Air Mass, Wind, and Air Mass, Wind, and Weather SystemsWeather Systems

Sixth GradeSixth Grade

GPS Earth ScienceGPS Earth SciencePam MyersPam Myers

Quick ReviewQuick ReviewWhat causes wind?Answer: UNEVEN HEATING OF THE EARTH BY THE SUN.

Air MassesA large body of air that has nearly the same temperature, humidity & air pressure throughoutThey have similar properties as the part of the earth’s surface over which they form

                                          

Why are Air Masses important?Why are Air Masses important?

They • can cover an area of thousands of square kilometers. • are responsible for day to day weather changes.• Move/change – so does weather in area over area over

which it moves.

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Which Way Do The Winds Blow?Which Way Do The Winds Blow?

From ___________ pressure to _____ pressure.From ___________ pressure to _____ pressure.high low

Do you know what instrument we use to measure air pressure?

A Barometer

Quick ReviewQuick Review

Is hot air high pressure or low pressure? Answer: LOW PRESSURE means it rises, and it holds more moisture than cold air

WEATHER SYSTEMS

What is a FrontFront??

• boundary between two air masses of – different density– moisture– temperature

• Four types of fronts; can you name them??

_____________, ___________________________, ______________

_____________, and _______________________________, and __________________

Warm frontCold front

Occluded front Stationary front

Precipitation Along a Cold Front lifting the warm moist air ahead of it

Precipitation Along a Warm Front warm moist air overriding colder air

Quick ReviewQuick Review

Is cold air high pressure or low pressure? Answer:

HIGH PRESSURE means it sinks, and it holds less moisture than cold

air

Cool, dryAir mass …

…butts against an equally strong mass of warm, humid air.

Stationary front

Warm AirCool Air

Battle for control ends with no winners; front moves little.

#1 Cold Front

#2 Warm Front

#4 Occluded Front

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Quick ReviewQuick Review

Which type of air rises? Which one sinks?

Answer: HOT AIR (LOW PRESSURE) rises,

and cold air (high pressure) sinks.

What information do you need to know to forecast What information do you need to know to forecast weather?? weather?? TemperatureTemperatureWindsWindsAir pressureAir pressureHumidityHumidityPrecipitationPrecipitation

RainFROZEN

PRECIPITATION MELTS AND

REACHES THE GROUND AS

RAIN.

Freezing RainFROZEN

PRECIPITATION MELTS IN WARM AIR.

RAIN FALLS AND FREEZES ON COLD

SURFACE

SleetFROZEN

PRECIPITATION MELTS IN SHALLOW

WARM AIR. THEN REFREEZES BEFORE

REACHING THE GROUND.

SnowPRECIPITATION

FALLS THROUGH

COLD AIR AND REACHES THE

SURFACE.

So What is a So What is a HailstoneHailstone??

begins as frozen raindrop or begins as frozen raindrop or ice crystalice crystal

– Travels through different Travels through different levels of storm cloudlevels of storm cloud

– Strong warm air updrafts & Strong warm air updrafts & cool air downdrafts cool air downdrafts

– move frozen particles up & move frozen particles up & downdown

So What is a So What is a HailstoneHailstone?? encounters different encounters different

forms of moistureforms of moisture layers of frozen ice layers of frozen ice

particles accumulate on particles accumulate on surfacesurface

The resulting hailstone The resulting hailstone has a layered structurehas a layered structure

http://www.classzone.com/http://www.classzone.com/books/earth_science/terc/books/earth_science/terc/content/visualizations/content/visualizations/es1805/es1805page01.cfm?es1805/es1805page01.cfm?chapter_no=visualizationchapter_no=visualization

Quick ReviewQuick Review

What about cold air? Is it high pressure or low pressure?

Answer: HIGH PRESSURE means HIGH density, HIGH

pressure, it sinks, and

it does not hold much moisture

Do you know the scientific name for Do you know the scientific name for a weather forecaster?a weather forecaster?

A A MeteorologistMeteorologist

measuremeasure temperature, air pressure, winds, temperature, air pressure, winds, humidity, and precipitation.humidity, and precipitation.

Tools Tools Doppler radar, satellites, instruments Doppler radar, satellites, instruments attached to balloonsattached to balloons

gathergather information from Earth’s upper information from Earth’s upper atmosphere and the surfaceatmosphere and the surface

A weather map showssurface-pressure systems, air masses, fronts(GREEN-SHADED AREA REPRESENTS PRECIPITATION)

isobars (millibars): SOLID GRAY LINES. LARGE ARROWS IN COLOR SHOW AIR FLOW. (GREEN-SHADED AREA REPRESENTS PRECIPITATION.)

Isotherms: SIMILAR TO ISOBARS, EXCEPT THEY SHOW TEMPERATURE (NOT SHOWN HERE)

ReferencesReferences

Glencoe ScienceGlencoe Science http://www.nhc.noaa.gov/aboutsshs.shtmlhttp://www.nhc.noaa.gov/aboutsshs.shtml http://www.spc.noaa.gov/faq/tornado/f-scale.htmlhttp://www.spc.noaa.gov/faq/tornado/f-scale.html