MeteorologyMeteorology meteorologymeteorology = study of atmosphere = study of atmosphere1. 1. weatherweather = present state of atmosphere and describes = present state of atmosphere and describes

current conditionscurrent conditions a. caused by interaction of air, water, and solar energya. caused by interaction of air, water, and solar energy b. variation can take place over minutes, hours, days, b. variation can take place over minutes, hours, days,

weeks, or monthsweeks, or months2. 2. climateclimate = average of all weather = average of all weather

conditions of area over conditions of area over long period of timelong period of time

energy balance on Earth:energy balance on Earth:1. Earth radiates back to space about as much energy as it 1. Earth radiates back to space about as much energy as it

receives over a year’s timereceives over a year’s time2. sun feels hotter in afternoon due to rays striking Earth more 2. sun feels hotter in afternoon due to rays striking Earth more

directlydirectly3. morning and evening rays strike Earth at lower angle and 3. morning and evening rays strike Earth at lower angle and

energy is spread over larger areaenergy is spread over larger area4. solar radiation reaching poles is less intense4. solar radiation reaching poles is less intense5. tropics and other places maintain fairly constant average 5. tropics and other places maintain fairly constant average

temperatures due to heat being redistributed around the temperatures due to heat being redistributed around the worldworld

6. continual motion of air and water reallocate heat energy 6. continual motion of air and water reallocate heat energy among surface, oceans, and atmosphereamong surface, oceans, and atmosphere

air massair mass = large body of air that has same properties as = large body of air that has same properties as region over which it developsregion over which it develops

1. 1. source regionsource region = area over which an air mass forms = area over which an air mass forms2. originate in parts of world where winds are light2. originate in parts of world where winds are light3. can be several thousand kilometers in diameter and 3. can be several thousand kilometers in diameter and

several kilometers deepseveral kilometers deep4. temperature determined by whether it comes from tropics 4. temperature determined by whether it comes from tropics

or polar regionsor polar regions5. humidity determined by whether it comes from land or sea5. humidity determined by whether it comes from land or sea

6. classified according to source region6. classified according to source region a. a. “c”“c” = continental (dry) = continental (dry) b. b. “m”“m” = maritime (moist) = maritime (moist) c. c. “P”“P” = polar (cool) high latitudes = polar (cool) high latitudes d. d. “T”“T” = tropical (warm) low latitudes = tropical (warm) low latitudes e. e. “A”“A” = arctic = arctic7. weather maps use two symbols together to describe 7. weather maps use two symbols together to describe

temperature and humiditytemperature and humidityEx: mT = warm moistEx: mT = warm moist

8. five major types affect weather in United States8. five major types affect weather in United States a. a. mTmT = maritime tropical = maritime tropical 1) forms over warm waters of Gulf of Mexico and 1) forms over warm waters of Gulf of Mexico and

tropical North Atlantic Ocean tropical North Atlantic Ocean 2) holds warm, moist air2) holds warm, moist air 3) comes into U.S. from Pacific and Atlantic oceans and 3) comes into U.S. from Pacific and Atlantic oceans and

Gulf of MexicoGulf of Mexico 4) summer = hot, humid weather, thunderstorms, 4) summer = hot, humid weather, thunderstorms,

hurricanes hurricanes 5) winter = mild, often cloudy weather5) winter = mild, often cloudy weather

b. b. mPmP = maritime polar = maritime polar 1) come from cold ocean water (North Pacific Ocean)1) come from cold ocean water (North Pacific Ocean) 2) holds cold, moist air2) holds cold, moist air 3) forms over Pacific Ocean in winter and summer as well 3) forms over Pacific Ocean in winter and summer as well

as North Atlantic in summeras North Atlantic in summer 4) winter = rain and snow to Pacific Coast; summer = cool, 4) winter = rain and snow to Pacific Coast; summer = cool,

foggy weather foggy weather 5) maritime polar Atlantic = form over North Atlantic 5) maritime polar Atlantic = form over North Atlantic

