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•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.