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Weather. Click HERE for Discovery Channel Guide to Extreme Weather (50 min). Weather -It’s what’s happening outside NOW!. Weather. All weather is a result of humidity, condensation and pressure. Water Cycle. Humidity—Water Vapor in the Air.

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weather
Weather

All weather is a result of humidity, condensation and pressure.

humidity water vapor in the air
Humidity—Water Vapor in the Air
  • Specific humidity: actual amount of water vapor in the air at a given time & place (grams of vapor per kilogram of air)
  • Warmer air can hold more water vapor
humidity
Humidity

Relative humidity: how close the air is to reaching its maximum capacity of water vapor

  • expressed as a percentage
  • 100% means it has reached maximum capacity
humidity1
Humidity

Measured with a psychrometer

A psychrometer has two thermometers to determine humidity. The dry bulb thermometer measures the room temperature, and wet bulb thermometer is wrapped in a wet cloth. Air is passed through the psychrometer to evaporate moisture on the wet bulb. The readings on the dry bulb thermometer and the wet bulb thermometer are then compared to determine the actual humidity.

condensation
Condensation

When water changes from a gas to a liquid

  • Dew point: the temperature at which the air becomes saturated with water vapor & condensation occurs
  • If air cools below the dew point, water starts condensing into a liquid, forming dew or cloud droplets
condensation1
Condensation
  • Fog & clouds form only when there are condensation nuclei (like dust particles) for the water to condense on
  • Air must cool below its dew point
slide16

Smog over LA

from car exhaust

cloud formation
Cloud Formation
  • When warm, wet air from the surface rises, it begins to cool. Eventually, the temperature drops to its dew point, and the water vapor can condense onto the condensation nuclei
  • Condensation level: the atmospheric level at which condensation occurs
warm air rises taking the water vapor along with it once it cools it condenses forming a cloud
Warm air rises taking the water vapor along with it. Once it cools, it condenses forming a cloud.
cloud types
Cloud Types

Classified by altitudeand shape

cloud types1
Cloud Types

Stratus: clouds that form inlayers

Cirrus: high,featheryice clouds

Cumulus: fluffyclouds with flat bases

Nimbus: darkrainclouds

precipitation
Precipitation

Any form of water that falls from a cloud to Earth’s surface

types of precipitation
Types of Precipitation
  • Rain
  • Snow
  • Sleet: raindrops that refroze on their way to the surface
  • Freezing Rain: raindrops that only freeze when they hit the surface
  • Hail: when frozen raindrops are bounced up & down in the cloud until they fall in a huge ball of ice
types of precipitation1
Types of Precipitation

depend on the temperature of the atmosphere, both at the surface & on the way down

snow

sleet

freezing rain

measuring precipitation
Measuring Precipitation
  • Rain gauge: measures liquid precipitation
  • Measuring stick: measures frozen precipitation
where is precipitation1
Where is Precipitation?

Rain Shadow effect: near a mountain range, the windward side gets lots of rain and the leeward side gets little/no rain – the rain shadow

extreme weather 1 minute video
Extreme Weather1 minute video
  • http://science.discovery.com/videos/against-the-elements-mashups-devastating-winds.html
air mass
Air Mass
  • A large body of air in the lower troposphere that has similar characteristics throughout
  • Temperature & humidity depend on origin and move with the air mass
types of air masses
Types of Air Masses

Continental: dryPolar: cold

Maritime: wetTropical: warm

  • Continental polar (cP): cold & dry
  • Maritime polar (mP): cold & wet
  • Continental tropical (cT): warm & dry
  • Maritime tropical (mT): warm & wet
fronts
Fronts
  • Cold Front: boundary between advancing cold air mass & a warmer air mass it is displacing
    • Rising warm air usually produces precipitation if wet
    • Air becomes colder after front passes
fronts1
Fronts
  • Warm Front: boundary between advancing hot air mass & a colder air mass it is displacing
    • 1st clouds days in advance, then RAIN
    • Air becomes warmer after front passes
fronts2
Fronts
  • Occluded Front: when cold front ‘catches up’ to a warm front, producing clouds & precipitation
fronts3
Fronts

Stationary front: when a front stops moving forward, producing clouds & precipitation – causes floods if stationary too long

locating a front
Locating a Front
  • Wind direction changes
  • Temperature changes sharply
  • Dew Point changes sharply
weather forecasting
Weather Forecasting
  • Satellites
  • Radiosondes
  • Surface observations
forecasting
Forecasting
  • Computer models take current data & plug it into equations to predict weather
  • Meteorologists take computer models & tweak them to fit their experience with local conditions
forecasting1
Forecasting

Trend Method: using past movement of a front & precipitation to predict future movement

bibliography
Bibliography
  • http://www.eas.slu.edu/People/CEGraves/Eas107/mteffect1.jpg
  • http://www.auxonline.org/~futureweb/Weather/Aviation_weather/Wx_symbols/front_symbols.gif
  • http://cimss.ssec.wisc.edu/wxwise/station/station.gif
  • http://antwrp.gsfc.nasa.gov/apod/image/0409/frances2_noaa_big.jpg
  • http://www.librarypreservation.org/management_and_planning/monitors3b.htm
  • http://www.photolib.noaa.gov/historic/nws/wea02047.htm
  • http://www.ashcreekimages.com/Cloudscape5.html
  • http://www.capetownskies.com/6027/may_jun03.htm
  • http://met.no/met/met_lex/l_p/nimbostratus_bilder/image002.jpg
  • http://www.weatherstock.com/cloudcat3.html
  • http://www.srh.weather.gov/srh/jetstream/synoptic/precip.htm
  • http://www.accessnoaa.noaa.gov/aug0701/oncamera.html
  • http://www.clas.ufl.edu/users/emartin/GLY3074S03/images/atmcirccells.jpg
  • http://rst.gsfc.nasa.gov/Sect14/airmasses_schem.jpg
  • http://fcgov.com/oem/oem-images/cold-front.jpg
  • http://www.metoffice.com/education/curriculum/lesson_plans/weathersystems/partb.html
  • http://geography.radley.org.uk/metlink/ppt/depression/HTML/sld001.htm
  • http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/tstorm/occl_front.html
  • http://members.aol.com/pakulda/stpptnts.htm
  • http://www.wrh.noaa.gov/fgz/science/svrwx.php?wfo=fgz
  • http://www.econet.org.uk/weather/tornad.html
  • http://www.tnema.org/images/Misc/TORN1.jpg
  • http://www.nhoem.state.nh.us/mitigation/Hurricane%20Structure%20Graphic.gif
  • http://www.estatevaults.com/bol/images/%20%20Boston%20Blizzard.jpg
  • http://www1.ncdc.noaa.gov/pub/data/images/blizzard-midwest-19990102-g8ir.gif
  • http://www.erh.noaa.gov/buf/neaster.jpg
  • http://www.chincoteaguechamber.com/62-poling.jpg
  • http://www.iac.ethz.ch/en/groups/richner/cd/doc/radiosonde/images/sonde.jpg
  • http://www.msc.ec.gc.ca/education/teachers_guides/module08_image_files/stn_model.gif
  • http://66.208.12.20/amsedu/dstreme/images/sfc_map_12.gif
  • http://ngwww.ucar.edu/ncl/images/climate.gif
  • http://www.hprcc.unl.edu/nebraska/september30-2004YearTDataUS.png
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