OceanOcean a) winter = cold, cloudy weather and precipitationa) winter = cold, cloudy weather and precipitation b) summer = cool weather b) summer = cool weather

with low clouds and fogwith low clouds and fog 6) can produce heavy snow 6) can produce heavy snow

and cold temperaturesand cold temperatures

c. c. cTcT = continental tropical = continental tropical 1) form over the deserts of south-western U.S. and Mexico1) form over the deserts of south-western U.S. and Mexico 2) flow over North America only 2) flow over North America only

in the summerin the summer 3) brings in clear, dry and very hot weather3) brings in clear, dry and very hot weather 4) produces a warm, dry climate4) produces a warm, dry climated. d. cPcP = continental polar (Canadian) = continental polar (Canadian) 1) forms over interior of Canada and Alaska covered by ice 1) forms over interior of Canada and Alaska covered by ice and snowand snow 2) move southeastward across 2) move southeastward across Canada and into northern U.S.A.Canada and into northern U.S.A. 3) brings in cold, dry air (summer)3) brings in cold, dry air (summer) 4) during winter can produce 4) during winter can produce extremely cold temperaturesextremely cold temperatures

e. e. AA = arctic air = arctic air 1) basically same as continental polar air mass, but much 1) basically same as continental polar air mass, but much

coldercolder 2) brings most frigid outbreaks of winter2) brings most frigid outbreaks of winter 3) usually associated with very high pressure systems3) usually associated with very high pressure systems 4) develops over latitudes above 604) develops over latitudes above 60ooN in ice and snow N in ice and snow

covered regions of Siberia and Arctic Basincovered regions of Siberia and Arctic Basin 5) during winter this region receives almost no solar 5) during winter this region receives almost no solar radiation but continues to radiate heat out to space radiation but continues to radiate heat out to space causing it to be very cold areacausing it to be very cold area

9. 9. air mass modificationair mass modification = occurs when air mass starts to gain = occurs when air mass starts to gain some of characteristics of new surface beneath it some of characteristics of new surface beneath it

a. usually an exchange of heat or moisture with surface a. usually an exchange of heat or moisture with surface over which air mass travelsover which air mass travels

b. modified some as move away from source regionb. modified some as move away from source region c. eventually modified to have same characteristics as new c. eventually modified to have same characteristics as new

surface it moves oversurface it moves over

WEATHER SYSTEMSWEATHER SYSTEMSFactors responsible for air movement:Factors responsible for air movement:1. Earth’s surface is curved rather than flat1. Earth’s surface is curved rather than flat a. causes uneven heating in areas around worlda. causes uneven heating in areas around world b. equator heated more than any other place causing air to b. equator heated more than any other place causing air to

have low density and risehave low density and rise c. poles are cooler so air is more dense and sinks and c. poles are cooler so air is more dense and sinks and

moves along the surfacemoves along the surface

2. 2. Coriolis effectCoriolis effect = apparent deflection of objects (air) moving = apparent deflection of objects (air) moving across earth’s surfaceacross earth’s surface

a. caused by an apparent force that results from earth’s a. caused by an apparent force that results from earth’s eastward rotation (to the right)eastward rotation (to the right)

b. objects in Northern Hemisphere moving south would be b. objects in Northern Hemisphere moving south would be turned west (deflected right)turned west (deflected right) air movement = northeast to southwestair movement = northeast to southwest

c. objects in Southern Hemisphere are deflected to the left c. objects in Southern Hemisphere are deflected to the left air movement = southeast to air movement = southeast to

northwestnorthwest d. combines with global wind systems d. combines with global wind systems

that transport colder air to warmer that transport colder air to warmer areas and warmer air to colder areas and warmer air to colder areasareas

3. 3. convection cellsconvection cells = looping pattern of flowing air = looping pattern of flowing air a. North and Southern hemisphere each have threea. North and Southern hemisphere each have three b. form by air rising and sinking at various latitudes b. form by air rising and sinking at various latitudes across surfaceacross surface

WIND SYSTEMS:WIND SYSTEMS:Victor StarrVictor Starr (American meteorologist) = designed model of major wind (American meteorologist) = designed model of major wind

systems which suggested that major wind patterns were controlled systems which suggested that major wind patterns were controlled by combination of unequal heating and Earth’s rotationby combination of unequal heating and Earth’s rotation

windswinds = formed by the movement of air from one place to another = formed by the movement of air from one place to another1. caused by differences in temperature and pressure1. caused by differences in temperature and pressure2. named for direction from which they blow (flow)2. named for direction from which they blow (flow)

Global winds:Global winds:1. 1. doldrumsdoldrums = windless zone at equator (0 = windless zone at equator (0oo latitude) latitude) a. receives much of sun’s energya. receives much of sun’s energy b. warm air rises producing low pressure areab. warm air rises producing low pressure area c. cooler high pressure air warmed so c. cooler high pressure air warmed so rapidly that winds formed don’t reach arearapidly that winds formed don’t reach area d. any winds that form are very weakd. any winds that form are very weak

