins when all the updrafts have been cut off, and only downdrafts exist. This cuts off the supply of moisture, and the rain decreases as the thunderstorm dissipates. The anvil-shaped top is a characteristic sign of this stage.

(C) The final stage begins when all the updrafts have been cut off, and only downdrafts exist. This cuts off the supply of moisture, and the rain decreases as the thunderstorm dissipates. The anvil-shaped top is a characteristic sign of this stage.

LightningLightningLightningLightning

Different parts of a thunderstorm cloud develop centers of electric charge. Lightning is a giant electric spark that discharges the accumulated charges.

Different parts of a thunderstorm cloud develop centers of electric charge. Lightning is a giant electric spark that discharges the accumulated charges.

ThunderstormsThunderstormsThunderstormsThunderstorms

Types of thunderstormsAir massFrontal Upslope (orographic)

Types of thunderstormsAir massFrontal Upslope (orographic)

HailHailHailHail

These hailstones fell from a thunderstorm in Iowa, damaging automobiles, structures, and crops.

These hailstones fell from a thunderstorm in Iowa, damaging automobiles, structures, and crops.

CumulonimbusCumulonimbusCumulonimbusCumulonimbus

Distance to a Storm

Distance to a Storm

Thunderstorm

Bad IdeaBad IdeaBad IdeaBad Idea

CumulonimbusCumulonimbusFrom SpaceFrom Space

CumulonimbusCumulonimbusFrom SpaceFrom Space

Boundaries between air Boundaries between air masses = frontsmasses = fronts

Boundaries between air Boundaries between air masses = frontsmasses = fronts

ColdWarm StationaryOccluded

ColdWarm StationaryOccluded

Types of FrontsTypes of Fronts

Weather FrontsWeather FrontsWeather FrontsWeather Fronts

FrontA boundary between two different air

massesCold Front

When a cold air mass moves into a warmer area, displacing the warm air mass

Provides lift to adiabatically cool the warm air, resulting in towering cumulus and thunderclouds.

FrontA boundary between two different air

massesCold Front

When a cold air mass moves into a warmer area, displacing the warm air mass

Provides lift to adiabatically cool the warm air, resulting in towering cumulus and thunderclouds.

Cold Front PixCold Front PixCold Front PixCold Front Pix

A cold air mass is similar to a huge, flattened bubble of cold air that moves across the land. The front is the boundary between two air masses, a narrow transition zone of mixing.

A front is represented by a line on a weather map, which shows the location of the front at ground level.

A cold air mass is similar to a huge, flattened bubble of cold air that moves across the land. The front is the boundary between two air masses, a narrow transition zone of mixing.

A front is represented by a line on a weather map, which shows the location of the front at ground level.

Warm FrontWhen a warm air mass moves into an

area, displacing the cold air massA gently sloping front as the Warm air

moves over top of the cooler air.Stationary Front

When the edge of a front ceases to advance

Warm FrontWhen a warm air mass moves into an

area, displacing the cold air massA gently sloping front as the Warm air

moves over top of the cooler air.Stationary Front

When the edge of a front ceases to advance

Warm Front PixWarm Front PixWarm Front PixWarm Front Pix

An idealized warm front, showing a warm air mass overriding and pushing cold air in front of it. Notice that the overriding warm air produces a predictable sequence of clouds far in advance of the moving front.

An idealized warm front, showing a warm air mass overriding and pushing cold air in front of it. Notice that the overriding warm air produces a predictable sequence of clouds far in advance of the moving front.

Occluded FrontOccluded FrontOccluded FrontOccluded Front

One that has been lifted completely off the ground

Has a low pressure center and cyclonic activity

One that has been lifted completely off the ground

Has a low pressure center and cyclonic activity

CyclonesCyclonesCyclonesCyclones

CycloneA low pressure area with winds

moving into the low pressure area and being forced upward.

Friction and the Coriolis effect cause the air to move to the right of the direction of movement.

AnticycloneA high pressure center

CycloneA low pressure area with winds

moving into the low pressure area and being forced upward.

Friction and the Coriolis effect cause the air to move to the right of the direction of movement.

AnticycloneA high pressure center HHHH

LLLL

Hurricane JohnHurricane JohnHurricane JohnHurricane John

This is a satellite photo of hurricane John, showing the eye and counterclockwise motion

This is a satellite photo of hurricane John, showing the eye and counterclockwise motion

Storm TracksStorm TracksStorm TracksStorm Tracks

Cyclonic storms usually follow principal storm tracks across the continental United States in a generally easterly direction. This makes it possible to predict where the low-pressure storm might move next.

Cyclonic storms usually follow principal storm tracks across the continental United States in a generally easterly direction. This makes it possible to predict where the low-pressure storm might move next.

“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Weather ForecastingWeather ForecastingWeather ForecastingWeather Forecasting

Computer ModelsComputer ModelsComputer ModelsComputer Models

Weather PredictionsWeather PredictionsWeather PredictionsWeather Predictions

Weather predictions are based on information about air masses, fronts, and associated pressure systems in an area.

This information is used to produce a model of behavior for weather using a computer. Many models are used and then summarized

when the different models agree fairly closely to a model of the weather.

Weather predictions are based on information about air masses, fronts, and associated pressure systems in an area.

This information is used to produce a model of behavior for weather using a computer. Many models are used and then summarized

when the different models agree fairly closely to a model of the weather.

Surface Pressure/Precipitation PlotSurface Pressure/Precipitation Plot

PredictedPredicted

ActualActual

Forecast for todayForecast for todayForecast for todayForecast for today

SupercomputersSupercomputersSupercomputersSupercomputers

Supercomputers make routine weather forecasts possible by solving mathematical equations that describe changes in a mathematical model of the atmosphere. This "fish-eye" view was necessary to show all of this Cray supercomputer at CERN, the European Center of Particle Physics.

Supercomputers make routine weather forecasts possible by solving mathematical equations that describe changes in a mathematical model of the atmosphere. This "fish-eye" view was necessary to show all of this Cray supercomputer at CERN, the European Center of Particle Physics.

Example of Atmospheric Example of Atmospheric RReeffrraaccttiioonn

Example of Atmospheric Example of Atmospheric RReeffrraaccttiioonn

Where’s the pot of goldWhere’s the pot of gold??