1

Lect

ure

10: W

ind

Introduction to Oceanography Chris Henze, NASA Ames, Public Domain, http://people.nas.nasa.gov/

~chenze/fvGCM/frances_02.mpg

Winds at ~jet plane

altitude

Introduction to Oceanography

Pacific surface wind forecast-hindcast, National

Weather Service Environmental Modeling

Center/NOAA, Public Domain, GIF by E. Schauble

using EZGif

2

pH Scale •  pH scale = Logarithmic scale

•  Neutral (pure) water:

– 1/(5.5x108) water molecules is disassociated –  there are about 55 moles of water per liter Concentration of H+= 55/(5.5x108) = 10–7 moles/liter

– Neutral water pH = 7 •  lower pH = acid, higher pH = base

€

pH = − log10(H +)

pH Scale

Stephen Lower, Wikimedia Commons,

CC A S-A 3.0, http://en.wikipedia.org/wiki/

File:PH_scale.png

3

The Carbonate Buffer System •  Seawater pH = ~8.0 (slightly basic) •  Maintained by carbonate buffer system:

•  Increase CO2 in water, acidity increases What happens to pH?

•  Add acid and CO2 is produced

€

CO2 + H2O ⇔ H2CO3 ⇔ H+ + HCO3− ⇔ 2H+ + CO3

2–

Carbonic Acid Bicarbonateion

Carbonateion

The CO2 system and carbonate

•  Deep waters form at the poles: High CO2 and therefore acidic

•  Acidity interacts to dissolve calcium carbonate (CaCO3) deposits on the deep sea floor – Acidity and temperature control carbonate

compensation depth (CCD)

4

Questions

Image from UNESCO, Presumed Public Domain, http://ioc3.unesco.org/oanet/FAQacidity.html

Wind

•  Lecture 8: Atmospheric Circulation

Wind sea, N. Pacific, Winter 1989, M/V NOBLE STAR/NOAA, Public Domain, http://commons.wikimedia.org/ wiki/File:Wea00816.jpg

5

Atmosphere-Ocean Coupling

•  Why study atmospheric circulation? – Atmosphere & ocean processes are

intertwined – Atmosphere-ocean interaction moderates

surface temperatures, weather & climate •  Weather: local atmospheric conditions •  Climate: regional long-term weather

– Atmosphere drives most ocean surface waves and currents (our next topic)

Composition of the Atmosphere •  Dry Air: 78% Nitrogen, 21% Oxygen •  BUT it is never completely dry

– Typically contains about 1% water vapor Chemical residence time of water vapor in the air is

about 10 days (liquid water residence time in

ocean: 3x103 years!) –  Liquid evaporates into the air,

then is removed as dew, rain, or snow

– Warm air holds much more water vapor than cold air

Figure by Greg Benson, Wikimedia Commons Creative Commons A S-A 3.0,

http://en.wikipedia.org/wiki/File:Dewpoint.jpg

6

Density of Air •  Typical air density ~ 1 mg/cm3

–  About 1/1000th the density of water

•  Temperature and pressure affect the density of air

•  Temperature: Hot air is less dense than cold air

•  Pressure: Air expands with elevation above sea level –  Air is much easier to compress

than water

Figure by E. Schauble, using NOAA Standard Atmosphere data.

0

2000

4000

6000

8000

10000

12000

0 40000 80000 120000

Ele

vatio

n (m

)

Pressure (N/m2)

Everest 8848m

Passenger jet 10-13km

Mt. Whitney 4421m

Empire State Bldg. 450m

Density & temperature of Air

•  Rising air expands & cools –  Vapor condenses

into clouds, precipitation

•  Sinking air is compressed and warms –  Clear air

Figure adapted from Nat’l Weather Service/NOAA, Public Domain,

http://oceanservice.noaa.gov/education/yos/resource/JetStream/synoptic/clouds.htm

2000 meters

1000 meters

15ºC 15ºC

24ºC 15ºC

34ºC 15ºC

(1.4% H2O)