2. 2. trade windstrade winds = winds that move from north or south toward equator = winds that move from north or south toward equator a. occur usually at 30a. occur usually at 30ooN and 30N and 30ooS latitudesS latitudes 1) air sink, warms, and moves toward equator in westerly 1) air sink, warms, and moves toward equator in westerly

directiondirection 2) when air reaches equator, it will rise again and move back toward 2) when air reaches equator, it will rise again and move back toward

3030oo latitude where it sinks and process starts over latitude where it sinks and process starts over 3) 3) Northeast trade windsNortheast trade winds = in Northern Hemisphere, blow from NE to = in Northern Hemisphere, blow from NE to

SWSW 4) 4) Southeast trade winds Southeast trade winds = in Southern Hemisphere, blow from SE to = in Southern Hemisphere, blow from SE to

NWNWc. 30c. 30ooN and S latitudes are also called N and S latitudes are also called horse latitudeshorse latitudes 1) at times winds become calm stranding ships for days or weeks1) at times winds become calm stranding ships for days or weeks 2) those carrying horses began throwing them 2) those carrying horses began throwing them overboard when food supply ran outoverboard when food supply ran outd. d. convergence:convergence: 1) wind from both hemispheres move together 1) wind from both hemispheres move together

from two different directionsfrom two different directions 2) air converges, is forced upward, and creates 2) air converges, is forced upward, and creates area of low pressurearea of low pressure 3) 3) ITCZ (intertropical convergenence zone)ITCZ (intertropical convergenence zone) = large area near = large area near

equator where convergence occursequator where convergence occurs

3. 3. prevailing westerliesprevailing westerlies a. located between 30a. located between 30oo to 60 to 60oo latitudes (north and south) latitudes (north and south) 1) circulation pattern opposite of trade winds1) circulation pattern opposite of trade winds 2) surface winds move toward poles in generally easterly 2) surface winds move toward poles in generally easterly

directiondirection b. responsible for movement of weather across United b. responsible for movement of weather across United States and CanadaStates and Canada c. Northern Hemisphere = blow SW to NEc. Northern Hemisphere = blow SW to NE Southern Hemisphere = blow NW to SESouthern Hemisphere = blow NW to SE d. are often particularly strong windsd. are often particularly strong winds

4. 4. polar easterliespolar easterlies = cold, dense, horizontal air currents = cold, dense, horizontal air currents a. occurs at the 90a. occurs at the 90oo latitudes forcing air up at 60 latitudes forcing air up at 60oo latitudes latitudes b. have weak winds but provide large amounts of energy to b. have weak winds but provide large amounts of energy to westerlieswesterlies 1) strongest where flow off Antarctica1) strongest where flow off Antarctica 2) 2) polar frontpolar front = form where easterlies meet westerlies producing = form where easterlies meet westerlies producing

stormy areastormy area 3) characterized by cold air3) characterized by cold air c. causes changes in weather across United Statesc. causes changes in weather across United States d. d. subpolar lowssubpolar lows = belt of low air pressure at about 60 = belt of low air pressure at about 60ooN and 60N and 60ooS S

latitudelatitude e. Northern Hemisphere = blow e. Northern Hemisphere = blow

NE to SWNE to SW Southern Hemisphere= blow Southern Hemisphere= blow

SE to NWSE to NW

jet streamsjet streams = narrow belts of fast, high altitude, westerly winds = narrow belts of fast, high altitude, westerly winds 1. located in upper troposphere and lower stratosphere1. located in upper troposphere and lower stratosphere2. strong, high speed, high pressure air2. strong, high speed, high pressure air3. flow from west to east 3. flow from west to east 4. two in each hemisphere4. two in each hemisphere a. a. polar jet streampolar jet stream 1) separates prevailing westerlies from polar easterlies 1) separates prevailing westerlies from polar easterlies

(60(60oo latitude) latitude) 2) altitude of 10-15 km, ~100km wide, 2-3 km thick2) altitude of 10-15 km, ~100km wide, 2-3 km thick 3) maximum wind speed = ~ 500 km/hr3) maximum wind speed = ~ 500 km/hr 4) winds change speed and direction4) winds change speed and direction 5) control path of storms and 5) control path of storms and

effect airline routeseffect airline routes

b. b. subtropical jet streamsubtropical jet stream 1) separates trade winds from prevailing westerlies 1) separates trade winds from prevailing westerlies

