Download • A Circulation is an organized movement of air.

Ch 7
Sec A
Ch 7
Scales of Atmospheric
Circulation
Sec A
• A Circulation is
an organized movement of air.
Scales of Atmospheric
Circulation
A. Microscale: movements less than 1 mile
1. Tornado
2. Dust Devils
3. Thermals
4. Turbulence
B. Mesoscale: 1 mile to 1000 miles
1. Thunderstorms, Downburst
2. Land/Sea Breeze, Lee Wave
3. Cyclones, Hurricanes, Fronts
1
Ch 7
Sec A
2
Ch 7
Scales of Atmospheric
Circulation
Sec B
C. Macroscale
1. Synoptic: 500 miles to approx. 2000 miles
A. Large Lows and Highs
2. Global or Planetary: Greater than 2000 miles
A. Jet Streams
B. Monsoonal Circulations
C. General Circulations
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• General Circulations: > 5000 miles
• Hadley Cell: Warm moist air rises at the
Equator; the water vapor rains out; the air flows
north at high altitude, is cooled and sinks near
the horse latitudes(near 30o North and South
latitudes) as dry air producing deserts in Mexico,
Africa, and Australia
• Produces Surface winds toward the Equator
near the Equator that are tilted into a more
easterly direction by the coriolis force.
3
Ch 7
Sec B
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• General Circulations: > 5000 miles
• Polar Cell:
from 90(N,S) to about 60(N,S) Latitudes
• Near the poles cold air sinks because it is more
dense(High Pres. Area)
• Produces winds away from the poles that are
curved into easterly winds by the coriolis force.
• Both Poles have Polar Easterly Winds
4
Ch 7
Sec B
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• General Circulations: > 5000 miles
• Ferrel Cell:
from 60(N,S) to about 30(N,S)
Latitudes
• Surface winds in this area move toward
the poles and are tilted toward a westerly
direction by the coriolis force.
5
6
1
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
Ch 7
Sec B
Ch 7
Sec B
• Winds Produced by Global Cells.
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• j
– A. Polar Easterlies (Both N and S Poles)
– B. Prevailing Westerlies 30o Æ 60o Lat.
• Near 30o Latitude is called the Horse Latitudes
– C. NE & SE Trade winds from 0o Æ 30o Lat.
• Around the equator the winds can have large
areas of calm called the Doldrums
7
Ch 7
Sec
B
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
8
Ch 7
Sec
B
• >
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• Monsoonal Circulations
– In the summer time Continents heat up more
than the oceans, making the continental air
massses lower in pressure than the oceanic
air massess
– In the winter time Continents cool down more
than the oceans, making the continental air
massses higher in pressure than the oceanic
air massess
9
Ch 7
Sec
B
Scales of Atmospheric
Circulation: Largest Circulations:
Macroscale
• Monsoonal
10
Ch 7
Sec
C
Scales of Atmospheric
Circulation: Global Circulation:
Macroscale
• The Global Circulation is Different
depending on the time of YEAR!!
• In December – March, Northern
Hemisphere continents have Highs
S. Hemisphere Continents have Lows
• In June – September:
N. Hemisphere continents have Lows
S. Hemisphere Continents have Highs
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12
2
Ch 7
Sec
Ch 7
Sec
Atmospheric Circulation:
Global Circulation Aloft
C
Atmospheric Circulation:
Global Circulation Aloft
C
• Predominently Westerly Flow, but
• >
– In DecemberÆ March Upper Altitude Lows
develop in the Far North
• Jet Streams Are Westerlies
– Occur near the Tropopause
– Polar Front Jet Stream: Affects North America
• Weakens and moves poleward in the Summer
– Subtropical Jet Stream: flows over Mexico,
Northern Africa, and Central Asia
13
Ch 7
Sec
C
14
Ch 7
Sec
Atmospheric Circulation:
Global Circulation Aloft
D
• >
Atmospheric Circulation:
Global Circulation and Climate
• Climatology: the study of the average
conditions of the atmosphere
• Global Cells produce long term climates at
several locations.
– Near the Equator the Hadley Cell drops a
large amount of rain as the air rises.
– Near 30 degrees latitude cool dry air sinks,
warms and produces deserts.
15
Ch 7
Sec
D
16
Atmospheric Circulation:
Global Circulation and Climate
• >
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