Oceanography Notes Midterm Corrections

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  Lines of latitude measure north-south with respect to the equator
  
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  Old, cold oceanic lithosphere more dense than:
  
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    underlying warm aesthenosphere
    
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    continental lithosphere
    
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    younger oceanic lithosphere
    
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  Continental Margin order: Shelf, Slope, Rise
  
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  Oceanic crust floats lower on mantle because it is denser
  
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  Free oxygen produced by photosynthesis
  
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  Evaporation is a warming process
  

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  atmosphere and ocean interdependent
  
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  surface currents correlate with wind belts
  
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  interchangeable results b/w ocean/atmos
  
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  radiant energy from sun responsible for motion in atmos and ocean
  
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  ecliptic: the plane traced by earth’s orbit
  
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  earth tilts at 23.5%
  
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  earth axis is always pointing in same direction, toward Polaris [N Star]
  
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    -causes seasons
    
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  vernal equinox: occur about 21 March, sun directly overhead along equator.
  
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    -during this, all placed on earth experience same length night and day
    
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    -N hemis, this is spring
    
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  summer solstice: june 21. sun at most northerly point in sky, directly above tropic of cancer
  
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    -at noon this day, sun seems to pause in sky.
    
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  Tropic of cancer: 23.5 degrees N lat
  
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  Autumnal equinox: sept 23. sun directly overhead along eq again.
  
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    -also known as fall equinox in N hemis.
    
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  winter solstice: dec 22. directly overhead at tropic of Capricorn
  
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    -S hemis seasons reversed, this is when S hemis most directly facing sun. This is beginning of S hemis summer.
    
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  tropic of Capricorn: 23.5 degrees S lat
  
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  declination: angular distance from equatorial plane
  
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    -sun’s declination varies b/w 23.5 degrees N and S lats on yearly cycle
    
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  tropics: region b/w Capricorn and Cancer
  
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    -receive greater annual radiation that poles
    
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  N hemis: longest day-summer solstice, shortest day-winter solstice
  
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  Exceptions to daily cycles of light and dark:
  
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    Arctic circle: 66.5 degrees N lat
    
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    Antarctic Circle: 66.5 degrees S lat
    
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    -during N hemis winter, area N of arctic circle experiences 6 months darkness, area S of Antarctic circle experiences 6 months daylight
    
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    half a year later, this situation reversed
    
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  sunlight strikes low lat at high angle; radiation concentrated in small area
  
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  sunlight strikes high lat at low angle; same amount of radiation spread over larger area
  
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  atmosphere absorbs radiation, so less radiation at high lat, b/c passes through more atmosphere
  
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  Albedo: percentage of incident radiation that is reflected back to space.
  
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    -avg albedo of earth’s surface: 30%
    
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    -ice has higher albedo than soil or vegetation so more radiation reflected back into space at high lats
    
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  -angle at which sunlight strikes ocean surface determines how much absorbed and how much reflected
  
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    -directly: 2% reflected
    
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    -5 degree above horizon: 40% reflected
    
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    -so, ocean reflects more radiation at high lats
    
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    Elevation of sun above atmosphere: 90 60 30 15 5
    
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    Reflected radiation [%] 2 3 6 20 40
    
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    absorbed radiation [%] 98 97 94 80 60
    
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  amount of radiation varies annually due to Earth’s seasons
  
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  amount of radiation varies daily b/c of day and night due to rotation
  
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  temperature difference b/w equatorial zone and poles remains the same, b/c excess heat transferred from equatorial zone to poles [circulation atmos and ocean]
  
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  Composition of dry air:
  
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    Nitrogen 78.1%
    
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    Oxygen 20.9%
    
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    Argon .9%
    
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    CO2 .037%
    
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    Other trace
    
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  troposphere: surface-12km[7m]. all weather produced here. much atmospheric mixing.
  
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    -temperature is cooler with altitude in troposphere
    
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  air has density
  
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  higher temperature, lower density [for air]
  
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    -warm air rises, cool air falls
    
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  convection cell: rising and sinking air moving in circular fashion
  
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  warm air holds more water vapor because it has more contact with water vapor due to quick moving particles.
  
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  warm air moist, cool air dry
  
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    -warm breezy air-evaporation
    
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  more water vapor in air=decreased density
  
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  atmospheric pressure= 1.o atmosphere [14.7lbs/sq inch] at sea lvl
  
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    -decreases with increasing altitude [pressure depends on weight of air column above]
    
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  column of cool dense air: high pressure at surface; leads to sinking air
  
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    -movement toward surface and compression
    
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  column of warm, less dense air; low pressure at surface; leads to rising air
  
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    -movement away from the surface and expansion
    
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  air always moves from high to low pressure areas
  
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  principles that drive physical movement of air remain same whether earth is spinning or not
  
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  Coriolis Effect: changes the intended path of a moving body. Gaspard Hustave de Coriolis [1835].
  