(30(30oo latitude) latitude) 2) warm equatorial air meets cooler air of middle latitudes2) warm equatorial air meets cooler air of middle latitudes 3) do not change much in speed or position3) do not change much in speed or position5. average wind speed range = 60 km/h up to 350 km/h5. average wind speed range = 60 km/h up to 350 km/h6. tend to wander up and down as they flow around Earth6. tend to wander up and down as they flow around Earth7. wind speed, depth, positions in latitude and altitude change 7. wind speed, depth, positions in latitude and altitude change

from season to season or even day to dayfrom season to season or even day to day8. large scale weather systems generally follow path of these 8. large scale weather systems generally follow path of these

windswinds

LOCAL WINDS:LOCAL WINDS:1. breezes = gentle winds that extend over distances of less 1. breezes = gentle winds that extend over distances of less

than 100 kmthan 100 km2. 2. sea breezessea breezes = flow of air from the sea to the land = flow of air from the sea to the land a. cool, dense air from over the water flows inland and a. cool, dense air from over the water flows inland and

forces warm air over land upforces warm air over land up b. forms 3-4 hours after sunrise and peaks in early b. forms 3-4 hours after sunrise and peaks in early afternoonafternoon c. caused by the water being cooler than land during the c. caused by the water being cooler than land during the dayday d. surrounding area temperature d. surrounding area temperature

may drop by as much as may drop by as much as 55ooC within an hourC within an hour

3. 3. land breezesland breezes = flow of air from the land to the sea = flow of air from the land to the sea a. cool air from land flows over the warmer water and pushes a. cool air from land flows over the warmer water and pushes warm air over sea upwarm air over sea up b. occurs at night because land loses its heat to the b. occurs at night because land loses its heat to the

atmosphere while water retains its heatatmosphere while water retains its heat c. starts to form in late evening and peaks near sunrisec. starts to form in late evening and peaks near sunrise

4. 4. valley breezevalley breeze = flow of air up the = flow of air up the slopes of mountains slopes of mountains

a. occurs during the daya. occurs during the day b. caused by warm air from valleysb. caused by warm air from valleys moving up slopemoving up slope5. 5. mountain breezemountain breeze = flow of air from = flow of air from

mountain peaks to valley mountain peaks to valley a. occurs during the nighta. occurs during the night b. mountains cool more quickly b. mountains cool more quickly 6. 6. monsoonmonsoon = seasonal winds = seasonal winds a. part of the year it blows from a. part of the year it blows from the land to the ocean the land to the ocean →→ winter winter usuallyusually b. part of the year it blows from the b. part of the year it blows from the ocean to the land ocean to the land →→ summer usually summer usually c. summer monsoon causes rainy c. summer monsoon causes rainy season with warm temperatures and season with warm temperatures and huge amounts of rainhuge amounts of rain

frontfront = boundary formed between two air masses that have = boundary formed between two air masses that have collidedcollided

1. area where temperatures and humidities change1. area where temperatures and humidities change2. greater the difference between air masses, greater the 2. greater the difference between air masses, greater the

change in weatherchange in weather3. can stretch over thousands of km across Earth’s surface3. can stretch over thousands of km across Earth’s surface4. interaction between colliding air masses can cause dramatic 4. interaction between colliding air masses can cause dramatic

changes in weatherchanges in weather

Four Types of FrontsFour Types of Fronts1. 1. warm frontwarm front = warm air is pushing ahead and = warm air is pushing ahead and

displacing colder airdisplacing colder air a. lighter warm air slides over heavier cold aira. lighter warm air slides over heavier cold air b. presence of high cirrus cloudsb. presence of high cirrus clouds c. stratus clouds form as front continues c. stratus clouds form as front continues to move into an areato move into an area d. may produce precipitation over a d. may produce precipitation over a large area (rain, snow, sleet, or freezing rain)large area (rain, snow, sleet, or freezing rain) e. weather map symbol = e. weather map symbol =

