Atmospheric Motions

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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-cell
ed Circulation Wind Patterns Pressure
Patterns Rainfall Patterns Land-Water
Effect Global Climate Relationship to Global
Circulation
The Earth System (Kump, Kastin Crane) Chap.
4 (pp. 59-65, 79)
2
Atmospheric Scales
Object of Space Scale Time Terminology
Study or Size Scale Macroscale Climate Global Yea
rs Seasons Hemisphere Weeks National Cyclo
nic Highs Lows (5000 km)
or Hurricanes Synoptic Regional Days Fronts (10
00 km) Mesoscale Squalls Thunderstorms Local Ho
urs Convective Showers (100 km)
or Cumulus Tornadoes Terminal (10 km)
Minutes Microscale Gusts Eddies Spot Seconds
(1 meter)
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Thermally Driven Wind Systems
Examples Global circulation Midlatitude
cyclones Monsoons Hurricanes Land-sea
breezes Heat island circulations Mountain-va
lley winds
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Thermally Driven Wind Systems
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.
Global Circulation
http//visibleearth.nasa.gov/Sensors/Terra/
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Thermally Driven Wind Systems
Hurricanes Hurricane Georges battering the
Gulf Coast on September 28, 1998
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Thermally Driven Wind Systems
Hurricanes (Cont) Ocean cooling effects of
hurricanes Katrina and Rita, each cooled
Gulf temperatures more than 4C in areas, and
the entire Gulf 1C Hurricanes cool the ocean
by gt transferring heat to the atmosphere
through evaporation gt upwelling of cold water
due to the suction effect of the storms low
pressure gt cold raindrops that remain on the
ocean surface for a time gt shielding the ocean
surface from direct sunlight by cloud cover
http//earthobservatory.nasa.gov/Newsroom/ NewImag
es/images.php3?img_id17164
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Thermally Driven Wind Systems
Sea Breezes
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Global Circulations
Net Radiation vs Latitude
400

Radiation Received

Radiation Lost

300

Surplus

Radiation Intensity ( W / m 2 )
200

Deficit
Deficit
100

Heat Transfer

Heat Transfer

0

10N

10S

30S

30N

50S

50N

90S

90N

Latitude

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Global Circulations
What do you think the global distribution of
precipitation should look like?
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Global Circulations
Global Rainfall 1/00 to 4/06 precipitation
in mm/day
http//earthobservatory.nasa.gov/Observatory/Datas
ets/rainfall.gpcp.html
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Global Circulations
Average Precipitation (mm/day) 79 - 05
average January, July and Annual
precipitation - Dashed lines are 0, 30, 60
north and south latitudes
January
Annual
July
http//www.gewex.org/ GPCP_data_products_9-2006.pd
f
What latitude has the highest annual
precipitation?
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Global Circulations
Rainfall vs Latitude
Rainfall

2000

Evaporation

1500

1000

Millimeters per year
Runoff

500

0

-500

90N

60N

30N

0

30S

60S

90S

Latitude

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Global Circulations
Inter- Tropical Convergence Zone
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Global Circulations
Annual Average Cloud Amount 1983-2001
http//isccp.giss.nasa.gov/climanal2.html
Zonal Mean
Cloud Amount ()
Total Cloud Amount ()
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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
http//rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
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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
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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
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Global Circulations
http//airs.jpl.nasa.gov/Data/FeaturedProducts/AIR
S_T500.mov
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//rst.gsfc.nasa.gov/Sect14/Sect14_1c.html
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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
Melvilles 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)
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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.
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Global Circulations
Can we have deserts in the ocean?
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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
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Global Circulations
Ocean Deserts (Cont) 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.h
tml
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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
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Global Circulations
Summary (Cont) 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
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Global Circulations
January Mean Surface Pressure (mb)
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Global Circulations
July Mean Surface Pressure (mb)
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Global Circulations
Semi-Permanent Pressure Systems
Ocean Strength Strength Location Position in
Winter in Summer Aleutian low 60-
65 Strong Weaker Icelandic low 60-
65 Strong Weaker Hawaiian or 30-
35 Weaker Stronger Pacific high Bermuda
high 30- 35 Weaker Stronger
Continental Strength Strength Location in
Winter in Summer Siberian high Strong Absent N
orth American high Strong Absent SW U.S.
thermal low Absent Strong India thermal
low Absent Strong
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Atmospheric Motions
Science Concepts Seasonal Effects
Global Circulations (Cont) Monsoons
The Blue Planet (Skinner, Porter
Botkin) Chap. 13 (p. 303)
Science quotes of 5th and 6th graders - A
monsoon is a French gentleman.
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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 Indias 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
countrys 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
http//earthobservatory.nasa.gov/Newsroom/ NewImag
es/images.php3?img_id16985
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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.
Degrees Kelvin
263
273
283
293
303
http//airs.jpl.nasa.gov/ multimedia/products_suit
e/ products_suite_temp.html
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Monsoon
Jan Average Pressure (mb)
Jul Average Pressure (mb)
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Monsoon
Monsoon Winds Winter (top) winds
offshore Summer (bottom) winds onshore
http//earthobservatory.nasa.gov/Study/Monsoon/mon
soon4.html
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Monsoon
Jan Average Precip (mm/day)
Jul Average Precip (mm/day)
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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/1998mon
soon.png http//www.wrh.noaa.gov/images/twc/monsoo
n/2005monsoon.png