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    does not influence the body’s speed [not a force]
    
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    this effect causes moving objects on earth to follow curved paths
    
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    N hemis; object goes right
    
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    S hemis; object goes left
    
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    the directions right and left are the viewer’s perspective looking I the direction in which the object is traveling
    
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      -ball thrown b/w two people will curve slightly to right in N hemis from the thrower’s point of view
      
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      -greater effect on objects going long-distance, especially N-S
      
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    result of earth’s eastward rotation
    
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    the difference in the speed of Earth’s rotation at difference lats causes this effect
    
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    maximized at poles and zero at the equator.
    
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    merry-go-round; fall off tangent to circle
    
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    Coriolis effect perspective; the one looking in direction object is moving
    
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    distance that a point must travel in a day shorter with increasing lat
    
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    1600 km/hr earth sping rate [0 at poles]
    
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    this change in velocity w/ lat is true cause of Coriolis effect
    
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    1400km/hr at 30 degrees lat N and S
    
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    missile launched straight at target will curve right [to the eye], but really, that target [point on earth] has a faster or slower velocity that the launch point
    
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      friction not taken into account; has a great effect
      
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    rate of change of rotational velocity [per degree of lat] increases as the pole is approached from equator
    
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      [from 200km/hr b/w eq and 30 deg N lat to 600km/hr b/w 30 deg N lat and 60 deg N lat]
      
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      60 deg N lat- N pole -> 800km/hr difference
      
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    max Coriolis effect at poles, no Coriolis effect at equator
    
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    Coriolis effect summary:
    
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      -caused by earth rotation and resulting decrease in velocity with increased latitude
      
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      -influences all moving objects, esp those moving over large distances
      
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      -changes only direction, not speed
      
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      -deflection to the right in N hemis, left in S hemis
      
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      -O at equator; increases with increasing lat; strongest at poles.
      
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  Hadley Cells: George Hadley [1658-1768] circulation cells resulting from dry air mass at equatorial zone traveling N or S of equator at 30 deg lat becoming dense enough to sink and complete the loop
  
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  Ferrel cell: 30deg-60deg lat. William Ferrel [1817-1891]. Invented 3-cell [er hemis model. Cell moves coinciding with adjacent cells.
  
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  Polar cells: 60deg-90deg lat.
  
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  subtropical highs: high rpessure cones caused by descending air at 30deg N and S lat.
  
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  polar highs: high pressure regions caused by descending air at poles
  
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    -both areas: warm under own weight; dry, clear, fair conditions. Not necessarily warm
    
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  equatorial low: rising air causing a band of low pressure at the equator
  
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  subpolar low: rising air causing a band of low pressure at 60 deg lat.
  
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    -both areas: cloudy with much precipitation, because rising air cools and cannot hold its water vapor
    
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  trade winds: massed of air moving from subtropical high pressure belts to equatorial low pressure belts
  
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    -steady winds named from “to blow trade” [to blow in regular course]
    
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    -if earth did not rotate, trade winds blow NS
    
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    N hemis; northeast trade winds: curve to right; from NE to SW
    
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    S hemis; southeast trade winds: curve to left; from SE to NE
    
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      -the coriolis effect curves these winds
      
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  prevailing westerly wind belts: some of descdending air in subtrops moves along surface to highest lat
  
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    -SW to NE in N hemis; NW to SE in S hemis
    
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  polar easterly wind belts: air moving away from high pressure at poles
  
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    -Coriolis effect at poles strongly deflects winds
    
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    -blow from: NE in N hemis, SE in S hemis.
    
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  When polar easterlies collide with prevailing westerlies at subpolar low pressure belts [60 deg lat], the warmer, less dense air of westerlies rises above.
  
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  doldrums: boundary between trade belts. Lack of winds here.
  
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  Intertropical Convergence Zone [ITCZ]: doldrums. Between where trade winds converge.
  
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  Horse latitudes: boundary between prevailing westerlies and trade winds [30 deg lat]
  
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    -high pressure, clear, dry, fair conditions
    
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    -air is sinking and surface winds are light and variable [not much rain]
    
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  polar front: boundary between westerlies and easterlies [60 deg lat]
  
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    -cloudy, much precipitation. Battelground for different air masses
    
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  poles are cold deserts [not much precipitation]
  
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  Ferrel 3-cell idea is only general. Other factors:
  
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    1] tilt of earth’s rotational axis, producing seasons
    
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    2] low heat capacity of continental rock: colder winter, hotter summer than over oceans
    
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    3] Uneven distribution of land, particularly affecting N hemis patterns
    
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  during winter on continent: atmospheric high pressure, summer: low pressure.
  
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  such seasonal atmospheric pressure over Asia causes Monsoon Winds.
  