2. 2. cold frontcold front = cold air is advancing and displacing warmer air = cold air is advancing and displacing warmer air a. heavier, cold air is shoving under warm air, pushing it a. heavier, cold air is shoving under warm air, pushing it upward rapidlyupward rapidly b. cumulus and cumulonimbus clouds formb. cumulus and cumulonimbus clouds form c. produces rain and thunderstorms that can be violentc. produces rain and thunderstorms that can be violent d. d. squall linesquall line = long line of heavy thunderstorms just ahead = long line of heavy thunderstorms just ahead

of frontof front e. fair, cool weather usually followse. fair, cool weather usually follows f. weather map symbol = f. weather map symbol =

3. 3. stationary frontstationary front = two air masses collide and neither can = two air masses collide and neither can advance the other advance the other

a. front does not move; boundary between air masses stallsa. front does not move; boundary between air masses stalls b. pressure differences cause warm front or cold front to b. pressure differences cause warm front or cold front to stop moving forwardstop moving forward c. usually remains for several daysc. usually remains for several days d. widespread clouds can form on both sides of frontal d. widespread clouds can form on both sides of frontal boundaryboundary e. light winds and precipitation may occur across entire e. light winds and precipitation may occur across entire frontal regionfrontal region f. weather map symbol = f. weather map symbol =

4. 4. occluded frontsoccluded fronts = created when cold, warm, and cool air = created when cold, warm, and cool air come in conflictcome in conflict

a. two cooler air masses merge, forcing warm air between a. two cooler air masses merge, forcing warm air between them to risethem to rise

b. often called b. often called occlusionsocclusions c. two types:c. two types: 1) 1) cold occlusioncold occlusion = cold air is shoving under cool air at = cold air is shoving under cool air at

Earth’s surfaceEarth’s surface 2) 2) warm occlusionwarm occlusion = cool air rises over cold air at the = cool air rises over cold air at the

surfacesurface d. usually see strong winds and heavy precipitationd. usually see strong winds and heavy precipitation e. weather map symbol = e. weather map symbol =

5. 5. polar frontpolar front = boundary where cold polar air meets = boundary where cold polar air meets warmer air of middle latitudes warmer air of middle latitudes

a. circle between 40a. circle between 40oo and 60 and 60oo latitudes N and S latitudes N and S b. winter - average position is across middle of U.S.b. winter - average position is across middle of U.S. c. summer - north of Great Lakesc. summer - north of Great Lakes d. d. wavewave = bend formed in a cold or stationary front = bend formed in a cold or stationary front

Pressure Systems:Pressure Systems:high pressurehigh pressure = form when air is cooled = form when air is cooled1. air molecules more densely packed1. air molecules more densely packed2. result of cold, dense air that is sinking and spreads outward 2. result of cold, dense air that is sinking and spreads outward

from centers when reach Earthfrom centers when reach Earth3. warming of air decreases its relative humidity and water 3. warming of air decreases its relative humidity and water

vapor is evaporatedvapor is evaporated4. Northern Hemisphere 4. Northern Hemisphere →→ rotates clockwise; Southern rotates clockwise; Southern

Hemisphere counterclockwiseHemisphere counterclockwise5. usually means clear weather5. usually means clear weather6. weather map symbol = 6. weather map symbol = HH

low pressurelow pressure = form when air is warmed and rises = form when air is warmed and rises1. molecules farther apart 1. molecules farther apart →→ less dense less dense →→ rises rises2. rising air must be replaced by air from outside system, so net 2. rising air must be replaced by air from outside system, so net

flow is toward center and upwardflow is toward center and upward3. forms along fronts where warm air meets cold air3. forms along fronts where warm air meets cold air4. Northern hemisphere counterclockwise; Southern 4. Northern hemisphere counterclockwise; Southern

hemisphere clockwisehemisphere clockwise5. cause most of weather changes across United States5. cause most of weather changes across United States6. associated with clouds and precipitation6. associated with clouds and precipitation7. weather map symbol = 7. weather map symbol = LL

8. 8. wave cyclonewave cyclone = specific type of low pressure system = specific type of low pressure system a. main producers of inclement weather in middle latitudesa. main producers of inclement weather in middle latitudes b. usually begins along stationary frontb. usually begins along stationary front c. part of front moves south as cold front and another part c. part of front moves south as cold front and another part moves north as warm frontmoves north as warm front d. sets up counterclockwise circulationd. sets up counterclockwise circulation* Air moves from an area of high pressure to one of low * Air moves from an area of high pressure to one of low

pressure.pressure.

