Announcements Exam #2: Tomorrow, 7PM, 160 English Bldg.Exam #2: Tomorrow, 7PM, 160 English Bldg....
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Transcript of Announcements Exam #2: Tomorrow, 7PM, 160 English Bldg.Exam #2: Tomorrow, 7PM, 160 English Bldg....
AnnouncementsAnnouncements
•Exam #2: Exam #2: Tomorrow, 7PM, 160 English Bldg. Tomorrow, 7PM, 160 English Bldg.
•Quiz 6: Due before 7PM tomorrowQuiz 6: Due before 7PM tomorrow
•No Class THIS Friday: EOHNo Class THIS Friday: EOH
Class 21 -- The OceansClass 21 -- The Oceans
ATMOSPHEREATMOSPHEREComposition -- review, human impactComposition -- review, human impactTroposphere, StratosphereTroposphere, StratosphereConvectionConvectionPressurePressureGlobal wind patterns Global wind patterns
Why do we detour and study the Why do we detour and study the atmosphere?atmosphere?
OO22 and CO and CO22 for life processes for life processesGreenhouse effect- linked to oceansGreenhouse effect- linked to oceansOcean-atm. interactionsOcean-atm. interactions
**Heat, moisture exchange****Heat, moisture exchange****Winds drive ocean currents****Winds drive ocean currents**
Ignoring water vapor…
•Variable constituentsVariable constituentsGases: ozone (OGases: ozone (O33), CO, CH), CO, CH44, N+O gases, S+O , N+O gases, S+O gasesgases
Aerosols: dust, pollen, water dropletsAerosols: dust, pollen, water droplets
Water vaporWater vapor
Human modificationHuman modification•Added COAdded CO22
–Enhanced greenhouse effect Enhanced greenhouse effect
•Ozone destruction by CFC’s -- Increased UV Ozone destruction by CFC’s -- Increased UV • Skin diseasesSkin diseases• Reduces globalReduces global photosynthesisphotosynthesis??????
The global CO2 Cycle
Where is most of the C found on the earth?
Here it comes again- CONVECTION:
Ionosphere- above thatIonosphere- above that
ATMOSPHERIC ZONESATMOSPHERIC ZONES
Troposphere -- 0-12 kmTroposphere -- 0-12 km
Stratosphere -- 12-50 kmStratosphere -- 12-50 km
1) Troposphere -- 0-12 km1) Troposphere -- 0-12 km• Heated at its base (surface) -- Heated at its base (surface) -- • Convection, turbulent motionConvection, turbulent motion
•Warmed at bottom --> warm air risesWarmed at bottom --> warm air rises•Also: Also: Humid airHumid air tends to rise tends to rise
Why does the troposphere have thermal convection?
Why does the troposphere have thermal convection?
troposphere
stratosphere
warm
2) Stratosphere -- 12-50 km2) Stratosphere -- 12-50 km–Stratified -- little vertical mixingStratified -- little vertical mixing–"Lid" on the turbulent troposphere"Lid" on the turbulent troposphere–Ozone absorbs UV radiationOzone absorbs UV radiation
ATMOSPHERIC ZONESATMOSPHERIC ZONES
•Weight of overlying atmos. creates pressureWeight of overlying atmos. creates pressure•We don’t notice -- equal in all directionsWe don’t notice -- equal in all directions
Variations in pressure:Variations in pressure:•Decreases with altitudeDecreases with altitude•Pressure at Earth’s surface -- varies….Pressure at Earth’s surface -- varies….–high pressure = descending airhigh pressure = descending air–low pressure = ascending airlow pressure = ascending air
ATMOSPHERIC PRESSUREATMOSPHERIC PRESSURE
GLOBAL WIND SYSTEMGLOBAL WIND SYSTEM
Prevailing wind “belts”Prevailing wind “belts”Trade Winds: Low latitudes, E --> W Trade Winds: Low latitudes, E --> W Westerlies: Mid latitudes, W --> EWesterlies: Mid latitudes, W --> EPolar Easterlies: High latitudes, E --> WPolar Easterlies: High latitudes, E --> W
What causes this pattern?What causes this pattern?1)1) Convection- Convection-
Temp. diff. -- Low vs. High Lat. Temp. diff. -- Low vs. High Lat. 2) Coriolis effect (next time)2) Coriolis effect (next time)
Global Convection in the atmosphereGlobal Convection in the atmosphere
Equatorial zoneEquatorial zone: Hot, Humid: Hot, Humid--> rising air masses--> rising air masses
Polar zonesPolar zones (and elsewhere- more later) (and elsewhere- more later)--> sinking air masses.--> sinking air masses.
Result:Result:– Global convection cellsGlobal convection cells– Global Wind Patterns at surfaceGlobal Wind Patterns at surface
Note: Local convection cells exist, tooNote: Local convection cells exist, too
Fig. 6-7
If the earth were NOT rotating, convection cells in the atmosphere would look like this.
Coriolis Video
Thanks to UIUC Atmospheric Science
Google: coriolis video UIUC
Student animations CD-ROMCoriolis effect animations
Coriolis Effect: Practical result:
•Things moving long distances on earth tend to be deflected by Coriolis “force”
•Deflection in N hemis.: RIGHT-HAND TURN
•Deflection in S hemis.: LEFT-HAND TURN
Why? --Speed due to earth’s rotation…Why? --Speed due to earth’s rotation…90˚90˚ 0 km/hr 0 km/hr60˚60˚ 800 km/hr 800 km/hr30˚30˚ 1400 km/hr1400 km/hr 0˚0˚ 1600 km/hr1600 km/hr
Coriolis effectCoriolis effect
Winds traveling long distances are deflectedWinds traveling long distances are deflected……turn to the turn to the rightright in Northern Hemis. in Northern Hemis.……turn to the turn to the leftleft in Southern Hemis. in Southern Hemis.
Why? --Speed due to earth’s rotation…Why? --Speed due to earth’s rotation…90˚90˚ 0 km/hr 0 km/hr60˚60˚ 800 km/hr 800 km/hr30˚30˚ 1400 km/hr1400 km/hr 0˚0˚ 1600 km/hr1600 km/hr
Think of a missile moving southward:
•Fire from North Pole, southward•Watch from space- a straight line path•Earth rotates beneath it•But, a person in Chicago looking up at it is moving eastward in space- ~1000km/h!•Ask this person: Is the missile moving due south?
Winds and ocean currents have both.......initial velocity and direction, and.......initial rotational velocity that depends on latitude
As they cross latitudes, winds and currents are rotating at different velocities than Earth's surface
Result: Apparent deflection to Earth-bound observers.always right in N.H.always left in S.H.
Analogy -- launching a missle from different latitudes
Fire from North Pole (no rotation)Earth rotates beneath itDeflection -- to the west (right)
Fire from Equator (max. rotation)Missle rotates faster than Earth beneath itDeflection -- to the east (right)
Amount of wind/current deflection depends on ... ... time of travel (how long it moves)... distance of travel (how far it moves)
Winds and currents are deflected a lot because they are in continuous motion over long distances.