Atmospheric Pressure
Global Pressure and Wind Systems
Preliminary / Review Questions
Idealized Belts
- in a perfect world
Intertropical Convergence Zone
(ITCZ)
surplus of insolation
thermally
induced "trough"
shifts with sun's movement
globe-circling zone of low pressure &
clouds
rising and unstable air
area known as "
Doldrums
" (very calm)
large-scale updrafts
pump enormous amount of energy
into atmosphere
sensible heat
and
latent heat of condensation
Subtropical High
(STH)
centered at approx. 30 degrees north and south latitude
derived from ITC energy and
upper atmospheric subsidence
dynamically
induced "ridge"
shifts with suns movement
creates
world's major deserts
at sea - associated with "horse" latitudes
(
Note: not nearly as calm as "doldrums")
source of two (2 of 3) major global wind systems - Trade Winds and Westerlies
Class Exercise
Pacific High
Azores High (off Africa)
Trade Winds
(Commerce Winds)
most consistent winds blowing from east
originate as warm, dry winds
winds then evaporate large amounts of water contained in water vapor
releases moisture when encountering
landmasses
(like
Hawaii
)
Westerlies
(winds of the mid-latitudes)
winds blow from west (geostrophic winds)
not as consistent as Trade winds due to landform barriers
brings in much winter storms
Rossby wave
- meandering flow or undulation in jet stream
mixing of northerly cold air and southly warm air
sometimes resulting in severe weather
Polar Highs
- Polar areas and interior landmasses
cold sinking air -
thermally
induced
Siberian High and Canadian High
Polar Easterlies
third (3rd) broad scale global wind system
most of the area between the polar highs and 60 degrees latitude
Subpolar Lows
60 degrees latitude -
dynamically
induced
collision of air masses (cold poleward & warmer adjacent)
resulting in rising air or low
So. Hemisphere -
continuous belt
due to ocean
No. Hemisphere -
cyclonic cells
(Icelandic Low and Aleutian Low)
Monsoons
- seasonal reversal of winds
Example: South Asian
Monsoons
inland during
summer
outward during
winter
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