Climate and Global Change Notes 21-1 Atmospheric Motions Circulation Scales Thermally Driven Winds 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 Science Concepts Potential Energy Coriolis Force e Earth System (Kump, Kastin & Crane) Chap. 4 (pp. 59-65, 79)
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
QuickTime™ and aSorenson Video decompressorare needed to see this picture.
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
• 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