GATHERING WEATHER DATA:GATHERING WEATHER DATA:thermometerthermometer = used to measure temperature = used to measure temperature1. 1. bimetal thermometerbimetal thermometer = bar made of two strips of different = bar made of two strips of different

types of metals types of metals a. curve when heata. curve when heat b. straighten when cooledb. straighten when cooled2. 2. thermographthermograph = measures temperature change by recording = measures temperature change by recording

movement of bar movement of bar3. electrical thermometer3. electrical thermometer a. as temperature rises, electric current flow increasesa. as temperature rises, electric current flow increases b. current flow translated into temperature readingsb. current flow translated into temperature readings

barometerbarometer = instrument measures atmospheric pressure = instrument measures atmospheric pressure1. 1. mercurial barometermercurial barometer = uses mercury to determine = uses mercury to determine

atmospheric pressureatmospheric pressure a. pressure presses on liquid Hg in well at basea. pressure presses on liquid Hg in well at base b. squeezes Hg up to certain height in tubeb. squeezes Hg up to certain height in tube c. height varies with pressurec. height varies with pressure d. expressed by how high Hg rises in tubed. expressed by how high Hg rises in tube e. e. standard atmospheric pressurestandard atmospheric pressure = 760 mm = 760 mm 1) indicates average atmospheric pressure at sea level1) indicates average atmospheric pressure at sea level 2) 760 mm or 29.92 inches of Hg = 2) 760 mm or 29.92 inches of Hg =

one atmosphereone atmosphere f. f. millibarsmillibars(mb)) - used on weather maps(mb)) - used on weather maps

1 mb = 0.001 standard 1 mb = 0.001 standard atmospheric pressureatmospheric pressure

2. 2. aneroid barometeraneroid barometer = works without liquid = works without liquid a. most common type used todaya. most common type used today b. seal metal container from which air has been removedb. seal metal container from which air has been removed 1) pressure decreases 1) pressure decreases →→ sides bulge out sides bulge out 2) pressure increases 2) pressure increases →→ sides bend inward sides bend inward c. shown by pointer on a scalec. shown by pointer on a scale d. usually marked in mm (inches of Hg) or mbd. usually marked in mm (inches of Hg) or mb e. e. altimeteraltimeter = barometer used to measure altitude above sea = barometer used to measure altitude above sea

level level 1) lowered pressure reading interpreted1) lowered pressure reading interpreted

as increased altitudeas increased altitude 2) must be corrected for local weather 2) must be corrected for local weather

conditions to be accurateconditions to be accurate

anemometeranemometer = used to measure wind speed = used to measure wind speed1. expressed as meters/second, miles/hour, or knots1. expressed as meters/second, miles/hour, or knots2. one knot = 1850 m/s2. one knot = 1850 m/s

wind vanewind vane = used to determine the direction of the wind on = used to determine the direction of the wind on Earth’s surfaceEarth’s surface

* points into the wind* points into the wind

hygrometershygrometers = used to measure relative humidity = used to measure relative humidity1. 1. psychrometerpsychrometer = works on principle that evaporation causes = works on principle that evaporation causes

coolingcooling a. wet bulb thermometer has a water soaked wick wrapped a. wet bulb thermometer has a water soaked wick wrapped

around its bulbaround its bulb b. other is a dry bulb thermometerb. other is a dry bulb thermometer c. wet bulb usually shows a lower temperaturec. wet bulb usually shows a lower temperature d. readings give signs of how dry the air isd. readings give signs of how dry the air is e. difference between wet bulb and dry bulb is used to e. difference between wet bulb and dry bulb is used to

determine RH by using a chartdetermine RH by using a chart f. when both thermometers read the same the air is f. when both thermometers read the same the air is

saturatedsaturated

2. 2. hair hygrometerhair hygrometer = based on principle that human = based on principle that human hair stretches when it is humid hair stretches when it is humid

a. one end of a bundle of hair is fixed while a. one end of a bundle of hair is fixed while the other is attached to pointerthe other is attached to pointer

b. when air is humid b. when air is humid →→ stretches; when air is dry stretches; when air is dry →→ shrinks backshrinks back

Measuring Precipitation:Measuring Precipitation:1. 1. rain gaugerain gauge = measure amount of rainfall = measure amount of rainfall a. measure in inchesa. measure in inches b. measure only precipitation that falls in one spotb. measure only precipitation that falls in one spot c. represents depth of water that rain would leave c. represents depth of water that rain would leave if it did not soak into ground, flow away, or evaporateif it did not soak into ground, flow away, or evaporate d. types varyd. types vary 1) wide mouth funnel over cylindrical container1) wide mouth funnel over cylindrical container 2) funnel and small divided bucket2) funnel and small divided bucket 3) water caught in large bucket and weighed continuously3) water caught in large bucket and weighed continuously

