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Atmospheric Motions. Science Concepts Potential Energy Coriolis Force. Circulation Scales Thermally Driven Winds Global Circulations Rainfall Versus Latitude Observed Global Circulation Three-celled Circulation Wind Patterns Pressure Patterns Rainfall Patterns - PowerPoint PPT Presentation
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Climate and Global Change Notes
21-1
Atmospheric Motions
Circulation Scales
Thermally Driven Winds
Global Circulations
Rainfall Versus LatitudeObserved Global Circulation
Three-celled CirculationWind PatternsPressure PatternsRainfall PatternsLand-Water Effect
Global ClimateRelationship to Global
Circulation
Science Concepts
Potential Energy
Coriolis Force
The Earth System (Kump, Kastin & Crane)
• Chap. 4 (pp. 59-65, 79)
Climate and Global Change Notes
21-2
Atmospheric Scales
Object of Space Scale TimeTerminology Study or Size Scale
Macroscale Climate Global YearsSeasons Hemisphere
WeeksNational
Cyclonic Highs & Lows (5000 km) or HurricanesSynoptic
Regional DaysFronts (1000 km)
Mesoscale SquallsThunderstorms
Local HoursConvective Showers (100 km) orCumulus Tornadoes
Terminal(10 km)
MinutesMicroscale Gusts
Eddies Spot Seconds(1 meter)
Climate and Global Change Notes
21-3
Thermally Driven Wind Systems
Examples
• Global circulation
• Midlatitude cyclones
• Monsoons
• Hurricanes
• Land-sea breezes
• Heat island circulations
• Mountain-valley winds
Climate and Global Change Notes
21-4
Thermally Driven Wind Systems
Global Circulation
http://visibleearth.nasa.gov/Sensors/Terra/
Science quotes of 5th and 6th graders -
Clouds just keep circling the earth around and around. And around. There is not much else to do.
Climate and Global Change Notes
21-5
Thermally Driven Wind Systems
Hurricanes
• Hurricane Georges battering the Gulf Coast on September 28, 1998
Climate and Global Change Notes
21-6
QuickTime™ and aTIFF (Uncompressed) decompressor
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Thermally Driven Wind Systems
Hurricanes (Con’t)
• Ocean cooling effectsof hurricanes
• Katrina and Rita, each cooled Gulf temperatures more than 4°C in areas, and the entire Gulf ~1°C
• Hurricanes cool the ocean by > transferring heat to the
atmosphere through evaporation
> upwelling of cold water due to the suction effect of the storm’slow pressure
> cold raindrops that remain on the ocean surface for a time
> shielding the ocean surface from direct sunlight by cloud cover
http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17164
Climate and Global Change Notes
21-7
Thermally Driven Wind Systems
Sea Breezes
Climate and Global Change Notes
21-8
Global Circulations
Net Radiation vs Latitude
400
300
200
100
0 10N 10S 30S 30N 50S 50N 90S 90N
Latitude
Surplus
Heat Transfer Heat Transfer
Radiation Lost Radiation Received
Deficit Deficit
Radiation Intensity ( W
/ m 2 )
Climate and Global Change Notes
21-9
Global Circulations
What do you think the global distribution of precipitation should look like?
Climate and Global Change Notes
21-10
Global Circulations
Global Rainfall
• 1/00 to 4/06precipitation in mm/day
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http://earthobservatory.nasa.gov/Observatory/Datasets/rainfall.gpcp.html
Climate and Global Change Notes
21-11
Global Circulations
Average Precipitation (mm/day)
• ‘79 - ‘05 average January, July and Annual precipitation
- Dashed lines are 0°, 30°, 60° north and south latitudes
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http://www.gewex.org/GPCP_data_products_9-2006.pdf
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January
JulyAnnual
What latitude has the highest annual precipitation?
