The General Circulation of Earth's Atmosphere
The General Circulation
The large-scale wind patterns of the earth
Mission: to mitigate global temperature
contrasts (decrease temperature gradients,
redistribute warm and cold air across the
globe)
Caused by the unequal heating of the
earth’s surface
The General Circulation (High Latitudes)
“Polar Cell” = sinking/descending air at
highest latitudes
Purpose is to bring warm air poleward (aloft)
and cool air equatorward (below)
Atmospheric “Dump”
–
Mid-Latitude pollution carried there
–
Very stable troposphere, on average, so there is
little mixing and a build-up of
pollutants
–
Nearly permanent high
pressure, sinking air, lead
to very little precipitation
(which would help clean
the air)
The General Circulation (Tropics)
The Hadley Cell: large convection cell
where air rises near the equator and
sinks near 30 degrees north and south
latitude
Purpose is to bring warm air poleward
(aloft) and cool air equatorward (below)
–
Trade winds
–
Eckman transport (ocean)
–
ITCZ
–
Subtropical jet stream
–
Subtropical highs
G.C.: Hadley Cell: Trade Winds
Fairly constant tropical winds that transport
air equatorward
–
Blow from the NE in
the northern
hemisphere
–
Blow from the SE in
the southern
hemisphere
G.C.: Hadley Cell: Eckman Transport
Vast stores of oceanic heat are distributed
through this process
Upwelling: bring cold water up, heat it and
send it poleward
G.C.: Hadley Cell: ITCZ
Where NE and SE trade winds meet
Convergence into belt of weak low pressure
Ascending branch of the Hadley Cell
NOT a straight line at the equator
–
Unequal heating of land and water
–
Follows the sun
–
Monsoon: seasonal reversal of wind direction
India, SW
United States
(wimpy one)
NOT a
synonym for
rain storm!!!
ITCZ
in July
ITCZ in
January
G.C.: Hadley Cell: Subtropical Jet Stream
Farthest poleward (upper troposphere) part of
Hadley Cell
Eastward momentum is transferred from tropics
Coriolis effect turns winds, resulting in a fast-
moving ribbon of air
generally moving west-
to-east near 30
degrees latitude
G.C.: Hadley Cell: Subtropical Highs
Descending branch of Hadley Cell caused by
upper tropospheric convergence
Very persistent
Convergence causes semi-permanent regions
of surface high pressure
–
World’s deserts are found underneath and east
–
Horse Latitudes
El Nino
El Nino
An irregular warming of the topmost layers of
the eastern Pacific ocean
–
Generally occurs once every 3-7 years
–
Trade winds weaken
Upwelling of cold, nutrient-rich water off Peru ceases
Warm water sloshes eastward from western Pacific
Upwelling near equator weakens, water warms
–
Not fully understood
–
Teleconnections
–
NOT a weather event
–
La Nina
From the Met Office (U.K.)
Key Figures
10.2, 10.8, 10.11, 10.12, 10.22, 10.28,
10.34, 10.35, 10.39, 10.41
The general circulation of the Earth's atmosphere plays a crucial role in mitigating global temperature contrasts by redistributing warm and cold air. This system includes the Polar Cell at high latitudes, the Hadley Cell in the tropics, trade winds, oceanic heat distribution through Eckman Transport, and the Intertropical Convergence Zone (ITCZ). These atmospheric phenomena work together to regulate temperature distribution across the globe and influence weather patterns.
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Presentation Transcript
The General Circulation The large-scale wind patterns of the earth Mission: to mitigate global temperature contrasts (decrease temperature gradients, redistribute warm and cold air across the globe) Caused by the unequal heating of the earth s surface
The General Circulation (High Latitudes) Polar Cell = sinking/descending air at highest latitudes Purpose is to bring warm air poleward (aloft) and cool air equatorward (below) Atmospheric Dump Mid-Latitude pollution carried there Very stable troposphere, on average, so there is little mixing and a build-up of pollutants Nearly permanent high pressure, sinking air, lead to very little precipitation (which would help clean the air)
The General Circulation (Tropics) The Hadley Cell: large convection cell where air rises near the equator and sinks near 30 degrees north and south latitude Purpose is to bring warm air poleward (aloft) and cool air equatorward (below) Trade winds Eckman transport (ocean) ITCZ Subtropical jet stream Subtropical highs
G.C.: Hadley Cell: Trade Winds Fairly constant tropical winds that transport air equatorward Blow from the NE in the northern hemisphere Blow from the SE in the southern hemisphere
G.C.: Hadley Cell: Eckman Transport Vast stores of oceanic heat are distributed through this process Upwelling: bring cold water up, heat it and send it poleward
G.C.: Hadley Cell: ITCZ Where NE and SE trade winds meet Convergence into belt of weak low pressure Ascending branch of the Hadley Cell NOT a straight line at the equator Unequal heating of land and water Follows the sun Monsoon: seasonal reversal of wind direction India, SW United States (wimpy one) NOT a synonym for rain storm!!!
ITCZ in January ITCZ in July
G.C.: Hadley Cell: Subtropical Jet Stream Farthest poleward (upper troposphere) part of Hadley Cell Eastward momentum is transferred from tropics Coriolis effect turns winds, resulting in a fast- moving ribbon of air generally moving west- to-east near 30 degrees latitude
G.C.: Hadley Cell: Subtropical Highs Descending branch of Hadley Cell caused by upper tropospheric convergence Very persistent Convergence causes semi-permanent regions of surface high pressure World s deserts are found underneath and east Horse Latitudes
El Nino An irregular warming of the topmost layers of the eastern Pacific ocean Generally occurs once every 3-7 years Trade winds weaken Upwelling of cold, nutrient-rich water off Peru ceases Warm water sloshes eastward from western Pacific Upwelling near equator weakens, water warms Not fully understood Teleconnections NOT a weather event La Nina
Key Figures 10.2, 10.8, 10.11, 10.12, 10.22, 10.28, 10.34, 10.35, 10.39, 10.41
