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
#3 S
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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