Climate and Global Change Notes
21-12
Global Circulations
Rainfall vs Latitude
90°N 60°N 30°N 0° 30°S 60°S 90°S
0
-500
500
1000
1500
2000
Latitude
Rainfall Evaporation
Runoff
Millimeters per year
Climate and Global Change Notes
21-13
Global Circulations
Inter-TropicalConvergenceZone
Climate and Global Change Notes
21-14
Global Circulations
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Annual Average Cloud Amount
• 1983-2001
http://isccp.giss.nasa.gov/climanal2.html
Zonal Mean
Cloud Amount (%)Total Cloud Amount (%)
Climate and Global Change Notes
21-15
Global Circulations
Simple One-Celled Circulation
• Upward motion at the Equator
• Downward motion at the poles
• Equatorward motion at low levels
• Poleward motion at upper levels of the troposphere
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http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
Climate and Global Change Notes
21-16
Three-Celled Circulation Surface Winds
• Polar Cell- Polar Easteries
• Mid-latitude Cell- Highly variable- Storms move from west to east- Zone of Westerlies
• Equatorial Cell- Northeast Tradewinds in the
northern hemisphere- Southeast Tradewinds in the
southern hemisphere
Global Circulations
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
Climate and Global Change Notes
21-17
QuickTime™ and aTIFF (Uncompressed) decompressor
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Global Circulations
Three-Celled Circulation
• Polar Cells- Thermally direct- Downward motion at
the Poles
• Equatorial Cells- Thermally direct- Upward motion at
the Equator
• Mid-latitude cell- Thermally indirect- Downward motion
at 30°- Equatorward motion at
upper levels of the troposphere- Poleward motion at lower levels
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
Climate and Global Change Notes
21-18
Global Circulations
Three-Celled Circulation
• Temperatures at 500 mb (about 5.5 km or 3.4 miles above sea level)
• Total water vapor above 500 mb to the top of the atmosphere
• Note Northern hemispheremid-latitude systems move eastward
• Note Northern hemispheretropical systems move westward
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
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http://airs.jpl.nasa.gov/Data/FeaturedProducts/AIRS_T500.mov
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Climate and Global Change Notes
21-19
Global Circulations
Three-Celled Circulation Surface WindsThe Nantucket whaleship Essex was sunk by an attacking whale just south of the Equator in the Pacific in 1820 and was the inspiration for the Melville’s Moby Dick.
“Like a skier traversing the face of a mountian, a Nantucket whaleship took an indirect route toward Cape Horn, a course determined by the prevailing winds of the Atlantic Ocean. First, pushed by westerlies, the ship sailed south and east toward Europe and Africa. There she picked up winds called the northeast trades, which took her back across the ocean again, in the direction of South America. After crossing the equator in an often airless region known as the doldrums, she worked her way south and west through the southeast trades into an area of variable winds. Then she encountered the band of westerlies that could make rounding the Horn so difficult.”
In the Heart of the Sea; The Tragedy of the Whaleship Essex - Nathaniel Philbrick (p. 37)
Climate and Global Change Notes
21-20
Global Circulations
Northern Deserts Southern Deserts
Science quotes of 5th and 6th graders -
It is so hot in some places that the people there have to live in other places.
Climate and Global Change Notes
21-21
Global Circulations
Can we have deserts in the ocean?