2. 2. measuring stickmeasuring stick = measure amount of snowfall = measure amount of snowfall a. snow is measure by both depth of accumulation and a. snow is measure by both depth of accumulation and

water contentwater content b. measured in inches and tenths of an inchb. measured in inches and tenths of an inch c. on average, 10 inches of snow equals 1 inch of rainc. on average, 10 inches of snow equals 1 inch of rain d. dry snows are deeper than equal weights of wet snowd. dry snows are deeper than equal weights of wet snow

Automated Surface Observing SystemAutomated Surface Observing System (ASOS) = collects (ASOS) = collects multiple data at regular intervalsmultiple data at regular intervals

1. 1. ceilometerceilometer = measures height of cloud layers and estimates = measures height of cloud layers and estimates amount of sky covered by cloudsamount of sky covered by clouds

2. continuously record air pressure, temperature, wind speed 2. continuously record air pressure, temperature, wind speed and direction, runway visibility, cloud ceiling, and precipitation and direction, runway visibility, cloud ceiling, and precipitation intensityintensity

3. many units being used at major airports3. many units being used at major airports

Upper Level Data:Upper Level Data:1. 1. radiosonderadiosonde = balloon borne package of sensors = balloon borne package of sensors

for measuring at high altitudesfor measuring at high altitudes a. measure temperature, air pressure, and humiditya. measure temperature, air pressure, and humidity b. readings sent back by radio signal to ground station that b. readings sent back by radio signal to ground station that

tracks movement of balloontracks movement of balloon c. can determine wind speed and direction by tracking how c. can determine wind speed and direction by tracking how fast and in what direction balloon is movingfast and in what direction balloon is moving

2. 2. weather radarweather radar = used to locate areas of rain = used to locate areas of rain

a. waves are reflected from precipitation particlesa. waves are reflected from precipitation particles

b. screen shows location and shape of precipitation b. screen shows location and shape of precipitation areasareas

c. also gives a rough idea of how heavy precipitation isc. also gives a rough idea of how heavy precipitation is

3. 3. Doppler radarDoppler radar = used to determine movement of weather = used to determine movement of weather systemsystem

a. provides good estimates of wind speeds in a. provides good estimates of wind speeds in precipitation areasprecipitation areas b. show echoes with more detailb. show echoes with more detail c. can also show wind directionc. can also show wind direction d. echoes and winds show up on color screend. echoes and winds show up on color screen 1) different echo strengths or wind speeds show up as 1) different echo strengths or wind speeds show up as

different colors different colors 2) makes it easier to spot strong thunderstorms and even 2) makes it easier to spot strong thunderstorms and even

tornadoestornadoes

4. 4. weather satellitesweather satellites = observes weather that is missing by = observes weather that is missing by computer models and local weather computer models and local weather

a. observations track clouds but not necessarily a. observations track clouds but not necessarily precipitationprecipitation

b. provides continuous pictures of cloudsb. provides continuous pictures of clouds c. make it possible to track lows, hurricanes, and c. make it possible to track lows, hurricanes, and

thunderstormsthunderstorms d. can see nearly half of Earth’s surfaced. can see nearly half of Earth’s surface e. every 30 minutes its television cameras take infrared e. every 30 minutes its television cameras take infrared

as well as visible picturesas well as visible pictures

WEAHTER ANALYSIS/ FORECASTINGWEAHTER ANALYSIS/ FORECASTINGforecastforecast = prediction of future weather conditions = prediction of future weather conditions

- most are made for periods of a few hours up to 5 days- most are made for periods of a few hours up to 5 days

meteorologistmeteorologist = person who studies weather = person who studies weather1. make measurements of temperature, air pressure, winds, 1. make measurements of temperature, air pressure, winds,

humidity, and precipitationhumidity, and precipitation2. gather data using radar, computers, and instruments 2. gather data using radar, computers, and instruments

attached to balloonsattached to balloons3. interpret information from local weather observers, balloons, 3. interpret information from local weather observers, balloons,

satellites, and weather stations around worldsatellites, and weather stations around world

weather mapweather map = collection of weather data from many = collection of weather data from many collecting stationscollecting stations

surface weather mapsurface weather map = essential in following rapidly = essential in following rapidly changing weather or in compensating for poor computer changing weather or in compensating for poor computer model forecastsmodel forecasts

