Download Wind-Driven Ocean Circulation What Drives Circulation of Upper

Wind-Driven Ocean Circulation
What Drives Circulation of Upper Ocean?
Short answer: Energy from the Sun and
Earth’
Earth’s rotation
Atmospheric circulation on an
idealized non-rotating Earth
Hadley cell
60o
 Energy from Sun
H
Su
rfa
ce
flo
w
causes differential
heating of ocean
and atmosphere
Equator
L
Coriolis Effect
Maximum apparent
rotation
30o
1450
km/h
1670
km/h
0o
L
L
30o
H
Arises from motion on a
rotating earth
830
km/h
Equator
Depends on observer’
observer’s
frame of reference
1450
km/h
Hadley cell
1
Coriolis Force
Coriolis Force
Magnitude: F/m = 2Ω sin∆ v
Where: 2 Ω is earth’
earth’s
rotational velocity
(constant)
∆ is latitude,
and
v is velocity of the
object.
From space, we
see that it
arises from the
conservation of
momentum as
the earth
rotates under a
moving object
a= initial north or south wind
velocity of poleward moving air
b= initial eastward velocity minus the
eastward velocity of the earth at a
higher latitude
c= resultant velocity of the wind
Direction:
a= initial north or south wind velocity
moving toward the equator
b= initial eastward velocity minus the
eastward velocity of the earth at a lower
latitude
c= resultant velocity of the wind
Atmospheric circulation on an idealized
rotating earth (with Coriolis Effect)
Right in the Northern Hemisphere
Left in the Southern Hemisphere
Initial direction
Resultant direction
Climatic Zones
Vertical Circulation
POLAR
EASTERLIES Earth’s Rotation
Air sinks
POLAR
Polar front
Polar easterlies
SUBPOLAR
o
60
Westerlies
Westerlies
EQUATORIAL
“Doldrums”
0
30o
Westerlies
Subpolar low
Polar easterlies
Air rises:
persistent
cloudiness and
rain
ITCZ
0o
o
Southeasterly Trades
30oS
SUBTROPICAL
“Horse Latitudes”
TEMPERATE
SUBPOLAR
Air sinks: clear
skies, low
rainfall
High
Westerlies
Air rises:
persistent
cloudiness
AF
Antarctic front
Subtropical high
POLAR
Antarctica
60o
Atmospheric
circulation and
source of
planetary winds
Northeasterly Trades
Subtropical high
SE trade winds
Air sinks: clear
skies, low
rainfall
High
30oN
30o
NE trade winds
Low
60oN
PF
TEMPERATE
SUBTROPICAL
“Horse Latitudes”
Subpolar low
Air rises:
persistent
cloudiness
Air sinks
ITCZ Intertropical
convergence
zone
PF Polar Front
AF Antarctic
Front
2
The weather patterns of
Temperate Regions
80
80
80
70
70
Polar
80
70
60
80
70
60
Polar
70
60
50
Subpolar
50
Temperate
Temperate
40
40
40
40
40
40
Subtropical
Subtropical
30
80
70
60
50
50
Atmospheric Pressure Systems
30
Land masses heat in summer and cool in winter faster
than ocean, because land has lower heat capacity than
water
Tropical
Tropical
Monsoon
50 60 70 80
90
120
140
140
120
100
90
50 40
30 20 10
0
30
50
Subpolar
60
Subtropical
30
Subtropical
40
60
70
50 50
Subpolar
70
80
40
This leads to seasonal effects: formation of cold high
pressure systems over continents in winter and warm
low pressure systems over continents in summer
Temperate
Temperate
50
60
70
80
Tropical
40 40
Temperate
60
Polar
70
80
50
Subpolar
60
60
Polar
70
80
70
80
80
Atmospheric Pressure Systems:
Northern Hemisphere Summer
Atmospheric Pressure Systems:
Northern Hemisphere Winter
180
90
180
90
90
1008 Icelandic low
180
90
90
180
1008
1014
1008
0
H Pacific High
1014
H
L
60
1026
L
1026
1002
1020
L
L
H
0
1014
30
1020
1020
H
H
H
30
1008
1002
996
60
60
1014
0
1020
1026
30
H
H
1014
30
1014
ITCZ
0
1014
1020
H
1014
1020
30
L
1014
1020
H
30
H
1008
1008
1014
1020
L
H
996
1002
1008
1014
1020 H Bermuda High
1020
H
1020
ITCZ
30
1020
L
H
30
Latitude
Pacific
high
Thermal low
Icelandic low
Siberian
1002
High
1032
Aleutian low L
60
1008
60
1026
60
L
1008
90
1020
Latitude
50
Equatorial
160
Tropical
Subtropical
40
180
Equatorial
Tropical
30
160
1014
1008
60
60
1002
996
990
90
180
90
Longitude
180
90
90
180
90
Longitude
180
90
3
Undulations in the Jet Stream
and Polar Front
High and Low Pressure Cells:
Geostrophic Balance
North Pole
Easterlies
Jet Stream
30o
60o
60o
Upper
Westerlies
Cold
Air
30o
Warm
air
Equator
Falling air
A
Coriolis force
effect
Northern
Hemisphere
Rising air
Warm
winds
B
L Low
H High
Jet Stream
4