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  Christopher Columbus: Italian navigator. Toscanelli: astronomer
  
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    -reached canary islands Aug 3, 1942
    
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    -called West Indies inhabitants “Indians” because he thought they were near India
    
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    -1498; South America 1502; Central America
    

Solar energy creates winds

Example of interactions: El Nino, Greenhouse Effect

Theory: Earth tilt due to Mar’s affect.

35degN-35degS->heat gained

Other lats, heat lost

Heat gained moves to poles

troposphere: 60degC-50degC at min temp

Topopause-Stratosphere-Ozone layer-Mesosphere

dry air and cool air sink <-more dense

moist air and warm air rise<-less dense

-moist air less dense than dry air because water has less mass than N2+O2

high pressure->air coming down; low pressure->air rising

deserts have cool/dry air coming down

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  weather: conditions in atmosphere at given time and place
  
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  climate: long-term average of weather
  
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  cyclonic flow: CCW flow of air around low pressure cells as a result of Coriolis effect on air moving from high to low pressure curving it to the right [N hemis]
  
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  anticyclonic flow: air leaving high pressure region and curves right, establishes CW flow of air around high pressure cells [N hemis]
  
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  low pressure->clouds high pressure->sun
  
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  winter high pressure cells replaced by summer low pressure over continents, so continental wind patterns often reverse themselves seasonally.
  
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  land breeze: cool air sinking, blowing over ocean in early morning hours.
  
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    -due to cool sinking air over continents at night as a results of continents having low heat capacity
    
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  sea breeze: warm air rising, blowing cool air from ocean over continent in afternoon.
  
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    -due to warm air rising over/above continents during day as a result of continental low heat capacity.
    
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  Wind Belts and Boundaries:
  

  Region	Name	Pressure	Characteristics
  0-5	Doldrums	L	Light variable wind. Cloudy/Precip. Hurricanes breed here
  5-30	Trade Winds	-	Strong, steady winds generally from E
  30-60	Horse Latitudes	H	Light, variable wind. Dry, clear, fair. Little precip. Major deserts here
  60	Prevailing W	-	Winds generally from W. Brings US-influencing storms
  60-90	Polar Front	L	Variable wind. Stormy/cloudy year-round
  Poles	Polar E	-	Cold, dry winds generally form E
  	Polar High Pressure	H	Variable winds. Clear, dry, fair, cold temp, min precip. Cold deserts here.

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  Very high and very low lats, little daily and minor seasonal change in weather
  
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  midlatitudes: where storms are common
  
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  storms: atmosphere disturbances: strong wind, precip, thunder/lightning
  
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  air masses: large volumes of air: definite area of origin, distinctive characteristics.
  
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    -polar and tropical air masses influence US
    
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    -most originate over sea. those from land are drier
    
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    -US influenced more by: polar air masses in winter/tropical air masses in summer
    
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    -[c]continental [m]maritime [T]tropical [A]arctic [P]polar
    
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  warm front: contact between warm air mass moving into area of cold air
  
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    -as air masses move to midlats, they move E some
    
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  cold front: contact between cold air mass into warm-air area
  
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  jet stream: narrow, fast, Eastward-flowing air mass. Causes fronts.
  
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    -above mid lats just below top of troposphere, 6miles high
    
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    -follows wavy path; causes unusual weather by steering [P] or [T] too far N or S
    
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  warm always rises above cold
  
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  temperature difference across cold front greater than warm front
  
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    -so, rain of cold front usually heavier, briefer
    
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  Tropical cyclones: huge, rotating masses of low pressure: strong wind, torrential rain
  
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    -largest systems on Earth
    
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    -no associated with fronts
    
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  hurricanes: name in N, S America
  
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  typhoons: W N Pacific ocean
  
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  cyclones: Indian ocean
  
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  energy of single hurricane greater than all that created in US in 20 years.
  
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  tropical cyclone begins as low pressure cells break from equatorial low pressure belt, grows as heat energy from ocean picked up
  
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    -the surface winds feed moisture [water vapor] into storm
    
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    -the release of vast amounts of water’s latent-heat of condensation power tropical cyclone.
    
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  Tropical cyclone classification:
  
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    tropical depression: winds below 38mph
    
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    tropical storm: 38
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    tropical cyclone: 74mph
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  Saffir-Simpson Scale: hurricane intensity; further classifies; wind speed, dmg
  
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  250mph a high
  
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  100 tropical cyclones each year. conditions to create:
  
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    ocean water temperature > 25C -> for evaporation
    
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    warm/moist air -> supplies latent heat
    
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    Coriolis effect; cyclone spin CCW in N hemis, CW in S hemis
    
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      No cyclone directly on equator, because Coriolis is zero. Happens on equator once every 300-400 years
      
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  June 1-Nov 30 “hurricane season” [not limited to this time frame]
  
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  hurricanes typically remain in tropics. Driven by trade winds so they move E to W. Last 5-10 days.
  