1. data is taken hourly at stations all over the world1. data is taken hourly at stations all over the world2. United States has about 700 National Weather Service 2. United States has about 700 National Weather Service

stationsstations3. official U.S. weather maps are made every 3 hours 3. official U.S. weather maps are made every 3 hours

(made at the National Meteorological Center in Camp (made at the National Meteorological Center in Camp Springs, Maryland)Springs, Maryland)

station modelstation model = symbol that describes local weather of = symbol that describes local weather of collecting station collecting station

1. where possible direct readings are given1. where possible direct readings are given2. in other cases, codes are used2. in other cases, codes are used3. models and codes are determined 3. models and codes are determined by World Meteorological Organizationby World Meteorological Organization4. show various measurements4. show various measurements a. wind direction and speeda. wind direction and speed 1) shown by a line attached to circle 1) shown by a line attached to circle 2) direction line points is from 2) direction line points is from which wind is blowingwhich wind is blowing 3) small lines at end of the line are 3) small lines at end of the line are used to indicated wind speedused to indicated wind speed b. cloud cover shown by circleb. cloud cover shown by circle c. other data includes atmospheric pressure, temperature, c. other data includes atmospheric pressure, temperature, dew point, types of precipitation, types of clouds, and dew point, types of precipitation, types of clouds, and change in barometric pressurechange in barometric pressure

isoplethsisopleths = lines that connect points of equal or constant values = lines that connect points of equal or constant values1. can represent different weather variables1. can represent different weather variables2. 2. isothermisotherm = lines that connect locations with same = lines that connect locations with same

temperature on weather maptemperature on weather map- number on end of line indicates temperature at all points - number on end of line indicates temperature at all points along linealong line

3. 3. isobarsisobars = lines that connect locations with the same air = lines that connect locations with the same air pressure on a weather mappressure on a weather map

a. number at end of line represents air pressure at each a. number at end of line represents air pressure at each location on linelocation on line

b. can be given in millibars or inches of mercuryb. can be given in millibars or inches of mercury c. indicates the locations of highs or lowsc. indicates the locations of highs or lows d. if close together d. if close together →→ great pressure difference over great pressure difference over

small area small area →→ strong winds strong winds e. if spread apart e. if spread apart →→ less difference less difference →→ gentle windsgentle winds

TYPES OF FORECASTSTYPES OF FORECASTSSHORT-TERM:SHORT-TERM:1. 1. dailydaily = predict weather conditions for 48 hour period = predict weather conditions for 48 hour period2. 2. digital forecastingdigital forecasting = relies on numerical data from computer = relies on numerical data from computer

calculations calculations a. main method used by modern meteorologistsa. main method used by modern meteorologists b. highly dependent on density of data available (more data, b. highly dependent on density of data available (more data,

more accurate forecast)more accurate forecast)3. most accurate and detailed forecasts; can be made for 3 to 5 3. most accurate and detailed forecasts; can be made for 3 to 5

daysdays4. accuracy decreases with each additional day4. accuracy decreases with each additional day

LONG-TERM:LONG-TERM: 1. 1. long-rangelong-range = cover monthly and seasonal outlooks = cover monthly and seasonal outlooks2. 2. extendedextended = up to 6 to 10 days = up to 6 to 10 days3. 3. analog forecastsanalog forecasts = compares current weather patterns to = compares current weather patterns to

patterns that took place in past patterns that took place in past a. uses assumption that weather systems behave in similar a. uses assumption that weather systems behave in similar

fashionfashion b. also look for patterns that are analogous to current b. also look for patterns that are analogous to current

patternspatterns c. to be accurate past event must be similar through all c. to be accurate past event must be similar through all

levels of atmosphere and over large arealevels of atmosphere and over large area d. used for monthly or seasonal forecastsd. used for monthly or seasonal forecasts4. 4. computer modelcomputer model = copy of atmosphere in computer = copy of atmosphere in computer a. contains data on wind, temperature, pressure, humidity, a. contains data on wind, temperature, pressure, humidity,

clouds, and precipitationclouds, and precipitation b. can predict future weather patternsb. can predict future weather patterns5. now better than human forecasters at predicting movements 5. now better than human forecasters at predicting movements

and strengths of highs and lowsand strengths of highs and lows