7

Expanding Air Cools and Condenses

mov1

•  Like opening a pressurized bottle of soda •  Air expands and cools •  Water vapor condenses -- cloud formation

MMovies by J. Aurnou, E. Schauble, UCLA

2000 meters

1000 meters

15ºC 15ºC

24ºC 15ºC

34ºC 15ºC

(1.4% H2O)

Questi

ons

Figure adapted from Nat’l Weather Service/NOAA, Public Domain,

http://oceanservice.noaa.gov/education/yos/resource/JetStream/synoptic/clouds.htm

8

Solar Heating of the Earth •  Solar energy absorbed unevenly over Earth’s surface •  Energy absorbed / unit surface area varies with:

–  Angle of the sun –  Reflectivity of the surface (i.e., ice v. ocean) –  Transparency of the atmosphere (i.e., clouds)

Przemyslaw "Blueshade" Idzkiewicz, Creative Commons A S-A 2.0, http://

commons.wikimedia.org/wiki/File:Earth-lighting-winter-

solstice_EN.png

23.5º

Solar Heating of the Earth Sunlight heats the ground

more intensely in the tropics than near poles

•  file:///Users/schauble/EPSS15_Oceanography/Images_and_movies/Insolation2.swf Heilemann CCU/

NSF Flash

Sunlight intensity (top of atmosphere)

Sunlight intensity (ground)

Figure by William M. Connolley using HadCM3 data, Wikimedia Commons, Creative Commons A S-A 3.0, http://commons.wikimedia.org/wiki/File:Insolation.png

9

•  Seasons are caused by Earth’s 23.5o tilt •  Northern summer: north hemisphere points at sun

Solar Heating & the Seasons Not to scale!

Oct. 26: We are here

Dec 21-22: N. Pole tilted away

from Sun

June 20-21: N. Pole tilted

towards Sun

March 20-21: Sun shines on both poles

equally

Sept. 22-23: Sun shines on both poles

equally Background image: Tauʻolunga, Creative Commons A S-A 2.5, http://en.wikipedia.org/wiki/File:North_season.jpg

Solar Heating & the Seasons

NASA animation by Robert Simmon, Public Domain, data ©2011 EUMETSAT http://earthobservatory.nasa.gov/IOTD/view.php?id=52248&src=ve

10

Redistribution of Solar Heat Energy

•  Equator absorbs more heat from the sun than it radiates away (net > 0). •  Polar regions radiate much more heat than they absorb from the sun(!) •  E.g., Equator isn’t that Hot; Poles aren’t that Cold •  Evidence that the atmosphere (~2/3) & oceans (~1/3) redistribute heat •  Result: convective heat transfer moderates climate

CERES/NASA animation, Public Domain, http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=CERES_NETFLUX_M

11

Redistribution of Solar Heat Energy

•  Convective heat transfer moderates Earth climate •  Heated air expands & rises, then cools & sinks

EQU

ATOR

POLE

S

Adapted from image at http://www.yourhome.gov.au/technical/images/62a.jpg, Public Domain?

Atmospheric Circulation Without Rotation

Warm, less dense air rises

near the Equator

Cold, more dense air sinks near the Poles

Cold, more dense air sinks near the Poles

Background image from Smári P.

McCarthy, Creative Commons A S-A 3.0,

http://commons.wikimedia.or

g/ wiki/File:Earth_equator

_northern _hemisphere.png

12

Questions

Not quite right!