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  If more over land, energy source is lost, so they dissipate
  
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  diameter avg 124miles but can be 500+
  
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  eye of the hurricane: low pressure center: air here spirals upward; usually calm
  
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  spiral rain bands compose hurricanes; several inches of rainfall per hour
  
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  storm surge: responsible for most of a hurricane’s dmg. [90% deaths]. Hill of water
  
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    -low pressure center produces hill up to 40ft high.
    
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    -hill where wind blowing shoreward climbs shallow water onto shore. Very bad at high tide.
    
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    -dramatic increase in sea lvl at shoer
    
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    -where onshore winds further pile water hit most severely
    
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  Galveston Texas, 1900; 7000 dead. Category 4.
  
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  Category 5 3x; 1935[Keys], 1969[Mississippi], 1992[Andrew FL]
  
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  Mitch [Central America 11k dead]
  
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  most of world’s tropical cyclone formed in water N of equator in West pacific ocean.
  
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  1970 [Bangladesh 40ft Storm Surge killed 1 million] another in 1972; 500k dead. ’91; 200k
  
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  ocean climate patterns run E-W, are stable. modified by ocean surface currents.
  
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  equatorial: region spanning equator. abundance solar radiation. Major air movement upward.
  
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    -storms form here.
    
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  tropical: regions N/S to cancer, Capricorn. Strong trade winds. NE in N hemis, SE in S hemis. Rough seas.
  
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    -storms gain energy here.
    
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  subtropical: regions beyond tropics. High surface salinity. belts of high pressure. little precipitation, much evaporation. Winds weak, currents sluggish. strong boundary currents N-S, particularly along west margins.
  
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  temperate: regions [midlats] strong westerly winds; from SW in N hemis, NW in S hemis. severe storms, heavy precip. winter esp
  
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  subpolar: regions; extensive precip due to subpolar low. sea-iced-covered in winter, melts in summer. icebergs common, surface temp rarely greater than 41F in summer
  
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  polar: region; temps remain at or near freezing. covered with ice, most of year. No sun in winter, all sun in summer
  
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  sea ice: masses of frozen ice. low temp/high lat
  
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  icebergs: break off [calve] from glaciers that originate on land
  
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  pancake ice: forming slush into thin sheet broken by wind and waves
  
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  ice floes: layer of ice when further freezing occurs to pancakes
  
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  rate of ice form slows as it thickens, because top ice insulates water below
  
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  calm water and low temp aid ice formation
  
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  most of dissolved substances remain in water, notice. Salinity increases under ice.
  
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    -decreases the freezing point of water
    
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    -ice becomes ink below surface-> lower surface salinity water freezes in place
    
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  17% decrease in overall ice extent
  
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  accelerated melting at interior poles
  
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    -due to shifts in N hemis atmosphere circulation patterns
    
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  most breaking-up [calving] occurs in summer high temps
  
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  icebergs from in Greenland narrow valleys to ocean.
  
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    -E and W Greenland current carry bergs into N Atlantic shipping lanes
    
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    -may take years to melt
    
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  shelf ice: thick floating sheets of ice formed at edges of glaciers in Antarctica
  
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    [B-15 4250 sw mile iceberg from shelf ice breaking off]
    
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    90% icebergs mass below sea lvl
    
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    flat tops up to 650ft high. Most below 530ft high
    
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    Larsen ice shelf decreased by 40% since 1997
    
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    rate of warming; .5C per decade
    
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  Argo located Titanic 1985 Robert Ballard
  
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  World average temp Earth and troposphere: 15c [59F]
  
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  greenhouse effect: keeps Earth’s surface and lower atmosphere warm.
  
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  most of sun energy that reaches earth surface: short wavelength, visible almost
  
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  longer-wavelength infrared radiation; heat; short-wavelength energy converted to this energy when it strikes the surface.
  
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  energy trapped in atmosphere by ozone layer
  
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  heat budget: 100 units shortwave solar radiation reflected, absorbed, scattered by various components of Earth
  
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    47% of solar radiation absorbed by oceans and continents
    
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    23% absorbed by atmosphere and clouds
    
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    20% reflected to space by backscatter, clouds, and Earth’s surface
    
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  peak of intensity of energy of sun; .0002inch wavelength, within visible spectrum
  
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  earth materials that absorb energy reradiate it back to space as longer wavelengths: infrared [heat. .004 inch long]
  
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  rates of absorption and reradiation are equal
  
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  greenhouse effect produced by heat-trapping gases trapping reradiated heat, and reradiating this heat once more.
  
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  change of wavelength from visible to infrared is the key to understand how greenhouse effect works
  
  
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