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Chapter 6 Atmospheric and Oceanic Circulations

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Chapter 6 Atmospheric and Oceanic Circulations Geostrophic wind (Vg) Results from the balance between the PGF and Coriolis force Flows parallel to straight isobars at ... – PowerPoint PPT presentation

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Title: Chapter 6 Atmospheric and Oceanic Circulations


1
Chapter 6 Atmospheric and Oceanic Circulations
2
(No Transcript)
3
Wind Essentials
  • Air Pressure and Its Measurement  
  • Mercury barometer
  • Aneroid barometer
  • Wind Description and Measurement  
  • Wind
  • Anemometer
  • Wind vane
  • Global Winds  

4
Barometers
Figure 6.2
5
Air Pressure Readings
Figure 6.3
6
Wind Vane and Anemometer measures wind direction
and speed
NEN
N
NWN
NE
NW
ENE
WNW
E
W
ESE
WSW
SE
SW
S
SWS
SES
Figure 6.4
7
Driving Forces within the Atmosphere  
  • Pressure Gradient Force  
  • Coriolis Force  
  • Friction Force  

8
Pressure Gradient changes in air pressure over
a horizontal distance Pressure gradient force
(PGF) points from higher to lower pressure,
perpendicular to isobars. Isobars lines of equal
air pressure.
Figure 6.7
9
Coriolis Force an apparent force caused by the
rotation of the earth 1) deflects to the right
(of the movement) in northern hemisphere. 2)
Maximum in the poles and zero in the equater 3)
Proportional to the wind speed.
Figure 6.9
10
Geostrophic wind (Vg)
  • Results from the balance between the PGF and
    Coriolis force
  • Flows parallel to straight isobars at a constant
    speed
  • Speed in determined by the PGF

PGF
1012mb
Vg
1016mb
COF
11
Frictional force
  • Opposite to the wind direction
  • Slows down the wind speed
  • Reduces Coriolis force
  • Creates surface wind (Vs)
  • Flows from high to low pressure across isobars at
    an angle

PGF
Vs
1012mb
1016mb
COF
12
Cyclone (low pressure) and Anticyclone (high
pressure)
In northern hemisphere Cyclone wind flows
counter-clockwise towards the center across
isobars at an angle Anticyclone wind flows
clockwise away from the center across isobars at
an angle
13
Cyclone air converges on the surface and moves
upwards over the center clouds forms and is
likely to be associated with precipitation Anticy
clone air diverges away and subsides over the
center clear sky and sunny
Figure 6.8
14
Atmospheric Patterns of Motion  
  • Primary High-Pressure and Low-Pressure Areas  
  • Upper Atmospheric Circulation  
  • Local Winds  
  • Monsoonal Winds  

15
General circulation If the earth were not
rotating simple one cell model
N. Pole
cold
H
L
warm
equator
16
General circulation pattern with rotation
H
L
60N
L
30N
H
equator
H
L
H
17
General Atmospheric Circulation
Hadley Cell rises from equator subsides over
Subtropical High
Figure 6.12
18
Primary High-Pressure and Low-Pressure Areas
  • Inter-tropical convergence zone-ITCZ (equator)
  • Polar High Pressure (poles)
  • Subtropical high pressure (30N/S)
  • Subpolar low-pressure cells (60N/S)

19
JuneJuly ITCZ
Figure 6.11
20
Global wind pattern
  • Northeast trade wind (between equator and 30N/S)
  • Westerlies (between 30N/S-60N/S)
  • Polar northeasterly (between 60N/S-poles)

21
Global Barometric Pressure -winter
Figure 6.10
22
Global Barometric Pressure-summer
Figure 6.10
23
Semi-permanent system associated with Subtropical
High
  • Bermuda high
  • (Azores high Atlantic high)
  • Pacific high
  • (Hawaii high)

Figure 6.13
24
Semi-permanent system associated with Subpolar
Low Pressure
  • Aleutian low
  • Icelandic low

25
General Atmospheric Circulation
Figure 6.12
26
Local Winds
  • Land-sea breezes
  • Mountain-valley breezes
  • Katabatic winds

27
Land-Sea Breezes
Sea breeze wind flows from ocean to land occurs
during the day.
Land breeze wind flows from land to ocean
occurs during the night
Figure 6.18
28
Mountain-Valley Breezes
Wind flows from valley to hill during the daytime
Wind flows from high to valley during the night
Figure 6.19
29
Monsoonal Winds reversal of wind directions
between seasons
Figure 6.20
30
Oceanic Currents
  • Surface Currents  
  • Deep Currents  

31
Major Ocean Currents Gyre a circular flow
pattern occupies the entire ocean basin
Figure 6.21
32
Deep-Ocean Thermohaline Circulation
Figure 6.22
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