ACTUAL Atmospheric Circulation

Figure from NASA, Public Domain, http://sealevel.jpl.nasa.gov/overview/climate-climatic.html

13

Lab Coriolis Movies

•  Movies made by Rob Hyde, UCLA

Lab Coriolis Movies

Stat

iona

ry O

bser

ver

14

Lab Coriolis Movies C

CW

Rot

atio

n, 2

5 rp

m

Lab Coriolis Movies

CW

Rot

atio

n, 4

1 rp

m

15

Coriolis Effect Movies

Movie: University of Illinois (not sure if that’s the original source) http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/fw/crls.rxml

The Coriolis Effect on Earth

National Snow and Ice Data Center, free for educational use, http://nsidc.org/arcticmet/factors/winds.html

•  Surface velocity increases from pole to

equator •  Points on the equator

must move faster than points near the poles to go around once a day •  Latitude velocity

differences lead to curving paths

–  Example: Merry-go round

16

The Coriolis Effect •  To an Earthbound observer (i.e., us): •  Northern Hemisphere: Earth’s

rotation causes moving things to curve to their right

Moving things: Air masses, oceanic flows, missiles, anything with mass

•  Southern Hemisphere: Earth’s rotation causes moving things to curve to their left

National Snow and Ice Data Center, free for educational use, http://nsidc.org/arcticmet/factors/winds.html

The Coriolis Effect

•  Strength of Deflection varies with latitude: – Maximum at the poles – Zero(!) at equator

– Faster a planet rotates, the stronger the Coriolis effects

– The larger the planet, the stronger the Coriolis effects

17

Questions ?

Southern Hemisphere: Cyclone Drena (1997) NASA, Public Domain, http://www.ngdc.noaa.gov/dmsp/hurricanes/1997/drena.vis.gif (now moved)

Northern Hemisphere: Hurricane Isabel (2003) NASA, Public Domain, http://visibleearth.nasa.gov/view_rec.php?id=5862

But wait – why do storms (including hurricanes and cyclones) go

backwards?

Atmospheric Circulation including Coriolis

Figure from NASA, Public Domain, http://sealevel.jpl.nasa.gov/overview/climate-climatic.html

18

Actual forecast of

surface winds

Pacific surface wind forecast-hindcast, National

Weather Service Environmental Modeling

Center/NOAA, Public Domain, GIF by E. Schauble

using EZGif

Atmospheric Circulation including Coriolis

•  3 convection cells in each hemisphere – Each cell: ~ 30o latitudinal width

•  Vertical Motions – Rising Air: 0o and 60o Latitude – Sinking Air: 30o and 90o Latitude

•  Horizontal Motions – Zonal winds flow nearly along latitude lines – Zonal winds within each cell band

•  DUE TO DEFLECTIONS BY CORIOLIS!

19

Atmospheric Circulation including Coriolis

3 Cells per hemisphere: Polar

Active (updraft on hot side, downdraft on cold side)

Ferrel Passive (downdraft on

hot side!) Hadley

Active H

AD

LEY

POLAR

FERREL

UCLA figure – background image unknown.

Atmospheric Circulation including Coriolis

•  Latitudinal winds: – 0-30o: Trade

Winds – 30-60o:

Westerlies – 60-90o:

Polar Easterlies

Figure by Hastings, Wikimedia Commons, Creative Commons A S-A 1.0 Generic, http://en.wikipedia.org/wiki/File:AtmosphCirc2.png

20

Atmospheric Circulation including Coriolis Cell Boundaries:

60o: Polar Front

30o: Horse Latitudes

0o: Doldrums

Vertical air movement (up at Polar Front and Doldrums, down at Horse Latitudes)

Doldrums

Horse Latitudes

Polar Front

Figure by Hastings, Wikimedia Commons, Creative Commons A S-A 1.0 Generic, http://en.wikipedia.org/wiki/File:AtmosphCirc2.png

Questions

Figure from NASA, Public Domain, http://sealevel.jpl.nasa.gov/overview/climate-climatic.html

21

Local Meteorology of Southern California

Marine layer against the Southern California mountains Photo by Dr. Jonathan Alan Nourse, CalPoly Pomona, http://geology.csupomona.edu/janourse/Storms,%20Floods,%20Landslides.htm

Mediterranean Climate

•  LA: Subtropical latitude, abutting ocean •  Subsiding flow: sinking air

–  Clear most of the year •  Effects of coast:

–  Higher humidity--- thermal buffer •  Winter Storms

–  Pole-equator temp difference larger in winter –  Speeds up jet stream, big storms get pushed our

way