chapter 6 atmospheric and oceanic circulations
DESCRIPTION
Chapter 6 Atmospheric and Oceanic Circulations. Wind Essentials. Air Pressure and Its Measurement Mercury barometer Aneroid barometer Wind: Description and Measurement Wind Anemometer Wind vane Global Winds . Barometers. Figure 6.2. Air Pressure Readings. Figure 6.3. - PowerPoint PPT PresentationTRANSCRIPT
Robert W. ChristophersonCharlie Thomsen
Chapter 6Atmospheric and
Oceanic Circulations
Wind EssentialsAir Pressure and Its Measurement
Mercury barometer
Aneroid barometer
Wind: Description and Measurement Wind
Anemometer
Wind vane
Global Winds
Barometers
Figure 6.2
Air Pressure Readings
Figure 6.3
Wind Vane and Anemometermeasures wind direction and speed
Figure 6.4
N
S
W E
NE
SW
NEN
ENE
SE
NW
ESE
SESSWS
WSW
WNW
NWN
Driving Forces within the Atmosphere
Pressure Gradient Force
Coriolis Force
Friction Force
Pressure Gradient : changes in air pressure over a horizontal distancePressure gradient force (PGF): points from higher to lower pressure, perpendicular to isobars.Isobars: lines of equal air pressure.
Figure 6.7
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 equater3) Proportional to the wind speed.
Figure 6.9
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
1016mb
1012mb
PGF
COF
Vg
Frictional forceOpposite 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 1016mb
1012mb
PGF
Vs
COF
Cyclone (low pressure) and Anticyclone (high pressure)
In northern hemisphere:Cyclone: wind flows counter-clockwise towards the center across isobars at an angleAnticyclone: wind flows clockwise away from the center across isobars at an angle
Figure 6.8
Cyclone: air converges on the surface and moves upwards over the center; clouds forms and is likely to be associated with precipitation
Anticyclone: air diverges away and subsides over the center; clear sky and sunny
Atmospheric Patterns of Motion Primary High-Pressure and Low-Pressure Areas
Upper Atmospheric Circulation
Local Winds
Monsoonal Winds
equator
N. Pole
warm L
cold HGeneral circulation:If the earth were not rotating: simple one cell model
L equator
30N
60NH
H
L
H
L
H
General circulation pattern with rotation
General Atmospheric Circulation
Figure 6.12
Hadley Cell: rises from equator subsides over Subtropical High
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)
June–July ITCZ
Figure 6.11
Global wind pattern
Northeast trade wind (between equator and 30N/S)
Westerlies (between 30N/S-60N/S)
Polar northeasterly (between 60N/S-poles)
Global Barometric Pressure -winter
Figure 6.10
Global Barometric Pressure-summer
Figure 6.10
Semi-permanent system associated with Subtropical High
Bermuda high
(Azores high; Atlantic high)
Pacific high
(Hawaii high)
Figure 6.13
Semi-permanent system associated with Subpolar Low Pressure
Aleutian low
Icelandic low
General Atmospheric Circulation
Figure 6.12
Local WindsLand-sea breezes
Mountain-valley breezes
Katabatic winds
Land-Sea Breezes
Figure 6.18
Sea breeze: wind flows from ocean to land; occurs during the day.
Land breeze: wind flows from land to ocean; occurs during the night
Mountain-Valley Breezes
Figure 6.19
Wind flows from valley to hill during the daytime
Wind flows from high to valley during the night
Monsoonal Winds: reversal of wind directions between seasons
Figure 6.20
Oceanic CurrentsSurface Currents
Deep Currents
Major Ocean CurrentsGyre: a circular flow pattern occupies the entire
ocean basin
Figure 6.21
Deep-Ocean Thermohaline Circulation
Figure 6.22