Climate and Global Change Notes
21-22
Global Circulations
http://aquarius.gsfc.nasa.gov/overview-sss.html
Ocean Deserts
• Note higher values of salinity north and south of the Equator
• Salinity reflects the total amount of dissolved solids in ocean water
- PSU (practical salinity unit) describes the concentration of dissolved salts in water - 35 ppt means 35 lbs of salt per 1,000 lbs of seawater
Climate and Global Change Notes
21-23
Global Circulations
http://aquarius.gsfc.nasa.gov/science-watercycle.html
Ocean Deserts (Con’t)
• Ocean salinity is increased by evaporation and freezing of seawaterand decreased by precipitation and melting of snow and ice
Climate and Global Change Notes
21-24
Global Circulations
Summary
• Driven by differential or uneven heating between the poles and the equator
• Three circulation cells in each hemisphere. In the Northern hemisphere
- 0° to 30° - zone of “Northeast Trade Winds”- 30° to 60° - zone of “Prevailing Westerlies”- 60° to pole - zone of “Polar Easterlies"
• Both the Polar Easterlies and the Northeast Trades are very consistent,
while the Prevailing Westerlies are characterized by being variable and
highly changeable
• As part of the three-celled circulation pattern
- 0° is characterized by upward motion- 30° is characterized by subsidence- 60° is characterized by upward motion- 90° is characterized by sinking motion
Climate and Global Change Notes
21-25
Global Circulations
Summary (Con’t)
• Three-celled circulation results in
- 0° is wet with heavy precipitation
- 30° is dry with more evaporation than rain
- Zone of Prevailing Westerlies has more precipitation than evaporation
- 90° is dry with little precipitation
• This simple latitudinal pattern is modified by the land and water distributions
- More in the Northern Hemisphere because there is more land in the Northern Hemisphere
Climate and Global Change Notes
21-26
Global Circulations
January Mean Surface Pressure (mb)
Climate and Global Change Notes
21-27
Global Circulations
July Mean Surface Pressure (mb)
Climate and Global Change Notes
21-28
Global Circulations
Semi-Permanent Pressure Systems
Ocean Strength Strength Location Position in Winter in SummerAleutian low 60°- 65° Strong Weaker
Icelandic low 60°- 65° Strong Weaker
Hawaiian or 30°- 35° Weaker StrongerPacific high
Bermuda high 30°- 35° Weaker Stronger
Continental Strength Strength Location in Winter in SummerSiberian high Strong Absent
North American high StrongAbsent
SW U.S. thermal low AbsentStrong
India thermal low Absent Strong
Climate and Global Change Notes
21-29
Atmospheric Motions
Global Circulations (Con’t)
Monsoons
Science Concepts
Seasonal Effects
Science quotes of 5th and 6th graders -
A monsoon is a French
gentleman.
The Blue Planet (Skinner, Porter & Botkin)• Chap. 13 (p. 303)
Climate and Global Change Notes
21-30
Monsoon
Mumbai (Bombay) Monsoon 2005 Rainfall
• Mumbai (formerly Bombay), India received a record-breaking 942 millimeters
(37.1 inches) of rain in a 24-hour period on Tuesday, July 26, 2005
• India’s previous all-time single-day record (838 mm; 33 in) set in 1912
• Heavy monsoon rain triggered deadly floods, which have claimed more than 500 lives in the country’s western Maharashtra state, with 273 fatalities in Mumbai alone, as of July 28
• Monsoon-related flooding is not unusual in summer when heating landmass generates winds that pull warm, moisture-laden air over the Indian subcontinent
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http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16985
Climate and Global Change Notes
21-31
Monsoon
Jan 2003 Temperature (K)
Jul 2003 Temperature (K)
Science quotes of 5th and 6th graders -
Isotherms and isobars are even more important than their names sound.
http://airs.jpl.nasa.gov/multimedia/products_suite/products_suite_temp.html
263 273 283 293 303
Degrees Kelvin
Climate and Global Change Notes
21-32
Monsoon
Jan Average Pressure (mb)
Jul Average Pressure (mb)
Climate and Global Change Notes
21-33
Monsoon
Monsoon Winds
• Winter (top) winds offshore
• Summer (bottom) winds onshore
http://earthobservatory.nasa.gov/Study/Monsoon/monsoon4.html
Climate and Global Change Notes
21-34
Monsoon
Jan Average Precip (mm/day)
Jul Average Precip (mm/day)
Climate and Global Change Notes
21-35
Monsoon
Tucson Average Daily Surface Dewpoint Temperature (°F)
• 1998- Start date July 3
• 2005- Start date July 18
http://www.wrh.noaa.gov/images/twc/monsoon/1998monsoon.pnghttp://www.wrh.noaa.gov/images/twc/monsoon/2005monsoon.png
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