21-1
Atmospheric Motions
Circulation Scales
Thermally Driven Winds
Science Concepts
Potential Energy
Global Circulations
Rainfall Versus Latitude
Observed Global Circulation
Three-celled Circulation
Wind Patterns
Pressure Patterns
Rainfall Patterns
Land-Water Effect
Global Climate
Relationship to Global Circulation
Coriolis Force
The Earth System (Kump, Kastin & Crane)
•
Chap. 4 (pp. 59-65, 79)
Climate and Global Change Notes
21-2
Atmospheric Scales
Terminology
Object of
Study
Space Scale
or Size
Time
Scale
Macroscale
Climate
Seasons
Global
Hemisphere
Years
Weeks
Cyclonic
or
Synoptic
Mesoscale
Convective
or
Cumulus
Highs & Lows
Hurricanes
Fronts
Squalls
Thunderstorms
Showers
National
(5000 km)
Regional
(1000 km)
Days
Local
(100 km)
Hours
Tornadoes
Terminal
(10 km)
Minutes
Microscale
Gusts
Eddies
Spot
(1 meter)
Seconds
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
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.
http://visibleearth.nasa.gov/Sensors/Terra/
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
Thermally Driven Wind Systems
Hurricanes (Con’t)
•
Ocean cooling effects
of hurricanes
•
Katrina and Rita, each
cooled Gulf temperatures
more than 4°C in areas,
and the entire Gulf ~1°C
•
QuickTime™ and a
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Hurricanes cool the ocean by
> transferring heat to the
atmosphere through
evaporation
> upwelling of cold water due to
http://earthobservatory.nasa.gov/Newsroom/
the suction effect of the storm’s
NewImages/images.php3?img_id=17164
low pressure
> cold raindrops that remain on the ocean surface for a time
> shielding the ocean surface from direct sunlight by cloud cover
Climate and Global Change Notes
21-7
Thermally Driven Wind Systems
Sea Breezes
Climate and Global Change Notes
21-8
Global Circulations
Radiation Intensity ( W / m 2 )
Net Radiation vs Latitude
400
Radiation Lost
300
Radiation Received
Surplus
200
Deficit
Deficit
100
90N
Heat Transfer
Heat Transfer
50N
30N
10N 0
10S
30S
50S
90S
Latitude
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 4/06
precipitation
in mm/day
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
http://earthobservatory.nasa.gov/Observatory/Datasets/rainfall.gpcp.html
Climate and Global Change Notes
21-11
Global Circulations
Average Precipitation (mm/day)
•
January
‘79 - ‘05 average January, July and
Annual precipitation
-
Dashed lines are 0°, 30°, 60°
north and south latitudes
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Annual
July
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http://www.gewex.org/
GPCP_data_products_9-2006.pdf
What latitude has the highest annual precipitation?
Climate and Global Change Notes
21-12
Global Circulations
Rainfall vs Latitude
Rainfall
2000
Millimeters per year
Evaporation
1500
1000
Runoff
500
0
-500
90°N
60°N
30°N
0°
30°S
60°S
90°S
Latitude
Climate and Global Change Notes
21-13
Global Circulations
InterTropical
Convergence
Zone
Climate and Global Change Notes
21-14
Global Circulations
Annual Average Cloud Amount
•
1983-2001
http://isccp.giss.nasa.gov/climanal2.html
Zonal Mean
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Total Cloud Amount (%)
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
Global Circulations
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
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
Climate and Global Change Notes
21-17
Global Circulations
Three-Celled Circulation
•
Polar Cells
Thermally direct
Downward motion at
the Poles
•
Equatorial Cells
Thermally direct
Upward motion at
the Equator
•
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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 hemisphere
mid-latitude systems move
eastward
•
Note Northern hemisphere
tropical systems move westward
http://airs.jpl.nasa.gov/Data/FeaturedProducts/AIRS_T500.mov
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
Climate and Global Change Notes
21-19
Global Circulations
Three-Celled Circulation Surface Winds
The 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
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
http://aquarius.gsfc.nasa.gov/overview-sss.html
Climate and Global Change Notes
21-23
Global Circulations
Ocean Deserts (Con’t)
•
Ocean salinity is
increased by
evaporation and
freezing of seawater
and decreased by
precipitation and
melting of snow
and ice
http://aquarius.gsfc.nasa.gov/science-watercycle.html
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
Location
Aleutian low
Position
60°- 65°
Strength
in Winter
Strong
Strength
in Summer
Weaker
Icelandic low
60°- 65°
Strong
Weaker
Hawaiian or
Pacific high
30°- 35°
Weaker
Stronger
Bermuda high
30°- 35°
Weaker
Stronger
Continental
Location
Siberian high
Strength
in Winter
Strong
Strength
in Summer
Absent
North American high
Strong
Absent
SW U.S. thermal low
Absent
Strong
India thermal low
Absent
Strong
Climate and Global Change Notes
21-29
Atmospheric Motions
Global Circulations (Con’t)
Monsoons
Science Concepts
Seasonal Effects
The Blue Planet (Skinner, Porter & Botkin)
•
Chap. 13 (p. 303)
Science quotes of 5th
and 6th graders A monsoon is a
French gentleman.
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
•
QuickTime™ and a
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are n eeded to see this picture.
Monsoon-related flooding is not
unusual in summer when heating
landmass generates winds that pull warm,
http://earthobservatory.nasa.gov/Newsroom/
moisture-laden air over the Indian subcontinent NewImages/images.php3?img_id=16985
Climate and Global Change Notes
21-31
Monsoon
Jan 2003 Temperature (K)
Jul 2003 Temperature (K)
Degrees Kelvin
263
273
283
293
http://airs.jpl.nasa.gov/
multimedia/products_suite/
products_suite_temp.html
303
Science
quotes of 5th
and 6th
graders Isotherms and
isobars are
even more
important
than their
names sound.
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.png
http://www.wrh.noaa.gov/images/twc/monsoon/2005monsoon.png
Climate and Global Change Notes